How do you select the right injection molding material? This is a very difficult question. Making the decision even harder is the fact that there are over 300,000 different types of material available, and that number grows by 750 more every year.

Injection Molding SampleSome people think the best thing to do is just select the latest and greatest material that has the best properties and can take super high heats. They might think that their requirements will never exceed these properties and their part will be fantastic. This is almost never the case. When selecting resins, it is a good idea to contact your local representative whether it is for Sabic, Bayer, or DuPont. Let them know what your product is for, the conditions that it will be exposed to, and the colors that you would like it in, and they will certainly point you in the right direction. Most of the time, simple resins like: PP, ABS, PC, or PC/ABS will be more than sufficient for your needs. If you have an out of the norm requirement, resin makers can blend additives into the resins to meet your requirements. 

So how do you select the right material? Ask for help first or go to the resin manufacturer’s website, you will be amazed. Remember, it does not have to be the most expensive resin to be a quality material.

I hope you find this information helpful. If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

Quickparts | Injection Molding SampleDesigning plastic parts is a complex task involving many factors that address a list of requirements of the application. In addition to functional and structural issues, processing issues play a large role in the design of an injection molded part. Adhering to some basic rules will result in a part that, in addition to being easier to manufacture and assemble, will typically be much stronger in service.

Quickparts has created an injection molded sample to illustrate the different design basics and things to keep in mind when designing for injection molding.

>> Click Here to Request a Sample!

What do a leather wallet and a ketchup bottle cap have in common? You got it…they both implement the living hinge to bring the object to life through movement.

When speaking in terms of manufacturing, a living hinge is a thin flexible web of material that holds two rigid plastic pieces together. The living hinge concept has been around for years, but in terms of plastics, its full potential wasn’t realized until the inception of polypropylene in the late 1950’s.

So, what is the secret behind the “living” part of it?

It’s all in the design…

Injection Molding | Living Hinge Diagram | Quickparts.com
The key details to a successful living hinge include:

  • Hinge thickness
  • Radius
  • Recessed notch above the hinge feature

The hinge thickness controls the overall stiffness of the hinge; each application has its own requirements so make sure you find your part’s ideal thickness. Also, because the hinge plastic is so thin, it may be susceptible to tearing at the edges, so giving just the ends of the hinge extra thickness while adding radii will increase its tear resistance.

The overall radius applied will help to orient the plastic molecules flowing through the hinge, ensuring that the hinge bends along a straight line. This molecular orientation gives the hinge its strength and long life. Another way to ensure proper material flow and hinge operation is to choose a gate location that will place weld lines away from the living hinge feature.

I hope you find this information helpful. If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

One of the most common questions we are asked is “How much draft do I need for the texture that I want?”

The general rule of thumb is that you allow for 1.5 degrees of draft for each .001″ of texture finish depth. However, there are other considerations that must be taken into account due to the many new resins and polymers, molding improvements, and various other factors that come into play in modern plastic molding. Examples of situations that require additional draft are thin wall part design and high pressure molding.

Some important considerations to keep in mind are:

  • Is the vertical wall in question an inside or outside wall? If it is an inside wall, the part will shrink onto it during molding, so you will need more draft in order to apply a texture, or apply the texture at a lighter depth.
  • Certain plastics have very little shrinkage and will therefore not shrink away from outside walls as easily as other plastics. Thermosets, Ryanite, Glass Filled Nylon, Glass Filled Polypropylene, ABS, Polycarbonate, etc. will usually require more draft in order to mold parts without scuff or drag marks.
  • If the core is very simple, and there is nothing on the core to hold the part in place during ejection, the part will tend to hang onto the cavity, creating scuff marks. The part may require more draft, or perhaps texture could be applied to the core side. This helps hold the part onto the core during ejection. This method has been used very successfully to solve this sort of problem.

I hope you find this information helpful. If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

As plastic product designs become more complex, Design for Manufacturing (DFM) plays an instrumental role in successfully launching new products on time and under budget.  Our DFM service allows customers to take advantage of the vast manufacturing experience and knowledge of the dedicated Quickparts manufacturing team.  This service (valued at $300) is offered free of charge to customers working with Quickparts on injection molding projects.  A comprehensive DFM report is available which includes process flow details, expectations for the build, and final DFM recommendations.

Quickparts is a business that has been providing custom-designed plastic and metal parts to product development companies since 2000. Many companies, from the multi-billion dollar operations to the two-man design shops, have utilized the benefits of using Quickparts.

You can find a sample report and learn more about Design for Manufacturing in the Learning Center at www.quickparts.com.

If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

FREE Injection Mold SampleI hope the end of the year is treating you well. We have had a few conversations with customers recently regarding shut off angles, and I wanted to get one final post out to everyone this year to briefly discuss the subject.

A shut off angle is where two parts of the mold shut against each other to prevent plastic from passing through. This term applies where one part of the mold closes against another to form a slot or hole, or it is sometimes used to refer to the interface where a slide shuts against a core or cavity. Sometimes, the shutoff surfaces are parallel to the direction that the mold opens. When this happens, draft has to be added to avoid grinding the parts of the mold against each other. A 3 – 5 degree draft is ideal for these shutoff areas and will ensure the life of the mold. Without this amount of draft the mold will get damaged, and may potentially even “lock up” and not open. Even with hardened steel, lack of draft in this area will ruin the mold.

