6 Common Plastic Resins for Injection Molding

6 Common Plastic Resins for Injection Molding

6 Common Plastic Resins For Injection Molding

There are hundreds of plastic resins on the market. Each one with unique properties, advantages, and disadvantages. And, considering the importance of achieving the precise fit, form, and function for your part designs, material selection can be a bit overwhelming.

Never fear. Xcentric’s team of application engineers and material experts are here to help! We have extensive experience working with plastic resins and have a deep understanding of how the different strengths and limitations could impact your products—during and after production.

In this blog we provide details for 6 of the most common plastic resins used in the injection molding process. You can also download the Quick Guide for easy access to the bullet points, advantages, and disadvantages.

Quick Guide: 6 Common Plastic Resins

Injection Molding

ABS: Acrylonitrile Butadiene Styrene

As far as plastic resins go, ABS is by far one of the most popular and versatile. It’s an affordable, highly moldable engineering plastic with mechanical and electrical properties that make it one of the most widely used thermoplastics in the world.

With ABS you get the collective benefits and properties of three monomers. It combines the strength and rigidity of acrylonitrile and styrene polymers with the toughness of polybutadiene to deliver superior hardness and toughness.

In addition, ABS provides a colorfast, high-gloss surface finish. And finally, this resin has excellent stress, impact, creep, and heat resistance properties. And, it can be heated, cooled, and re-heated without compromising its characteristics.

Common applications include small appliances, medical devices, enclosures for electronics and electronic assemblies, office equipment, and toys.

Design Considerations

Parts molded with ABS are susceptible to forming knit lines, which are visible lines on the surface of the part. One solution is to ensure the appropriate wall thickness to help slow the resin cooling. Recommended wall thickness for ABS is 0.045 in. – 0.140 in.

Medical part molded using ABS plastic resin.

Advantages and Disadvantages of ABS Plastic Resins

Understanding the advantages and disadvantages will help you make an informed decision for your product design.

Advantages

  • Structural/Dimensional stability
  • High impact resistance
  • High rigidity and strength
  • Heat and chemical resistance
  • Abrasion and stain resistance
  • Surface brightness and high-gloss finish

Disadvantages

  • Maximum continuous use temperature approx. 70 °C ( 160 °F )
  • Poor solvent and fatigue resistance
  • Poor UV resistance unless protected
  • Poor bearing properties (high friction and wear)
  • High smoke evolution

PC: Polycarbonate

PC polymers are amorphous engineering thermoplastics with a toughness down to -20°C. They are naturally transparent and can transmit over 90% of light as good as glass.

Because of these properties, polycarbonate resins are often used as a light-weight alternative to glass and when high-impact resistance is a requirement.

Some applications include bullet-proof glass, medical device components, light fixtures, and green houses. In addition, PC is a natural UV filter which makes it an optimal material for eyewear.

Another feature of PC is its pliability. In fact, it can often be processed at room temperature without breaking or cracking. This property makes it a popular material for prototyping—especially when transparency is required.

Design Considerations

Though it provides outstanding impact resistance, polycarbonate is susceptible to scratching. Therefore, for applications where this will be an issue, consider adding a scratch-resistant coating.

Advantages and Disadvantages of Polycarbonate Plastic Resins

PC is a great light-weight alternative to glass. It is a very popular, well-known plastic that offers product designers opportunities for design freedom and cosmetic enhancements.

Still, there are some disadvantages that may eliminate PC from your material selection process. Here are some advantages and disadvantages of PC to consider.

Advantages

  • High impact strength and toughness down to -20°C
  • Naturally transparent. Can transmit over 90% of light as good as glass
  • Can be designed to 100% protection from harmful UV rays
  • High dimensional stability
  • Pliable at room temperature without breaking or cracking. Good for prototyping
  • Good Heat resistance and thermally stable up to 135°C

Disadvantages

  • Though resistant to high impact, PC plastics are susceptible to scratching
  • Considered hazardous for food the release of Bishphenol A (BPA)

PC/ABS: Polycarbonate-ABS

PC-ABS is one of the most widely used industrial-grade thermoplastics. It is a high-impact engineering polymer that combines the strength and heat-resistance of polycarbonate with the flexibility and high-quality surface finish of ABS.

