Plastics Technology: November 2011 Archives
I received this follow-up question regarding the processing of PVC...
I would like to know if it is safe to mold parts in PVC and acetal in presses that are next to each other?
It should be safe to process, but it is critical that you vent the fumes from both machines to prevent corrosion of your equipment. You should also take the time to educate your employees on the dangers of combining these materials.
It is critical that you create a system to prevent any chance of cross contamination. This may be as simple as a color-coded system so that the color of the container matches a panel next to the machine. Personally, I would create a fool-proof system where the container for VC is not compatible with the acetal material delivery system and vice-versa.
I was recently working with a company who had an interesting tale regarding the sale of one of their larger, older, hydraulic molding machines with a very large cylinder clamping unit and corresponding hydraulic reservoir...
When we were trying to sell one of these pieces of junk, my recommendation was to drain the oil and sell it for scrap metal or parts. Purchasing then told me they had agreed to sell the machine for a few thousand dollars, hydraulic fluid and all.
note: After a quick calculation, he explained to them that they had just lost money since the value of the hydraulic fluid currently in the machine is worth almost twice the amount they are getting for the machine.
Although complicated to quantify, most of these older machines are a real drag on the company and their resources. In this case, oil in the machine was more valuable than the machine itself. The machine was being sold because it was slow, unreliable, and wasting resources. It will provide the same drain of resources on the next molder who tries to operate it. Especially when your incorporate the expense of relocating, configuring, and hooking up the machine. In this case, I believe the engineer is right... the fluid should have been reclaimed and the machine should have been either scrapped or sold for parts rather than be brought back into service.
I was recently at a company with many older (30+ years) home-made molding machines. Although the machines have a large number of moving components and cams, the molder did a great job of adding full guarding around the entire machine. This guarding was not particularly complex, or expensive, but it is a great way to ensure your employees stay safe.
Make sure all your older machines are well guarded to protect your employees and your company from liability. Even though your machine was legal the day it was purchased does not mean it is not a liability today.