Best way to cut 1/8" clear polycarbonate?

[Bimmerboy]

Best way to cut 1/8\" clear polycarbonate?

Hi all. I'm having some difficulties in making some nice, neat strips of 1/8 inch thick, clear plastic polycarbonate out of a sheet of the stuff. It's not stiff, firm plastic, but rather flexible. The strips need to be made to somewhat precise measurements.
The recommendation (from the guy at Home Depot) was to score it heavily with a straightedge and a heavy duty razor, then simply snap off my piece. Yeah well, it's not working out that way.
It's snapping alright, just mostly in the wrong spots. That would suggest I'm not scoring it enough, but I've already worn out two super thick razor blades just for the little pieces I've made so far. Half the sheet has been turned into unusable broken pieces. I've even tried putting the scoring along the edge of a table to help get a clean snap. There's got to be a better way! Any ideas out there?

 

[Lynx_Arc]

Re: Best way to cut 1/8\" clear polycarbonate?

I used my scroll saw to cut the plastic on a CD case for a mod I did awhile back and then used an upright sander to clean the edges off. It works fairly well. I wonder if those high speed router bits and a dremel would work well if you put the plastic in a water bath to keep the melting down.

The ultimate solution is to use an abrasive water blaster to cut it I bet.

 

[mahoney]

Re: Best way to cut 1/8\" clear polycarbonate?

If it's really polycarbonate, a well tuned tablesaw is the perfect tool to cut it with.

But it doesn't sound like it's behaving like polycarbonate. Polycarbonate relieves stress by becoming white and fiberous, it's basicly unbreakable, so if your plastic is cracking sort of like glass, just not where you want it to, you are probably dealing with acrylic. Acrylic can be cut on a tablesaw too, but I'm guessing that you may not have acess to one.

Go to a better hardware store and find some plastic cutting blades for your utility knife (or buy a plastic cutter which is basicly the proper shape blade mounted on a handle). They will have a cutting edge bent forward at an angle from a sharp corner. The corner does the cutting. As you drag the corner over the plastic, it will remove a small curl of plastic leaving a groove behind. Make many passes until you are almost through the sheet and then snap it off. Or just keep cutting till you're through the sheet. This method works well, it's just a bit time consuming. If you dull the blade, hone the flat face of the corner and the sides of the cutting edge.

 

[.308]

Re: Best way to cut 1/8\" clear polycarbonate?

Have you tried clamping something like a block on top of the poly along the cut line to force the poly to break at your score? I would try this on a piece.

 

[HarryN]

Re: Best way to cut 1/8\" clear polycarbonate?

Mahoney is dead on - you are most likely working with acrylic not polycarbonate. Either way, using a snap- off technique requires more luck than I ever had.

The other way to cut it that works pretty well is with a very sharp router bit and a variable speed router. You will need to run the router along a fence to have any luck. Melting is always a problem.

Tap Plastics will also cut for you, but my experience is that they are not so willing to target precision cuts.

Edit - It seems like I may have had some improved luck by using masking tape on the cut (both sides). I did some very thick pieces a long time ago on a a radial arm saw and they came out very nice, but I do not remember the setup.

 

[Bimmerboy]

Re: Best way to cut 1/8\" clear polycarbonate?

Lynx - Speaking of Dremel's, I got a few 409 cutting wheels that I hope will do the job. If anything starts to melt, I'll file it off. The measurements only need to be somewhat precise, so this should work. Gonna' start with a couple of the broken scrap pieces for practice.
Did some research since posting this thread, and it seems cutting polycarbonate has it's parameters. Chipping, cracking, and melting are problems. The abrasive water jet is, in fact, the ultimate. Short of that, a circular saw with carbide tipped square teeth or an overhead panel saw is the shiznizzle for straight cuts. Band saws for shaped cuts. Certain RPM's are recommended in all circumstances, blah, blah. What a pain!
I'll be back with the results.

 

[Bimmerboy]

Re: Best way to cut 1/8\" clear polycarbonate?

Mahoney & HarryN - Next time I'm at HD, I'm gonna' find out exactly what I got. I did ask for polycarb, but the same guy who got it out for me also told me to use the razor and snap technique.
What research I did though, does talk about severe cracking and chipping with polycarb if pushed past it's tensile strength limits. The info came mostly from manufacturing and/or machining websites.

308 - I didn't actually try something clamped on top, but the scoring was placed along the fine edge of the kitchen table, and the cracks tended to happen within the piece I was making instead of outside the line. Experimentation with moving the score a couple mm's in either direction in relation to the table only resulted in more broken pieces.

In high volume production, sheet metal shears (not the hand held ones) are often used with gauges .125" or thinner, as long as the tolerances are less than .xxx" to prevent rolling the edge (.002" I think?).

All this because I want to cut a few stupid pieces of plastic, which I thought would take about 15 minutes. That's materials for ya'.

 

[Luna]

Re: Best way to cut 1/8\" clear polycarbonate?

Cut it on a saw and sand or route the edges clean and square. If a more rounded edge is ok, use buffing wheels.

 

[bitbyte]

Re: Best way to cut 1/8\" clear polycarbonate?

Skip the razor blades.

I've done a fair amount of work with plexiglass in the past. You can cheaply buy a tool for scoring the acrylic so you can snap it off.

It's roughly the size of a utility knife but the blade looks more like the barb on a fishhook (but bigger). You draw it across the acrylic and the rake angle of it cuts deeply into the material, much like a drill bit or other cutting devices such as a bit on a lathe might.