In addition, PC/ABS plastic provides improved processing during the injection molding process. Product designers and engineers often choose it for functional prototyping, tooling, and low-volume manufacturing. This because PC/ABS is likely to provide stronger parts and prototypes that mimic the material properties of the final product.

Advantages and Disadvantages of PC/ABS Plastic Resins

Though PC/ABS can provide the best properties of two polymers, it is critical to understand key pros and cons to ensure it will achieve your fit, form, and function.

Advantages

  • High impact strength even at low temperatures
  • Heat resistance
  • High stiffness
  • Easy processing
  • Low overall shrinkage and high dimensional accuracy

Disadvantages

  • Poor solvent resistance
  • Low dielectric strength (not a good insulator)
  • Low continuous service temp. (melts easily)

|Download: Quick Guide: 6 Common Plastics for Injection Molding

PP: Polypropylene

Polypropylene is a crystalline thermoplastic that is tough and flexible with outstanding heat and chemical resistance properties. It’s one of the cheapest plastic resins available and is used both as a plastic and a fiber in a variety of applications across industries.

For instance, PP is used in automotive manufacturing, packaging, furniture assembly, textiles, and aerospace. In addition, PP is also a successful material option for special parts like living hinges—a flexible plastic bridge that connects two hard pieces of plastic.

Design Consideration

Polypropylene may be the cheapest option, but that doesn’t mean it’s the best option for achieving your fit, form, and function. For example, if your part requires impact resistance properties, consider PC/ABS instead.

Medical fluid delivery component molded with PP.

“I worked with a customer recently who wanted to use polypropylene because it was the most expensive option. But after reviewing the part, I realized it was multi-part assembly that would be at risk of being dropped. So I suggested PC/ABS instead because it will provide more structural integrity and impact resistance than PP.” 

Drew Davis, Application Engineer at Xcentric

Advantages and Disadvantages of Polypropylene Plastic Resins

Polypropylene may be the cheapest option, but that doesn’t mean it is the best choice for your injection molding project. In fact, selecting the wrong material can add to your production costs in the end.

Instead, consider these pros and cons of using polypropylene before making a material selection.

Advantages

  • High impact strength even at low temperatures
  • Heat resistance
  • High stiffness
  • Easy processing
  • Low overall shrinkage and high dimensional accuracy

Disadvantages

  • Poor solvent resistance
  • Low dielectric strength (not a good insulator)
  • Low continuous service temp. (melts easily)

Nylon

Nylon is a semi-crystalline polyamide with low density and high thermal stability. Polyamides are a group of technical thermoplastics with properties that range from the hard and tough PA 66 to the soft and flexible PA 12, for example.

In generally, nylon plastic resins provide fantastic wear resistance, good coefficient of friction, and very good temperature and impact properties. Further, nylon also provides chemical resistance and has proven to be a good oil resistant plastic.

This balance of properties make nylon a good candidate for metal replacement in some applications that require toughness and weight reduction. For instance, automotive parts and industrial components.

Design Considerations:

Nylon absorbs water. So if your part will be exposed to moisture, nylon may not be the ideal plastic because it could damage the dimensional and structural integrity.

Advantages and Disadvantages of Nylon

Nylon is easy to process and can be a cost-effective solution for your injection molding project. Like all of the plastic resins on our list, it’s important to understand how the properties will impact your design intent.

