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How do you shape plexiglass...acrylic...Lexan...???

M

Moose777

2[H]4U
Joined
Oct 10, 2004
Messages
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I've seen on here repeatedly how people have taken a flat piece of plexi applied heat to it and have bent it into boxes.

How do you do that? What are you guys using to make the bends? Straight edge? Piece of pipe? What?

I'm asking because I'm trying to make a box that is approximately 1 1/4" high by 5 1/2" deep by 8 1/4" long. I just went into my shop, took a pice of cardboard 21" long by 2" deep and measured it up. Folded it and made sure everything was correct.

Then I took my piece of plexi, marked it up where all the cuts and folds were supposed to be, cut it out. Then took my trusty torch heated up the plexi and used a vise to help bend it. The first bend came out a little shorter than I wanted. But I continued. Heated up the plexi then used a ruler to bend it. I put the ruler where I drew the line and bent the plastic. Still, it didn't bend where the line was it bent a little above that.

Needless to say. The box isn't much of a box since nothing lined up once I applied heat to it. It warped a little which isn't a big deal.

Where it doesn't line up is where I measured for the bends, even though I used my template to make the marks. So, everything theoretically, before I applied the heat to it was right where it needed to be.

It ended up being the right depth of 5.5" and on one end it was close to being 1 1/4" the other end was way off and it ended up being about 7 1/4" long with almost a 2" overhang.

What happened?

When I draw my line where I want my fold to be do I apply heat to that line or do I move it 1" or so back? Do I use a straight edge to fold the plexiglass? Or do I use a pipe or something with some mass?

I have just enough plexiglass to do this again, but...before I start I want to get some input as to where I'm supposed to be applying heat and where I'm supposed to be bending and how and with what tools am I supposed to be using to bend with.

And before you ask what the small box is going to be used for heres your answer.

I'm removing my 2 SATA HDDs from inside my case to a remote box outside of the case. I have a hub which gets attached to teh back of the case where I can run the wires from. I have the wires in some flexible tubing that will be attatched to the back of the case and run up to the satellite box ontop of the tower. It'll be fastened to the top of the tower so it doesn't move. The box is going to be made out of plexiglass and carbon fiber the plexi since it discolors when heated will be painted black to match the rest of the case.
 
I smell a raptorX inside that external plexi box.

I have tried bending plexi with your same results (i used a heat gun), things were off by about 1/8". If you can keep the 1/8" consistent you could design for it. Have you considered cutting the plexi and using glue?
 
I have considered using glue but, I'd rather not go that route because I wanted to keep the gluing to a minimum, as it is I'll be glueing the shelves for the HDDs in and then glueing the front of the box on.

And unfortunately, at the moment I don't have a job so a Raptor X although I'd really like one isn't going to happen for some time. I'm just using two Maxtor 7k RPM HDDs at the moment. One is 300Gig. and the other 200. Hence the reason why you won't be able to see through the box.
 
Bending Plexi is an aquired skill. Your method is correct. Clamp, heat (heat gun recommended), bend. But i think it's just something you have to do more than once to get good at. And quite honestly, bending a box is by no means an easy feat for anybody. I would take the other poster's suggestion. cut the box out. But if you are intent on bending it, use a small diamater pipe as the fold guide, and clamp the hell out of it. Apply the heat a bit before the bend, but again that is something you just need experience doing to get good at.
 
I saw mentioned somewhere just a day or two ago that what one person did was to put it into an oven on top of whatever shape they wanted, then once it got flexible they bent it to the right shape with some oven mitts on.

Sounds like it'd work, but I'm not sure if it'd work for a box shape. Gravity might not like that idea.
 
It is indeed a skill. Here are some shelves I made from 5/8" Plexi. I use them to hold a STB and a DVD player up with (Made 2 of them).

plexishelf1.JPG


plexishelf2.JPG



From experience you want a fair sized heat gun, or you will be there forever. The more hot air it can move the better (not necessarily the hotter the better). You may end up melting the plexi if you get it too hot, therefore causing it to REALLY warp.

