Category Archive: Article
Surface finish options for plastic injection molded parts can vary a great deal depending on the part and its chemical make-up. Determining the best surface finish for a part requires communication between your design engineer and injection molder to achieve the desired appearance and performance of the finished part. The surface finish can be a critical factor in either the appearance or performance of your product. Will the finish play a role in creating a more attractive part – or will it simply act as a functional component of the design?
The answer to this question will give the necessary direction in determining the injection molding process to be used as well as any steps in the finishing process that will be required for your part.
Consider these key fundamentals when selecting a surface finish for your injection molded part.
Visual Appeal vs. Functionality
Part designers may choose texture for several aesthetic reasons. Texture can give a part the appearance of depth and a finished look that will grab the attention of customers. In some cases, it may even improve a part’s perceived value.
Textured finishes are valuable because they can be used to hide imperfections such as flow lines, knit lines, blush marks, sinks, and shadow marks. Another great factor is that texture can also provide a surface that may withstand contact damage in shipping and fingerprint smudges from handling.
Beyond the simple aesthetic considerations of texture, it also has a number of functional benefits that include:
- Using texture to make undercuts. If you have a part that will not consistently come across to the moving half of the mold, texture on some hidden surfaces could give the pull you need.
- Improved paint adhesion. Paint holds more firmly to a textured part during additional molding operations.
- Improved grip. Textured parts are easier to hold. This improves usability and can increase safety in certain applications.
- Better sticker adhesion. Like paint, stickers applied to plastic parts are more likely to stay affixed if the surface has a slight texture.
- Trapped gasses escape more quickly. When texturing is applied, trapped gasses have the opportunity to escape quickly because venting to parting lines can happen within the cavity.
- Plastic flow creases can be eliminated. These creases can be eliminated through the addition of textured thickness that also adds strength, non-slip qualities and even adds an increased safety measure.
Working with an experienced injection molder will provide you with the information needed to make the best decision on the right surface finish for your process parameters. Considering the surface finish will impact the type of material used, tooling and other process decisions, it is very important to determine the surface finish as early as possible during the design stage.
Surface Finish Options
There are many more surface finish options available working with a steel mold compared to working with an aluminum mold. Steel can be polished to create a smoother surface finish for your parts. The many options for plastic part surface finishes include:
- Bead blast
- Matte finish
- Leather grains
- Many more
Surface finish should be considered early in the design process because the type of material used can have a significant impact on the type of finish implemented to create the best part for your product. Specifically, gloss and rough finishes can be affected by the material selected, additives, and other parameters such as fill rate, pressure and temperature. In addition, working with an injection molder that utilizes mold flow simulation software will allow you to explore how a material choice will affect surface finish and possible defects prior to the production process.
In the case where a gloss finish is used, material type is especially important. Higher melt temperatures are required for products made from crystalline resins which increase gloss and reduce roughness – creating the smooth surface desired.
A strong knowledge of material science is required when considering additive compounds be mixed into the part material. Depending on the surface finish desired, some additives should be avoided (or substitutes considered). For example, adding certain particulate fillers may increase surface roughness. However, design engineers will have a strong understanding of what can be mixed and matched to create the right combination that produces a surface quality that enhances your part.
Injection Speed and Temperature
Injection speed and temperature affect surface finish for a few reasons. When you combine fast injection speeds with higher melt or mold temperatures, the outcome will be enhanced gloss or smoothness of the part’s surface. In actuality, a fast injection speed improves overall gloss and smoothness. Additionally, quick filling of a mold cavity can produce less visible weld lines and a strong aesthetic quality for your part.
Deciding a part’s surface finish is an integral consideration in the overall product development and should be thought out during the design process to achieve the desired results. Have you considered the end use of your injection molded part?
Let Nicolet Plastics help you decide on a surface finish that improves the aesthetics and functionality of your part.
When plastic part designers take a collaborative approach to involve mold makers early in the design process, many cost and time to market benefits are realized. Working with an injection molder who can provide expertise and recommendations throughout the design project to ensure your part is developed with the intended use, quality, budget and timeframe in mind will greatly increase the likelihood of a positive outcome.
The most successful parts are created when there is constant communication between a part designer, tool designer and manufacturer. With open consultation and communication, the team can avoid project delays and create efficiencies.
Designing a production-ready part goes beyond aesthetic and function. Here are three important considerations when optimizing a part for manufacturability:
1. Smart Design & Material Selection
The most important first step in part design and material selection is to consider the environment in which the part will be used. This is called design intent – or the intended use of the completed part. What will the wear and tear be for the part? What temperatures will it be exposed to? Consulting with an experienced molder will help you make informed decisions about the most innovative and widely used materials to ensure your part performs at the highest level. Additionally, specialized tool designers can help you take the following design elements (among many others) into consideration:
2. Efficient Mold Design & Fabrication
A part designer and mold maker should work hand in hand to create a mold that will produce a successful part. Molding experts provide invaluable insight not only on how to produce the best part, but also how to get the mold made quickly and cost efficiently. Using design software, designers and engineers can create a mold blueprint and as part design and material selection are tested, can help with making critical adjustments.
- A mold needs to be designed around a part and specific factors taken into consideration such as: Where is the gate(s) located and what is the optimal size? How will the part be ejected? Most often, computer simulation techniques such as Mold Flow Analysis are used to provide a predictive analysis and measurement to determine the success or failure of a part. Additionally, the analysis shows how the material will orient with the mold as well as expose potential warp and stress points.
3. Benefit of Working with a Trusted Partner
Relying on an experienced molder to provide guidance and recommendations during the design and development process can save you significant time and cost for a project. Many service providers do not factor in the costs associated with material testing, radius adjustments, diameters and more. A lack of flexibility or inability to provide what is needed to produce a successful part is another roadblock that manufacturers run in to when trying to take a quick and lowest cost route.
Do your research and have a good understanding of your molder’s expertise and services provided. Working with a partner that will listen to your needs and has the expertise to make cost-saving recommendations throughout the project process, will not only save you money, but time as well
Manufacturers can spend as much on a mold that you may spend on a high performance car. The difference is that YOU get to drive the car, while your molder gets to “drive” your mold. How do you know that your molder is taking good care of your tooling investment and not using it like Burt Reynolds used his Trans-Am in Bandit? Or like the Dukes of Hazzard used General Lee?