Advantages

  • Excellent abrasion & wear resistance
  • High tensile and compressive strength
  • Low coefficient of friction.
  • Lightweight option that’s 1/7th the weight of conventional materials
  • Easy to machine

Disadvantages

  • High shrinkage in molded sections
  • Lack of stability
  • Does not absorb water well

POM: Polyoxymethylene (Acetal)

POM, also known as acetal, is a naturally white semi-crystalline engineering thermoplastic and is characterized by its high rigidity to −40 °C. It is used in the injection molding process to produce parts that require high precision, stiffness, and low friction. It has excellent dimensional stability and resistance to abrasion, heat, water absorption, and creep.

Because of its low coefficient of friction, POM is good material choice for producing high-performance engineering components, medical equipment, and electrical housings. By nature, POM is a slippery material, which makes it a good fit for products that require sliding mechanisms and gears.

It is important to note that POM has a very high shrink rate of about 2%.

Design Consideration

If you are designing parts that have large variations in wall thicknesses, POM can be dimensionally unstable. Large parts molded with POM are more likely to experience warping than smaller parts. Therefore, consider adding fillets or strengthening ribs.

Advantages and Disadvantages of POM Plastic Resins

POM is one of the most common plastics used in the injection molding process. Here are some advantages and disadvantages to help determine whether POM is right for your achieving your design intent.

Advantages

  • High strength
  • Rigidity to -40C
  • High resistance to impact, creep, abrasion, and solvent
  • Good  fatigue endurance and low coefficient of friction

Disadvantages

  • High shrinkage of about 2%
  • Very poor resistance to UV radiation
  • Poor resistance to acids/alkalies
  • Burns easily, is not available with flame retardants
  • Does not absorb water well

Conclusion

Don’t be discouraged when choosing a plastic resin for your part design. Xcentric can  help guide you through the process to help bring your concepts to life faster and on budget. Get connected with an Xcentric team member today: sales@xcentricmold-newdev.dev.varcm.com or 586-598-4636. If you you’re ready to get started with a project, simply upload your part to request a custom quote

Aluminum Molds Vs. Steel Molds | Plastic Injection Molding

Aluminum Molds Vs. Steel Molds | Plastic Injection Molding

Aluminum Molds vs. Steel Molds: Five Critical Points of Comparison for Product Designers and Engineers 

Choosing between steel and aluminum tooling is a critical decision for product designers. This is because the tool impacts part quality, cycle time, cost, and even time-to-market.

Therefore, understanding how each material will perform during the injection molding process will help you to make more informed decisions—for today and future needs.

In this blog we provide a critical comparison between P20 Steel and QC-10 Aluminum for five key areas:

  • USA vs China: Where you quote tooling impacts the cost/time to create and change molds
  • Tool life comparison: how many parts can be produced with steel vs. aluminum molds?
  • Thermal conductivity and the ability to control the temperature of each mold type can influence fill, form, and cycle time
  • Part size and complexity by mold type
  • Material and surface finish options for aluminum and steel

Where you quote tooling matters: USA vs. China

Deciding between an overseas and domestic supplier for tooling can influence your entire injection molding project—from supply chain management and production cost to the time it takes to build and change your mold.

For one, vast discrepancies in material cost between the USA and other countries, notably for this discussion, between aluminum and steel as raw material.*

 

In the USA, for example, aluminum is the default material used to create molds because it is cheaper than steel. Conversely, in China raw steel is used as the default material because it is cheaper than aluminum. One country uses a soft material while the other uses a hard material.

Therefore, if you quote tooling in different locations, chances are you will not be looking at an apples-to-apples comparison. This is because soft and hard materials perform differently during the injection molding process. Which can impact cycle time, cost, and time-to-market.

Cost and time to create or change steel molds vs. aluminum molds

When quoting tooling there are two critical costs to consider. First, the initial cost to create the mold. And second, the cost to make changes to the mold. Below is a comparison of cost and time for steel vs. aluminum tooling.

 

Cost  to create or change steel molds vs. aluminum molds

The cost to create an aluminum mold is about ¼ to ½ the cost of creating a steel mold. In general, aluminum tooling will prove to be the most cost-effective option even when comparing a quote from a China-based vendor for steel tooling to a USA aluminum quote.

