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Author Topic: The making of a vacuum form box  (Read 1060 times)
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Dan Snow
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« on: March 03, 2019, 08:44:20 PM »

I was going to make this part of my Chieftain build since that project is the incentive behind my attempting this project, but hey, it's a tool for the shop to be used on this and future projects so I think it belongs here.

So why am I building it?  I sometimes like to scratch build, but not a real big fan of canopies and windshields and such.  I tried heating some plastic and quick as I could pulling it down over a mold. Results were slightly below mediocre at best.  I tried heating the plastic and then pushing the mold down into it.  That was even worse.  I was about to give up and make the canopy for the Chieftain 2 pieces.  Yeah, I know, ugly.

But then I decided to search out youtube, found some links here in the forums, and decided to give it a shot.  So this will be a build thread for a small-ish vacuum forming box.

Pic #1 - The pieces for the box itself. The top and sides are some 1/2" ply from another project and the bottom is a piece of leftover 1/8" door skin. Overall box is 9"x7.25"x2.63"

Pic #2 - The hole grid laid out on the top. I marked the 6" x 7" grid on 1/2" centers, but for the first trail I only drill the holes on 1" centers to see what sort of suction my old Lowes shop vac can           
             pull. The pattern is made up of 1/8" holes

Pic #3 & #4 - Making the box side assembly. The corner clamps I inherited from my Dad have been well used. I could never hope to get square corners otherwise!  Grin

Pic #5 - Bottom is screwed on, top is aligned by the corners so of course I had to tape up the seams and give it go!! Heated up an overly thick piece of plastic with the heat gun and it actually
            started to suck it down over a block I had lying on the bench nearby. That was encouraging!!   Grin

Pic #6 - All the holes for attaching the top have been drilled.

The plan going forward is to permanently attach the top with nails and silicone sealant. The bottom will be screwed on over a gasket so it I want to get inside the box to try baffles or other things I
can do so easily. I'm going to build some different sized frames to hold the plastic. Don't want to use a whole 9" x 7" piece of plastic for a small part!  I can tape over the unused holes around the edges.  For heating element I will pick up a single burner hot plate. Will need a stand to support the plastic over that.

Stay tuned, more pics to follow.

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« Reply #1 on: March 04, 2019, 12:18:39 PM »

beautiful craftsmanship!
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« Reply #2 on: March 05, 2019, 12:03:14 PM »

Suppose it's impolitic to suggest, at this point..
That a Plastic beverage bottle...Heat shrunk onto a plug inserted into it's cut open bottom
 (in your oven at 320+ F  for anywhere from 5 to 15 mins (watch carefully) makes for a V nice and durable canopy or whatever ?
 Couple of advantages:
Donor Bottles are ubiquitous /free .. pick one that seems suitable.
Plugs do Not require a perfect smooth finish .. no telegraphing of imperfections as with a Vacuformer.
 
Do Note tho... that Every technique requires experimentation and experience.
 Usually 6 attempts for a first useable item, whatever technique you use.
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Dan Snow
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« Reply #3 on: March 10, 2019, 11:17:25 AM »

After a brief hiatus, back to working on the vacuum box.

Pic #1 - Picked up an inexpensive hot plate as a heat source, about $10 at WalMart.
Pic #2 - An idea for getting the heated plastic onto the vacuum box. I sorta remember this from a Mattel Vacu-Form I had as a kid in the very early '60's. The idea is a sliding hinge point that allows me to keep the plastic well above the element, but also allows me to lower it to the box without having to mount the box on stilts!  It'll take a little trial and error with cardboard to get the geometry  right but shouldn't' be too hard.

Speaking of spacing above the heating element, I figure at least 2" to safely allow for the 1/2"-1" sag in the heated plastic I've read recommended, depending on type and thickness. What have folks found is a workable starting point?

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Glenn (gravitywell) Reach
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« Reply #4 on: March 10, 2019, 03:54:06 PM »

That's a very slick idea.  I'm stealing it! Grin
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« Reply #5 on: March 10, 2019, 08:00:21 PM »

Glenn, I'm always honored when someone thinks one of my ideas is worth using, enjoy!

I did a little experimenting and came up with a slightly different hinging idea than I first considered.

Pic #1 - Instead of a sliding pivot point I looked at a double pivot point with stops. If I build it with a slight bit of friction in the pivots, the stops should help keep things lined up easier than the sliding pivot design.

Pic #2 - Starting with it in the heating position. I will likely have something attached to the base plate that will support the tray above the heating element to prevent the plastic from being pushed down onto the burner.

Pic #3 - When flipping it over the top arm stop locks the top pivot forcing the movement down to the second pivot.