In a plastic manufacturing environment, consistent quality parts start with a quality, well-made and maintained mold. The process should include a solid mold design and a high-quality tool build. Once the mold is in place and ready for use with your molder, what expectations should you have for the care of your investment?
Understanding Mold Maintenance Basics:
It’s important for a manufacturer to have a basic understanding of the cleaning and repair required for proper tool maintenance. To keep a tool in the best working order, maintenance is essential not only when issues arise, but also routinely over time.
Overall, the condition of your injection mold affects the quality of the plastic components produced. Molds and tools are critical assets to your company, yet many manufacturers overlook maintenance needs when making a decision about selecting an injection molder. How your supplier maintains your mold can be a critical element of the success and longevity of your relationship.
Like any maintenance program, there are certain checks and procedures that should be performed regularly. For example, mold cavities and gating should be inspected for wear or damage. The ejection system should be inspected and lubricated and all surfaces cleaned with a non-toxic solvent to remove dirt and sprayed with a rust preventative. Additionally, all water lines should be flushed and drained to remove excess moisture.
Molds should also get a proper maintenance review prior to storage including:
- All plates separated
- The ejector system should be cleaned and lubricated
- Replace and / or repair parts including ejector pins and springs, worn bushings or leader pins
When these preservation tactics are completed, molds are able to be put back into service quickly and easily.
Understanding Problems with Mold Neglect:
What happens when your injection molder neglects your mold? Over time, the molding process can cause significant wear and tear. Without a proper preventive maintenance program in place, material may build up on your molds surface which can eventually cause tool denting, flash and other part defects.
The unfortunate reality is that some molders wait to do maintenance until part quality problems arise or the tool becomes damaged. Waiting until this point to make repairs can result in added expense, supply / stock issues and a longer time to market. However, when molders have a clear maintenance procedure in place, production times and overall costs can actually decrease.
Molds are a significant investment for all manufacturers and extending the life of your tool takes collaboration, communication and a maintenance plan that has been agreed upon by both parties. Now that you understand the expectations that should be put into place, below is a checklist of questions to help evaluate your supplier with regard to the care and maintenance of your asset:
- How do you schedule preventative maintenance?
- What does the molder maintain prior to the warranty expiration?
- What are the preventative maintenance steps you take?
- How do you track the number of cycles on the tool?
- What do you consider regular mold maintenance, and why is this valuable to me?
- How do you maintain part quality with the mold maintenance?
- What components are you using, and why?
- How do you maintain water line integrity?
- How do you minimize the amount of required up-keep?
- How are maintenance findings reported?
Are you looking for an injection molder who can provide expert guidance from concept, development to production? Contact Nicolet Plastics to learn about our formula to develop exceptional products in a timely and cost-effective manner.
The manufacturing process can be a complicated one and there are many factors to consider when choosing a plastic injection molding partner that best suits your industry, unique products and production requirements. First and foremost, the best place to start is by gaining basic knowledge of the plastic molding process. Explained in its simplest form, the process uses polymers or plastic resins that when heated, melted and injected under high pressure into a custom mold, will produce plastic parts to be utilized in product manufacturing. While that process seems straightforward, many manufacturers need an injection molder partner that can produce highly complex parts and caters to their unique industry needs, specifications, end-uses and time / budget constraints.
These are the key factors any product manufacturer should consider when choosing a plastic injection molder:
1. Volume Specialization & Capacity:
With over 16,000 injection molders in the U.S., selecting the best molder for your part can seem overwhelming. The best place to start is by narrowing down your options based on your volume and size requirements. Low to moderate volume molders specialize in the production of parts under 10,000 units. Selecting a low to moderate volume molder may be an ideal choice if you need to quickly produce a prototype to test a part.
In addition, low to moderate volume molders are perfect for applications that don’t require hundreds of thousands of parts (such as medical devices, aerospace, agriculture and more), or bridge tooling (tooling that bridges the gap between small production runs for market testing and full-production tooling).
High volume molders specialize in jobs requiring over 750,000 parts and typically produce parts requiring small-sized molds.
2. Compliance with Specifications:
Having to compromise puts product manufacturers in a challenging situation. Regardless of the details involved, there is likely a company that can produce your part without specification sacrifices. Injection molder partners should be able to make strong recommendations based on the specifications you require without having to make significant compromises.
Recommendations should stem from the injection molder’s experience, expertise and knowledge of the latest technologies. Specification changes may include minor design tweaks, alternative resin suggestions, and other ways you can save time and money during the design, development and production process.
3. Expanded Services & Technology:
Not all injection molders offer expanded services or the technology needed to help design parts for manufacturability. Working with a molder who offers prototyping, part design services, quick response manufacturing, in-depth mold flow analysis and more – in addition to their traditional service offerings – will help you create valuable cost and timing efficiencies in regard to getting your product to market.
An important factor to note is that the greatest efficiencies with overall project time and budget happen early in the development cycle – specifically the design process. That’s why it is critical to choose an injection molder that can become involved early in the design process, understand your objectives and can predict production issues before they occur.
4. Quality & Efficiency:
In addition to complying with your specifications, your injection molder partner should be established and committed to providing the best service possible. Answering these questions will help provide the necessary insight for you and your team to select an injection molder that best suits your company’s needs:
- Do they own high quality and efficient machines that work well?
- Have they been recognized in the industry as a manufacturer of status or has the company won awards for performance?
- Do they focus on the elimination of dysfunctional variability, such as organizational issues that can cause rework?
- Do they offer a robust mold maintenance program?
- Is project management software used to ensure the highest level of communication and efficiency throughout every step of the part design and development process?
- Do your parts need to pass strict inspections or meet high safety and quality standards?
- Is your injection molder ISO certified?
