Age of Plastic Blasting Media for Elastomers

[Llm89]

Hi
As an aerospace engineer I have come across an issue related to plastic blasting media.
Our supplier uses plastic blasting media to clean off (Deflash) molded rubber from the metal plate into which grooves the rubber is molded. Fragments of old plastic media may get embedded in the molded rubber. Yet the supplier uses guidelines such as "Too dusty to see through the chamber window" for replacement of the plastic media. I could not find any guidelines in specs. or literature? Any ideas?

Thanks,
LM

 

[MintJulep]

Have you contacted the media manufacturer?

Lacking any established standard, how about defining a standard target (steel plate with known thickness of paint perhaps). Blast at defined distance and pressure and measure time to clean off the paint. If it exceeds some time, replace the media.

 

[BillPSU]

When using any sort of blasting process the media will either fracture or be worn away by abrasion. When using steel shot or grit the cyclone dust units remove the smaller particles and the shot falls through the cyclone. Plastic media will do the same thing in that it is probably fractured when it impinges on the object being blasted. Without some sort of method to removing the fines, watching the appearance of the blasting chamber is probably an acceptable method for changing the media.

A sifting screen could be a way to seperate the fines but the screens themselves will be subject to wear and will need continual monitoring. I do not believe the cyclone units could differentiate between plastic fines and media. You might check with the cyclone dust manufacturers they may be able to seperate.

 

[unclesyd]

I have never seen a standard on recycling plastic media even though we made it. If there isn't a separator on the blasting system it is up to the operator to determine if the media is effective, unless he is just making 8. Normally a blasting media quickly becomes ineffective if there is very much particle attrition and dust. This loses money which is the same as cash.

There was a recommendation on using the media in small cabinets, not due to dust but to heat build up causing the media wanting to stick to the part being blasted. When we used plastic media we used it as a one through system and then ran it through a screen classifier with dust collection to keep the average particle size large.

As stated, one time we compounded a material for blasting media but got out of the business due to a lawsuit stemming from an explosion in a blast room. I wasn't privy to any of the proceedings but we were led to understand that they were recycling the plastic media and paint particles with dust collector not functioning correctly and when the door to the booth was opened there was an explosion. Though no source of ignition was determined, it was strongly thought that a person who had just left the booth was lighting a cigarette.

 

[Ron]

Frequently check the gradation of the media against its specification. If more than 10 percent out of any sieve, replace it...particularly the finer sieves.