Pic #4 - The lower pivot lines up with the top of the vacuum box so the plastic tray is flat. I'm not 100% sure this will work as the plastic won't be coming down vertically and parallel to the surface of the vacuum box. Probably not a big deal for low molds but could be an issue for taller ones.  Will need to do experimenting to see.
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« Reply #6 on: March 11, 2019, 07:40:31 AM »

I had worked on this last year but a lot of other projects superseded my effort.  I had 2 drawings one similar to the Mattel vacuform using a toaster heater element to heat up the plastic.  The other is similar to the dental vacuforms  but large enough for modeling use.   Not sure which would work the best.
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Dan Snow
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« Reply #7 on: March 11, 2019, 08:19:33 AM »

Interesting ideas there. I like them.

I'm still thinking about the transference of the heated plastic to the vacuum box. The more I think about it the less I think my double pivot will work.  Now wondering about a tray that slides and then can be pushed straight down. Need to try sketching something along those lines.
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« Reply #8 on: March 11, 2019, 09:03:06 AM »

The drawing I have like the dental vacuform you could rotate the plate with the plastic so it was over your heating element then rotate back and push it down.  I was thinking of having a bearing of some sort that would make it slide easily on the pole.  When I designed it I was going to use the heating element on top but I think it may be a bit harder to heat the plastic and the hood for the heating element would get pretty hot.
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« Reply #9 on: March 11, 2019, 09:59:01 PM »

Interesting ideas there. I like them.

I'm still thinking about the transference of the heated plastic to the vacuum box. The more I think about it the less I think my double pivot will work.  Now wondering about a tray that slides and then can be pushed straight down. Need to try sketching something along those lines.

Not Rokit science  being discussed here Grin
 Hows' about flipping the Vacu Box onto the  plastic holder ? Your diagram has the wrong part 'flipping over '.
Zero heat loss /transference issues... as the heated plastic  remains heated right up to the point its being vacuformed.
 Yer Welcome.
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« Reply #10 on: March 12, 2019, 06:18:00 AM »

You don't actually need the vac box and heating element parts connected to each other.

I have seen a pal's set up working and he just has the heating element on the bench alongside the vac box and the frame holding the mouldable sheet of plastic is free. 
A set of 4 stand-off height posts to set the distance of the frame above the heating element and when hot enough, he uses oven gloves to pick up the frame and drops it onto the top of the vac box.
The frame loosley locates over the top of the vac box but there is no complicated seal arrangement.  It works fine.
Vac box is about 10" x 8" and frame half an inch bigger (A4 size).
For really small items he tapes up the vac box top holes with 2" wide tape around the outside and has a smaller frame for the plastic.
Works for him and would remove all your complicated hinges and sliding bearings and the attendent hassle of constructing them.

All for a simple life I am!

John M
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« Reply #11 on: March 12, 2019, 06:50:57 AM »

I was pleased the you started this topic Dan because a vac box is something I have pondered over for years and it is becoming an increasingly important tool if like me you are into building small models.

I could never get my head around it but reading this topic the sun is beginning to emerge from behind the clouds!

I quite liked your hinge idea and John I like little gadgets, but what you say about just dropping the tray on the box is good news. You see i thought that there had to be some sort of seal etc. and wondered how this was achieved with a hot tray! But yes, no reason why with a good suck the molten plastic won't succumb to air pressure?

So, Dan, can you press on please because I feel that this is a project I can handle.  Any chance of photos or a video of it in action  - doing its stuff please.  And if you can throw in a bit on the buck as well please that will be really good.
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« Reply #12 on: March 12, 2019, 08:16:25 AM »

Have you seen Chris Boehm’s simple set up on You Tube? If all you want to do is vac-form plastic parts, you can really keep it simple. If you are having fun making gadgets, that’s really what you’re doing...as long as you are in a zone where you can forget the clock and wallet, stay there it’s good for you!










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« Reply #13 on: March 12, 2019, 08:19:29 AM »

I relied on a fairly long pivot arm to reduce the amount of sideways movement as the arm approaches the box.
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Dan Snow
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« Reply #14 on: March 12, 2019, 09:20:17 AM »

Fascinating ideas gang!

When I embarked on this project I had a simple goal. I wanted something that would allow me to make the occasional canopy, wheel set, etc for my models. An added bonus would be to have it all one unit. Why? So on the rare occasion I needed it I didn't want to have to search the shop for the bits, gather them together and then find a place to set them up. Ideal would be all mounted to one base that can be stacked in a corner or on a shelf.

