Bending Injection Molded Styrene

[jpd158]

Greetings All!

Does anyone have any experience in bending injection molded styrene?  I'm NOT talking about the thin sheets, such as those made by Evergreen.  I'm attempting to bend injection molded styrene, specifically parts from Design Preservation Models modular wall system.  (The part I'm trying to bend is 30142.)  These pieces are pretty thick - sorry, I couldn't find my metric ruler, so I can't tell you the exact thickness - but it's pretty thick.

I've heard of using hair dryers, and boiling water.  I tried it over a hot plate, but the plastic distorted in places where I didn't want it to distort.  

I'm trying to take a straight piece and bend it into a 90 degree curve.

Thanks for any help.

Jim - jpd158

[matt56]

Hmmm....bending a flat piece into a 90 degree angle is gonna be a challenge.  The key whenever bending plastic is the way you heat it.  You gotta do it in a way that the area to be altered must be evenly heated but not too much that the plastic melts or sags.  This leaves a very very small window in which you can form the plastic then, especially with thick parts.  I would say just cut the pieces and then assemble in a 90 degree angle, but since you want a curve I'm not sure about doing that.  Only thing I guess I can say is experiment with some scrap plastic with roughly the same dimensions and see what happens

[m horton]

When I kit bashed an old AHM Rico station I changed the bottom of the roof to flair out flat. I made many scores on the underside and kept slight applying bends in it to get the shape I wanted. I  also was bending outwards,so scores released the back edge. If you're bending inwards, you'll need small notches to give plastic some flex. You may also find a can with the desired radius, and clamp piece on and put in warm oven. Good luck.mh.

[doctorwayne]

No guarantee that it'd work, but try thinning the plastic (from the back, of course) using an autobody file - thin only the area where you want to make the curve.  It should take only a couple of minutes.  Then clamp the piece in a curling iron and turn it on.  Most have at least a couple of heat settings, so you should be able to control the temperature somewhat.  (If you're using an iron that's still used for its intended purpose, sheath the wall section with aluminum foil.)

 

Wayne

[Anonymous]

I have tried bending a styrene wall and I am inclined to simply say forget about it. The only way you can do this is by applying heat exactly on "the spot", for which we usually lack the tools. If you use a hair dryer or hot air gun, the part will most likely be distorted and useless, as a consequence. Hot water works only with resin cast parts. I tried using a micro-flame torch, giving the part only a few "strokes", but that left the part with an even distribution of softness, resulting in partial cracking while bending.

The only way I see is to cut the part and glue it together again at an angle, with some strips of styrene supporting it at the inside.

[ndbprr]

Plastic is called plastic because at a certain temperature it enters a plastic state where it is very fluid.  So injection molded parts are made by heaing styrene to a plastic state, forcing it into a die and leaving it there until it cools below the solidification temperature..  If you lay the part on a surface and heat it up it may try to move back to something like it's original shape.  I am not sure if you want to make a curving wall or one with two straight sides and a 90 degree bend in the middle.  In the firt case I would use a table saw or radial arm saw to make parallel vertical cuts to thin the material before bending it. In the other case a vee shaped router bit would make a vee shaped groove that would allow the wall to bent to a 90.  In either case some solvent based cement in the grooves would facilitate the bending process.

[ctyclsscs]

Unless I missed it, did you say how tight of a bend you're trying to make?

Jim

[jpd158]

ctyclsscs

Unless I missed it, did you say how tight of a bend you're trying to make?

Jim

I'm trying to make a 90 degree bend.  I'm using a piece of one inch black pipe as the form for the bend.

I'm inclined to agree with Sir Madog, where he said, quite simply, "Forget about it."  I think the material is just too think.  By the time it heats up to the point where it will bend, other areas are over heated and distort.  

Taking some ideas from the other guys who replied, I think I'll go the route of scoring or sawing several grooves in the material and simply bending it by hand, while cold.  I'll then fill in the grooves with Green Putty and sand it smooth.  What do you think of that?

