Step 5: The Platen

The Platen is the surface on which the molds are placed and on which the plastic forms a seal for the vacuum. There are many different platen designs but most are designed with many small holes that the air is pulled through to create the vacuum. My platen follows this design. To make the platen I used two sheets of 1/4in. plywood cut to 23in. long and 11in. wide. In the bottom piece I cut about a 1in. hole in the middle so that I could put the PVC fitting in to it. The PVC parts were chosen so that I connect the Shopvac to the platen, and of course this will create the vacuum. In the top piece I drilled a bunch of 11/64in. holes in a pattern. The pattern and size of holes is up to you, just be reasonable. These two pieces are separated by the balsa wood strips. The balsa wood is 1/2x3/16in. and cut to fit around the perimeter of the top and bottom platen parts. Then the whole thing was glued together. The idea here is to keep the volume inside the platen as small as possible. That way when you flip on the shopvac you don't have to pull a bunch of air out of the platen and then out from under the plastic.
I don't see how the heating elements are made, or I should say, it would be nice if there was a drawing with dimensions and materials so you could copy your design. The calculations could be done to vary your basic design, but a starting point would be useful.
Practice will make perfect. Dont give up now!
Great instructable! A couple of other people have commented that the heat source being underneath the plastic will give you the potential of fire (as you found out) but I would like to add a little more on that. Another benefit you get from having the heaters above the plastic is that 1) the sag can go further which helps if you are pulling heavier guage stuff or tougher stuff like plexi and 2) when styrene first sags from the heat (in the overhead heater formers) it will sag a long way then it will pull up a little as the heat affects the other side of the styrene, this is usually the best time to get a pull because the material is at the perfect blend of strength and pliability. Having said all that, your design is very cool and it will work great for the home hobbyist!
hey guys can someone tell me where the pdf for the &quot;wiring&quot; is? I can't seem to find it anywhere... all I found were pictures of the oven. Can someone draw or explain how to wire these dimmer switches from the outlet and to the terminal block??? Thanks!<br>
Anyone know of any projects i can do with mr coffee coffee makers? I recently bought a bunch off of http://coffeemakersmrcoffee.com and need to find uses for them. Thanks!
hmmm.... you should try using a heat gun for your heat source. its a bit slower but no flames
With a heating gun you won't be able to get even enough heat for the whole sheet. The easiest and best way is actually to have your heater placed directly abouve the table upside downso that the sheet gets heated from above and away from the coils not closer to the coils. You're gonna have to mount your sheet frame on rails, but it's a much safer approach to vacuum forming.
Good job and nice build. I worked for a company that made items by vacum forming (Sailing Specialties Inc) a few years ago working in the CNC department. First suggestion, stop using styrene, styrene is a light weight plastic that is not very good for heating amd forming. If possible try to PVC, ABS, or even lexan. They are much better suited to heating and forming. Number two, instead of the hinged tray that flips make a tray that slides like a drawer. Which takes me to the third. Instead of the heating elements on the bottom, place them on top, or better yet elements top and bottom with metal plated for heat spreaders (they would also cover the elements and should prevent fire and make clean up easier.
Like you said. it sags and then touch's the element. An easy solution to a even and uniform heat is to have say a hotplate with lid that covers all you have. Thus heating from the top down to your styrene. So it is basically a box where your styrene is the bottom and small venting around its perimeter. I have seen a few guys using the top element in the oven. And you can notice when the plastic(styrene) is ready due to the mat finish it receives from heat. If you have at least a 1000W vacuum it will help pull a bit better if it happens to be to the cooler side of readiness. Man vacuum forming is fun. i feel like i am running a sweat shop some days.
I think some sort of heat spreader mounted over the heaters would give you more even heating and prevent melting plastic from falling onto the heaters and catching fire. Maybe a sheet of aluminum or thin steel.
you get a x10 in XP for the humble pie you just ate. thanks for sharing!
Quite agree! &quot;There are no experimental failures - there's just more data...&quot; If I might suggest: Masonite for the platen/vacuum manifold - hard and smoooooth surface, can be had in both solid and perfboard, tolerates heat pretty well, less work, greater hole-pattern precision at, probably, slightly greater expense... Also, some kind of heat-resistant &quot;honeycomb&quot; separator atop the elements would keep the sheet from sagging into the &quot;free-fire-zone&quot; when it goes too floppy, too fast like that.
I like that while doing your first test and having it catch on fire that you still took the time out to photograph it!! I've always wanted one of theses and now I have a basic design... have you considered using IR lamps instead of the wire heater?
We needed a video from your work please add a video !!!
you know, i think you could have still salvaged this design. Perhaps you could have moved the oven to the top, burners down like you did, but have it roll to one side w/ cabinet rollers or something. That way, you can have your fire safety deal, and even more so, because you could roll the heat aside if it did catch fire. You could also perhaps put some clear acrylic to hold up the plastic-frame-holder thing, so the heat would still stay in (not sure if that's desirable in this application) and you could still see the plastic sag. but then again, perhaps flipping the plastic would ruin it. idk.
additionally, this would take up a lot of space. More than your new design, but i think it's still simpler.
Very cool idea. I like how you hinged the material holder to make the switch from heater to vacuum plate easy. I may borrow this idea for some of my projects.<br><br> Also, congratulations on a successful test of your fire suppression system. I hope your next test goes better.
Oh wow... That took guts to post your epic fail. Bravo.
