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QSIMDO
07-16-2006, 10:57 AM
What would be an appropriate material to build a chip guard for fitting around the chuck on my lathe?
Something that wouldn't immediately scratch to totally opaque.

I've been considering Lexan but is there another I should consider?

Seems all the information here has resulted in the bare minimum of competence on my part and I've got hot, blue chips just a-flyin' everywhere!

More little burn marks than welding ever gave me. Must be a streak of masochism as I just stand there giggling with the old woman shaking her head. :)

LES A W HARRIS
07-16-2006, 11:06 AM
QSIMDO,
Lexan, (polycarbonate) does not shatter, Yes IMHO.
Acetates, nice and clear, will crack & shatter.

BobWarfield
07-16-2006, 12:28 PM
Those little blue buggers sting, don't they! I find I can stand where they are a minimum with the lathe, but there is no escaping my mill.

Not sure its worth building a guard unless you'd just like to. There are several possibles available commercially including flat shields as well as some pretty nice curved shields for your lathe.

For example, on flat shields:

http://www.penntoolco.com/catalog/products/products.cfm?categoryID=4210

I know there has been a curved shield making the rounds on the sale flyers recently, and thought it was also from penn, but I couldn't find it when I looked.

I grabbed this picture of a Chinese CNC mini-lathe because I really liked the travelling chip guard feature:

http://www.thewarfields.com/img/Toys/MachineTools/OthersProjects/CNC-Mini-Lathe.jpg

Building something like that would be the ultimate. I haven't seen one anywhere. You'd need at least one rail at top for it to travel on, and a way to lock it down on the apron while in use, and flip up when not in use. Sure would be nice, and you could run coolant behind it too without getting wet. This is a CNC, so you'd have to design one to clear the handwheels and such, but it could be done.

Best,

BW

DancingBear
07-16-2006, 02:03 PM
I think Lexan would be a pretty good choice, Flexbar makes them commerically and that's what they use. Acrylic might also work OK, at least for a while. I made one for my mill using acrylic, but I haven't had it long enough to comment on its lifespan. Regardless of which material you use, don't mistake the guard for eye protection.

If all else fails, you can back off on the speed and feed rate, and produce cooler chips! :D

Walt

Backyard
07-16-2006, 02:28 PM
Yes use Laxen, When i Make my Guards for my Mill and lathe i will use Laxan. I found out about Laxan in the Fire Department and that high rise windows use it and that you cant brake it with a Axe or cut it without the right saw blade and if you use a torch it melts together.

Rich Carlstedt
07-16-2006, 10:35 PM
Don't do what I did on my first Lathe guard...and I noticed that the Chinese did the same wrong thing on that CNC lathe.
Do not make the guard top flat and horizontal.
When you look down at the spindle, you will have nothing but glare.
I had to redo mine so it is slanted about 30 degrees towards the operator to eliminate the reflections.
Since no one has the same lighting situation as the next guy, take a blank piece of Lexan and put it ontop of the headstock area....you will see what angle is needed to prevent the problem.

Also lexan and Plexiglass are about 4 to 6 bucks a square foot (1/8)
while the other stuff is 1 to 2 bucks. I would not use less than 3/16 if you do heavy work like 3 pound pieces ie..
Rich

Fasttrack
07-16-2006, 10:40 PM
"More little burn marks than welding ever gave me."

I was just thinking about that a few days ago. My arms and hands have gotten to where little burns, or even bad burns don't really bother me anymore. I've still got plenty of feeling but i heal fast and i'm use to the pain- but when those little blue ones go down your shirt or hit you in the neck...ouch! It takes a good bit of concentration to keep from flinching when they nail me in the neck or face. Sure am glad i've got good safety goggles!

TGTool
07-16-2006, 11:08 PM
Fasttrack,

You sound like the guy I heard the story about. At the dentist, he was getting a particularly painful procedure but didn't even flinch. The dentist was impressed. "Boy, you've got quite a pain threshold! Doesn't anything ever bother you?"

"Oh, yeah," the guy said, "there was the time on that hunting trip I accidentally squatted over the bear trap. That was probably the second most painful thing that's ever happened."

"Second most!?!?" said the doc. "What was the most painful?"

"When I hit the end of the chain!"

snowman
07-16-2006, 11:53 PM
lexan scratches really easy. whatever you do, dont clean it with acetone. it will cloud up. It's still better than acrylic, which will shatter if something hits it.

So, lexan yes, use IPA and a very clean rag to clean it. If you have chips stuck to it, soak it down good with IPA, then use a paintbrush to try to loosen the chips, if you use a rag and drag them across, it will scratch up.

