chip shields

[Loose nut]

I would like to make some curved chip shields to put around the cutting area of the mill, just to keep the chips under control, does anyone know of a good way to bend or mold materials like lexan or Plexiglas.

 

[BobWarfield]

Pretty sure you want Lexan (polycarbonate) not plexiglass as the latter will shatter.

You can use a heat gun and a form to bend the Lexan. I understand it has a lot of springback, so you'll want to experiment with how far to bend it.

Best,

BW

 

[gary55ford]

Try cutting say a 4inch dia. piece of poly tubing in half

 

[greenie]

Do a Google for 'How to bend Plexiglass', plenty of information available, like this lot,

http://www.wizdforums.co.uk/showthread.php?t=4119

regards radish

 

[Rog02]

As Bob mentions "Lexan" or equivalent poly-carbonate is the preferred material. "Plexi-Glass" will shatter resulting in some nasty shards.

As for bending procedures? The overall design will dictate how to proceed. A folded design is the easiest and can be done with a simple shop built heater made from some scrap wood, aluminum, and a piece of heating element from an old space heater or toaster oven. For a sweeping curve the entire sheet will require heating which can be done in a kitchen oven providing it is not too large. The sheet will be supported at the perimeter and slid under the broiler element. When the material begins to sag it is removed from the heat source and draped over a suitable form shape.

"Lexan" can also be cold formed in a sheet metal brake, but as Bob mentioned the spring back is a factor and therefore over bending is needed. Cold forming will result in a weakening of the bend area and optical distortion is typical.

A little experimenting will give you some feel for the material and how it works.

 

[Circlip]

If you heat polycarbonate incorrectly little bubbles form inside the material, looks real pretty, but is a dog to see through.

 

[Tin Falcon]

L N : Problababy the best advise is find a good supplier and follow there recommendations or factory recommendations. Or research the various plastic suppliers on line. Bodecker plastics comes to mind.
I worked in a shop for a while that worked with plexi and poly carb. IIRC we had some stuff that was kind of a blend that had the better properties of both. do not reall the brand name.
IIRC you need heat to bend plexi we had an oven that was large enough to hold the pieces vertically by the edge. curved surfaces were made on a wooden form covered with a felt like material. The sheet was placed on the form after oven heating.
Polycarb will take a 90 degree bend cold but requires some force.
As others have said poly carb is the better choice for safety shields.
Tin

 

[Loose nut]

. A folded design is the easiest and can be done with a simple shop built heater made from some scrap wood, aluminum, and a piece of heating element from an old space heater or toaster oven.

I have a 220 volt "contractor" shop heater that should do the job then, I just need to make the forms for it.

Thanks

 

[Cedge]

Last shield that I built, I used an inexpensive heat gun from Harbor freight. I gently heat formed the lexan to contour to the frame I'd made to mount it. Had to keep it moving, as I recall. The heat gun also drys Dykem quickly when you are too impatient to wait on it.

Steve

 

[Rog02]

If you heat polycarbonate incorrectly little bubbles form inside the material, looks real pretty, but is a dog to see through.

Those little bubbles are moisture in the material. Kind of hard to believe but poly-carbonates actually are hydroscropic and absorb moisture from the air.

At the helicopter shop we would dehumidify the material in a 150 degree oven for 4 hours before blowing the windscreen sections.

I have a 220 volt "contractor" shop heater that should do the job then, I just need to make the forms for it.
Thanks

That should work. Either suspend it overhead and allow the material to sag over the form or make a heat concentrator that will heat a narrow chord and then bend it over the form. I would probably do the spot heat and bend, so as to avoid the trouble with optical imperfections.

BTW Always remove the protective covering before heating of any kind. I saw a couple of thousand dollars worth of material ruined when it was put in the de-humidifying oven with the protector still attached. Needless to say the owner was none to happy about that. :fan:

 

[Rog02]

Last shield that I built, I used an inexpensive heat gun from Harbor freight. I gently heat formed the lexan to contour to the frame I'd made to mount it. Had to keep it moving, as I recall. The heat gun also drys Dykem quickly when you are too impatient to wait on it.
Steve

A heat gun is about as handy as pockets in pants! :big: Well worth the minimal investment for any home owner.

 

[PolskiFran]

A heat gun is the best way for the occasional use. I have used a hand held propane torch to bend lexan with good results. Be careful to get only the heat from the torch and not the flame close to the material. Try to heat both sides at the bend point. I always had a quench tank (bucket) filled with clean water to cool the part after bending. Air cooling tends to let the "memory" of the material return unless clamped in a fixture.

Frank

 

[tattoomike68]

I chip shield is a good idea for a mill. Im sure a small peice of plexiglass mounted to a good mag base would be the ticket.

When I was a machine tool repairman at a super busy screw machine shop they had this dumb chip guard on the lathe and one day it cut my hand wide open. I took the bolts out and put it in the dumpster that was the end of that peice of crap. :big:

Guards are nice on some items and silly on others. My brothers 70 ton Piranha iron worker had guards on the punch and the shear. the first thing we did was bust them off and throw them in the trash. If you are so dumb you need a guard on a machine that will punch holes in 1" plate then you are just too stupid to run that machine.

 

[Loose nut]

Here is an add on to my question, since I have never worked with these materials before, I realized I don't know what is the best way to cut lexan or plex, band saw,table saw with plywood blade maybe?????

 

[whatsit]

I cut both with a bandsaw. First put painters tape on both sides of the cut keeps it flaking or breaking.
For bending 90s, 45s or any straight bend I clamp 1 side down to a block of wood and use a heat gun
at the bend point apply even slow pressure with the heat and it will bend clean without distortion or change
in color. Clamp bent portion until material cools. For rounds I've used logs, coffee cans, etc. for shape and cargo straps to clamp. Bend material around form as far as you can cold then strap it and heat while tightening the straps. The rounds spring back some. So use a smaller form or keep the heat on. That's worked for me so far.

Kevin

 

[gilessim]

The best way to cut Plexiglass is with a tungsten tipped circular saw blade, the finer the teeth the better!, no chipping especially if you leave the plastic film on, over here in Europe ,polycarbonate is being phased out and replaced with acrylic, which is less brittle(less likely to shatter), less poisonous, easier to bend with a heat gun and optically superiour, Lexan is possibly more durable, but unless you're chunking out 1/2" chips at 2000rpm ,acrylic is fine!

Giles

 

[Rog02]

Here is an add on to my question, since I have never worked with these materials before, I realized I don't know what is the best way to cut lexan or plex, band saw,table saw with plywood blade maybe?????

Any of those will work. You can also use a router to make internal openings. For blanking sheets to size we just ran the lexan through the shear. Nice clean cuts with no chipping.