5. Product Application:
The intended use for your part or product application is critical as should be kept top of mind throughout every step of the design, development and production process. Plastics are an amazing material that can be used for many applications. While there are some circumstances that plastics cannot provide the required strength or tensile stress needed, there are many circumstances that metal parts can actually be converted to plastic to minimize weight and cost. Injection molders should consider a part’s end use to make the best recommendations in regard to design, material and production techniques.
Building a mold for a plastic injection molded part can range from 4-12 weeks. All representatives involved in the process should factor design revisions, part complexity, communication between designers, engineers and other individuals involved in the process, as well as account for unexpected events like shipping delays, etc. It’s always best to communicate your time constraints with an injection molder partner as early as possible to gauge their capacity and ensure you get the final production parts in hand on time.
If you’re like most product manufacturers, you have unique and specific needs. It is crucial to the success of your part that you work with an injection molder that understands your expectations and challenges. Taking these important considerations into account will help you streamline the process of choosing a plastic injection molding part manufacturer.
Are you looking for an experienced, quality-focused injection molder that specializes in low-volume production? Learn how Nicolet Plastics offers customized products and quick response in every stage of your part production.
If you’re a manufacturer of products that use plastic parts (or metal parts that can be converted to plastic), it’s likely you’ve considered the injection molding quote process. Injection molders are known for their ability to help product engineers create efficiencies with getting products to market faster and under budget. They also vary in their ability to produce low to high volume parts in a variety of sizes.
Obtaining an injection molding quote is the first step in determining which injection molder is the best fit for your part and unique specifications. In order to streamline your process, consider these questions before requesting an accurate quote for your part design, development and production.
1. Do you have access to CAD drawings or samples of the part to be quoted?
Injection molders can form the most accurate quotes when they have a clear picture of the part they are being asked to make. Ideally, detailed dimensional drawings (CAD drawings), provide very clear information on the size and complexity of a part. Additionally, a sample or prototype can help an injection molder make discoveries early in the process that will maximize design tweaks and the overall manufacturability.
A sketch or concept is very different from a finished part. There are factors leading from design to manufacturing that are important to consider when moving your idea to reality. In fact, many manufacturers cite the design process as the most prevalent area to create cost and time efficiencies in the injection molding process. If you do not have access to CAD drawings or part samples that have been proven in the production process, it is important to choose an injection molder with significant design engineering experience and / or prototyping capabilities. Let them be a resource to make recommendations that will improve the performance of your part.
2. What does the end use of your part look like? Are there any chemical or environmental factors to consider?
Do you have a clear description of the intended use for your plastic part? Having a clear explanation of the intended use will help your injection molder determine the appropriate design tweaks, material and recommendations for part improvements. The information you provide also offers a picture of the wear and tear a part will be exposed to over time and any environmental factors that may contribute to a part breaking down.
3. What quantity is needed?
Quantity projection is an important factor for many injection molders because it may determine if they can, or are willing to run your part. Most injection molders categorize their business as low volume or high volume. Low volume typically constitutes production runs under 10,000 parts, where high volume may include runs over 750,000 parts.
For shorter production runs, aluminum molds might be recommended. However, if your project will require large quantities over time or multiple runs over time, a hardened steel mold would be the best choice. While the upfront cost of hardened steel is greater, it will produce more consistent, higher quality parts – as well as pay for itself over the life of the tool.
4. What is the size and complexity of the part?
Simply put, more intricate part designs require elaborate mold designs, which generally increase the tool cost. Simple part designs require less complexity in the mold design, lowering the cost of the tool. Working with a knowledgeable injection molder with design engineer capabilities and resources early in your production process will help you find efficiencies across every stage of your project.
Also, understanding the size of your part will help your injection molder determine material quantity estimations.
5. What type of material or resin is required for your part?
There are many part design factors that help determine the best material that will drive the cost, function, versatility and production of your parts. Having a basic understanding of materials available and how they react to the environment your part will be exposed can help give you a starting reference point. Your injection molder should offer a detailed explanation of the materials or resins that best suit the unique needs and cost requirements for your production part.
While you don’t need to know all the ins and outs regarding the design, development, tool transfer and production process prior to obtaining a quote for an injection molded part – it’s always good to be prepared with the details related to your specific part’s needs. There’s no doubt that supplying this information to your injection molder will be valuable in every step of the process. Preparing your answers to these five questions will help you be prepared to establish a beneficial relationship with your injection molder.
Injection mold tooling and part production can challenge even the most experienced product manufacturers. In some circumstances, product designers may have minimal experience working with plastics or be managing a design that requires advanced consultation.
Ultimately, the goal that you and your injection molder should strive to achieve is an optimized mold for the type of plastic, part geometry and finish, desired cycle time, production volume and, of course, highest level of cost effectiveness.
Where do you begin with so many variables? These are the important aspects every product manufacturer should know about plastic injection molding.
Injection molding is one of the most commonly used methods of manufacturing plastic parts because it can be done at a reasonable price and with the use of a large variety of materials. This oftentimes fully-automated process can produce a high rate of output that is typically more budget-friendly than alternative production options.
Mold Price Factors
- Design Strategy: Have a strong understanding of your part’s end use and the requirements for volume, complexity, tolerances, surface finish, gating and molding material will allow your injection molder partner to determine the most appropriate and cost-effective solution for you.
- Mold Size: It’s a given that larger parts will require a larger mold and generally increase cost. However, there are ways to optimize mold and part design to help reduce cost. An additional consideration is when a part’s material feed system is properly sized, the cost of the injection molded part may be reduced.
- Offshore vs. Onshore: There are some common misconceptions regarding offshore mold production and cost savings. Oftentimes, offshore mold production does not reduce time or mold / part cost in the long run.
Not only are molds made in the U.S. generally higher quality, sometimes governmental regulations require that tooling be designed and built in the U.S.
In the case where you have a challenging mold build, working with a reputable injection molder in which you can establish a trusting relationship, will save you time and money over the life of the mold and part production. Challenging builds may include multiple cavities, moveable mold components, thin walls, complex textures, gating restrictions, tight tolerances and more.
Part Price Factors
- Part size: Part size is a factor with larger parts resulting in a greater material cost.