Thanks for all the help!

[modelmaker51]

You could laminate thinner sheets to form a curve and finish off with some thin brick sheet or something like Micromark's textured brick paper, they also have cinder block and other textures and it's inexpensive:  http://www.micromark.com/AGED-FACTORY-BRICK-PAPER-4-SHEETS-HO-SCALE,9658.html  The sheets can be weathered with powders and sprayed. You could do washes as well once you seal the texture with Dullcote.

[HobbyDr]

The DPM walls are definitely too thick to bend without distorting, unless you were making an inside bend. However, the Walther's  modular walls are thin enough to try bending.  It might be worth taking a chance.

Don

[richhotrain]

Cut it in two with a jeweler's saw and a very fine blade, then glue the two pieces together. 

Once it is painted, I doubt that you will notice any imperfections.

The key is to use a very fine blade.

Rich

[dknelson]

richhotrain

Cut it in two with a jeweler's saw and a very fine blade, then glue the two pieces together. 

Once it is painted, I doubt that you will notice any imperfections.

The key is to use a very fine blade.

Rich

I agree with Rich that assuming you want the result to look like a sharp edged normal corner, cutting and cementing is the way to go.  Squadron putty (green or white) carefully applied could mask any gaps or cracks that will give the joint away.

If what you seek is a sort of tightly curved corner - a real example of the bricklayer's art -- then heating and bending should work.  I would put a piece of lumber, say a short length of 2x4 or 2x2,  in a vise.  if you have a heat gun such as crafters use (perhaps a hair dryer would work), carefully train the heat on the part of the building to be bent and when it reaches its soft state, quickly bend it over at the 90 degree edge of the wood (I assume the modeled surface would be facing out, unless this is an interior corner).  Take care to get your edge exactly where you want it and not at a strange angle.  Have a spray bottle of very cold water handy and spray the plastic to harden it quickly to the desired shape.  My experience is that you get exactly ONE chance to get this right -- that the plastic will not respond well to a second reheating and bending.  Maybe you will be luckier than I.

I also advise experimenting and practicing with sheet styrene or a junker building (of which I have far too many!).  And warning.  The plastic gets extremely hot.  Dangerously and painfully hot.  And there will be fumes and a bad smell. 

But again I suspect Rich's advise actually gives you what you are looking for with far more control and a more probable and realistic looking result, with a bit of care and craftsmanship.

Dave Nelson

 

[hon30critter]

Jim: I have used thin styrene brick sheets around an ABS pipe for the curved front of a flat Iron building. Try 'The N Scale Architect' on Walthers web site. They have several different brick patterns in .020" thick styrene. One of them hopefully will be close enough to the DPM brick pattern.You will have to scratch build windows and sills etc because the windows by Grandt Line or Tichy will not bend very far and heat makes them shrivel into nothing. I would suggest gluing the brick sheet to your 1" tube for support, but do not use a solvent style glue because it can distort the .020 sheet if too much glue is applied. Ask me how I know! Also, I should qualify my suggestions by noting that I was trying to achieve a 2 1/2" diameter curve, not 1". Curving the styrene around 2 1/2" was quite easy. Yours will be more of a challenge. I would suggest starting with a piece of styrene which is a fair bit wider than the finished curve so you will have something to grab onto to pull the styrene tight. I would also suggest initially gluing just one edge of the styrene to the tube and letting that dry. Once is has dried it will be easier to pull the rest of the styrene tight around the tube without losing alignment. If you use PVC or ABS pipe you will then be able to cut in your doors and windows if any, and the thickness of the PVC will approximate the thickness of a real wall. Using a Dremel to rough in the openings would be fairly easy, followed by a #11 to clean them up.

If you try it and it works, please post some pictures. My project is still in bits and pieces so I don't have anything worthy of a picture.

Dave