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VACUUM FORMING IDEAS

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VACUUM FORMING IDEAS

Old 10-10-2005, 04:08 PM
  #1  
iaclmac
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Default VACUUM FORMING IDEAS

Hi All ...
There seems to be many threads on this topic. After reviewing most of them and consulting a couple of books, this is what I came up with. There is a controvercy concerning the type of table needed. One suggests that a table with a simple hole in the middle is good enough. The other prefers to have a pegboard top for the table. Both seem to be reasonable. However which is better? Since that is a difficult question to answer, I developed a table that can do both. The basic table is 14x14 with a usable area of 12x12. I selected this size because I can't ever imagine haveing to form anything bigger. Now I know you giant scale guys will differ with me on this. However I am not interested in building anything that big. It is my understanding that you can make the table any size. However, what I found in my research is that the bigger the table, the more vacuum power you will need. For my needs, a 16 gallon shop vac should be more than enough. Anyway, the pics listed below are of my construction methods. I hope that you guys find it useful
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Old 10-10-2005, 06:17 PM
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linclogs
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Default RE: VACUUM FORMING IDEAS

Several years ago, I built my own vacuum forming tool. I had read the book, "Do It Yourself Vacuum Forming". It's available from RCModeler magazine (or maybe not. I guess RCM is having some problems and it's questionable now if they are in business at all, although their website would seem to indicate they are). If you can still get them, look in the back of any issue where they sell books, etc. It's on the "Anthology Books" list. It's also still shown on their website, www.rcmmagazine.com.

Maybe you have already seen this book? I thought it was very good and it shows how simple it can be to make a vacuum former.

You had mentioned about using a Shop Vac for the vacuum source. The book states while you CAN use a Shop Vac for the initial source, it is not enough right at the end of the forming process. They say you need a higher source just for the final seconds of forming to dray the material all the way down at the very end. However, I found using the Shop Vac as the ONLY source works IF you raise the mold up off the platten just a little (I used the pegboard surface, too). I put some short dowels (the same diameter as the holes in the pegboard and matched to the pattern of the pegboard) to raise my molds just about 1/4" off the platen. Seemed to work just fine.
Old 10-10-2005, 06:26 PM
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linclogs
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Default RE: VACUUM FORMING IDEAS

For some reason, my photos aren't posting in one of the browser's I use. I've got a trouble ticket filed but haven't heard anything back from RCUniverse yet. So I'll try this again in another browser....

The first image is the cover of RCM's Anmthology Series book on vacuum forming. The other 2 pics are of my vacuum forming machine and the results of a couple of the molds and pulls I've made from them. One is a canopy and the other some wheel pants. Both were made without the secondary vacuum source the book says you must have. But all my molds use the little dowel "legs" to hold them up off the platten. It's not a process I'd want to use if I were to have a vacuum forming business, but it works fine for the few pieces I make for myself.

linclogs

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Old 10-10-2005, 06:29 PM
  #4  
iaclmac
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Default RE: VACUUM FORMING IDEAS

you certainly have some good tips. Seems to me I remember reading something about that, The vacuum source has always been the question. So in my design, I made the peg table only a scant 1/2" off the base. I figure the vacuum wont have to evacuate such a large area as you see on most vacuum box setups. In essence the pull may be a little stronger. Also my shop vac is a 5 amp unit and the hose is 2 1/2" in diameter. I stepped down the hose size so at the table it is half that of the original. Sort of like the principal of the crevace tool. Maybe with those 2 factors in mind and raising the mold slightly off the surface I should be able to get a reasonable pull.
I just noticed the pic of the book you recommended. That was one of the sources I used. I got my copy from MicroMark at the following link: http://www.ares-server.com/Ares/Ares...oduct&ID=80868
Old 10-10-2005, 06:34 PM
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linclogs
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Default RE: VACUUM FORMING IDEAS

There's still some demons floating around ... my pics are almost microscopic when you click on them. If you want to see them full size, go to the following link and look for my posts:

http://www.rcuniverse.com/forum/tm.asp?m=474875

linclogs
Old 10-10-2005, 09:15 PM
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rcalfred
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Default RE: VACUUM FORMING IDEAS