The type of mold you choose can also impact the cost of making changes. For example, aluminum tooling is roughly 1/10 of changing a steel tool—regardless of where it is manufactured. This is because it takes much longer and is harder to machine steel versus aluminum.

Time to create or change steel molds vs. aluminum molds 

The time required to create an aluminum tool, on average, is about 15-25 business days. In contrast, the average time required to create a steel tool is about 35-60 business days.

On average, the time required to change an aluminum tool is about 5 business days. Compared to an average of 20 business days required to change a steel tool. 

What is the tool life of P20 Steel Tooling vs. QC-10 Aluminum Tooling?

(And how much volume can I produce with each tool before investing more money to keep it running?)

The time required to create an aluminum tool, on average, is about 15-25 business days. In contrast, the average time required to create a steel tool is about 35-60 business days.

On average, the time required to change an aluminum tool is about 5 business days. Compared to an average of 20 business days required to change a steel tool. 

Please note, the estimated volume for steel and aluminum molds will depend on material selection for use during the injection molding process:

  • P20 Steel tooling, average life of 50,000-100,000 parts
  • QC-10 Aluminum tooling, average life of 10,000-25,000 parts

According to Taylor Foster, Account Executive at Xcentric, quantity often determines whether to choose steel or aluminum tooling.

“Simply put, steel tooling will always offer a longer tool life than aluminum tooling,” Taylor said. “This means, it can produce a higher volume of parts before the mold requires maintenance due to wear and tear, or total replacement.”

Therefore, if you are going to need hundreds of thousands—or millions of parts in a year, steel tooling is likely going to be the best option.

Alternatively, Taylor said “if you do not anticipate this level of production volume, and instead plan to stay in the 10s of thousands over the next year or so, then aluminum will be the best option.”

Aluminum Molds vs. Steel Molds: A Comparison

Video Presentation - Featuring Taylor Foster, Account Executive at Xcentric

When moving parts to production, product designers are faced with a choice: steel or aluminum tooling? Watch the webinar to learn common misconceptions between the two along with a side-by-side comparison that will help you to make more informed decisions. 

WATCH NOW

Thermal Conductivity of Aluminum is 5 times greater than Steel

Thermal conductivity is a material’s intrinsic ability to transfer heat. The thermal conductivity of aluminum is about five times greater than steel. This is important because it directly impacts the fill, flow, and cycle time of aluminum molds.

Fill, flow, and cycle time: benefits of aluminum molds

  • Material fills the mold faster and more evenly than steel molds
  • Plastic can flow longer distances with less injection pressure in aluminum
  • Cycle time is less due to quicker heating and cooling, meaning faster creation of your parts using aluminum molds
  • Parts have minimal warp and much better dimensional stability – giving a higher acceptance rate on parts

Aluminum molds’ superior thermal control can reduce cycle time up to 40%

In an article published in Moldmaking Technology1, Douglas Bryce provides details about an IBM tooling study of aluminum molds for high-volume production. The five-year study used identical steel and aluminum molds to produce identical plastic parts.

According to the study, the aluminum molds cost up to 50% less to build than steel molds and produced higher-quality parts. Further, the aluminum molds’ superior thermal control made it easier to manipulate areas of the tooling which resulted in cycle times up to 25-40% less than the steel molds.

Achieve better temperature control with aluminum molds, reduce cost and cycle time

Controlling the temperature of a mold is often a challenge because it depends on variables such as the material, design, ejection process, and other issues within the tool.

Still, achieving better temperature control can help to optimize cost and reduce cycle time. This has been tested and proven in studies like the one featured in Flow Front by Claudia Zironi2. (Table 1)

QC-10 Aluminum vs. P20 Steel; Polystyrene vs. Nylon

In this study, Claudia Zironi conducted a side-by-side comparison of two materials, polystyrene and nylon, being injected into a QC-10 aluminum mold and a P20 steel mold.

