Chad Veich

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Many visitors to the scale forum at RCU have expressed an interest in vacuum forming techniques to assist in detailing their airplanes. While I am certainly no expert I have done a fair amount, not only for my RC modeling, but also in my profession as an architectural model maker. While my techniques are certainly not the only way, nor the most technically advanced, they have proven to work well in most applications and require no exotic materials (in other words, it's cheap!). To get started using my methods will require the purchase and/or creation of the following:

1. a forming box, easily constructed
2. a source of vacuum, I use a shop-vac
3. a frame to hold your material while heating and forming
4. a source of heat, I use the household oven
5. a method of holding your frame and material off of the oven rack while heating

Below is a picture of my smaller forming box. The outside dimensions of the box are 9x11 inches and it's approximately 3 inches deep. The size of the box is really unlimited so long as your source of vacuum has enough capacity to evacuate the box quickly. Mine is constructed of ¾ inch MDF (Medium Density Fibreboard) but plywood or particleboard, etc. will work just fine. The forming bed of the box is ¼ pegboard. The box needs to be as air tight as possible so silicone sealer is used in all corners and for attaching the pegboard for a tight seal. Also visible is the hole for inserting the vacuum hose. This is just a slip fit but it must be a good one so cut accurately. I also have a larger 12x16 forming box but have not found much use for it as of yet as the small one is adequate for most scale details. Just for reference, a small 1-gallon shop-vac is sufficient for the small box but inadequate for the larger one. However, a regular shop-vac works fine with the larger box. All in all very simple, no voodoo here. (continued)

Chad Veich

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There is not much more I can say about the vacuum source. A shop-vac is not the only way but it works well and I had one available. There are other, better sources of vacuum but I have not experimented with any as of yet so can't comment. For more on this subject I recommend the book listed at the end of this post.

Next item is the frame for holding your material to be formed while you heat it and form it. I make mine from aluminum angle stock available at most hardware stores. Bend to the proper size and pop rivet or nut and bolt the last corner to hold it all together. The three frames shown below all work with the 9x11 box depending on the size of the part I'm forming. One is slightly larger than the box, one is the same size as the top of the box, and one is much smaller for those really small parts. When using a frame smaller than the box itself you must tape off the unused portion of the forming bed so that a seal can be formed by the hot plastic. (continued)

Chad Veich

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As stated above, I use the oven in my home to heat the plastic. I have had no problems other than the hot plastic does not leave a family friendly odor. I try to do my forming when the wife and kids are out! It may not hurt to open a window or something also although the smell is not nearly as bad as some other hobby products we use nor does it linger for too long.

Finally you will need something to hold the frame off of the oven rack. When forming a part the plastic must be heated and allowed to sag. The larger the plastic sheet the more sag. I have made my frames so that they fit some aluminum cake pans I had on hand. The cake pans allow for a couple of inches of sag, which is more than adequate for the size sheets I normally work with. You do not want to allow the heated plastic to sag far enough to touch anything or it will stick and ruin the sheet. If this does happen, allow the sheet to cool and it will generally pop right off of whatever it is stuck to. Below is a pic of my frame with a sheet of plastic clamped to it and set on the appropriate sized cake pan. Notice I use small clips to hold the plastic to the frame. Make sure you have enough to securely hold the plastic while it is stretching. Also, make sure the clamps do not interfere with the forming bed so much as to prevent the hot plastic from forming an airtight seal. Ok, let's form a part.

Chad Veich

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For a quick and dirty example I have formed a static spinner over an existing aluminum spinner. The pic below shows the spinner placed in the center of the box ready and the vacuum is connected. There have been many discussions on what temp to set the oven for different types of plastic. Personally, I always put the oven on broil and place the rack right in the middle of the oven. Let the oven get hot and then place the frame/material and cake pan (or whatever you're using) on the oven rack. Oh yeah, you will want to put some gloves on for this too! Now, leaving the oven door open, watch the plastic closely. You will find that nearly every type of plastic will do three things:
1. almost immediately it will pull up taught
2. some moments later it will begin to smoke
3. shortly after starting to smoke it will begin to sag

Once it begins to sag it is ready to form although different materials and thickness will require different amounts of sag. If you form to soon you run the risk of the plastic cooling before the part is completely formed. Wait too long and it may tear or, most aggravating, it is prone to forming webs. Webs occur when the hot plastic folds onto itself in which case it will not form properly around the mold. I have found no way other than trial and error for getting the hang of how much sag is required.

