Question about PP

[Hannu Rinne]

Hi to all,

Has anyone cut PP ( polypropylene ) and is it safe material for laser ? I "must" cut about 300 pieces really odd shaped coverings and the problem is that I can't make the cutting with the ideal focus - stays more than 50% off the ideal point, but seems that I can still cut it somehow with 2-3 passes... Funny, in this case the price, quality and the time are not the main issues as usual - I can charge a lot, I'm master to make bad quality and normally I'm really slow - - but I'm not sure that can I do the needed job ( sorry, the main question was the safe of PP... )

Regards, Hannu

[Michael Hunter]

Polypropylene is perfectly safe to cut (it's just a hydrocarbon material and should not have any nasties incorporated in it).

Watch out for flareups in the machine!
The waxy smell might be a bit unpleasant - do it on a windy day!

Could you make a jig from plywood or MDF to hold it flat?

Masking or transfer tape on both surfaces would probably make the cuts cleaner, but if the tape doesn't stick well, could make flareups much more likely.

I find with this sort of material that lots of power and air-assist helps get through cleanly in one pass.

[Richard Rumancik]

You might be able to cut polypropylene but the edge quality will not be very good. It is not on the "prohibited" list of laser materials.

PP will tend to melt back on itself. It is only a bit above wax as far as polymers go - in fact it will smell like candle wax when cut.

I have tried cutting thin polyethylene but the edges were not acceptable for my needs. You do not say the thickness. The thicker it is, the more difficult it will be as it will try to weld itself back together from the melt.

I don't know what you mean about being 50% off the ideal point with your focus.

[Andrea Weissenseel]

PP is save to laser, but it does not cut well at all. I ran y lot of tests with it, and most result were that the cuts melted back together as soon they where cut.

Andrea

[Hannu Rinne]

Thank's for your replys !!

Michael; From the pictures you'll see there's not any chance to keep the area flat... this was the "best" possible position for the item to cut ! About the smell; in Finland, here's only windy days - so every day is perfect for cuttings

Richard; The thickness is 4mm. With the 50% I meant the distance between the item and the lens. In my laser(s) I have 2" lens and in this case I had to leave the distance to 3" - I couldn't go any closer to this item, because for the shape of the cover...

Andrea; I agree 100% with you - I made 11 passes before cutting through the larger area ( in the pictures ) - just watching frustrated when it was melting back together !

Final conclusion; I'm going to refuse and I'll try to find some other unnecessary works to do

Best regards
Hannu

[Doug Griffith]

Looks like a 5-axis router job to me. We cut prisoner seats out of poly all the time. A laser just isn't the right machine for a job like that.

[Hannu Rinne]

Doug,

I agree with you ! Also shaped punch with press will do the needed job, but might be quite expensive solution for this size quantity (~300 pcs)... About your picture; is it from police car or some similar vehicle ? ( just curious )

Regards
Hannu

[Doug Griffith]

Doug,

I agree with you ! Also shaped punch with press will do the needed job, but might be quite expensive solution for this size quantity (~300 pcs)... About your picture; is it from police car or some similar vehicle ? ( just curious )

Regards
Hannu

The pic is from a police car. The company we work with is http://www.laguna3p.com

I'd think that punching pp that thick on multiple axis would require a matched steel die and a big a$$ press!