Video: 7 Ways to Save on Injection Molding

Coring reduces material volume, weight, and cycle time.

A lack of coring results in a chain of events which ultimately gives you a higher part cost. When you don’t have coring in your part, you get an uneven wall thickness. This in turn results in uneven cooling, which leads to sink marks. Because you have more material, and a greater material volume overall, you’ll get an increased cycle time (and higher cost as a result). This can also result in differential shrinkage and your part will go out of tolerance.

Drafts are angled wall sections that help parts eject smoothly. Without draft, the part will not exit the mold smoothly and leave scrape marks. Drafts also help protect textures and geometries in your parts.

To check if your part is die-locked, run a draft analysis in the direction the part will come out of the mold. Parts that are die-locked will require some action to pull the feature away at mold opening. This will greatly increase mold costs.

Without pass-thru coring, clips, snaps and similar features require additional lifters or slides to release the part from the mold. This increases the overall mold cost.

To use pass-thru coring, insert a cutout thru the parallel feature for steel to shut-off.

Annular features may require additional slides or lifters to eject. This can be avoided by taking certain considerations:

• Use soft materials, not hard or filled
• Use the 1:3 rule, where the feature’s width should be 3x its height
• Include “lead-in” and “lead-out” radii

Almost every material shrinks, and the rate of this must be compensated for. To understand shrink rate values well, a great resource is matweb.com, or checking with the supplier of your material to see what shrink rate you need to know.

Plastics generally shrink towards their centroid, which is their center mass. Some plastics do shrink linearly, so always be aware of your specific material’s specs.

The parting line is important because it marks how the part splits when the mold opens. Careful placement of the line is crucial to avoid die-locking and other issues. Always think about how the part will come out of the mold and design accordingly.

Injection molding is a fantastic process for both high and low volume production parts. Now that you know how to reduce costs and time to market for your design, use Xometry to get your parts with competitive pricing and fast lead times!

Learn more about our injection molding services and request a quote online from our expert injection molding engineers at Xometry—we turn quotes around within 24 business hours.

Want more design tips? Get a comprehensive design overview in our Injection Molding Design Guide.

Check out more cost-saving educational trade secrets:

• Top Ways to Save on CNC Machining
• Leveraging the 3D Printing Paradox
• 4 Easy Ways to Save on Injection Molding