Pic #1 - Why I haven't made a lot of progress on the box lately. I occasionally am asked to make wooden toys and buildings for our Children's Museum. The little jets are one of the most popular items.

Pic #2 - A sketch of another idea I'm thinking of. The plastic tray can be moved over the vacuum box and then pushed vertically down over the mold. A couple of light compression springs to hold the tray holder up even with the rails until light pressure is applied.
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« Reply #15 on: March 12, 2019, 09:53:17 AM »

I'm another - keep it simple - vacformer

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=23108.msg222965#msg222965
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Dan Snow
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« Reply #16 on: March 15, 2019, 08:54:24 AM »

The project has been put on hold do to health issues.
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Dan Snow
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« Reply #17 on: March 31, 2019, 06:33:53 PM »

Anyone out there with a homemade vacuum box that is willing to share photos of their frames for holding the plastic during heating and sucking?

I've tried a couple different prototypes and haven't come up with a workable one yet.  First one was way too flimsy and the second was hard to seal.


thanks,
Dan
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« Reply #18 on: March 31, 2019, 07:28:29 PM »

I found that one big problem was getting the plastic used to heat up enough so that I could take it out and put it on the box with the vacuum.  I tried several methods but the best seems to be a toaster oven.  I can watch the plastic sags and then remove it (and the frame) with pliers and put it on the vac box very quickly.  The other sticking point was having the frame align over the vac box. I did that with 2 uprights in each corner to have the frame sit against.
Photos to follow this evening if anyone is interested.
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« Reply #19 on: April 01, 2019, 03:41:46 AM »

Yes please
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Dan Snow
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« Reply #20 on: April 01, 2019, 05:44:10 AM »

Photos will be very much appreciated.  Thank you.
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« Reply #21 on: April 01, 2019, 11:02:44 AM »

Here you are...

Note: I used sandpaper glued on one side of the frame to help hold the plastic sheet.  I also closed off some of the holes on the main alum pan to concentrate the vac. Hopefully these photos will explain it enough.
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« Reply #22 on: April 04, 2019, 10:38:15 PM »

Anyone out there with a homemade vacuum box that is willing to share photos of their frames for holding the plastic during heating and sucking?

I've tried a couple different prototypes and haven't come up with a workable one yet.  First one was way too flimsy and the second was hard to seal.


thanks,
Dan

Frankly I'm Not understanding the problem.
I've had a DIY vacu contraption for ~30 yrs.
 Initially I fitted  draught excluding type Foam taped edges so that I would get a max Seal for the plastic holding frame against the Platten.
Decades of use has proven that that affectation is unnecessary.
My aged Shop vac provides a surplus of suction.
Recently I've been using quickly assembled 3/4" square cedar rectangles (have lots on hand) to build Plastic holding frames,
 appropriate to plastic sheet and part to be formeds' size.
 To these I have staple gunned my Styrene .  Easy/quick And reliable.
A screwstick levers out the staples nicely and the frames are reusable for ~ 6 times.
Then I build a fresh frame .
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Dan Snow
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« Reply #23 on: April 19, 2019, 05:29:15 PM »

Once again asking for advice.
I finally had time to make a plastic holding frame that is good enough to practice with, so now I have another question.

What type of plastic should I get? For chuckles I used a piece I cut from a clear plastic vacu-formed food container. As it heated it turned opaque and never really got very soft.
I have some .005" thick Acetate I got from Peck Polymers. Is acetate good to use? But is .005" too thin?

And finally, what is a good, non fogging adhesive to use to glue on canopies? I really hate to make a decent model and then muck it up with a crappy glue job on the canopy.
Thanks

« Last Edit: April 19, 2019, 07:24:06 PM by Dan Snow » Logged

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« Reply #24 on: April 19, 2019, 07:25:02 PM »

Styrene, ABS and Polycarbonate are ideal for vac forming. If your doing canopies
or any other clear parts, PETG is the way to go.

If you reuse plastic containers and other packaging, use care and in a well ventilated
area. Some of these produce deadly gases and you may be overcome before you know
it. Better to be safe than sorry.

I highly recommend this supplier of plastics:
http://www.widgetworksunlimited.com/Vacuum_Forming_s/4.htm

I used to get mine back in the day in Tenn on 4 x 8 sheets.
The holding frame I use is simply made of wood, held together with drywall screws. I attach the plastic on
top by placing those large push pin thumb tacks. Not the Plastic ones but the wooden ones which are about 5/8" long.
Once the forming is pulled and cool, simply twist and lift. Your done. The pic below shows my inner stage and outer
plastic frame. If you look closely, you'll see where I place the tacks. When it gets worn out, I'll make another frame.

Skyraider
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