BobWarfield
07-17-2006, 01:12 AM
A couple of thoughts.

First, you may want a curved shield, like the one pictured in this link:

http://www.cnczone.com/forums/showthread.php?t=22508

That's the one I've seen in the sale flyers. It isn't cheap as I recall. Brings me to the second thought. You could make one of flat panels, or you could bend one up:

http://www.eaglerobotics.com/images/gallery2/main.php?g2_view=core.ShowItem&g2_itemId=1207

It takes a heatgun, but it's not that hard to work with. When you get done, if the plastic is hazy, or if you scratch it with chips, get some of the liquid plexiglass polish. Tap plastics sells the stuff and it works like a champ. Long ago, before I took up machine tools, I used to use it to make interesting "improvements" to PC's. Here is the machine I'm typing this out on now:

http://www.thewarfields.com/img/HotRodPC/UFOMod/Img_2774.jpg

I even made a water cooling block encased in Lexan:

http://www.thewarfields.com/img/HotRodPC/BorgCubeWaterCool/Img_2518sm.jpg

Fun stuff to work with!

Best,

BW

Peter N
07-17-2006, 03:19 AM
Polycarbonate (Lexan; Makrolon; etc) is really the only suitable material to use for any guarding. Acrylic will crack, not from small chips, but from any reasonable impact, whereas polycarb will absorb it.

Despite Snowmans recommendation don't clean it with isopropyl alcohol as this can cause stress cracking (looks like microscopic crazing). It will scratch and you may have to replace it every year or so depending on how bad it gets. With exposure to cutting oils and fluids this will affect the integrity (strength) of it over time anyway and cause embrittlement. A very mild diswashing liquid solution is about as strong as I would go to clean it.

Its a fantastically impact-resistant material but quite chemically pathetic.

To shape it you can heat it (slowly) with a hot air gun and bend it over a former held in the vice.

Peter

darryl
07-17-2006, 03:21 AM
Lexan would be the material of choice. What you could do is use two layers, one thicker which would be on the outside, and a thinner, expendable one for the inside. When it's messed up, try to clean it and if it's toast then change it. You can get 1/16 or 3/32 thick for this, and it's cheaper to replace. The thicker piece would give you a larger safety margin for impact resistance.

I would not use plexiglas for a shield because it can shatter too easily, and the pieces will be very sharp.

Lexan can be cold bent in a sheet metal bender, which shows that it has the ability to stratch without breaking. If you have some plastic on hand, and don't know what it is, try bending a piece. If it shatters, it's not lexan. If it bends without cracking, it's probably lexan, or if not it would still be better for a shield than an acrylic.

What you could do if you had some plexi on hand is use it for the inner part. It's a little more forgiving to cleaning, and if it shatters on you, the lexan outer window will contain the shrapnel.

SGW
07-17-2006, 12:02 PM
Mcmaster www.mcmaster.com and undoubtedly others sell "abrasion-resistant polycarbonate." It might be worth the extra money.

applescotty
07-17-2006, 12:22 PM
An idea for easily 'cleaning' the guard might be to buy some clear vinyl plastic, like what they sell at Walmart in rolls, used for protecting tablecloths and such. Cut that up into pieces that fit the guard. It should cling to the Lexan pretty well. When it gets too dirty, pull it off and put on another one.

applescotty

snowman
07-17-2006, 01:07 PM
IPA does not cause crazing. I worked for GE in their Lexan division and that is what we used. An IPA wash followed by DI H2O.

ttok
07-19-2006, 03:58 PM
Could you use a 3/16" piece of lexan (on the operator's side) and a piece of ordinary glass (on the lathe side) sandwiched together to keep the lathe side of the shield free from scratches? I have an old commercially made lathe shield which takes two transparent sheets of something (long gone when I got it on Ebay). Both openings are for flat sheets and have full perimeter aluminum framing. I am considering putting lexan/glass sandwiches in each opening. Seems that the glass would be prevented from reaching the operator in an accident, unless it fell out and was thrown around by the chuck. Might need some clear adhesive between the two sheets to prevent that. What do you guys think? A.T.

snowman
07-19-2006, 04:01 PM
It is very hard to find an adhesive that works. The change in temperature will mess with things. Glass and Polycarbonate have very different expansion rates.

Evan
07-19-2006, 04:09 PM
If you win the lottery you could have one made of transparent aluminum.

http://www.livescience.com/technology/051018_new_glass.html

smagovic
07-19-2006, 04:27 PM
BobW I really like your PC case. Very nice. You should consider to market it. I had a boss, he would have had went crazy to have something like that on his desk. Really nice. Vic