Once that's done make sure the material is supported on a board or table edge as you'd mentioned earlier, then snap it off. If you still have problems with it breaking in the wrong place you can use a second narrow piece of wood to press on the side you wish to snap off (both on the opposite side of the plexiglass from the table as well as the other side of the score mark). This will support it and place an even amount of force along the score line from both sides.

Using this method I've been able to cut a variety of thicknesses and widths with no trouble.

 

[billw]

Re: Best way to cut 1/8\" clear polycarbonate?

Bandsaws work pretty good on plastic, if you've got access to one.

 

[Lynx_Arc]

Re: Best way to cut 1/8\" clear polycarbonate?

The problem with any cutting of higher speed on plastic is you end up melting it some and have a blobby edge to sand off, but it is a lot easier than other methods. One method you could use if you have two pieces of metal the same size of what you want is to sandwich the plastic between the metal and use a grinder on it all.

 

[Bimmerboy]

Re: Best way to cut 1/8\" clear polycarbonate?

Well, I've accomplished the task... the Jerry rigged way.

The Dremel 409 cutting wheel did the job. The diameter of this wheel is too small to use for straight cuts along a plane if it's simply attached to the Dremel motor. You need the flexible shaft drive, where the handle that you attach parts to is much thinner as it doesn't have to house a motor. It's about 3 ft. long, so you just set your motor off to the side and use the flex drive.

An old Craftsman folding workbench worked great for this particular job because the surface is made of two halves that seperate by turning two cranks in tandem. Place the plastic on top with the score line going down the now open middle of the benchtop and turn on the Dremel. I found the RPM's need to be pretty cranked in order to get easy, effective cuts, and to get the neccessary control if doing this freehand, which I was.

With a steady hand, slowly make the first of three light passes with the wheel directly next to where you want to cut, not on the line of course, otherwise your work comes out too short. Make the second pass a little deeper, and the third pass all the way through.

There's two reasons for making three passes.
1.) The Dremel just simply doesn't have enough power to easily make the cut in one pass. .125" of plastic can be tough stuff.
2.) The cutting wheels break easily, so you don't want to put serious stress on them. I was warned about this, so I made sure to treat it as gently as possible and was able to cut all my pieces with one wheel. When I took it off the shaft, I gave it a little lateral pressure with my fingers and it practically crumbled into sharp little shards. You don't want that stuff grenading into your face at high RPM, so a light touch is needed.

When you're done, the line of melted plastic build up breaks off real easy with your fingers, and the cut edges clean up relatively well with a coarse file.

Some observations:
1.) Doing things the way I did, you will get covered in thousands of tiny pieces of melted plastic. Especially your face, hair, it gets in your ears, etc. Safety goggles are recommended. I did not use them and stupidly relied on my regular glasses, which resulted in getting one of those little pieces of flying melted plastic in my right eye. Last time I do that.
2.) The invisible smoke/fumes given off by cutting plastic aren't pleasant, so try not to breathe them.
3.) I had to keep pulling off these fibers wound up around the spinning shaft directly under the cutting wheel. It looked like cotton candy. I believe the fibers were spun from strings of the melting polymer.
4.) Wear the proper attire. I must've looked pretty silly out there on the driveway in sweatpants and sandals, with my head covered in plastic.

Thanks for the response, everyone!

 

[Lynx_Arc]

Re: Best way to cut 1/8\" clear polycarbonate?

If you are going to do a lot of plastic cutting I would look into picking up a cheap scroll saw. It is a lot easier to use and can cut intricate patterns easily.

 

[Bimmerboy]

Re: Best way to cut 1/8\" clear polycarbonate?

Thanks for the input, Lynx. Although I rarely have to do this specific kind of thing, I do often find myself making some kind of custom thing. Cutting plastic, making a dog bed, rack or cabinet, etc.
A scroll saw isn't a bad idea as I do many things freehand, with no plans, drawings, proper tools... lol. For example, the only time I ever used a jig on anything was when doing some routing on the face of a guitar. Don't know how, but the stuff I make actually comes out pretty good! The scroll would kinda fit my style.

 

[Lynx_Arc]

Re: Best way to cut 1/8\" clear polycarbonate?

There are two types of scoll saws out there.... the C arm and the parallel arm. The C arm tends to wobble the blade a little more but has the advantage of a longer throw or length of material you can spin around cutting, while the parallel arm has a nearly perfect up and down blade travel. Most people do not need the parallel arm type which I *think* probably cost more to acquire and is harder to find.
Make sure and measure the length from the blade to the back where it is the longest you can cut into an item if that is a concern. They also make variable speed scroll saws and it does help on some materials. There are many blades available too, and they are somewhat fragile so you will break one on occasion. I happen to have a parallel arm version made by hegner and my dad has a variable speed C arm delta which has a tilting table I believe you can tilt it up to 45 degrees.

 

[mrsinbad]

Re: Best way to cut 1/8\" clear polycarbonate?

I used to work with pelxiglass alot for my hobbies that required pretty long strps and I used to have this hook blade knife where the tip is shaped into the number 4. It was a draw style knife (pull towards you) that would pull curls of plastic off while I scored the plastic. I would score the plastic where I needed the break heavily (and the bladed did not dull) and then I would jam in into a file cabinet between the drawers and the frame. A quick snap and that was all I needed. I was able to snap off pieces as narrow as 1". I guess the Workmate would do the same as my file cabinet.

 

[Lynx_Arc]

Re: Best way to cut 1/8\" clear polycarbonate?

I used to work at a place that used plexiglass in store fixtures. They used a table saw to cut it probably with a fine tooth plywood blade. You endup up loosing up to 1/8 inch due to the saw blade but my guess is after that you just snap off any debris that probably melted due to heat possibly use a sander to clean the edge if needed.