Silverstreaking in PVC

PVC polymer chains break easily when they encounter shear. Any processing or equipment changes you can make to reduce the shear on the material will significantly improve your process. Question: We have tried increasing and decreasing the mold temperature. We have also tried to reduce the barrel temperature with the use of a blower fan but we cannot eliminate […]

Practice what you Learned

Just because you know the parts is supposed to 90-95% full does not mean you are actually practicing it. In a recent on-site training session the participants all understood the importance of molding a part short during 1st Stage Injection, but learned an important lesson in the lab. Situation: In lab, we were establishing the first stage […]

Check the Melt Temperature

Unless you actually measure the melt temperature, you really do not know what is happening with the material. Recently at a molding facility, we encountered a 65 F (36 C) difference between the melt temperature and barrel temperature. Comment from Technician: We always have to to run this mold with a hot material to get it to fill. […]

Is MFI Better than Nothing?

Having the Melt Flow Index of a material does not provide a real picture of how the polymer will actually process, but it can be a helpful indicator in some cases. This post will outline an example of how the data can be of use to a technician. Question: MFI is not supposed to be an accurate measurement of […]

Rear Zone Temperature Study

It is critical that your perform a rear zone temperature study on each of your molding machines. Just because two machines have the same brand and are running the same material, the optimal rear zone temperature is most often different. Question: We run the same grade of PP on all our jobs and all the […]