Both materials were run in the same process to showcase a completed part within the same spiral tool design. When completed, the overall cycle time for QC-10 Aluminum was much faster than that of the P20 Steel.

Per the study, the P20 steel molds retain more temperature during the molding process than the QC-10 aluminum molds.

Also, recovery after each shot does not come down as fast as the temperature in aluminum tooling. This is because thermal temperature releases out of aluminum faster than steel. Because of this, there was a 20-second freeze time in the P20 steel to ensure the part was cooled for ejection.

Table 1 Claudia Zironi, Flowfront Magazine, “Competitive Advantages of Aluminum Molds for Injection Molding Applications: Process Simulation Used to Evaluate Cycle Times,” April 2005.

Part size and complexity by mold type

Based on the data discussed so far, aluminum has more to offer than prototyping and low-volume production. Though it is softer than steel, aluminum molds can be a cost- and time-efficient option for high-volume production and larger parts.

Of course, there are applications where a steel mold would be a more optimal choice.

Will the type of tooling limit material selection, surface finish, or secondary operations? 

Choosing aluminum tooling instead of steel tooling will not drastically—if at all, compromise your options for material, finish, or secondary operations. Here is a brief overview when comparing P20 steel and QC-10 Aluminum tooling.

Plastic Material Selection

In general, you can expect the same material options for both steel and aluminum tooling. Please note two exceptions where steel tooling is likely to be the best option due to wear and tear:

  •  Exotic materials like Ultem which requires very high heat
  • Abrasive material such as glass fill or other ad

For more detailed information about materials, visit Xcentric’s plastic material selection guide.

Surface finish options

Whether using steel or aluminum, your options for surface finish will be the same. Please note, to achieve an SPI A-1 finish, you need special facilities and/or equipment.

Also, Finish and clarity are reliant on the material you choose; some materials are not capable of achieving an optically clear finish no matter the level of polish used.

FREE 8-Piece Sample Kit

Choosing the optimal surface finish for your material is critical when designing plastic parts for injection molding. Our 8-piece surface finish plaques can help you to make more informed decisions early in the process.

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Aluminum molds advantage: flow and fill rates

Aluminum molds demonstrate better thermal conductivity, flow rate, and fill advantages over steel molds. Which makes aluminum a better option when you are producing long, large parts.

Also, considering the superior temperature control, aluminum is a better option for part designs with complex geometries that could cause fill issues.

Steel molds advantage: thin walls and complex features

In contrast to aluminum, steel tooling proves to be a more effective for injection-molded parts and tooling that require extremely thin walls. This is because of the increased hardness of the mold material. The thin features and areas in the tool will hold up much better to the pressure during the molding process when using steel.

Conclusion: Steel Molds vs. Aluminum Molds

In conclusion, aluminum molds provide value beyond prototyping. Instead of choosing steel molds for high-volume production, consider aluminum molds instead. They prove to be a cost- and time-effective solution for plastic injection molding.

Xcentric is located entirely in the USA with two production facilities in Michigan. Though we specialize in aluminum tooling, we also offer steel tooling. Our on-site material experts are eager to help you make the most informed decision for your next injection molding project. Please contact an Xcentric Application Engineer with questions or concerns. We are here to help bring your concept to market on time and on budget.

Taylor Foster is an Account Executive at Xcentric. He has a background in Mechanical Engineering and Business, attended the University of Kentucky, and has been working in the manufacturing industry, specializing in injection molding consultation and education as well as customer experience for the past 2 years. Get connected on LinkedIn with Taylor Foster

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References

  1. Douglas Bryce, Moldmaking Technology, “Why Offer Aluminum Molds for Production”, April 2002
  2. Claudia Zironi, Flowfront Magazine, “Competitive Advantages of Aluminum Molds for Injection Molding Applications: Process Simulation Used to Evaluate Cycle Times”, April 2005

* While steel as a raw material is cheaper than aluminum in both geographies, several other factors including market share, labor, and production costs must be factored into the material of choice in each country.

