[Spinnetti]

Got a new 1100 Series III last summer, and almost instantly, the acrylic looking slide in front guard for the semi-enclosure crazed and spidered like crazy. I used Tormach everything, including their supplied coolant at the mix specified. Anybody else get this? Bad Plastic? It doesn't worry me overmuch as I hate that thing (can't use the 4th axis with it anyway), but was a bit surprised so thought I'd compare notes. I'm using the shower curtain method now, but would really like more of a real enclosure with big sliding door.

[toothandnail]

No problem with our 2 , however they do seem to bow in more over time,(close to .75") enough so that if they are off for any length of time , I lay them down on the handles and put about a 2# weight in the center.

[mike sr1]

Got a new 1100 Series III last summer, and almost instantly, the acrylic looking slide in front guard for the semi-enclosure crazed and spidered like crazy. I used Tormach everything, including their supplied coolant at the mix specified. Anybody else get this? Bad Plastic? It doesn't worry me overmuch as I hate that thing (can't use the 4th axis with it anyway), but was a bit surprised so thought I'd compare notes. I'm using the shower curtain method now, but would really like more of a real enclosure with big sliding door.

I dont know about coolant doing this but we had some electrical cleaner in a spray can that would destroy a lexan guard in about 15 minutes, it would spider crack around the bolt holes and fall off the machine.
This was 30 years or so ago and I dont remember what the cleaner was composed of.

[BAMCNC.COM]

I use Koolmist here, no issues other than bowing from me leaning it against the stand. I have the short and tall lexan guard.

[nitewatchman]

Got a new 1100 Series III last summer, and almost instantly, the acrylic looking slide in front guard for the semi-enclosure crazed and spidered like crazy. I used Tormach everything, including their supplied coolant at the mix specified. Anybody else get this?

I have had my Series II about 18 months and the plastic front guard did the same thing with a few months. I also use Tormach coolant and way lube.

nitewatchman

[SCzEngrgGroup]

Is that guard Lexan (polycarbonate) or Plexiglas (acrylic)? They are massively different in their tolerance to abuse. I've had a Plexiglas enclosure on my machine for years, and it still cleans up almost like new, with just Windex. Lexan is bullet-proof, but surprisingly easy to do cosmetic damage to.

Regards,
Ray L.

[LeeWay]

I use Koolmist 77 and I can tell you that it will deteriorate polycarbonate.

I have replaced several pieces because of it.
It seeps into the plastic somehow (it is porous) and unlocks the molecular binding. It will crack and craze and you can snap it with your hand. Totally the opposite of what you want polycarbonate for. I use a few different brands of it, so some brands may be different from others.
I know too, that you can get it with different properties and surfaces. It may be that typical machine guarding has a different coating on one side.
I know the plain stuff I use will not last long around any holes drilled in it.
The rest of the sheet still appears okay, but discolored. You can bet that it would no longer take a large impact.

[SCzEngrgGroup]

KoolMist 77 has no discernable effect on acrylic. It's all I've ever used.

Regards,
Ray L.

[LeeWay]

Right. As mentioned, acrylic and polycarbonate are two different animals. One is designed for machine guarding, the other is not.

[nitewatchman]

I have a long history with machine guarding and would not consider guarding made of acrylic. I believe that OSHA also shares this opinion.

I have had 3/8" polycarbonate (Lexan) stop a 1 foot long piece of 136# rail when it has broken in a bend testing machine loaded to 550,000 lbs with no more than a gouge in the surface and a noise that sounded like a train wreck. Acrylic lacks this impact resistance and as is sometimes seen will even crack around bolt holes when the screws are lightly tightened.

Polycarbonate can be bent in a press brake like metal. On project for a control cab window we required 1/2" Polycarbonate to be bend (cold) to a 75 deg angle, the edges may flare slightly (trim after bending) but it will not crack.

nitewatchman

[LeeWay]

Ditto here.
I make blade guards for table saws. You don't want to make those out of acrylic.

[kevinro]

My guard did the same thing. I just went all shower curtain.

Polycarbonite is definitely the correct material in terms of stopping materials. Acrylic shatters into sharp pieces, polycarb deforms and absorbs energy.

[keebler303]

There are abrasion resistant and other coatings for polycarbonate. Perhaps there is a coating that would protect it from chemical degradation?

http://corporate.plaskolite.com/prod...ting_imhc.html

Matt

[BAMCNC.COM]

Wonder what normal spray clear coat would do?
Or a Rain X type product, maybe xzilon or however its spelled.

[mayhugh1]

Polycarbonate will quickly fog and then eventually craze if it is exposed to alcohol. I had to learn this twice. The first was when I treated my brand new $400 motorcycle windscreen with Rainex. The second was in my model building when I tried to use polycarbonate for sight glasses and other parts that made contact with my alcohol based fuels. Within a few months the parts crazed to the point that they became opaque. - Terry

[keebler303]

I would think spray paint would not be good for it. Lots of petroleum distillates in there. There are polyester films meant to reinforce glass windows and keep them from shattering due to vandalism or a storm. 3M makes a bunch of them.

3M? Safety & Security Window Films - Residential safety and security window film for homes - 3M US

Matt

[MichaelHenry]

Ethanol will craze acrylic very quickly - any chance those of you with problems used that as a coolant (or even cleaner) one time or another?

Mike

[nitewatchman]

Ethanol will craze acrylic very quickly - any chance those of you with problems used that as a coolant (or even cleaner) one time or another?

Mike

No chance unless it is in the Tormach Coolant. The "crazing" on mine looks more like internal snow flakes in the plastic. It is not on the outside as far as I can tell.

Also I am fairly sure that this is not acrylic, mine at least would have cracked around the bolt holes as it goes in and out of the machine pretty often.

nitewatchman

[GLCarlson]

Here are two links which detail chemical resistance of several classes of polymers, including polycarbonate:

Plastic Chemical Resistance
Plastics Chemical Resistance Chart

The second chart is a general summary.

PET (polyester), the 3M material Keebler mentioned, is a bit more stable to oils and hydrocarbons than polycarbonate. Bit better against some oxygenated solvents, too.

I suspect that a layer of the 3M material, on top of polycarbonate on the inside, would be a pretty durable combination and might be a good way to protect an investment in polycarbonate safety enclosures. Might be worth a try, depending on cost.

[LeeWay]

You would pay about 2.5 times as much for polycarbonate with a scratch resistant coating. I'm talking Lexan from GE and Margard coating. It does have UV inhibitors as well as a longer guarantee, so may be work it.