- Part design: Complex part designs result in an increased tool cost. Working with a knowledgeable design engineer to simplifying part design can lower the cost of the tool. A mold that is well-designed ultimately has lower residual costs over time in addition to lower part reject rates.
- Material selection: There are many factors that can affect the cost of your material selection. Does the part need to withstand pressure, weight, temperature variations or elements / chemicals? Do any regulatory requirements apply? High performing and specialty resins come with a higher cost. Certain characteristics of your resin can also increase the maintenance cost of your mold.
- Part tolerance: Parts designed with tight tolerances will require more intricate manufacturing steps which may can increase manufacturing and tool maintenance costs.
- Volume: It’s obvious that the higher your annual volume, the higher overall cost is for part production. However, it’s important to also consider volume not only in the number of parts, but also hours of production. Parts that will be run at a higher volume, need high quality tools with possibly a higher number of cavities. That said, cost per part typically goes down as volume goes up.
- Cycle time: Cycle time is another example of where well designed tooling and part cost go hand in hand. Fast machine cycles during the production process require well-designed tooling and a high precision build for a part to cool uniformly throughout the cavity impression.
- Gate location: Proper gate location is a critical component to part quality. Parts that require design techniques where gates are not at the side of the part may increase tool cost.
Plastic injection molding continues to evolve with advances in technology and resin science. Many important decisions regarding tool build, materials, maintenance and production happens during the communication process between you and your injection molder. Each party should have a strong understanding of short-term and long-term expectations which should be shared early in the design / development process.
Like any profession, no plastic injection molder is the same. While there are certain terms, keywords and phrases with implied meaning, it is helpful to have an understanding of the terminology that will be used throughout the completion of your project.
Early Design Consultation
Choosing an experienced injection molder that provides design consultation is one of the most important factors in your production process. Designing a plastic part for manufacturability involves many important facets that touch on all areas of part design, tooling, material selection and production. First, it is essential to build parts around functional needs by keeping design intent or the end use in mind. Consider weight reductions, the elimination of fabrication and assembly steps, improving structural components, reducing costs and getting products to market quicker.
In addition to early design consultation, working with a partner that provides the latest technology in mold flow analysis can save significant time and budget dollars. Mold flow software can be used to evaluate the design to make sure it will produce the most consistent and highest quality parts from each cavity of the tool. A virtual model of the mold is created and, using the known data and characteristics of the chosen material, the software can predict how the material will flow into the mold and its cavities. Different data points can be assessed, including pressure, fill time and melt temperature. Doing so allows for optimization of the process before tool production ever begins.
The information provided above offers direction and recommendations for understanding the important aspects of injection molding prior to beginning your production process. Regardless of the elements you think your project requires, it is always vital to start with a thorough consultation to evaluate what will work best for your product, budget and timeline.
Injection molding is a complex process, but it doesn’t have to be overwhelming. Nicolet Plastics is here to help. Contact our knowledgeable design engineers, tooling and production experts to help you get started on your next project.
It’s no secret that consistent injection mold maintenance plan can help your mold last longer, run with less interruptions and will ultimately save you time, money and frustration. Mold (or tool) maintenance, refers to the cleaning and repairs that are needed to keep an injection mold in the best working order. Maintenance should be performed routinely over the life of the mold, in addition to if any problems arise. What a lot of manufacturers don’t know is that mold maintenance is crucial because it affects the quality of the plastic component as well as the company’s project budget.
Even though molds and tools are critical assets to your company, many manufacturers overlook mold maintenance as a service when making sourcing decisions. In fact, how your injection molder maintains your molds is a critical aspect of a successful long-term relationship. Here are some important mold maintenance tips to consider:
What problems does mold neglect cause?
A well-designed injection mold is created to withstand natural wear and tear that may occur during use. However, even with a superior mold design, there are many stressors placed on a mold and unpredictable situations arise.
One of the major causes of internal and external stress on a mold is temperature fluctuation. If mold design does not allow for uniform cooling, a mold can expand and contract – causing stress-related weakness and may potentially crack.
Friction is another stressor and cause for a mold to breakdown. If the mold doesn’t open and close smoothly, it may cause too much stress when the two halves meet each other. There may then be issues with ejector pins not functioning properly. Additionally, the added fiction may cause increased heat that will eventually wear away critical parts – creating compromised areas of the mold.
Destruction of the mold itself is not the only concern related to mold neglect. There are also important factors to consider with the material that is injected into the mold. As a mold is used again and again to complete the process of making parts, small amounts of material residue can build up inside the mold cavities. Eventually, this residue can build up and ultimately affect the shape of the cavity (and the finished part).
What does injection mold maintenance include?
The best mold maintenance begins before the mold is made. The first step should be ensuring the mold design follows best practices to allow for uniform cooling and the lowest possible level of stress both internally and externally.
After the mold is created, your injection molder should facilitate regular inspection by checking runners and mold cavities as well as checking for corrosion. It is also important to create a schedule to plan for regular injection mold maintenance and keep a log to track each inspection.
What are the benefits of a mold that is properly maintained?
Regular monitoring of your mold is the key to producing high quality injection molded parts. The likelihood that you will catch an issue early (rather than when you are forced to address them) will be greater and will give you more time to remedy the situation.
An additional benefit is the cost savings that is realized with preventive mold maintenance. With proper implementation, the time investment for maintenance will rarely equal the costs associated with having to repair or replace a mold.
What is the role of your injection molder?
In addition to minimizing cost and risk, working with a knowledgeable and reliable injection molder can help you implement a mold maintenance plan that fits your needs. Your injection molder can also explain the benefits and limitations of your specific mold, while helping provide direction throughout the life of your mold.
What challenges are you facing regarding proper tool maintenance and getting the most life out of your injection mold?
To learn how Nicolet Plastics, Inc. supports our customers and protects your assets with preventive maintenance, please contact us.