Chad Veich

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Once the plastic is ready quickly turn the vacuum on (make sure it is within quick reach!). Using your gloves, grasp the frame on either side of the material with both hands and remove it from the oven. Quickly position it over the vacuum box making sure it will cover the forming surface. Keeping the frame as level as possible thrust it down over the mold. It is best, especially with tall parts such as a spinner, to push the hot plastic over the mold very quickly. This creates a seal and forms the part almost instantaneously, which helps to prevent webs from forming. It is better to use a generous size frame and material and make sure you cover the entire forming surface of the box. You will end up with some waste but the plastic is fairly cheap and gives you some room for error when aiming to cover the box. The spinner here is 4.5 inches in diameter and about 4 inches deep. This particular one was formed from .030 styrene, which is adequate, but .040 would have been better. This is another area where experimentation is needed in order to gain experience at judging what material thickness is best suited to your part.

Chad Veich

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That is a basic introduction although, admittedly, it barely scratches the surface. As time permits I will post additional information if the interest is here. Namely, there is much to be said about making your molds to allow for the best forming. Also, for those who asked, I will post some pics and a few words on making the exhaust stacks for my Hawker Typhoon. Below is a pic of the finished static prop. The blades are cast from resin or polyurethane which is another topic to be covered if you guys are interested. I welcome any and all comments you guys may have on stuff I may have forgotten or on tips you may have to make things easier/better. Also, if you have any particular questions regarding the process please put 'em here so everyone can benefit from the replies. Regards, Chad.

Mike James

THANK YOU for posting "mini-tutorials" such as this. A photo makes all the discussed items more understandable. We need more of these, on all the various questions that come up.

polarisRCU

Great work Chad !!!! Have you ever tried publishing your educational articles ? Thank you for the great details and photos.

rcalfred

Brother Veich: Amen to the thank you's!!! Well done. Have always wondered about how to do this at home. Questions: 1. have you tried this method with clear plastic (for canopies). 2. Do you add to the bottom of the plug to give extra material for cutting and finishing of the formed part? 3. Do you lubricate the plug to ease the sliding during forming, if so, with what? Regards.

Chad Veich

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Thanks for the kind comments. I hope that some good discussion will result from this post that will give more modelers the confidence to try vac-forming. It is really simple and has a great many applications for scale modeling.

1. Yes I have done clear parts and they are a bit more involved. The plug has to be much, much better for doing clear parts as any imperfections are readily visible in a clear part. There was an article in RCM on a method for doing clear parts that I have not tried but I want to. I will give it a shot and do another post on it as time permits.

2. Yes again. Probably 90 percent of what I do needs to have a "pedestal" of some type to block the part up off of the forming bed. I will try and post some pics of some of my plugs in the next day or two showing this.

3. Occasionally I do lubricate the plug, usually with vegetable oil or similar. A very thin layer is all that is necessary. Mostly it depends on what the plug is made from and what kind of plastic is being formed. Some of the plastics are more "sticky" than others. I try to make my plugs from materials that do not need any type of finish as the plastic is very prone to sticking to any type of paint or primer. You cannot use lubricant with clear parts at all as it creates imperfections that will show up (even though they are invisible on opaque parts). Honestly, I have not tried too many different types of lubricant so there may be some that I'm unaware of. For example, I've not yet tried mold release or wax but I have some on hand and may run some expirements.

I will post back with another quick explanation of what materials I have found best for making molds in the next few days. Thanks again for the kind comments and best regards, Chad.

SDCrashmaster

Great basic primer on vacuuforming, Chad.
Thanks

Kickin Chicken

Thanks Chad,
Will start building a vacuum box tomorrow, after I get back from Dan Steven's house taking pictures of Mac Hodges 20 ft B-29, its completely finished and these will the last pic's before its maiden flight. Bubba Spivery/Lanier did all the vacuum forming for us, wished I had better access to their equipment, sounds like the plugs must be the key to getting a good finish part.
Thanks Again,
Charlie

Chad Veich

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Thanks Crashmaster.

