Purging Compound in a hot runner

[KyleH]

Hi All, new here but was wondering if any of you have experience with using purging compounds in hot runners? The purge compound supplier says its a go, the hot runner supplier says don't do it????? Any input????

Thanks

[Chris]

hey kyle,

welcome to the forum.

I have used a purging compound in a hot runner before, but it was not a multi-drop tool.

I have had great luck with ultra-purge in the past, seems to do a great job.

If it were me, i would listen to the manufacturer of the maker of the hot runner system.

Its not cheap to have them clean them out.

chris

[rickbatey]

I've used some in a manifold before, mostly for changing color. I like the Slide PDQ because you use it with your process resin. Why are you going to do this? That might be the bigger question. If for blockage or glass fibers; tear the manifold down and clear it out. Also don't lose your warranty if this is still intact.
I use the method Incoe recommends; turn heats up ~50*F, run screw rpm and back psi up to max, and extrude through tips. Great for clearing color out of valve gates drops.
Rick.

[Team JAG]

I agree, you should consider if there is a potential to lose your hot runner warranty before moving ahead.

I always told my customers that purging through our hot runners were fine under normal conditions. Some purge compounds can have abrasive or corrosive properties, but for short term usage under purging it is unlikely to be problematic to the system. However, different suppliers will make their own recommendations through experiences with their products and this should be evaluated beforehand.

Note - one theory about purging through the hot runner realted to temperatures: Raising the temps slightly above process temps, then letting the system cool down will pull the old material away from the walls and drops as it shrinks, then turning heats back on and flushing through will help the purge or color change process.

[Polyshot]

I agree with everyone here. There is a lot of back and forth on whether or not to use purging compounds and in which situations it's ok to use them. Kyle, I'd definitely make sure your supplier doesn't void the warranty for using it. Most don't, but better safe than sorry. Here are some of the main arguments

Argument: Purging compounds are all alike.
Fact: Purging compounds differ, and one size does not fit all; so choose the right one for your situation and it will serve you well.

Argument: Purging compounds just don’t work.
Fact: Purging compounds, like any other tool, work well when used correctly for the job intended.

Argument: Purging compounds are too expensive.
Fact: Purging compounds are a bargain when used to enhance productivity and avoid costly downtime and unplanned teardowns.

Argument: Purging compounds are hard-to-use/time-consuming
Fact: Some procedures are more demanding than others; but the results will justify the invested effort.

Bottom line is there are a lot more options and more advanced purging compounds available today than in the past. Ask the company you're buying the compound from whats the best product for you're situation and they should be able to help.

BTW are you using the purging compound for a color change or for some other reason?