That is a good book to have. My set-up follows the style shown with a pegboard top. I use a shop vac from Sears. It has a 6 horse motor and gives plenty of draw. Another site that gives some interesting ideas is: http://www.studiocreations.com/howto/index.html. Use the menu the left side. Regards.
Old 10-10-2005, 10:00 PM
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linclogs
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Default RE: VACUUM FORMING IDEAS

I can't remember where I read it, but probably in the book mentioned (mine's buried somewhere in my garage ). But what I read was trying to explain why just a Shop Vac wouldn't produce enough vacuum (so they said ). It was saying that ANY vacuum cleaner could not produce enough vacuum for our purposes. In other words, they said horsepower didn't matter - something about how many inches of vacuum a vacuum cleaner would produce and, because of the laws of physics, it was impossible to get more than that. Somewhere I also read (same book? ) that you can use 2 Shop Vacs in tandem and that would give slightly more vacuum, but still not that extra oomph at the end of a pull they claim is necessary. To be truthful, it was over my head. Besides, putting the molds up on little "legs" gave me good pulls - clear to the bottom of the mold. I think what they were talking about (needing that last bit of high vacuum) was evident in pulls I made with the mold sitting right down on the platen. I could never get the part to pull all the way to the platen right at the corner of the mold and the platen surface. The pieces would "web out" away from the mold at the bottom. By raising the mold, then it wasn't a problem - if this makes sense.

While my system is relatively slow, I did get good pulls. In fact, they looked as good as anything I've gotten in kits. However, I never tried the thicker styrene (? ), like some kit parts appear to made from. All I ever used was the clear (acetate? ) for canopies and the opaque white or yellow for wheel pants. It was fun trying to get it "right", though, and I enjoyed working with it.
Old 10-11-2005, 08:27 AM
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rcalfred
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Default RE: VACUUM FORMING IDEAS

The formula that I use is "whatever works is best" and "Experiment-and-see-for-yourself". As to thickness of plastic---for my last pulls I used .040 (40 mil) PETG and it worked fine. As the book says----you need to try it and see what works. There is a fine balance of height of the plug, plastic thickness, sag of the heated plastic in the frame, and skill in getting the frame to the 'box'. Regards.
Old 10-11-2005, 08:56 AM
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RCKen
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Default RE: VACUUM FORMING IDEAS

I've been thinking about building a vacuum forming machine, but I have one question. What is the best source for the styrene that is used to form the new parts?

Ken
Old 10-11-2005, 07:58 PM
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rcalfred
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Default RE: VACUUM FORMING IDEAS

All kinds of sources. Start with the phone book---yellow pages. Look under "plastic, rods, sheets...".
Depending on how big Lawton is you may have to try other cities. Expect to be told that you need to buy a full sheet, 4' by 8'. They are usually pretty cheap. You can have the warehouseman roll the sheet for you so that you can get in into your car. Also, hobby shops usually supply some types of plastic in small sizes----but relatively expensive on a per sheet basis. Regards.
Old 10-11-2005, 08:06 PM
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iaclmac
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Default RE: VACUUM FORMING IDEAS

Well I am close to Omaha, and there are at leats 3 places that sell plastic sheets. Most want you to buy 4'x8' sheets. Still that isn't a problem as it is really cheap. Strange the hobby and craft places get an arm and a leg for the stuff.
Old 10-12-2005, 07:00 PM
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Default RE: VACUUM FORMING IDEAS

What do you guys use to heat the plastic? I've been thinking about using the oven, but not sure if the wife would kill me or not.
Old 10-12-2005, 08:58 PM
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linclogs
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Default RE: VACUUM FORMING IDEAS

I use the oven. Wife would kill me ONLY if the plastic were to sag onto the rack and make a big mess! Therefore, I built a plywood box that my holder (which you attach the plastic to ) sits on while heating. If it were to sag too much, it would sag into the box - not onto the rack. But to be honest, while the book that is mentioned in the previous posts says to heat the plastic until it sags, I could NEVER get the plastic to sag. It just gets "funny looking" (like it was starting to melt ) and gets "floppy". That's the only way I can describe it. I even tried higher temps and leaving it in longer but if you leave it in too long it starts to form almost microscopic bubbles in the plastic. Definitely not acceptable for a canopy. I had the best results by immediately removing it from the oven as soon as it got "floppy" and immediately drawing it down over the mold. This while the Shop Vac was already hooked up and running. My experience is you only get a few seconds to pull it before the plastic starts to cool off. You'll probably ruin the first one or two attempts. Then you get the hang of it and it goes really well.
Old 10-13-2005, 02:17 PM
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rcamp
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Default RE: VACUUM FORMING IDEAS