Charlie, glad to hear you're going to give it a go. I'm sure Lanier's equipment is like the Space Shuttle when compared to my clunker. I suppose that is the point though, for most of what we do a Shuttle is not necessary. This is especially true when you're not interested in producing parts for anybody other than yourself. I admit, I spend alot less time on some plugs simply because I know I can fix a few minor defects in the molded part in less time than it would take to make a stellar plug. Having said that, you are correct that the plug is key to making a quality part. Kind of like the quality of a paint job is directly related to the time spent on surface preparation. I am working on a part two that will cover what I have learned to date about creating plugs. Regards to all, Chad.

G.F. Reid

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I really enjoyed this topic Chad. I've been meaning to make myself a box for vacuum forming for years. I even have a dedicated shop vac for just this purpose. This just might be the inspiration I need to do it.
I'm really interested in seeing your method for resin cast parts.

Chad Veich

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Hi Greg, I hope you take a crack at it. I've got several new little tricks that I want to try out and share as soon as I get the time. I'll start working up one on casting too. Take care and drop me a note anytime, Chad.

BoiseBee

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Chad,
Thanks for the vacuum forming info. This is an area where one never knows too much.
It is neat way to make parts that aren't available any other way or to replace broken ones.
Until I started using a shopvac, I didn't have much success - not enough oomph to pull the plastic over mold.
I've attached photo of my setup. Used 9x12 baking pan (wife didn't miss it for weeks - oops!). I cut pegboard for vac floor and siliconed heavily around edges.
The 1x2's are mounted from the bottom of pan with screwin rubber feet
See image 1

BoiseBee

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The next image shows the completed setup - hooked to shopvac.
See image 2

Robby

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Thanks for an informative lesson, Chad...

Question: Where does one get sheet plastic and preferably in clear and larger than 12X12 .. ?

Thank you,
Robby

Chad Veich

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Good looking set up BoiseBee, simple and effective.

Robby, there are several wholesale plastic suppliers in my area that sell the stuff from sheets 4 feet by 8 feet on down. Check your yellow pages or search the internet for one in your area. I use a place called Curbell Plastics and I think they are nation wide so that may be a place to start.

I have several more articles on vac-forming in the works but time has been at a premium lately. Anybody else out there that wants to put up a how-to like this feel free, it's not just for the moderators. Thanks and stay tuned, Chad Veich.

BoiseBee

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Robby
I assumed you meant 12" x 12". I found 11" x 14" and smaller sheets of .020 to .080 styrene at a hobby shop. They're manufactured by Evergreen Scale Models, Inc. Woodinville, WA 98072.
They may make larger and clear pieces.
At one time I bought 1/2 a large .030 sheet (4'x4' I believe) from a local chemical/plastics supplier. I'm still using it. (It's kind of like buying 1/2 a beef).
Slightly different topic: I used to struggle to make good molds (plugs?). I just used a new technique to form the oil tank for a Tiger Moth. I shaped hard balsa, sanded very fine (400 W/D), then coated with 3 coats of finishing epoxy. Then fine sanded the epoxy surface. I used vaseline as a release agent. The piece came out very smooth. I still have the mold so I could make another.

JoeR

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I have done a very small amount of vacforming on a comercial small machine. I have not have problems with priming a plug. I also use baby powder as a release agent on the plug.

Daren Savage

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Another thing you can do is when you get plastic parts with kits, before you cut them up, pour plaster of paris in to them to make a plug. This may save you later down the road; either money ('cause you won't need to pay $15.00+ for a canopy) or if the kit is no longer available.

Plaster works great for plugs, no release agent is needed. You probably will need to tap it to get the air bubbles out after pouring the mixed plaster into your master. I turn on the scroll saw and rest the mold on top of it and it does the work for me.

Daren

Chad Veich

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Darren, the plaster of paris idea is a good one. I use it quite often for molds and have found that the casting plaster available in many art and hobby stores is even better. It seems to be much stronger and holds an edge better. Thanks for the tips.

Canuck1

Chad:

I have found this post very informative. I always wondered how this was done and never thought that I had the skills to do this. You make it sound simple. I definately will have to give this a try.

Craig.

smchale

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I have seen orthostone used, and it works very well. Orthodontists use it....i don't think it is the cheapest route.