Some tips are, do NOT do it in the cold. Make SURE that you do it inside if you are in a cool climate. The reason for this is because the plexi absolutely needs to be uniformly warmed or else when you go to apply pressure it will crack (I wasted 2 perfectly new pieces of plexi that way).
Also, buy yourself a pair of QuickGrip clamps. When you have all of the bends drawn out clamp the plexi down (firmly) and begin warming. You will know when the plexi is hot enough, as it will begin to bend on its own (just slightly). Dont be surprised if it takes a really long time to warm up. To get the 5/8" I had to bend, it took a good 15 mins to fully warm up with a heat gun. Now, apply just a tad of pressure with your hand. Again if you press too hard and the plexi is not hot enough you will crack it. (*NOTE Use a glove or you will probably really burn the hell out of your hand). I used the edge of my sawhorse to get the bend in the shelf.

Lastly, remeber once you have bent it to hold it in place while it cools. If you do not do this the plexi will slightly bend in one direction, making it so you have to warm it up again. I found that if you bend it a little past where your desired angle is, that it will cool with the desired angle in mind.

Oh I allmost forgot, if you buy the plexi that they sell at home depot, it has some clear protective stuff on it (allmost looks like saran wrap). This part is up to you, but if you heat it up, and bend the plexi, it will actually begin to fuse to the plexi. I say begin because it doesnt fully fuse to the plexi. When you are all done and go to peel it off, prepare to set aside at least a 1/2 hr to peel all of it off. You WILL need to use alchol to aid in peeling it off. As of this point I have yet to ruin a piece of plexi this way, but I could imagine if you heated it up enough it would eventually pernamently bond to the plexi, ruining your piece.


Hope this helps :)
 
Thank you. That helps quite a bit actually. I have welders gloves that are fire retardent, a little big but they work. And I'm using a propane torch (yes, I know they went to butane many years ago but I've had this propane torch for years so until I run out of propane its waht I'm using).

I'm gonna go down and try it again right now. I'm also only using 1/8" plexi so it doesn't take too much heat to get it so I can bend it.
 
Just dont get too close with that torch. It will get all bubbly, that that is totally unrepairable!
 
Ok, tried it again. Even got the height of it correct at 1 /14".

Too bad again I came up short on the width. Instead of coming up with the 8 1/4" I projected and measured for I got 7 3/4". Close, but not close enough as I can't fit both of my HDD's in it.

So, needless to say. I'm out 23" x 12" worth of plexiglass and I'm quite irritated at the entire project.
 
Thats the problem with bending plexi. Its soooo easy to screw it up.

I too have done what you did. ALWAYS mark your measurements so you have at least 1/2" extra hanging off of the sides.

Youll probably be inspired to buy another sheet. Thats what happens to me, when I screw something up I say NEVER AGAIN then a week or so later I go through with the project and I am glad I did so.

Good luck :)
 
You may want to try and mock up a wooden jig that is the exact width of the piece you want to bend over. Just bend it in place over the jig and then it will take the guess work out of trying to get the width right. I've used that method many times and it has worked well for me. Keeps you from getting frustrated. Hope this helps.
 
when i bend a simple box, i like to use a metal pipe, with heat blower blowing the inside. i just choose a pipe od with the bend radius i want. works pretty good.
 
I looked for a piece of pipe. Couldn't find anythign small enough. I even though I had some 1/4" brake line that would've worked.

I thought about building a jig. But for some reason didn't feel the need to. I didn't think making a simple box would prove to be so difficult.

I don't really have any intention on trying it again. I can't justify buying and then ruining more plexi. Now I'm looking to buy a premade box the dimensions I need. But, who knows...I might buy another sheet and try it again and get frustrated. I am a glutton for punishment.
 
DudeItsMe said:
I saw mentioned somewhere just a day or two ago that what one person did was to put it into an oven on top of whatever shape they wanted, then once it got flexible they bent it to the right shape with some oven mitts on.

Sounds like it'd work, but I'm not sure if it'd work for a box shape. Gravity might not like that idea.
Click to expand...


That was me. I used this technique to make new front (and rear) bezels. It only works if you have a mold to bend the acrylic over. In this case it would simply be a block of wood. The advantage to this method is that you are guaranteed to have evenly heated plexi. The disadvantage is that you would have to do all of your bends at once. If you had clamps and blocks of wood all ready to go, it would be possible.
 
