Okay. Here's one for you. From time to time, I see reference in "How to" books and model rags about straightening out warped plastic in the oven. I have never had the need to try that.................. UNTIL NOW. I have a Red Caboose flat car kit that I started about 4 weeks ago.. worked on it, put it in the box, pulled it out last night. The center peice of the flat bed had warped and "popped" off the frame and was staring back at me as I opened the box. It should be simple to fix.. just put it in the oven on a flat baking pan w/ a flat weight forcing it true while it "bakes". QUESTION? Has anyone done this? At what temperature? Seems too low would take forever, and too much would .... would cause me looking for another kit at a show. I would think the thing to do is start it at a low temperature, take out of the oven, and then let cool WHILE STILL UNDER FLAT WEIGHT. Oh.. the other thing I think would be smart would be to do this while Mrs. Kitbash isnt home! -Kitbash [ 20 April 2002, 02:19: Message edited by: Kitbash ]
It is not wise to bake any plastic in your cooking oven! The plastacisers will contaminate the inside of your oven, and any food heated in the oven will taste like burning plastic after that! Most kitchen ovens wont even regulate down to 120 degrees anyway. Better to do it like the eyeglasses people do. Go to where they sell glasses, and ask to watch them fit a pair and they will show you how quickly they work, and how easy it is to do. You can also find out how hot the salt is too. I took a piece along with me, and learned lots about it in just minutes! They pour ordinary table salt into a low flat cake pan, and heat it on an electric hot plate so they can regulate the temperature. It will only take a second or two to heat the plastic part, so be careful, or it will drape around your finger like a wet dish rag! The salt carries the heat well and does not stick to the plastic. Start at about 120 (F) degrees, and work up slowly. A weight might deform into the plastic if the plastic is too soft, or the weight too heavy. A thermoplastic will re-soften, a thermo-seting plastic will not re-soften, ( like polyurethene or bakealite.) Injection molded plastics will work OK, but hand mixed room temperature curing plastics like epoxies, and polyurethanes will not soften. Vacuum forms will shrink and flatten back out!
Ahhh ha. Thanks watash. I hadnt thought about what is quoted above. Good stuff. However, from the rest of the answer, the lightbulbs have gone off "upstairs"... I have an idea. Stay tuned. Appreciate the reponse. -Kitbash
You might try a hairdryer. Advise using low heat and bringing the nozzle slowly towards the plastic from a distance. Stop immediately when you see the plastic just begin to deform. You can always do a little more, but you can never do a little less if you went too far
Great tip Watash and thank you for your suggestion for butt jointing MDF together (in the layout forum). I did see it and appreciate it. I borrowed a friends biscuit do hicky and used that.
I'm glad that did the trick for you rsn48! Made me think of something else.... When I was on a design team at Pollak Div. of St. Regis Paper Co., I learned a few things I'll share with you just to massage your brains. We developed a method of sealing bread wrappers at high speed automatically for Mrs. Baird's Bread Co. I prototyped the original idea by curling some thin walled brass tubing around the tip of a pencil soldering iron. The tube was curled four complete coils snug around the tip. One end was formed to extend straight out beyond the tip about a half inch. The other end was bent out away from where your hand would hold the soldering iron, and extended 8" away from the tip. (Brass carries heat very well.) I slipped surgical rubber tubing over the long end of this brass tube, and left enough length to hold the other end comfortably in my mouth, so I could control the amount of air I wanted to blow through the brass tube. I found, after some experimenting, that I could actually "weld" the bread wrapper film edge to edge like sheet metal, if I was careful, and steady. We built the sealing unit so hot air sealed the bread wrapper ends closed in mid air without touching the wrapper at all, as it zipped through our unit! A cooling blast was required imediately after at machine speed! Now these units have replaced all the Burford Tyers in all the bread plants. It is used on cup cakes, and even heats the wheels for sealing seams for lengths of film tubing. Nice bonus too. Since then, I have used this set-up to move the arms and legs of "my" people, bend and weld sprues and plastic wire stock, (like hand rails), and to soften plastic in small areas so it is easier to remove rivet detail, etc by carving, like balsa wood. It works well to bend pipe for a refinery, and will even melt solder on tiny brass parts! You have absolute control of the heat. Blow gently when you want to heat it up, stop and it cools down. Blow harder, and the plastic will melt and drip! NO ONE IN THEIR RIGHT MIND WOULD INHALE THROUGH THE TUBE!!! Do keep in mind that the brass tube can get up to 600 degrees F. so don't touch the plastic with it, or your finger! Now I use a house light dimmer switch to cut the temperature of my soldering iron down some when needed. Think on these things. [ 21 April 2002, 06:02: Message edited by: watash ]
Watash, exellent plastic forming tool ! I have only one question. What diameter of the thin walled brass pipe do you used? ----------- Helge SR&WF NARA member #5
MY APPOLOGIES FOR ANSWERING SO LATE HELGE! I just now saw your question! I'm sorry, here is the answer if you haven't already found out. It is a .125" diameter (outside diameter) with a .015" thick wall. It was available from most local hobby shops. I plugged one end, then poured table salt into the tube until full, then plugged that end too. This keeps the tubing from collapsing while forming around the soldering iron tip. This will also work with aluminum tubing of small diameter. Remove both plugs and the salt will simply flow out. Bending can be done cold. I have since then made another one. I used the metal (brass) tip from a mechanical pensil to obtain a fine tiny hole for tiny work areas. I silver soldered the pencil tip onto the end of the brass tubing, then using a wet grinder, removed the excess diameter of the pencil tip. This prooved great for bending people's arms and legs with out ruining the paint most of the time. To make an even finer sized tip, I inserted a piece of piano wire in one end of the brass tube, then flattened the tube in my big vice to close it off shut. Then I clamped the wire in this vice, and pulled the tubing off. The wire had been coined into the brass, leaving the desired size hole through for air flow. I did not try to remove the "wings" left when flattening the brass tube. The tube was only flatted for about an eigth of an inch, yet the wire was still tight to remove. This tip also works as well as the others. Holding two halves of an arm end to end, this tip will melt the plastic enough to stick back together again. You will have to re-paint this one though.
That´s OK Watash. Your answer is much appreciated, especially because there is a description how to fabricate thin needle hole with help of a piano wire. That is as usual a "Watash tool" based on long experience
Another way to soften the plastic is with hot water. It's dense enough to be able to carefully control the temprature, and it won't burn or ignite the plastic. A variation on this is to use steam from a teakettle to soften the plastic, but watch your fingers!
