Common Plastic Extrusion Defects and How to Troubleshoot Them

Plastic extrusion is one of the most commonly used plastic manufacturing methods that is used to create a wide variety of plastic products. However, this manufacturing method isn’t susceptible to defects.  

Let’s have a look at some of the possible defects and how we can troubleshoot them…

Rough Surface Finish 

This could be a dull, uneven, or textured finish, either way, it is not the desired finish an extruder is looking for. This could be caused by a range of things, including: 

• Incorrect temperature of the die 

• Moisture in the polymer 

• A worn or dirty extrusion die 

• Contaminated raw materials 

To fix this issue, there are a few things that you can do, including: 

• Check the temperature of your die – compare your die temperature settings to the recommended seconds to ensure it’s not too hot or too cold. 

• Ensure your resin is properly dry, using a desiccant dryer. 

• Inspect the die before using to ensure there are no scratches, dents or marks that may affect the final product. 

• Thoroughly check the raw materials that will be entering the machine to ensure there is no contamination. You can also screen out fine dust and dirt. 

Bubbles or Air Pockets 

Bubbles or air pockets in your extruded material can be a result of moisture in the raw material, air that has been trapped during the process or gases that have been produced from overheated polymers. But don’t worry, these things are preventable if you follow the following steps: 

• Properly dry materials before processing to avoid bubbles or air pockets. 

• Install vacuum venting in the barrel, so any bubbles are vaporised and pulled out of the material. 

• Reduce the melt temperature if degradation occurs – this will stop bubbles forming. 

Warping/Distortation 

Some materials may come out of the extruder with bends, twists or curls, which can be caused by uneven cooling rates or excessive stress during drawdown during the process. This can be frustrating when working under a time limit or when you have limited materials, so here are a few things you can do to reduce the risk: 

• Adjust the cooling system for consistency in the materials/final products. 

• Reduce the speed of the puller to ensure the same pressure is applied across the material. If the puller is too fast, it risks distorting the material. 

• Use annealing if necessary – this is a second form of heating, which allows you to adjust the shaping of the final product manually once it is out of the extruder. 

Poor Fusion 

This can occur when the extruder’s melt temperature is too low or there is insufficient pressure on the die, which can cause the material to crack or split. These issues can be solved by: 

• Raising the melting temperature to allow the materials to fuse together properly. 

• Adjust the screw or die pressure to help bond the plastic materials together. 

• If blending materials together, check compatibility between materials to ensure they will be fused together. 

Hopefully, these points will help you create a smooth plastic extrusion process, and you won’t face any issues. If you do face any other issues that you are unable to troubleshoot, or you have any general plastic enquiries, feel free to get in contact, and we will be happy to help!

For more information on Common Plastic Extrusion Defects and How to Troubleshoot Them talk to Rayda Plastics Ltd