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Home Vac Former For making RC car bodies 8 years 2 months ago #36346

Re having to put extra bits next to the wheelarches to avoid folds - I'm wondering if the original was formed vertically, possibly with two front end bucks back to back & nose in the air ...

I had thought of that as well, but the base is clearly the base of the car. Unless it was a reverse form?


Another thought was that the plastic is pre-formed or stretched in the area around the front to make it more accommodating. It might also help if I had a lot more sucking power, maybe my vac former doesn't suck enough :woohoo:

I'm also tempted to buy a cheap vacuum pump from eBay. If I have my numbers correct it should still have at least 4 times the sucking power from the vacuum cleaner I'm using. I will also try heating the buck too, so the plastic stays hotter longer and has more time to shape and settle. I did try continue heating with heat gun on one of my attempts, but I didn't find that particularly effective.

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Home Vac Former For making RC car bodies 8 years 2 months ago #36428

small update. I have found a source of .375 mm polycarbonate and the supplier is sending me a sample. However I think I should be using either 0.5 mm or 0.75mm (from measuring the ones I have), but the next size up that I can get is 1 mm. If I stick with 1 mm polycarb, I'm going to need to up the sucking power, and I will probably lose a little bit of detail. The best way to do this seems to be a vacuum pump and air tank. The idea being you evacuate the air tank, and use that for pulling down. The set up looks like this ( from instructables ).



New parts will cost around $300AUD all up and take the vacuum power from around 5 inHg to 25 inHg.

I've also discovered the reason for the bubbles in the polycarbonate that I was getting. Apparently is water migrating out of the plastic. So I will have to some timing and temperature tests.

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Home Vac Former For making RC car bodies 8 years 2 months ago #36429

Now, while I sort out the upgrade to my vac former, I will still test some other things. One of my goals is to copy bodies that I have that are a bit tattered. So last night I tried a Road Wizard body. I chose this as its not too big and its still in reasonable condition. So I used cloth tape around the front and back to make the level the same all the way around. I also taped up all holes. The next step is to support the shell when pouring the plaster of paris in. For this I used home made green sand. Its a sand used for casting and can hold its shape quite well. Its made from crushed clay kitty litter, refined river sand (although I think I need to use much finer white play sand next time) and a bit of water.



Mix and pour in some plaster of paris. I am slowly getting better at this, but still get bubbles on the surface. The other bonus of the sand is if it leaks, it won't matter too much. At this stage I'm not going to either placing the plaster mix in a vacuum or vibrating it, as ends up just on what becomes the base.



The sand clumps are where the plaster leaked through. Really easy to peel off.


Once dried, I carefully pulled out the cast. I was pretty happy with this overall. I'll leave it a few days and then do a test pull with ABS and HIPS. The front will need to be cleaned up and trimmed a little, as well as drilling a number of sink holes.
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Last edit: by yogi-bear.

Home Vac Former For making RC car bodies 8 years 2 months ago #36430

:y: Nice work. To avoid the bubbles, you can use vibrations it is lower cost than a vaccum clutch ;)
and the home made moulding sand is interesting too. 1mm polycarb is for me too thick. 0.5 looks to be the best. :y:

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Home Vac Former For making RC car bodies 8 years 2 months ago #36431

:y: Nice work. To avoid the bubbles, you can use vibrations it is lower cost than a vaccum clutch ;)
and the home made moulding sand is interesting too. 1mm polycarb is for me too thick. 0.5 looks to be the best. :y:

Good idea with vibrating, I've gotten some ideas for a simple vibrator which I will try.

As for polycarb thickness, still looking for a 0.5 mm supplier.

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Home Vac Former For making RC car bodies 8 years 2 months ago #36472

Tonight I wanted to try warming the buck as well, and with the Road Wizard body I'd made a couple of nights before. The body had come out reasonably well with the plaster smooth and consistent. I had intended to try polycarb as well, but started with 1 mm HIPS, which is about what I am expecting 0.5 mm polycarb to behave like. I ended up damaging the buck, so only got one pull in.



I gave it around 20 mins, until it had reached about 100C, but it turns out that wasn't anywhere near long enough. As soon as I took it out, it dropped to 34C. I could even touch it with my hand. So I will have to warm it a lot longer if I want to try that method.




Even though I had drilled extra holes, there is detail loss in the cockpit and the side indents aren't as sharp.



