Shenzhen Alu Rapid Prototype Precision Co., Ltd.

Yes, Delrin (acetal homopolymer) is one of the most common engineering plastics used in injection molding. It is highly valued for its high strength, rigidity, and low-friction properties, making it a "go-to" material for mechanical parts like gears and bearings.

However, molding Delrin requires more technical care than standard plastics like ABS or Polypropylene. Here is a guide to the best practices, challenges, and safety considerations:

1. Why Delrin is Molded (Key Benefits)

A.Mechanical Performance: It has the highest fatigue resistance of any thermoplastic and excellent creep resistance.

B.Low Friction: It is "self-lubricating," making it ideal for sliding parts and gears.

C.Dimensional Stability: Once cooled, it holds its shape very well and absorbs very little moisture compared to Nylon.

D.Surface Finish: Molded Delrin parts naturally have a high-gloss, premium-looking surface.

2. Technical Challenges

Molding Delrin is more difficult than molding its cousin, Acetal Copolymer, for a few reasons:

A.High Shrinkage: Delrin is a semi-crystalline material. It shrinks significantly as it cools—typically 1.8% to 2.5%. This must be accounted for in the mold design to avoid "sink marks" or dimensional errors.

B.Centerline Porosity: Because it cools from the outside in, homopolymer Delrin (unlike copolymers) often develops a small "porous" area in the center of thick sections. This usually doesn't affect performance but can be a concern for medical or high-precision parts.

C.Warping: Due to the high shrinkage rate, thin or non-uniform parts are prone to warping if the mold temperature isn't strictly controlled.

3. Critical Processing Parameters

A.Temperature Control: The standard melt temperature is usually between 205°C and 225°C (400°F–440°F).

B.Hot Molds: To get the best surface finish and dimensional stability, mold surface temperatures should be kept high—ideally 80°C to 120°C (176°F–250°F). Cold molds will cause the part to shrink after it leaves the mold, leading to size issues later.

C.Drying: While Delrin absorbs very little moisture, any surface moisture can cause "splay" (silvery streaks) on the part. Pre-drying at 80°C for 2–4 hours is recommended.

4. Vital Safety Warning: Formaldehyde Gas

This is the most important part of molding Delrin: Do not overheat it.

A.Thermal Decomposition: If Delrin is heated above 238°C (460°F) or left in a hot barrel for too long (over 30 minutes), it will decompose and release formaldehyde gas.

B.Danger: This gas is highly irritating to the eyes and lungs and is a known carcinogen.

C."The Pop": In extreme cases, the gas pressure can build up inside the injection barrel and cause a "blowback" or "mold pop," which can be physically dangerous.

D.Incompatibility: Never mix Delrin with PVC or other halogenated plastics in the same machine, as this can cause a violent chemical reaction.

Summary: 

Use Delrin if you need maximum mechanical strength and fatigue resistance (e.g., a gear that must turn a million times).

Use Acetal Copolymer if you want something easier to mold, with less shrinkage and better resistance to hot water or strong bases.