The best method I have come across for doing straight bends it to place the plexi on top of two boards of about 1/4 - 1/2" thick. Leave a gap between the boards about 1/2" wide. heat the plexi form underneath. This results in a fairly narrow strip of soft plexi so it has no choice but to bend along the heat line.

Second best method as already mentioned is to make a former the same size as you want then bend the heated plexi over that.
 
I've decided to try it again.

Only thing I I'm nailing two pieces of wood together. Then I'm drilling two holes, one on each end. Next I'll be taking another piece of wood drilling two holes one on each end they I'm taking some bolts and thumbscrews. I'll sandwich the plexi between teh pieces of wood and then bolt it down so it doesn't move. Then I'm going to heat it and bend it. Wait till it cools, and do it again.

I might have to build a few of these jigs different sizes because of how short the box is but I think I can make it work. I might even make it so that I can bolt the jig to the end of the work bench. This way I'm not fighting with it moving around.
 
Moose777 said:
So, needless to say. I'm out 23" x 12" worth of plexiglass and I'm quite irritated at the entire project.
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DaRkF0g said:
Youll probably be inspired to buy another sheet. Thats what happens to me, when I screw something up I say NEVER AGAIN then a week or so later I go through with the project and I am glad I did so.
Click to expand...
Moose777 said:
I don't really have any intention on trying it again. I can't justify buying and then ruining more plexi. Now I'm looking to buy a premade box the dimensions I need. But, who knows...I might buy another sheet and try it again and get frustrated. I am a glutton for punishment.
Click to expand...
Moose777 said:
I've decided to try it again.
Click to expand...
You can't fight the urge to mod!
tongue.gif
 
Yeah, I know. I just really want these HDs out of my case now.

I don't plan on tryign again for a week or so so I'll build the jigs first hen rebuy the plexi.
 
you know, if you haven't thrown away the other plexi yet... You could try heating up the bends and unbending them, then once it's closer to flat, throwing it in the oven on a cookie sheet and letting it flatten right out... and use it to practice with your new wood-vice idea. Might save yourself some material and frusteration.
 
i have a question i would like to add to this thread :)

if i put apeice of lexan in the oven, what would i need to set the temp to ?

i just got done doing the "clamp the lexan with pieces of wood and leaving a 1/4" gap deal", works great, but i want to bend a peice of lexan about 6" wide into a nice arc of about say 6" diameter, i can't seem to get the lexan to heat evenly so maybe i need to heat it in an oven.
 
Or just place the piece of lexan over an item with approximately the same diameter bend you're looking for, and just heat the bend from the top down, and the lexan should slowly form to the object you're using as a guide.
 
Logan321 said:
you know, if you haven't thrown away the other plexi yet... You could try heating up the bends and unbending them, then once it's closer to flat, throwing it in the oven on a cookie sheet and letting it flatten right out... and use it to practice with your new wood-vice idea. Might save yourself some material and frusteration.
Click to expand...
I thought about doing that but I figured it'd get a little too mangled. I did it on the original piece and ended up cutting sections of it off because it became to disfigured.

I'm just gonna go out and buy a new sheet.
 
I Want to make one of These for my 2 X 40 VFD. is a 900 Degree F Heat Gun enough to bend plex?
 
Considering that people have bent plexi by putting it in a 400F oven, I'd say 900F will probably heat it fast and blister it fast if you're not careful. Make sure you practice on a scrap piece first.
 
Hmm, precisely the right thread for my own little mini-project of making an all-plexiglass (or lexan or whatever) door for my P180.

I'm wondering, how effective is this method in making bends that are really close to the edge? For the shelves that were made, I can see it being a little easier to have a fair amount of surface area on each side to press down on, but I want to bend just a small width extending probably the entire side of the lexan (like, maybe 3/4", to make a hinge for the door, or a place to screw it in to the back). Does the lexan have to be uniformly warm to make a small bend such as that, or by "uniformly" does it refer to it just being the same temperature in the area where bending is required?

Hmm, I don't mean to hijack this thread entirely, but I have another question, too. What's recommended for bonding one piece of lexan to another? Something that'll be strong, but not leave anything too noticeable like a residue or something. I'm a total newbie at all of this. :)

Thanks.
 
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