I'll also have to think about the angles. I ended up having to cut it out. The final body curve a lot at the base too, so I will have to add a good 10 mm at least to the height.



Still, trimmed up properly it would do fine on a runner.



Here you can see the loss of detail a little better. I also ended up damaging the buck a little getting the body out. I'll have to fix that and add some angles around the back to make it easier to separate next time. I'm wondering if bodies like these are reversed formed, I think that will get more detail without having to drill holes everywhere. So that will most likely be my next attempt.

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Home Vac Former For making RC car bodies 8 years 2 months ago #36475

:) I showed your work to a friend and He said me that you have to (could, need) drill several small holes in the plaster to have a nice former by vaccum. After, to have better details, maybe you could make 2 molding. 1 for the interior of the body, your plaster one, and 1 for the exterior your sand one. And put your sheet in sandwich.
And why not melt a small quantityof plaster in your litter sand mixture to have rigidity.
You could accentuate details on your plaster molds to have better results on your bodies?
these are only ideas and suggestions. not advices or solutions ;)
Your work is always so interesting :y: :y: :y:

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Home Vac Former For making RC car bodies 8 years 2 months ago #36498

:) I showed your work to a friend and He said me that you have to (could, need) drill several small holes in the plaster to have a nice former by vaccum. After, to have better details, maybe you could make 2 molding. 1 for the interior of the body, your plaster one, and 1 for the exterior your sand one. And put your sheet in sandwich.
And why not melt a small quantityof plaster in your litter sand mixture to have rigidity.
You could accentuate details on your plaster molds to have better results on your bodies?
these are only ideas and suggestions. not advices or solutions ;)
Your work is always so interesting :y: :y: :y:

Cheers Stingray. I did drill some holes, but I might need more. And when I upgrade the vacuum available that will make a difference too.

The sandwich idea is good, but I will leave that for a bit, as I have to work out how I will set that up.

On the bright side though, today I found a supplier of 0.5 mm polycarbonate and have placed an order that hopefully I will have by the weekend.
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Home Vac Former For making RC car bodies 8 years 2 months ago #36526

ok, only a minor, disappointing update. After finding a supplier for 0.5mm polycarb, I ordered a box of sheets. Received them Wedesday and tried them out Wednesday night. Pulling a sheet out of the pack I was thinking "these aren't very stiff", coupled with the thought that these were a lot cheaper that I was expecting meant things probably wasn't going to go well. So I did a vac form anyway, and yep no good. Turns out they sold me PVC. :ohmy:

So I get back on the phone. Although offered a refund, I decided to keep the sheets. I was then told that they could get 0.5 or 0.75 mm lexan. So ordered the 0.75 mm lexan after confirming that is was indeed polycarbonate. Supplier rings a day later to say they actually can't get it. :blink: So that was really annoying, especially since I know lexan is supplied in 0.25, 0.375, 0.5 and 0.75 mm sheets, but seems not in Australia though. Maybe we don't have enough use here so that someone will import it.

My sample of 0.375 mm from another supplier also arrived this week. It was definitely polycarbonate, but it'll be too thin to make a body thats used for driving. Still I would have ordered some if I didn't have to order in lots of 20 sheets at over $10/per sheet. So I'll leave that alone for the time being.

From measuring a lot of the bodies I have, it seems its the 0.75 mm polycarbonate I need, so that means I'll have to stick with the 1 mm at the moment. Now thats only a 0.25 mm different, but its amazing what that difference seems to make, even just visually when comparing to a bought car. The extra pulling power from new vac pump when set up will help, so very keen to try that now.

Another idea is that since I have access to some heatable lamination rollers, I may try setting the temp on them to just over 155C and rolling the sheets, in a vain attempt to flatten them a little. I suspect that won't really work though, as the rollers have a fair bit of compression built into them.

On the bright side, my vac forming tank arrived, just waiting for the vac pump now.

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Home Vac Former For making RC car bodies 7 years 11 months ago #38003

So finally an update, over the last few weeks I've managed to build and test the vacuum system,

and started to build the frame for the new vac former. Currently its only hot glued together, so I can test fit the layout.


Its wide enough to vac form up to around 550 mm.


I've also been casting more. The bodies are difficult to separate from the castings, and I've found pumping in air helps a lot. So I'm going to add an air inlet to the vac former as well. This will help not only with any casting bodies I do, but also removing vac formed bodies.
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