Often times the 3D design of a new component or an assembly hits the mark in terms of easy manufacturing, quick injection molding, and it’s perfectly on target for cost. Other times, there is an unforeseen challenge that requires a modification to the injection mold to alleviate a problem during molding or in the use of the product. Removing material from a finished product is called “coring”, and it’s today’s subject in injection molding.
What is Coring in Injection Molding?
One of the design standards we often discuss is a uniform wall thickness in the injection molded component. A uniform thickness helps the molten material flow through the mold without restrictions. It can also remove the chance of sink marks in the surface of the finished product, plus removing material may reduce the overall material cost with reduced resin used and a faster injection cycle. Coring is the process of removing excess material from a cross-section of a molded part to achieve a more uniform wall thickness.
What Are the Benefits of Coring?
Reducing the cross-section of an injection molded component has these benefits:
- Reduced wall thickness – This will help material flow through the injection mold easier
- Reduced sink marks – The uniform wall thickness can reduce sink marks on the part exterior without the need for secondary rework for the sink marks
- Reduced material cost – Reducing the cross-section of the part slightly can save a small amount of molten resin in every shot from the mold. Across thousands of parts, that small amount can add up to a large savings
- Improved uniformity – A uniform wall thickness may be more than functional. Uniformity may add visual appeal if your product has multiple parts in an assembly
- No reduced function – You won’t see a reduction in function or performance from coring and molded-in-stresses may be eliminated
- Shorter cooling times – Thick sections of an injection molded part take longer to cool in the molded before removal. This will increase your cycle time and slow your productivity down. Coring reduces the need for a longer cycle time
- Elimination of uneven shrinkage – Shrinkage can occur as the part cools in the mold and after removal from the mold. Thick part sections may continue to hold heat that will cause the part to warp or have uneven shrinkage
Conclusion
Simulation software is the standard in the plastics industry to ensure products are made with uniform wall thicknesses and minimal errors. It’s very accurate, but there are occasions where adjustments need to be made to the injection mold to correct minor errors or increase manufacturing opportunities. It’s not a job that just anyone can do, and it should be left to skilled professionals that are well versed in the process. At SEA-LECT Plastics we pride ourselves in tool and die manufacturing that allows us to deliver high quality products free from defects, and we have multiple options for manufacturing to help your business succeed. SEA-LECT Plastics has an elite team that produces world-class prototypes and products, and we have decades of experience with plastic injection molding operations. Our tooling experts can create molds from 3D designs and make fine adjustments to ensure smooth molding operations on a daily basis. We can offer support to determine what type of tooling you need, what materials to choose, and can support the generation of documentation to win new business in your industry. Give us a call at (425) 339-0288 or email us at mattp@sealectplastics.com. We’ll help to determine the best manufacturing for your next project.
Matthias Poischbeg was born and raised in Hamburg, Germany. Matt moved to Everett, Wash., after finishing his bachelor’s degree in business in 1995 to work for Sea-Dog Corporation, a manufacturer, and distributor of marine and rigging hardware established in 1923.
In 1999, Matt took over the reins at Sea-Lect Plastics Corporation, a sister company of Sea-Dog and a manufacturer of plastic injection molded products with an in-house tool & die shop. Matthias Poischbeg is also a contributor to Grit Daily.