Budget is one of the most important factors a manufacturer faces with getting a product to market as quickly as possible. Designing a plastic part for manufacturability involves considerations that can ultimately have a significant impact on cost. Whether you are in the initial design phase, prototyping or production, controlling injection molding costs requires analyzing of various factors. Here are a few tips to help you control plastic injection molding costs:
Over the years, collaboration has taken a different form with the introduction of robust project management software. Working with a plastics manufacturer who incorporates highly effective project management software can create efficiencies within every phase of the planning and production process. With every step in injection molding building upon the next, communication and collaboration are key factors to addressing customer’s primary stress points such as timeline and budget.
Collaboration begins at the quoting state when individuals from both sides including designers, engineers and other experts will need to provide input that will help keep part budgets within or under budget.
Optimized Mold Design:
How many times have you encountered an issue in production that was the result of inadequate mold design? If the issue persists or is unresolvable with various tactics, you may have to modify or re-create the mold – both of which are expensive solutions. To avoid these costly situations, it is essential to review mold design in the early stages.
Additionally, in mold design it is beneficial to be able to produce as many parts as possible in a single shot. The ability for the plastic to eject quickly without wasting time / movements is another critical cost-savings factor.
Integrating the issues and recommendations identified in the design and simulation phases are a key aspect of effective mold design review. However, a mold’s true performance also relies on part design.
Optimize Part Design:
Wall thickness is one of the most important factors with part design. The first rule of thumb is to determine the minimum wall thickness that will meet your design requirements. It is always good practice to work with our injection molder / design engineer to check thickness specifications for the material(s) you are considering for your part. Typical wall thickness ranges from .04 – .150 for most resins.
Important wall-thickness facts:
- Thinner walls require easier flowing plastics
- Longer flow lengths (distance from nozzle to the furthest corner of the part) may require thicker walls
Undercuts are a feature that can add to part complexity and cost, and in some cases can even prevent part ejection. This feature is created by including holes or snaps and should be eliminated when possible. One solution would be to work with your design engineer and injection molder to include a side action, sliding shutoff or pick out.
Using sliding shutoffs, pass-through cores or by changing the parting line and draft angles may provide an easier mold build. These also reduce tooling and manufacturing costs.
Draft is a design feature that must be added to the walls of all injection molded parts. Allocating sufficient draft not only makes it easier to remove a part from a mold, it also minimizes tool wear. Without draft, parts may stick in the mold. Having 1 degree of draft is a good starting point, however, there are considerations that may determine exactly how much draft is needed. Drafting internal features like ribs and bosses is always good practice. Remember – the more draft, the better.
While draft facilitates the removal of the part from the mold, it is particularly important in rapid injection molding to maintain parting lines, part quality and tool functionality. It typically takes working with an experienced design engineer to know how much and where to add draft.
Each plastic part design must have a runner and ‘gate’, or a path and opening that allows the molten plastic to be injected into the cavity of the mold. Gate type, design and location can have effects on the part such as part packing, gate removal or vestige, cosmetic appearance of the part, and part dimensions & warping.
It is essential for a part designer and molder to work together to determine where the runner and gating system should be placed. To allow for the shortest overall flow length (the distance plastic flows from the gate to the outer most point of the part), gates should typically be placed at the center of a part.
If more than one gate is needed, the gates should be placed to both reduce the flow length, and must take into account the parting line created by plastic from each gate meeting. A ‘parting line’ is the line of separation on the plastic part where the two halves of the plastic injection mold meet. Ideally a part designer will account for the parting lines by designing the part in such a way that any blemish is visible on a non-cosmetic surface.
There are many resins that can be injection molded – but it is important to consider design intent and particularly what the piece needs to accomplish. For example, does the part need to be firm or pliable? Will the part be exposed to elements like extreme heat or cold? What safety factors should be considered?
The newest, most innovative materials may not be the best fit for your particular part – and may add more cost to the overall project. Working with a design engineer who is familiar to resin characteristics and behaviors when molded, will help you pick the material that best fits your needs and may save you critical time and budget in the long run.
Working with your injection molder to perform a flow simulation is an important step in verifying part design. Flow study allows designers and engineers the opportunity to strategize gate location, runner layout, as well as optimize water placements. The level of simulation needed depends on part complexity.
-Minimize Finishes & Coatings:
Finishes and coatings include textures or patterns that leave an imprint on a molded part’s surface and are often used to reduce surface wear. Finishes, however, can add to cost with medium to high cosmetic finishes (where tooling marks are removed and the surface is textured or polished) and high quality clear finishes being the most costly.
Overall, managing the design and complexity of your part can play a huge role in the overall time and cost. If your part has many variables that need to be addressed, your design engineer and injection molding partner should provide insight regarding what can or cannot be eliminated. Time efficiencies will come with simplified designs that are optimized to fit your time, budget and product needs.
How have you overcome challenges with design and controlling part production costs?
To learn how Nicolet Plastics, Inc. can help, please contact us.
1. Involve Injection Molder Early & Design Part for Manufacturability
Design is one of the most important factors in avoiding part defects. It’s your earliest opportunity to avoid mistakes that can be costly both in regard to time and budget later on. Good design takes into account objectives including part function, aesthetic, manufacturability and assembly. Working with a knowledgeable design engineer and involving your injection molder early will help you find solutions to meet the needs of your specific part.
There are a number of important design elements to consider to ensure costly part mistakes are avoided:
Wall thickness is one of the most important factors with part design. The first rule of thumb is to determine the minimum wall thickness that will meet your design requirements. It is always good practice to work with your injection molder / design engineer to check thickness specifications for the material(s) you are considering for your part. Typical wall thickness ranges from .04 – .150 for most resins.
Important wall-thickness facts:
- Thinner walls require easier flowing plastics
- Longer flow lengths (distance from nozzle to the furthest corner of the part) may require thicker walls
Sharp corners or angles can impede the flow of material. These abrupt transitions can cause the cavity to not fill or pack properly, creating a part with defects. Material flowing across a sharp corner creates stress in the plastic which can contribute to warp and dimensional instability.
Smooth corners that have a curve versus an angle are important in the injection molding process. The radius should be consistent on the inside and outside of the wall creating a uniform thickness. By incorporating this design element, the material will be able to flow through the cavity evenly.
