July 14, 2022

Molding sink marks determining

blog aco mold

The two biggest determining factors of molding sink marks are product design and processing with the assumption that the tool is functioning correctly. With that being said there is a fine line between the two. You can over compensate for poor product design with molding parameters, and vise versa. If you over pack a part you can begin to effect it dimensionally or ride on the fringe of flashing your parting line. You can very easily make a part that is too big by trying to pack out molding sink marks that are caused by poor product design. The other down fall of over packing is a small processing window.

A slight variance in other areas of your process could cause your scrap rate to go through the roof. For one example, different lots of material. Sometime the difference from one lot of material to the next will flow different (viscosity of your material during injection). Your process should always be based on a good rheology and gate freeze study. RJG pressure transducers in the tool run through an Edart system will also help you monitor your process for repeatability and quality control of your product. Once you have established a good repeatable process with as big of an operating window as possible, one that you can measure and monitor then, adjust your product design. You will be much happier with your end results doing the plastic molding sink marks determining. After a few times of going through this you will begin to establish some lessons learned that you can start applying to your product before you ever get to the press.

Few simple steps you should follow:

  1. At first stage of product design you should consider about bos/rib construction there are rules for it. So perfected by design first.
  2. If you find molding sink mark there are two factors mold related and machine/process related.
  3. Mold related take a look the feeding system (gate, runner, sprue, and orifice diameter of machine nozzle. Restricted area at the gate, undersize runner, insufficient nozzle diameter could cause insufficient packing. The point is plastic material must flow as easy as possible. And don’t forget proper venting at the mold. If show us the product, the runner, and the mold might help us to decide.
  4. Machine/process related, you can avoid thick ribs and bosses, increase injection pressure, increase back pressure, or apply melt cushion to product. Holding pressure might help to improve quality.

Related Blogs

blog injection molding
Plastic Injection Mold Factory in China

In the past 10 years, China injection mold making industrial has been through rapid developing and maintain 15% annual growth rate, Geographically, the Pearl River Delta, Yangtze River Delta are …

blog mold
China injection molds are NOT cheap any more

There are so many questions or doubts about injection molding always, especially for some people had good or bad molding experience in China. No matter for good or bad experience …

blog aco mold
Why companies seeking Chinese injection mold manufacturers

You might hear from someone that injection molds from China are bad quality, but still many companies are purchasing molds from China, some of them with bigger purchase volume even …

blog aco mold
Improve adhesion between PC and TPE

There is a bit you can do to help improve adhesion between PC and TPE; two materials that don’t typically love each other. I am working on a fix right …

Tell us your request right now and contact us today about getting started on your next project together!


Or Fill Out The Contact Form Below:

Support Your Business with Better Molding Solution

Contact Info
Copyright © 2023, ACO Mold. Terms of Service and Privacy Policy. All rights reserved.  Powered by ACO MOLD.