I've made a smaller version of his table and the frame holding the plastic is a little cruder. The frame has 4 legs on it and I place in one of those cheap aluminum baking pans from the grocery. That way if it sags too far, only the aluminum pad gets crap on it. At first I was afraid there might be an odor when heated but that's not the case. As long as you can take measures to keep melted plastic off the oven parts the wife shouldn't object too much, mine didn't. I wouldn't try this if the oven doesn't have a glass front. You need to be able to see the sagg to judge when to pull it.

I'm only mounlding little items at present, but I run into a lot of problems with the folds developing and trying to cure that. If anyone has ideas, please post them.
Old 10-13-2005, 09:35 PM
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Default RE: VACUUM FORMING IDEAS

Thanks for the help. I'll try that tomorrow - I'm forming an 18" canopy for a 1/4 scale Moni (60" span, about 30 - 40 oz).
Old 10-14-2005, 09:54 AM
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rcalfred
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Default RE: VACUUM FORMING IDEAS

I suspect that the subject of "sag" depends highly on what plastic is being heated. Also, the thickness may be a factor. I use the oven (electric) with no problem. I know from the chart in the book that there is a vast difference in the oven heat with the various plastics:
ABS 300-350 degrees
PVC 255-355 degrees
Polycarbonate 350-400 degrees
PET-G 260-300 degrees
CAB (butyrate) 265-320 degrees.
It takes experimentation to get the various factors down pat.....oven temp, plastic thickness, type of plastic, amount of sag, height of plug, shape of plug, etc. Once you get it right it is fun to do and the results are very satisfying. Regards.
Old 10-14-2005, 04:16 PM
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jstrawn
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Default RE: VACUUM FORMING IDEAS

Oven worked great for my Plycarb. I used just a shop vac, but raised the mold about 1/2" above the surface (my frame has the plastic about 3/4" above the surface). Unfortunately, I didn't get the plug smooth enough. I'm going to put a coat of poly resin (minus the glass) over it and try again.

Thanks for the help!
Old 10-15-2005, 01:28 AM
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linclogs
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Default RE: VACUUM FORMING IDEAS

I used Sugar Pine for my molds. Not easy to find - not in the home supply stores like Home Depot or Lowes. I got some at a specialty lumber supply store. Sugar Pine is very clear and light. It's a popular choice for professionally manufactured pine molding and for folks that do wood carvings. Forget using the lumber you find in the home centers. I tried several types of lumber from them and they were always too hard and not clear grained enough. Sugar Pine carves and sands extremely easy. I coated my molds with 3 coats of polyester finishing resin, sanded between coats. It's easy to tell where more sanding is needed - look for the "shiny" (low ) spots and sand the surrounding (high ) area more until the spots are gone. Of course, this is assuming the mold is pretty much perfectly shaped BEFORE you start the resin coats. Also, sand the last coat with very fine sandpaper. I used wet-or-dry 220. Water won't hurt the wood once it's sealed with the resin. Any sanding marks that can be seen in the finished mold will probably show up in the parts, so the mold has to be really smooth.

One mold I made from Douglas Fir and it had heavy grain in it. Even though the mold was perfectly finished and the resin coats were perfectly smooth, you could see the woodgrain pattern in the finished canopy. I'm not sure why but I suspect it had something to do with the different colors of the woodgrain acting differently when heated up. So stick with woods that are very soft and fine grained (or nearly non-detectable grain ). Never tried balsa. But someone said balsa was not a good choice. Don't know why not. Don't know why it would matter if finished with the resin anyway.

