Cutting Plexiglass

[handh]

Ok, I need to cut a piece of plexiglass, I am going to be cutting 1/10 of a inch thick material. I am using a onsrud single flute upcut bit, I need some advice on what speed for spindle and also move speed. This is my first time with plexiglass so any advice is helpful.

[richards]

Jeff,

Onsrud has an excellent web site with recommendations for all kinds of plastics. You'll find the site at www.plasticrouting.com (http://www.plasticrouting.com). You'll probably want to start at about 18,000 RPM with a feed speed of about 1-1/2 ips to 2-1/2 ips.

[paco]

I'm assuming you'll be using either a 1/8" CED or maybe a 1/4" CED.

The smaller the CED the faster you want to spin (RPM) but not anything above 18 000 RPM in Acrylics. For 1/8" CED I set 14 000 with a 1 O-flute tool and 12 000-13 000 RPM with a 1/4" CED depending on the shapes.

If you have a very good hold down and mostly straight cut (say rectangles), you can fee it up to 4-5"/sec. with a 1/4" CED and up to 3"/sec. with a 1/8" CED.

If you're doing odd shape (say letters), I suggest you go slower (down to 50% of the above). I'm basing that on a 1:1 Alpha... I can tell with the new geared motor; it's supposed to be better though you could feed faster even in curvy parts.

[handh]

Thanks guys, I did the cut this morning. I used the 1 0 flute tool. I ran the spindle at 13000 rpm and used a 1/4" cutter and 2" a second. Everything turned out great, cut was smooth and the cutomer was very happy. The panels that I cut out was for panels to go on a screen door on a RV so that they could keep the air conditioner on and still see outside. It fit perfect.

[geneb]

What exactly is a "1 O-flute" tool?

Is it this?
http://www.plasticrouting.com/Products.asp?Action=View&ID=1493&Page=Material

tnx!

g.

[paco]

Yes, that's on model from one brand. O-flute refer to the flute shape... know what the flute(s) is? Regular spiral bit have more like "V" shaped flute(s). O-flute are really round (O)... and preferably polished.

[geneb]

So it's basically a single flute tool with a twist, as opposed to a single flute, straight tool?

tnx.

g.

[geneb]

Another thing I just thought of - is this tool type good for pocketing operations?

tnx.

g.

[paco]

Not exactly; it's a single O flute spiral too bit. Flute shape is different than edge shape. There are V flute tool AND O-flute tool with straight edge AND spiral edge. If you have both in your hand you'll notice the flute shape. O-flute tend to be more larger AND round so they can expel the chips better. V- fluted are more rigid and thus can withstand heavier load (aggressive feed rate). Both flute shaped tool bit can be single fluted or two flutes. V-flute can accommodate up to 4 flutes on large diameter tools.

Does that make sense? What are you looking for exactly? You want the right tool for plastics?... or learn something new about tool bits?

[paco]

Pocketing with an O-fluted? Depends on the material...

[geneb]

Thanks Paco. I'm actually trying for both.


I've gotten comfortable with cutting plywood and MDF with my 'Bot, in fact it made my new cabinets for my shop a breeze.


I'm going to have to start working with acrylics and other plastics soon and I want to make sure I'm not going to have problems with melting, etc.
I figure if I start out with the right types of cutter, I'm already a step ahead.


The operations I need to do on the 'Bot will mostly be pocketing - I'll be cutting the profiles out on my laser as it will give me the smoothed edge I need without having to learn how to flame-polish the material.


Are any of the cutters that are included in the "starter" kit that ShopBot sells practical for pocketing plastics?

tnx!

g.

[paco]

Pocketing in plastics; depending on the required finish, you may use any bit that can cut the material but I've read and heard good things about Onsrud 66-300 (60-350 for metric) series. I cannot say if they pocket better than the cutter ones but if the tool cannot move more than it's radius in tight details, the cutter bits will leave a nipple while this bottom surfacing bit should be machining flat from a straight plunge. I'm considering trying one but they are quite expensive and very short cut length.

[geneb]

Thanks for the help Paco.

g.