How to Eliminate Knit Lines In Injection Molding

How to Eliminate Knit Lines In Injection Molding

Knit lines are formed when two or more plastic flow fronts collide and solidify or “knit” together during the molding process.

Overall, injection molding is a relatively simple process. A thermoplastic resin is heated to its melting point and injected into the cavity of an injection mold to produce a specific part geometry. The part is cooled in the mold until it reaches a temperature where it is solid enough to be ejected.

Knit lines most commonly occur around holes or other obstructions to the melt flow such as bosses. A boss is a feature with a hole that designed for a threaded fastener. A gate is an area where the resin is injected into the cavity.

Some thermoplastic resins with lower flow rates such as ABS and filled resins are more prone to having knit line issues. There are approximately 85,000+ thermoplastics available in the marketplace. Within the vast material options available, there are approximately 40 polymer blends or families.

While the presence of knit lines does not always compromise the structural integrity of the plastic part, they are almost always a cosmetic issue.

Changing the injection profile parameters – modifying the fill time for instance – may cause the knit line to move to a more favorable location.

Material selection, part design, tool design, and process parameters all also affect knit lines.

How to eliminate Knit Lines

  • Select resins that are less susceptible to knit line formation.
  • Change the boss or gate locations.
  • Thicken part walls to slow down the resin cooling process however be careful not to make them too thick that it causes sink marks.
  • Place knit line causing features farther from the edge of parts when the design allows for it to do so.

Do you have a question regarding knit lines? Send your design to one of our Technical Specialists for review at 586-598-4636 or sales@xcentricmold-newdev.dev.varcm.com.

Rapid Molding vs. Traditional | Digital Manufacturing

Rapid Molding vs. Traditional | Digital Manufacturing

The Difference Between Traditional and Rapid Molding

By Leslie Langnau, Design World 

Rapid molding is a key player as the “digitization” of nearly every process to make products continues. The latest industry to experience this shift is molding. Here’s a look at how digitization may affect traditional molding service providers.

Pierre Viaud-Murat | Senior Vice President of Sales

Digital manufacturing offers many benefits across multiple touch points: it can reduce time to market, labor overhead and asset use, plus it helps customers control quality and inventory. These advantages allow users to explore new revenue streams, develop and enhance innovative designs and respond to market demands. The digital age can enhance designers freedom to create and develop through one streamlined methodology.

The traditional manufacturing process
The traditional manufacturing process usually consists of a several-step sequence within the manufacturing flow. Team members monitor and ensure that safeguards are in place throughout the entire part lifecycle. Throughout the process, various testing for form, fit and function are required to discover any part flaws. Each team member should be aware of these critical-path processes, as the traditional method of manufacturing requires more manual than automated production.

traditional manufacturing

The traditional injection molding manufacturing process usually consists of several steps. Throughout the process, various testing for form, fit and function are required to discover any part flaws. Usually, the traditional method of manufacturing requires more manual than automated production.

For example, generating a quote using a DFM analysis and confirming an order manually can take approximately a week, if all of the process steps are accurate and on track the first time through. In the event that any modification is required, the same process steps would be repeated before finalizing the order.

Once an order has been placed, the mold design is reviewed for viability. When that design is finalized, it will go onto the next phase of the traditional manufacturing process. This can be a lengthier portion of the process, ranging from three to eight weeks. Additional delays may also occur if project issues are not identified early in the quoting process, which will result in re-quoting, redesigning or redefining the project. Any of the three can result in significant delays.

With all of the production factors in place, the part will then be molded. After the first shots, a visual and dimensional inspection will be done. If the part passes inspection, it is shipped out to the customer for review and feedback.