The location where the molten plastic material flows into the mold part cavity called a gate. Every injection-molded part has at least one gate, and some have several gates. The placement of the gate can help ensure the cavity fills properly; however, it is best to have a uniform wall. Uniform wall thickness helps the mold fill and cool properly. In unavoidable situations, having a proper gate location can be a deciding factor in the success of a part. It is recommended that parts be designed with the gate in a location at which the melt enters the thickest section of the cavity to then flows out of a narrower region.
Draft is an angle incorporated into the wall of a mold and the shape of the plastic part so the opening of the cavity is wider than its base. A plastic drinking cup is a good example of draft – it is smaller at the base than at the mouth so that the cup will come out of the mold. Draft is essential for injection molding.
Plastic heavily relies on mold draft in the removal of the part from the mold. When a part is designed without appropriate draft, removal of plastic parts is essentially impossible.
A design with sufficient draft is always considered to be a good practice. 1.5 degrees for a depth of 0.25mm is usually recommended by design engineers. General guidelines suggest that a draft angle of 0.5 degrees is recommended for core and 1.0 degree for cavity.
Surface textures also influence draft requirements. The more depth in a texture the more draft it requires. It is a good practice to determine the surface finish / texture requirements prior to starting you part design.
Ribs are used to help reinforce the overall part strength and support dimensional components of the design. Depending on the material used, ribs should be no greater than 2/3 of the wall thickness. Greater width could cause issues with the design and sinking may occur. To avoid this problem, a designer can often core out some material to reduce the shrinking. In addition, ribs cannot be too tall or too thin.
The height recommendations are generally no more than 3x the wall thickness. The corners should include radii and the height should include a draft (.5 to 1.5 degrees). The draft angle allows the part to be ejected from the mold.
Mold Flow Analysis:
When working with an experienced part designer and injection molder, mold flow analysis should be conducted before tooling production begins. Mold flow software can be used to evaluate the design to make sure it will produce the most consistent and highest quality parts from each cavity of the tool.
A virtual model of the mold is created and, using the known data and characteristics of the chosen material, the software is able to predict how the material will flow into the mold and its cavities. Different data points can be assessed, including pressure, fill time and melt temperature. Doing so allows for optimization of the process before tool production ever begins.
2. Don’t Skimp On Tool Design & Build
A perfect, defect-free part begins with the mold. Building the tool likely represents the largest investment in the manufacturing process; therefore, getting it right is critical to the success of a project. All of the design factors listed above are important considerations that can help you avoid costly mistakes. Additionally, the volume of parts required, as well as the material they will be made of will help drive how and with what materials to create the mold.
It’s important to keep in mind that more complex molds create a lot of intricate cavities that the plastic must flow through. Turns throughout the path in which the mold is filled can result in structural stresses and part cooling challenges. Designing a mold to have smooth turns can help with these stresses causing an issue for the part. Draft, as mentioned above, is not always compatible with a part’s design – both aesthetically and functionally. However, even a small amount of draft is preferred to no draft at all. Draft may vary with the surface finish or texture requirement of the part. For example, smoother tooling may require less draft.
Other part defects caused by mold design or maintenance issues include flash and short shots.
Flash occurs when melted plastic escapes the mold cavity and appears as a wafer-like extension on a finished part. This defect occurs most often along the ejector pin parting line and is caused by excessive injection speed or pressure, too high of mold temperature and excessive barrel heat. Flash can occur due to poor mold design or neglected maintenance.
A short shot occurs when resin falls short of filling the mold. It is often caused by gate blockages or too small of gate diameter. Short shot can also occur when the wrong resin type is used or improper process settings. Sometimes, the runner system needs to be redesigned to optimize flow.
3. Avoid Resin-Related Issues
Choosing the best material can drive cost, functionality and versatility of your part. It is essential to work with a knowledgeable design engineer and injection molder to learn how different materials and their characteristics can optimize the production and life of your plastic part. Material selection is often based on the application of the part. Plastic requirements for a medical part may be significantly different than that of an aerospace application. Considerations like temperature, biological and chemical interaction, food or animal contact and more are all critical factors in material selection to avoid part defects.
Discoloration is a defect that shows streaking or coloring in an injection-molded part. It usually occurs in one of two cases:
- Improper mixing of the masterbatch, the additive used for coloring material
- Impurities introduced to the material during the molding process
When a resin batch is not evenly mixed, you might see a streak of coloring in the end product. Additionally, you can have impurities introduced to a mold if the hopper, material feed area or mold plates of a machine are not cleaned properly prior to production. It is imperative that an injection molder clean the injection molding machine prior to producing parts.
Burn marks may appear as black or dark red discoloration when a material burns during the injection molding process and can be caused by one or more of the following:
- Overheating due to trapped air
- Excessive injection speed
- Excessive melt temperature
If burn marks occur, there are a few corrective actions a molder can take to avoid further defects.
Burn marks can be avoided by:
- Shortening the cycle time
- Lowering the temperature and/or slowing down the injection speed
- Trapped air can be avoided by ensuring adequate gas vents and gate sizes
Flow lines are streaks, patterns, or lines that are visible on a part. This defect is caused by the varying speed at which the molten plastic flows inside the mold tool. Flow lines may also occur as plastic flows through sections with varying wall thickness, or when the injection speed is too low causing the plastic to solidify at different speeds.
Flow lines can be avoided by:
- Increasing injection speeds and pressure to the optimal level
- Rounding corners and locations where the wall thickness changes to avoid sudden changes in direction and flow rate
Weld lines appear in a part where molten plastics meet each other as they flow from two different sections of the mold. This defect is caused by the inadequate bonding of two or more flow fronts when there is partial solidification of the molten plastic.
Weld lines can be avoided by:
- Raising the temperature of the mold or molten plastic
- Increasing the injection speed
- Adjusting the design for the flow pattern
- Switching to a plastic with a lower melting temperature
The majority of plastic part defects can be prevented by incorporating proper part and tooling design as well as material selection. The best way to avoid defects is to work with an experienced injection molder that understands the characteristics of various resins and their applications. Learn how Nicolet Plastics can help reduce part manufacturing lead times to get your product to market faster.
