Extruded Acrylic

[bill]

The artwork panel is cast acrylic but the base is extruded. This current base extruded Acrylic (Evonik Ind. by Cyro Ind.)cuts like chewing gum! I have tried from 3 flute, low helix to "O flute" sytle tools, even from different tooling suppliers. I have tried a variety of feeds and speeds. Normal machining for this part is about 6 min. and with the tool gumming (with just THIS BRAND NAME) I have to stop and clean the tool and contimue resulting in the machining time to >25 min. I have 7 5'x8' sheets of this stuff to be cut into a BUNCH of 2.5"x10" project pieces OR sit and cry in my beer for weeks on end! The supplier is no help and the mfg. will not talk unless you are a whlse buyer.
Problem: 1/8" tooling gums up (big time) and will snap the tool off. 1/4" tool gums and mars the edge where the tool needs to slow down.
P L E A S E help!

5174
5175
5176

[rb99]

Is gumming up not caused from the plastic melting?

Is melting not from too much heat? I would suggest going faster and turning down the router speed.

Also directing a jet of air at the bit might help as well.

Are you actually getting chips before it gums ups?

RIB

[bill]

Melting, without a doubt. With the cutting depth @0.1" tried combinations of 10Krpm (slow as I can go) thru 19Krpm with feeds from, 0.5ips to 2.0ips. Yes... I do get chips (better at the lower rpm) and cuts well but then all of the sudden the evil acrylic witch makes it start to wrap up. I'll hook up some air and try that. Thanks.

[cnc_works]

I feel your frustration...been there, done that.

It has been so long since I tackled that challenge that I forget the feeds/speeds that began to approach acceptable quality. The reason it has been so long is that I gave up on extruded plastic altogether for cutting on the CNC.

Good luck!
Donn

[rb99]

I was going to mention as well there are different types of plastic...

If you have the wrong type can you exchange or return what you have?

RIB

[bill]

Agree... extruded is not the best but this brand name is the worst! The new "Optix" by Plaskolite, Inc. brand extruded seems to machine very much like cast but with the extruded price.
Must keep in mind, I am woodworking oriented. This acrylic stuff is all new to me. It's just that when the jobber sends me the material for the task I need to be able to bid and deal with it. This job, thinking extruded was extruded, I unknowingly estimated @3.5hr while actual ended up @11.5hr.! No fun.

[rb99]

This might be way out there but would spraying a mist of water while cutting relieve the problem?

I am thinking enough water to sort of pool on the top surface as well to keep the bit cool and wet...

RIB

[bill]

Euew... don't know abut the water thing, with UDF vacuum and all. Have contacted Vortex and have ordered a few 2 straigh flute "O" flute tools. They feel due to cutting producing chips and then start gumming up as inconsistant mixing in the (inexpensive) material. Probably just this jobber trying to save a few bucks. All-in-all is a good learning tho somewhat expensive and frustrating.

[mikeacg]

Thanks for the heads-up Bill! I do most of my acrylic on my laser but with a 12 x 24 size limitation I have been tempted to try it on the Bot. Now I know what to look out for!!

Mike

[jim_ludi]

I think that I'd try cooling the bit with cold air guns like these: http://www.airtxinternational.com/air_guns/?gclid=CNfOjbfC1J0CFYNX2god_GUvSQ
http://www.vortec.com/cold_air_guns.php

And, there's a forum discussion on air cooling bits, with a cheaper option by Gary Campbell, at http://www.talkshopbot.com/forum/messages/15719/27082.html?1208916270

BTW, that's great looking work that you've posted.

[bleeth]

Been doing plastic signs lately and got a deal on some 1/2" extruded for the punch through letters.
First time I did extruded and sure had issues at first. I used single flute O flute and cut at 8k RPM and 1"/sec. No extra cooling. The bit was an up cut 3/16D (Onsrud). For cast cut with same bit but faster on RPM and speed. Up-cut fights holddown but gets more plastic out of the way.

[navigator7]

Richard wrote:
"I was going to mention as well there are different types of plastic. "

Richard, what is the brand of some carve able plastic you know?

Bill's problem reminds me of issue I had turning UHMW in a large manual lathe.