One word of caution about polyester resin. That's the stuff that's extremely dangerous to use. It comes with a part "B" to mix with the part "A". The part "B" is a small bottle of thin, clear liquid. You count the drops when adding to the part "A". It's not an equal mix like mixing epoxy. But the dangerous part is they say take care not to get the stuff in your eyes. It's said it will turn your eyeball into a hard, brown lump before you can ever get it washed out. And the damage is permanent, as in "non-reversable". So if you mess with that stuff, wear eye protection.

Other safer types of resin could probably also be used but I never tried them. I know the polyester type was easy to work with (and safe once it was cured ).

You fellas that are trying this for the first time, post some pics of your re****s. Many modelers are always posting questions about "where can I get this cowl or this canopy", etc. If they knew how easy it was to make their own, they'd know where to get those obscure, hard-to-find parts. And once you have the mold, you can make as many as you want of the part. Nice when you have to do a repair job and can't find the molded parts anywhere to buy.
Old 10-15-2005, 10:39 AM
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Default RE: VACUUM FORMING IDEAS

Yeah, I've read that about the Polyester finising resin. Last time I had that stuff, I ended up with half a can and the hardner bottle had gotten brittle and leaked all over the cupboard. Now I just use Marine Epoxy. I think it says that it's poly as well, but it mixes in two equal portions - doesn't stink as bad as the finishing resin either.

I'll try to post some pictures when I finish. It'll take me a couple of days to get the mold finished right.
Old 10-22-2005, 08:33 PM
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jstrawn
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Default RE: VACUUM FORMING IDEAS

Here's the pictures of my setup and the results. Worked great with just a Shop Vac! The mold is Balsa strips (1" x 1/2") and took about 4 coats of sealer (I used regular wood filler thinned with water), and a coat of epoxy. I raised the mold about 1" above the work surface.

The frame is from Hobby Lobby - it's a "build your own canvas frame" out of pine. Couple of strips of 1/4" x 1" basswod and some screw's & wing nuts to clamp the plastic in place. .030 PolyCarb from my local plastic supply house. Heated it in the oven (on broil). The box is 1" pine, with a 1/4" Ply bottom and a 1/4" mdf bottom, with the 3/16" holes hand drilled. Had to actually melt the plastic twice, as the first time didn't pull far enough.

I'll post pictures soon of the project - it's a 1/4 scale Monett Moni. Using an Axi 2028, with a 10x7 prop and a 3s2p 2000mah battery. I'll also let you know how it flies.
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Old 10-29-2005, 05:34 PM
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jstrawn
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Default RE: VACUUM FORMING IDEAS

And here's the finished pictures of the Moni.

Haven't flown it yet, as the winds today are 20 gusting to 35. Not good flying weather[:@]
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Old 10-30-2005, 12:45 AM
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Default RE: VACUUM FORMING IDEAS

Nice canopy [sm=thumbup.gif]
What power ShopVac? I just picked up a 5.5 hp vac that I plan to use for vacuume forming.

Scott
Old 10-30-2005, 09:21 AM
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Default RE: VACUUM FORMING IDEAS

12 Gallon, 2.0 HP.

As mentioned earlier, this didn't have enough oomph to suck the plastic all the way down and give sharp corners, but I just raised my mold and trimmed the plastic above the bad areas.
Old 11-01-2005, 10:15 PM
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Default RE: VACUUM FORMING IDEAS

I was on the phone today with a local plastic warehouse (GE Polymers), and learned a few things. He said that styrene is hard to 'pull'. He recommended PETG because its cheaper (<C$20 per 4x8 sheet), and "pulls well".

So I did a little research, and learned that PETG requires only 14 psi vacuum to "pull", which is within the the capability of a standard Shop Vac.

So I'm going to try this with PETG. I'm scratch building a Mosquito, and need cowls, clear nose, and windshield.

I've already carved my windshield mold out of spruce. I would welcome a suggestion for a filler coat that is less dangerous than polyester resin.

Thanks. What a great thread.
Old 11-02-2005, 09:43 AM
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Default RE: VACUUM FORMING IDEAS

I made a plaster plug and primed and sanded and was able to pull .040 PETG without a problem. You might be able to use a sanding sealer and prime! I am not an expert, but this is what i experienced so far. The pull was ok, but I am going back to do a few more to get the best...

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