Designing a plastic part for manufacturability involves many important factors that touch on all areas of part design, tooling, material selection and production. First, it is essential to build parts around functional needs by keeping design intent or the end use in mind. Consider weight reductions, the elimination of fabrication and assembly steps, improving structural components, reducing costs and getting products to market quicker. Here are 8 important factors to consider to meet your plastic part design goals for a successful production process.
1. Material Considerations
Manufacturers often select a familiar grade of plastic from a similar application or rely on recommendations from suppliers. Resins chosen this way may be adequate, but are rarely optimal. Plastic selection is a complex task that involves many considerations, such as:
- Temperature: Thermal stress that may occur during normal and extreme use conditions, as well as during assembly, finishing and shipping.
- Chemical resistance: The effects that occur when any solid, liquid or gas come in contact with the part.
- Agency approvals: Governmental and private standards for properties such as heat resistance, flammability, and electrical and mechanical capabilities.
- Assembly: The plastic’s cooperation with all assembly steps like bonding, mechanical fasteners and welding.
- Finish: The material’s ability to produce the desired finish such as gloss, smoothness and other appearance values as it comes from the mold.
- Cost: Resin pricing as well as the cost calculations for manufacturing, maintenance, assembly and disassembly to reduce labor, tooling, finishing and other costs.
- Availability: The resin’s availability in regard to amount needed for production.
Radius should always be a consideration in regard to the part’s thickness – eliminating the likelihood of areas of high stress and possible breakage of the part. A general rule of thumb is that the thickness at a corner should be in the range of 0.9 times the nominal thickness to 1.2 the nominal thickness of the part.
3. Wall Thickness
Designing your part so that wall thickness is consistent can help avoid many part defects that can occur during the manufacturing process. When plastic melts, it flows to the areas of leas resistance. If your part has inconsistent thicknesses throughout, the melt may flow into the thick areas first (depending on gate locations). When this occurs, the thin areas may not fill properly. Additionally, thicker areas tend to cool more slowly and are at risk for voids or sinking defects. Designing your part with rounded corners will also aid in the proper filling of the part during the molding process.
4. Gate Location
Gates are critical to ensuring the resin flows properly into the mold. These small components of your design are what directs the flow of resin from the runners to then be distributed through the part. Type of gate and placement has an important impact on the part’s overall quality and viability.
Draft is the amount of taper on the vertical walls of the plastic part. Without draft, a part may not eject from the mold, or may sustain damage during ejection. Typically, draft angles between 1° and 2° are required, but can vary depending on part restrictions and specifications.
6. Inclusion of Ribs
A plastic part that has been designed with a minimal wall thickness will not be as strong as a thicker part – which is why the inclusion of ribs may be needed to help reinforce the part’s strength. Depending on the material used, rib thickness should be between 50 – 70 percent of the relative part thickness to avoid sink marks. To avoid sinking, designers may core out material to reduce defect risk.
7. Mold Shrinkage
The shrinkage that occurs during the plastic part molding process can be as much as 20 percent by volume. Crystalline and semi-crystalline materials are most prone to thermal shrinkage. Amorphous materials are known to shrink less. Here are a few easy ways to avoid molding shrinkage issues:
- Adjust the formulation
- Adjust the mold design to get the dimension you want based on the expected shrinkage that will occur
- Optimize the processing parameter such as molding temperature, melt temperature, and injection speed/pressure/time, cooling time.
8. Special Features
Plastic parts should be designed so that mold tools open and eject the part easily. When a part is released, the two sides of an injection mold separate in the opposite direction. When special features like holes, undercuts or shoulders prevent the release from happening, it may be required that side actions be incorporated into the design.
Side actions pull coring in a direction other than the direction of the mold separation. This adds flexibility to the part design and at times, may increase the cost of the mold.
Working with an experienced plastic injection molder and engineering team is a critical component to avoiding many issues that can occur during the design and development process. If you keep these factors in mind during the design process, and align with a knowledgeable plastics engineer, you will be on track to get your product to market quicker and within your budget.
Getting products to market fast and on budget are two critical factors in the manufacturing process. The design for manufacturing process is cited by both product manufacturers and injection molders as the step that can have the greatest impact on production outcomes. When plastic injection molders are involved early in the part design process including prototype development and mold flow analysis, many cost and time efficiencies will be realized.
Designing a plastic part for manufacturability from the outset involves several considerations that can ultimately have a significant impact on key variables. While some manufacturers don’t account for design adjustments in their timelines, early collaboration with your molder may uncover aspects of a design that can be optimized to improve the efficiency of part production and performance. Here are a few of the most common elements caught in the design for manufacturing process:
As an essential requirement in injection molding, draft angles make it easier for a finished, cooled part to be released from a mold. Minimizing friction during the part release process is important to prevent damage to the parts, provide a uniform surface finish and reduce wear and tear on the mold.
Draft angles are calculated as a degree measurement from the direction of pull. Designing a part with sufficient draft is critical, which is why design engineers typically recommend minimum draft angles of 0.5 degrees for core and 1.0 degree for the cavity. More draft is also needed if a textured surface is desired and if there are steel shut off surfaces in the tool design.
2. Wall Thickness
Another important factor in part design is wall thickness. A proper and uniform wall thickness reduces the risk of structural and cosmetic defects in injection molded parts.
While typical wall thickness ranges from .04 – .150 for most resins, it is recommended that you work with a knowledgeable injection molder/design engineer to verify thickness specifications for the material(s) you are considering for your part.
Analyzing wall thickness is an essential step in the design process to avoid producing parts that have sink, warp or are ultimately non-functional.
Ribs are used to strengthen the walls of your part without increasing wall thickness, making them a valuable element in injection molded parts. Particularly in complex parts, good rib design should shorten the mold flow length while ensuring the proper connection of ribs to enhance the strength of the part.
Since thickness and location are essential in rib design, ribs should be no greater than ⅔ of the wall thickness, depending on the material used. Using wider ribs may create design and sinking issues. To mitigate this, a design engineer will typically core out some of the material to reduce shrinking and maintain strength.