Once the customer inspects the part, they have the opportunity to approve or reject the run. In the event of a non-approval, the process would be modified and revisited again with continual iterations until the optimal part is achieved. Any combination of these factors can impact the cost, quality and timing in a traditional manufacturing process.

The digital manufacturing process
Another approach to injection molding involves the digitization of as many injection-molding steps as possible. This approach is referred to as rapid or digital manufacturing, and is a natural progression of traditional manufacturing. The streamlining possible by digitizing many traditional molding steps can reduce total costs.

digital manufacturing

An evolution of traditional injection molding manufacturing is referred to as digitization. It involves digitizing as many injection-molding steps as possible to streamline many traditional molding steps to reduce total costs.

Digital manufacturing begins with the upload of a 3D CAD file to a service provider’s servers. The geometry and part requirements are analyzed, usually with proprietary software. Then the customer receives an interactive quote. Once the customer approves the quote, an order is generated and the mold design finalized and a tool-path created, often within hours.

The initial mold can often be created with modular components, which is another cost savings. Then, the mold is usually machined, a process that takes a couple of days. After benching and finishing, the mold tool is assembled for first production shots and inspection.

This process of rapid mold development can shorten development lead-time to weeks instead of months.

Digital manufacturing can accelerate every step of a part creation process. In traditional manufacturing, the retooling investment could push the break-even manufacturing numbers into the thousands – a cost-prohibitive change for many smaller businesses. Digital manufacturing, however, can implement that small design change for approximately a quarter of the investment in a quarter of the time.

Digital manufacturing is scalable and flexible. Should demand rapidly increase, the digital manufacturing process can move between low-volume to mass production. Thus, designers can react to market behaviors quickly and easily. If demand drops, rapid manufacturing enables adjustments while still achieving the lowest total cost. Thus, regardless of a market’s volatility, digital manufacturing lets users respond accordingly.

The digital manufacturing process allows customers to quickly go through multiple iterations easily. Low-cost tooling makes low-production runs economical enough to test on select markets and use the feedback as a learning curve. Customers can maintain their existing quality controls, while developing good parts that can get to market faster.  Some service providers offer optional services, such as inspection and project management consulting. Digital inspection allows for rapid feedback and tool modifications, if necessary. Service providers usually have experienced tooling experts who can consult during the mold development process to solve any problems that arise.

Mold considerations
Mold service providers strive to ensure a mold tool is available over the lifecycle of a project. Often, the tool is made from a high-grade aluminum base material, like QC-10, which offers an excellent strength-to-weight ratio.

Compared to steel, aluminum is softer and less dense, dissipates heat quickly and efficiently and costs up to 75% less. It’s also a recyclable material, an attractive feature when material waste can be higher than 50% per part. Recyclability and material reuse can help recoup initial material costs.

Although aluminum may not be the right material for every type of mold, it works well for prototyping, bridge tooling and low volume production. Depending on the size and structure of the parts, the heat dissipation within an aluminum mold can be up to 50% higher than steel or other metals, creating faster production turnaround times. Aluminum molds will usually last through production runs of several thousands of parts. DW.

The article above is featured in Design World’s Make Parts Fast.

If you would like additional information on the rapid molding process, contact one of our Technical Specialists today at 586-598-4636 or sales@xcentricmold-newdev.dev.varcm.com.

Plastic Molding Processes: Know The Basics

Plastic Molding Processes: Know The Basics

4 Plastic Molding Processes

We are frequently asked about different plastic molding processes and how each effect the process of part design and production. In this post we explain the basics of 4 plastic molding processes: plastic injection molding, blow molding, rotational molding, and vaccuum molding.

Plastic Injection Molding

Xcentric Mold specializes in plastic injection molding for low-volume and protyping. Injection molding is one of the most versatile manufacturing processes. It is used for producing simple and complex plastic parts for nearly every industry.

The injection molding process involves injectiong molten material into a mold. The, material is fed into a heated barrel, mixed (using a helical shaped screw), and injected into a  mold cavity. Finally, the material cools and forms the plastic part.

