Cutting Sintra

[GVP]

Greetings,

Does anyone have any tips regarding cutting out simple flat panels of 1/8" Sintra?

I'm finding if I use an up-spiral bit, it lifts the material off the bed in places and can cause the shape to come away, often hitting the bit and ruining it.
If I use a down-spiral, the kerf fills up with the chips and often re-welds itself back together. Perhaps I need better feeds/speeds? Currently around 16000rpm & 125ipm using a 1/8" bit.

Any suggestions appreciated - we don't have a vacuum hold-down and clamp everything down.

Thanks,
Graham

 

[letterman7]

125ipm? You sure about that? Way, way too fast if it is. Back it down to 2, maybe 3 ips depending on your machine. Are you using a climb cut or conventional with the upspiral? Try cutting the opposite way with the upspiral and see if that changes anything.

 

[Techman]

compression bit.
Up cut on the lower side down cut on the upper side..

 

[J Hill Designs]

125ipm? You sure about that? Way, way too fast if it is. Back it down to 2, maybe 3 ips depending on your machine. Are you using a climb cut or conventional with the upspiral? Try cutting the opposite way with the upspiral and see if that changes anything.

Just checking my math here, but doesnt 2 IPS = 120 IPM?!?

 

[Z SIGNS]

Glue it down to a sacrificial sheet of coro and use tabs if need be.

 

[Ditchmiester]

Use a straight O Flute From Onsrud, They cut with no up or down pressure. I cut plastics with them all day long. I love them. I run about 12K RPM and 100IPM.

 

[SebastienL]

one pass with the up cut, leave .025" on the bottom(Don't break thru) and .025" on the wall. Finish with the downcut.
Upcut will evacuate chip better, Downcut will leave a cleaner edge on top.
If it's very small part.... Transfer tape on the back, Spray "3M Super 77" or equivalent glue on the tape. Just peel off after cutting.

 

[letterman7]

Just checking my math here, but doesnt 2 IPS = 120 IPM?!?

:Big Laugh yes it does... I read his post as IPS instead of IPM..

 

[synergy_jim]

1/8" 2 flute straight - 2 pass - 300 ipm 18000 rpm

1/4" 2 flute straight - 1 pass - 400 ipm 20000 rpm

1/4" 2 flute downcut spiral - 400 ipm - 20000 rpm



The enemy of thin plastic is any upcut bit.

 

[synergy_jim]

also.... the worst thing you can do on a cnc cutting PVC is run to slow. the second worst thing is bad bit selection.

 

[fixtureman]

I use a .125 single flute up spiral bit at 10000 and 4.5 IPS

 

[johnnysigns]

I'm running these right now: https://www.onsrud.com/product/Item...nid=D95555493C10BFF78BC39E3078F440BB?q=63-710 I'd normally use these on mirror/hard plastics

1/8" - 1/4" PVC
Generally 60-120 IPM at 12500RPMs
Good chip evacuation
Super Clean cuts
Very little part movement

I usually run double spiral up cuts too, but they were moving my parts around too much so we switched to these.

 

[fixtureman]

I also use a pressure foot at times to keep it down