What is decompression in injection molding?

What Is Decompression in Injection Molding? 🏭
You've probably heard of injection molding - but have you ever heard of decompression?
It's one of those small settings that makes a huge difference in part quality. Let's break it down 👇

🔩 Quick Recap: How Injection Molding Works
A screw inside the barrel melts plastic pellets and injects the molten material into a mold under high pressure. The plastic cools, solidifies, and - pop - you get your part.
Simple enough. But here's where it gets interesting.

❓ So What Is Decompression?
After each injection, the screw pulls back to prepare the next shot of material.
But there's a problem - residual pressure is still trapped in the nozzle and barrel. That pressure forces molten plastic to ooze out of the nozzle like a leaky toothpaste tube, causing:

💧 Nozzle drool
🕸️ Stringing or wisping
⚖️ Inaccurate shot weight
❌ Defects in the next part

That's exactly what decompression fixes.
The screw pulls back a tiny extra distance to actively suck the pressure back, stopping the melt from leaking out between shots.

⚙️ Two Types of Decompression
TypeTimingPurposePre-decompressionAfter plasticizing, before mold opensPrevents drool during mold openingPost-decompressionAfter injection, during screw recoveryPrevents leaking during refill

📐 How Much Decompression Do You Need?
Typically 2-10mm, depending on:

Material viscosity - lower viscosity materials flow more easily and may need more decompression
Nozzle type - open nozzles need more; hot runner systems often need less or none
Processing temperature and injection speed

⚠️ More is NOT always better. Too much decompression sucks air into the barrel, causing silver streaks, splay, or bubbles in your parts.

✅ One-Line Summary

Decompression is the machine taking a tiny "breath in" - pulling back pressure so molten plastic stays exactly where it should between shots.

It's a small parameter. But get it wrong, and you'll be chasing defects all day.
Get it right, and your process runs clean, consistent, and efficient. 🎯

Found this useful? Save it for your next molding troubleshooting session 🔖

Drop your questions in the comments - let's talk molding! 💬
#InjectionMolding #Plastics #Manufacturing #MoldDesign #ProcessEngineering #Decompression #Plasticsindustry

Contact : Annie He
Mob:+8615917239823
Company name : Shenzhen Alu Rapid Prototype Precision Co., Ltd
Address: NO.1605, Hongyu Building, Longhua Street, Longhua District, Shenzhen, Guangdong Province, China 518109

Shenzhen Alu Rapid Prototype Co., Ltd.
Our company is a professional manufacturing service provider, offering a wide range of advanced manufacturing processes, including CNC machining, Vacuum Casting , 3D printing, injection molding, sheet metal fabrication, and various precision machined components services.

This release was published on openPR.