PlastiCert

Injection molding solutions

Untitled MadeInMinnesotaLogoBlueFade www-award-logo-16-win
(507) 523-2300
ISO 9001:2015 Certified
UL Registered
Do you have a problem part/design? Send us what you have, we will take a look and offer up some advice.
(507) 523-2300
ISO 9001:2015 Certified
UL Registered
Do you have a problem part/design? Send us what you have, we will take a look and offer up some advice.

Follow us on LinkedIn!Follow us on Twitter!

  • Who WE ARE
    • About PlastiCert
    • PlastiCert Mission Statement
    • Key Company Individuals
    • News
    • Community Involvement
  • What WE DO
    • Overview of Capabilities
    • Small and Short Run Production
    • FAQ
    • Begin a Discussion
  • Who WE WORK with
    • Testimonials
  • BLOG
  • CAREERS
  • CONTACT US

August 20, 2014 By craig

Blowing off steam? We do it all the time!

The injection cycle includes pressing the two mold halves together with tonnage and shooting plastic into the cavity during injection. However, thinking about that injection process, the plastic is displacing air that is in the cavity at the time of closure. Where does the air go?

Venting in the mold is there to allow the air and gas to escape. As it injects, the leading edge of plastic pushes the air and gas into the venting, allowing the plastic to fill out the cavity. The vents are so small, that the viscosity of the plastic prevents the plastic from entering or “flashing” as we call it. The press settings tell the injection press how much plastic to push into the cavity. If air and gas take up some of that volume, the injection press does not know that and will continue to push. If there was no venting, or as we see in production inadequate venting, the plastic would push air and gasses into the last areas of the cavity to fill. Then, with nowhere to go, the injection pressure super compresses the air and gas. Compression of gas leads to extreme heat being generated and the neighboring plastic will be scorched or even burned.

As different plastics have different viscosities when liquid, the mold designer calculates the vents based on the plastic that the part designer has selected for the part(s) the mold will make. This is one of many reasons why changing resins once a mold has been finished is not as easy as pouring a different resin in the dryer and ultimately shooting it.

Mold designers provide venting by placing them along the parting line edge of the mold or using the circumference of ejector or core pins. Naturally, the larger the part being molded, the larger the cavity, the more entrapped air and the more venting required. You cannot have too much venting. Once in place, vents have to be monitored and maintained. Sometimes during the build but certainly postproduction, cleaning and maintenance should be done prior to shelving the mold.

So yes, we plan for and constantly blow off “steam” on our production floor. It gets you the part you designed and need for your products!

 

Similar articles:

A mold is a mold is a mold?

When coming up short is not a bad thing.

Speed can be trouble; less speed can also be trouble.

Shrinkage, it’s no laughing matter

3D Printing – It’s cool, but not ready for our prime time yet.

PT 2015 WCP Logo

Click to Start Discussion

Join Our Email List

For Email Newsletters you can trust.
 

Company News

PlastiCert: The Ins and Outs of Injection Molding

PlastiCert is a Lewiston-based small business with approximately 30 employees. It was also recently named one of the top … [Read More...]

PlastiCert announces promotions and reorganization

Lewiston, MN March 30, 2022 - PlastiCert, a veteran of innovative and quality composite injection molding celebrating 41 … [Read More...]

[MORE NEWS]

Blog

Life after an Industrial Sourcing “Me Too”

Globalization, Free Trade, Off Shoring; while around since people started sailing the seas, it came to the forefront … [Read More...]

Getting OVER the small things

One of the more frequent services we are asked about is overmolding or two shot molding. Seems people are of the opinion … [Read More...]

[MORE POSTS]

  • What we do
  • Who we are
  • Who we work with
  • Begin a Discussion
  • Careers at PlastiCert
  • Privacy Policy

(507) 523-2300

PlastiCert Inc.
300 Wilson Street N.
P.O. Box 670
Lewiston, MN 55952

© 2022 PlastiCert Inc. All rights reserved. | Employees

Website design & hosting by Vision Design Group, Inc.