Rib length should not exceed 3 times the length of the wall thickness, as anything over this could lead to part shorting/not being able to fill the part completely. Identifying the proper placement, thickness and length of ribs in the early phases of part design is an important element to the viability of a part.
4. Gate Location
A gate is the location where molten plastic material flows into the mold part cavity. While every injection molded part has at least one gate, many parts are manufactured using several gates. Because gate location affects the orientation of the polymer molecules and how the part will shrink during the cooling process, gate location can either make or break your part design and functionality.
For example, if a part is long and narrow and must be absolutely straight, it is best to place the gate at the end of the part. For parts that need to be perfectly round, a centrally located gate is recommended.
Sharing preliminary part designs with your injection molding engineering team, leveraging their knowledge and expertise in material flow, will result in optimal gate placement and injection points.
5. Ejector Pin Location
After a plastic part is molded, ejector pins (located within the B-side/core of the mold) apply just the right amount of force required to eject the part from a mold. Ejector pin location is typically a relatively minor concern in the early phases of design, but marks and indentations can result from improperly placed ejector pins, which is why design and positioning should be considered as early as possible in the process.
The location of ejector pins depends on a number of factors, including draft and texture of sidewalls, depth of walls and ribs, and the type of material used. Reviewing part designs will either confirm that your initial ejector pin placement is correct or may generate further recommendations to improve production outcomes.
6. Sink Areas
When the material in the area of thicker features, such as ribs or bosses, shrinks more than the material in the adjacent wall, sink marks may result in the injection molded plastic part. This occurs because thicker areas cool at a slower rate than the thinner ones, and the different rates of cooling leave a depression on the adjacent wall that is commonly referred to as a sink mark.
Several factors contribute to sink mark formation, including the processing methods used, part geometry, material selection and tooling design. Depending on the part specifications, it may not be possible to adjust geometry and material selection, but there are many options available to eliminate sink areas.
Depending on the part and its final application, tooling design (e.g., cooling channel design, gate type and gate size) can be leveraged to influence sink. In addition, manipulating process conditions (e.g., packing pressure, packing time, length of packing phase and conditions) offers several options to reduce sink. Finally, minor tooling modifications, such as retrofittable components or process modifications (e.g., gas assist or foaming) are also available to combat sink. As a result, it is best to collaborate with your injection molder to determine which methods will work best to mitigate sink in your specific injection molded parts.
7. Parting Lines
Parting line location is worth noting and planning for when producing more complex parts and/or when complicated shapes are required.
Since part designers and molders tend to evaluate parts differently, sharing your design with your injection molder can dramatically affect the production and function of your finished product. If parting line challenges are found, there are several ways to address them.
Being aware of the significance of the parting line in your initial design is a good first step, but that may not be your only option. By leveraging CAD software and mold flow analysis, you may be able to determine other possible locations. Working with a knowledgeable injection molder will keep your part end use top of mind and will guide you to the best possible location for parting lines.
There is no question, engaging your plastic injection molder early in the design for manufacturability process and working closely with a design engineer to identify efficiencies will help get your product to market quicker and on budget. What challenges are you currently facing with the plastic part design process?
Learn how Nicolet Plastics can help you reduce lead times and identify turn-key solutions for every product.
Are you a product designer or engineer that is looking for more information on how to make your plastic part design more efficient in regard to cost and production time? One important consideration during the part design process is to have a good understanding of plastic injection press basics including the size of machine needed for your part.
“Bigger the better” is not always the case when determining the press size needed. In the molding process, plastic is injected into the mold at an exceptionally high-pressure rate, which creates a natural pull to force the mold open. A press is designed to keep the mold shut with larger parts requiring more tonnage and force, and smaller parts requiring less. A general calculation for determining press size needed is as follows:
Pressure (lb/in2) x Projected Area (in2) = Force (lb.)
Here are a few other important tips for calculating the right press size for your plastic injection molded part.
1. Understand press size tonnage.
Your plastic injection molder should help you determine the size of the machine needed to help you achieve the best result for your product. Knowing an approximate size of what will be needed can help you determine the best injection molding partner based on the press capacity they have available. For example, larger presses cannot accommodate smaller molds because they can’t close far enough and the injection process will not work.
Additionally, smaller presses have tie bar spacing too narrow to accommodate larger products. If the mold doesn’t fit between them horizontally or vertically, you must move up in press size. Many injection molders offer press sizes ranging from 68 tons up to 400 tons.
2. Calculate your total projected shut-off area and shot volume.
When determining press size for your plastic part, it’s important to calculate the total projected shut-off area. This area consists of only the space that is 90 degrees to the direction of the injection molding machine platens. Thickness does not have any implication on the clamp tonnage and the general rule is to have 2 to 5 ton of clamp tonnage per square inch of projected area.
Calculating shot volume to make sure your barrel has enough capacity can be accomplished by working with your injection molder to run a mold flow analysis. On some engineered materials, the increased residence of the material in the barrel can cause the material to degrade, resulting in poor part quality. Mold flow analysis will help you determine the volume of your part and runner while determining any factors that would cause safety issues.
3. Know how much clamping force or pressure is required.
Pressure plays a significant role in the overall quality of a plastic part. Pressure keeps the mold closed during the injection process. Too much or too little pressure can cause various issues such as flashing and viscosity. One important consideration in regard to pressure is that plastic compounds react differently from one another based on their Melt Flow Index (MFI). MFI measures the ease of flow of a thermoplastic polymer and the higher the MFI, the higher pressure needed to create a successful part.
“Safety factor” is an additional percentage added to your calculation as a buffer to help reduce defects in your part. Most injection molders will recommend 2.5 times the surface square inches of the part and an additional 10% as a safety factor. If you have a part that is 120 square inches, you would need a press size with 300 tons of pressure. When you add the 10% safety factor, the required press size would have 330 tons of clamping force.
Having a general understanding of how to calculate press size is a good first step in determining what injection molding partners are available to you. Strong partners will make recommendations on how to appropriately tweak your part to ensure the final design fits your manufacturing needs and reduces upfront tooling costs. Nicolet Plastics has press sizes up to 610 tons.