We were making rollers for the phone company and these chips wanted to reach out and touch somebody.
I once had a chip reach out into a previous pile, suddenly snag and I had a ball of UHMW as big as a four or six yard dumpster attacking the lathe chuck.

We later sent some UHMW to a cnc shop and discovered the CNC machine had a "peck" feature. The machine would cut and stop and the air blast kept the cutting area free. Only tiny little chips were produced.

@ Bill,
You said the plastic machines like chewing gum?
What about using dry ice to give the plastic some chill?

[rb99]

I am not sure. I have seen extensive spec sheets from GE Plastics though. I bet a search would yield something, or talk to your plastic suppliers about what works.

RIB

[bill]

As they say "spilt milk under the bridge" er sumfin' like that... the job is done, delivered and a happy customer.
For now, in belief that it was a bad batch of acrylic with consistancy at fault (fingers crossed). The next time will bid higher on this brand of material just in case. I am going to set up for cooling air as well. Want to thank all for your help! Vortex (tooling) suggested the straight, 2 flute O flute to try and prevent the wrapping issue. Have off-cuts to experiment with once the straight O flute tooling gets here and will let all know what becomes of it all.
Once again, Thanks to all.

[navigator7]

Never heard of O flute so I googled it:

http://www.toolstoday.com/p-5879-solid-carbide-spiral-plastic-o-flute-up-cut-down-cut.aspx

[clueless]

I cut some extruded, although it was 1/8", but used a 1/4" O-flute, single flute. Cut very nice and left a decent edge as well.

[bill]

... just give an initial close watch if the material is brand named Evonik Ind. by Cyro Ind. That's the only extruded material brand I have had problems with.

[carlcnc]

Bill
could yu share source /techniques for the led strips that you use?
thanks
Carl

[magic]

Is it possible to do some of the perimeter cutting on a table saw>

[jerry_stanek]

what bits are you using to engrave the clear acrylic?

[bill]

@ Carl, http://www.environmentallights.com/categories/1303_2398_3408/regular-led-strip-kits is where I started. I have found some less expensive places to buy but they ALL originate from China. Only to eliminate the middle man, I now order quantity from China to save a few bucks.

@ magic
Yes, can do the parts cutout on the table saw.

@ Jerry
Have had good results with Vortex brand tools. 90' and 60' V tools.

To all: The artwork panel is cut in the back of cast material because it's a MUCH cleaner cut. The base is whatever off-cuts I may have in the shop.

[carlcnc]

Bill
thanks,
any chance of buying a couple sets of strips ?
I've been wanting to do a couple as gifts for years.
email is in my profile
Carl

[bill]

Carl,
My e-mail is down.... will try again this evening.

[joe]

Bill,

I want to complement you and the excellent website. It's the kind of layout I really like. Not a bunch of fly-outs, just strait forward good views of you work.

Joe
www.normansignco.com (http://www.normansignco.com)

[bill]

Joe,
Thank you! That's going into "Bill's Ego Book" for sure. :-)

[aaasigncom]

I SPRAY PAM ON THE BIT TO HELP THE BUILDUP

[bill]

Hummmm.... gonna have to try that. Thanks.
I'll have to sneek into the kitchen while the wife's not looking.

[robtown]

Butter flavored? Or regular?

[aaasigncom]

garlic - keeps the vampires away too

[jerry_stanek]

With the vampires just tell them you are cutting wooden stakes.

[aaasigncom]

i agree with all of you. it doesent seam to matter about bits and speed when cutting this material. you can have several good cuts, then for some reason the next one will be bad. i figure in an extra blank when doing this kind of work because because of these problems.
> bill l looks like your surface is not level,
the stroke of the letters gets wider on the right side of your piece. when the z depth is important, i usually take some scrap and cut a pocket to fit the piece i am working with. that way i start off with a perfectly flat surface. *** i have several cases of 8" x 10" acrylic award blanks with beveled edges for sale if anyone is interested $ 12.00 each

[bill]

Thanks for everyone's support here in the forum and to Brian at Vortex Tools. Sent material to Vortex for them to experiment with. Ta-Da!!!!!! Vortex 4200 tool series makes short work of the problem material. Once again, many thanks to all.