Not all materials heat (or cool) the same.

When designing for plastic injection molding, material selection is a critical for success. After all, materials do not all perform the same – during or after the injection molding process. To achieve the intended fit, form, and function of your part design, work with your supplier to choose the optimal material.

The injection molding process can be performed with a host of materials including: plastic, metal (for which the process is called die-casting), glass, elastomers, confections, and most commonly, thermoplastic and thermosetting polymers.

Common examples of plastic injection-molded parts include medical equipment and medical devices, automotive, marine, industrial, agriculture, aerospace and tight tolerance parts.

Other Molding Types

Below are some molding types which are not specialties of Xcentric Mol. However we may be able to provide you with recommendations of other suppliers who can assist you.

Blow Molding

Blow molding is a specific manufacturing process by which hollow plastic parts are formed and can be joined together. In general, there are three main types of blow molding:

  • Extrusion blow molding
  • Injection blow molding
  • Injection stretch blow molding

The blow molding process begins with melting down the plastic and forming it into a parison or in the case of injection and injection stretch blow molding (ISB) a preform. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass.

The parison is then clamped into a mold and air is blown into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

Common examples of blow molding products include bottles, containers and other hollow shapes.

Rotational Molding

Rotational molding is comprised of a heated hollow mold which is filled with a charge or shot weight of material. It is then slowly rotated (usually around two perpendicular axes), causing the softened material to disperse and stick to the walls of the mold. In order to maintain even thickness throughout the part, the mold continues to rotate at all times during the heating phase and to avoid sagging or deformation also during the cooling phase.

Common examples of rotational molding include parts larger than 2’ such as containers, utility carts, storage bins, car parts, tanks (oil, septic, water) and leisure products such as kayaks.

Vacuum Molding

Vacuum molding is a process by which a sheet of plastic is heated until it becomes pliable, stretched onto a single-surface mold and forced against the mold by a vacuum to create a shape.

This process can also include thick-gauge thermoforming, a type of vacuum molding, that is known for producing a variety of products including disposable cups, containers, lids, trays, blisters, clam shells, and other products for the food, medical, and general retail industries.

Common products produced with the vacuum molding application include industrial containers and crates, pallets, exterior door panels, plastic totes, plastic trailers, passenger cabin window canopies for winged aircraft, and lawn mower hoods.

Would you like additional information about the plastic injection molding process and its capabilities?  Contact our Application Engineers today at 586-598-4636 or sales@xcentricmold-newdev.dev.varcm.com.

Wall Thickness Guide For Plastic Part Design

Wall Thickness Guide For Plastic Part Design

Wall Thickness Guide For Plastic Part Desgns

Our wall thickness guide will come in handy when you’re designing plastic parts for the injection molding process. Regardless of industry or application, designing plastic parts can be a challenge. Investing time early in process to optimize your design for manufacturability can help to save time and money.

Top 5 design tips for optimal wall thickness

Maintaining uniform wall thickness throughout your plastic injection molding part design is critical.  Without uniform wall thickness, many issues can occur such as sink, warping, short shot (meaning the material in tool does not fill correctly), and cosmetic imperfections.

  • A 10% increase in wall thickness provides approximately a 33% increase in stiffness with most materials
  • Walls should be no less than 40%-60% that of adjacent walls
  • Core out all unneeded thickness and wall stock
  • Sharp internal corners and long unsupported part spans should be avoided
  • Use ribs as stiffening features and supports to provide equivalent stiffness with less wall thickness

plastic injection molding

Material Selection

Selecting the proper material for your part design has a significant impact on wall thickness.  How the part is expected to perform and under what conditions will play a considerable role in material selection.

There are thousands of materials available to choose from.  Material properties not only effect wall thickness but also effect strength and durability.  Below are some recommended wall thickness guidelines with some common materials.

wall thickness

For further information, please visit our material selection guide.