Understandably, many customers do not understand why we ask for this draft, but without it, every time the mold opens and closes, the steel will wear out in this area in a very short time. When this happens, repairs can be costly.

If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200. Thanks, and Happy Holidays.

Last month’s design tips discussed how draft angles are specific to each part that is built.  This month we will look at some standard injection mold resins and some of the properties that they possess.

When deciding which molding resin to use, one must consider the mechanical properties, molding properties, and cost of the resin selected for the given application.  Application-specific requirements will always drive the need for particular material properties, like tensile strength and elasticity.  Successful plastic part design is based on an understanding of processing related issues during manufacturing, such as mold filling, likelihood of flash, part ejection and the potential for warp and sink.  The table below lists some commonly used resins, along with brand names, and a high-level summary of their material properties and moldability characteristics.

Standard Injection Molding Resins

Please keep in mind that this is a concentrated view of how to select the right resin for your plastic part.  All major material representatives have application specialists that can help you with your selection.  We strongly urge you to discuss your project with one of these specialists prior to making your mold.

We hope this gives you some ideas for your next molding project.  If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

Draft angles are needed so that a plastic part can be released from the mold without distortion or damage. The high pressures of injection molding force the plastic to touch all the surfaces of a mold’s cores and cavities. The cavity becomes so tightly packed that it is often difficult to remove the part. Sometimes, shrinkage will actually make it easier to take the part out of the mold, but in other cases, shrinkage will cause the part to stick to the mold’s cores. These natural occurrences call for draft angles.

No single draft angle is suitable for all parts. Each individual part requires a unique specification. Large parts call for more draft than small parts. Thin-walled parts that undergo high-pressure injection molding need more draft than parts that are subjected to lower-pressure molding. When calculating appropriate draft angles, the plastic material’s shrinkage and physical properties are also considerations. Sizeable draft angles and smooth polish should be used for parts molded in strong, stiff, abrasive, and gluey materials. Smaller draft angles can be utilized on soft, malleable, and slippery plastics.

From a cost and manufacturability viewpoint, the ideal draft angle is the largest angle that will not lessen the customer’s satisfaction with the product. The minimum allowable draft angle is harder to quantify. Plastic material suppliers and molders are the authority on what is the lowest acceptable draft.

I hope this gives you some ideas for your next molding project. If you have any questions regarding this or any other injection molding information, please feel free to contact me at (770) 901-3200.

Injection Molding SampleWe learned last month that selecting the optimal gate size and location is vital in the creation of any molded part. However, that is just half the story. Just as pivotal to the success of the design is the type of gate that is used.

There are actually four main types of gates that are frequently used when molding parts. Edge gates are often popular since they are fairly simple and cost effective, but may not always be the best choice. Here is a brief description of some gating options that will help you customize your design and really take your part to the next level.

Edge Gate • Suitable for medium and thick sections
• Used on multi-cavity two plate tools 
• Gate located on the parting line and the part fills from the side, top or bottom
DOWNSIDE: leaves “vestige” at gate location which should be trimmed with a secondary process
Submarine Gate • Used in two-plate mold construction
• As parts and runners are ejected, the gate is sheared at the part
• Tunnel can be located either in the moving mold half or in the fixed half
• Sub-gate is often located into the side of an ejector pin on the non-visible side of the part when appearance is important
Sprue Gate • Recommended for single cavity molds or for parts requiring symmetrical filling
• Suitable for thick sections where holding pressure is more effective
• A short sprue is favored, enabling rapid mold filling and low-pressure losses.
• A cold slug well should be included opposite the gate.
DOWNSIDE:  a gate mark is left on the part surface after the runner (or sprue) is trimmed off.

We hope this gives you some ideas for your next molding project. If you have any questions regarding this or any other injection molding information, please send us an email or give us a call at (770) 901-3200.

“Out of which material should you build your mold, steel or aluminum?” This is a very common question that we receive from our injection molding customers and is an important decision to make. The answer is usually dictated by your project requirements, expectations, and what ultimately defines “success” for your project.

QC10 aluminum is an incredible product that machines quite easily (40% faster than those made out of P20 steel). This saves you time and money, with parts in hand in as little as 1-2 weeks. On the other hand, if we were to make a mold out of steel, it will typically run around 100,000 parts while maintaining a polished A2 finish on the cavities.

Will the parts look good if you buy an aluminum mold?

Absolutely, unless you are trying to obtain an optical grade finish, which would likely require a steel mold. Aluminum transfers heat almost 5 times greater than steel, and this gives us a large window for processing. Typically we can run 5,000 to 15,000 parts off an aluminum mold before resurfacing the part line.

So what kind of mold should you buy?

For low volume parts at a reasonable price with a fast lead time, aluminum is the way to go. If you need a few hundred thousand parts, or something that is optical grade, then we would suggest building your mold out of P20 or another grade of steel.

If you have any questions regarding this or any other injection molding information, you can email us at quote@quickparts.com or give us a call at (770) 901-3200.