Great project. I would like to see the conclusion. I'd like to suggest to use a chicken wire screen over the heating elements so that the plastic melts, it will drape over screen instead of the elements. You can always cut another piece of chicken wire screening, if the first one proves impossible to clean.
vist www.tk560.com/vactable4.html there you will see something similar, based on Thurston James' machine.
I want to build something similar but will use Quartz heaters from small oven. Backerboard is nice but the problem is that is to big in my opinion to buy. You use only one portion of it and have big leftover. It is bulky to transport to and not so easy to cut. Another solution is to make your own concrete boards with concrete mixed with sand and fiber (search 'concrete board' here). That way you can make any size you want. You can also make one piece shell (in steps). This method has its own benefits. When mixture is poured, wooden pegs can be added for screw holes. I think that Vacuum Former Design 2 is better than this one. Most industrial formers are done with heater above (plastic sagging and melting problem). I've made few of my own forming machines and none was as good as I wanted. Forming is simple, but I have to repeat few key points for success: -Good uniform heater. Working with kitchen oven is fine for tests but for good results good custom made oven is needed. -Good plastic holder frame. Has to be robust and accurate, otherwise vacuum will not be achieved. I always add strips of 150 Al sand paper around to hold plastic better. -Good and accurate frame sliders. It is important that frame with heated plastic be transferred to vacuum plate quickly and accurately. -Good vacuum plate. Having good seal is even more important than vacuum source. Vacuum cleaner can produce enough of vacuum for forming but only if there is a good seal. High end vacuum pumps will help if finest detail is needed (but only if all above is achieved).
a circular saw with fine blade is the best for thin strips just make sure to setup a fan to blow the dust away
OOOPS, Awsome, I thnk yoou did a good job for your first time!
So far so good, could figure the Wattage of the burners from ohm's law. can I make a suggestion? Don't use a fan to help heat the material, it blows the sag and makes it wavey that causes imperfections in the part when it pulls. If youwant to use a fan, use it to help cool the part after your pull time is done. I rettro fitted a former at work, changed the the heat source from "cow rods" to inferred ovens, added a PLC for the controls, and wished I would have made the material move over the heat source instead. It came out fine, been wanting to make one for home to tinker with, I have a heat source and that's about it....
I'm with you so far......
I'm building something VERY similar to what you have here, and i have a question about the nichrome wire mounting... what are you using there to isolate the wire from the frame of the box ? does it matter if it's metallic, or conductive ? i guess being pretty conductive, most metals wouldn't alter the resistance factor too badly, so it shouldn't affect your heat output... i'm just curious as to whether you could possibly short the system out.
The wire I had came mounted in the x-shaped ceramic mount. I've seen other guys use ceramic stand-offs. I would not use anything conductive, the chances of some thing being shorted would be to high. Your dealing with many amps of current you need to be as safe as possible.
ahh ok, thanks for the quick reply! i couldn't tell from the pic if that "X" shaped mount was metallic or not. i was planning on using some sort or ceramic insulator... anyone here know anything about using plaster for such an application? i've heard of people using it for lower temp installations, and if i can't use it on this, I have another project that is low temp ( <200 degrees F ). You did a good job on this project though, looking forward to seeing your final design!
My final design is on instructables too <a rel="nofollow" href="http://www.instructables.com/id/Vacuum-Former-2/">http://www.instructables.com/id/Vacuum-Former-2/</a><br/>
Does anyone know how to make something enclosed? Everything on these types of vacuum formers have a 3d front and no back. I want to make something that has a 3d front and 3d back with a seam along the side. I know I'm not explaining very well, but the first thing that comes to mind is hollow plastic toys with a seam on the side and a small hole in the bottom. I'm trying to figure out how to make plastic pink flamingo's that can be staked in a yard.
Toys that you see with a seam and a hole are injection molded. Those machines are much more complicated than a vacuum former. If you need two sides you could make two molds, one for each side, then vacuum form them and stick them together.
What gauge wire did you use for the burners?
Finally! An intellegent, useful instructable. Lots of useful detail. Nice work!
he must be a new member, ha ha
whats a good site to get polystyrene? and are there any substitutes? I need a few 12" X 12" sheets. hopefully cheap
I would recommend heating your styrene plastic in the oven until it sags instead of building a stove. Would have liked to se a better seal around the base. Good Instructable none the less.
do you have a layout for the nichrome wiring for a 24 by 24 inch oven? I could use that. Im trying to source up prefabbed heating coils, but if I cant Im going to have to build my own oven. I could use some help with this, its my only hurdle on this build
I haven't see any type of prefabbed coils for that large of an oven. If you just want a layout so you can build it yourself use the oven calculator, I put the link on the equations page. Check out the tk560 forums for other ideas for the oven.
Equations page? I'm new here. Dont know where that is. I'm looking for as much prefabbed stuff as I can also price is an issue so I can keep the overall price down. I have the layout of what I'm building, I just need to find heating coils 110vac that will provide even coverage. I'm needing to have a heating coverage for this large of an area, so I can perform pulls on larger items like costume chest plates, and prop weapons. Id like to stay away form the nichrome wiring as it would take alot longer, and be more complicated to do.
The equations page is step three of this instructable
This is a really great and detailed instructable! Good Job...<br/><br/>I was thinking earlier today (dangerous I know). Couldnt you just use some burners such as <a rel="nofollow" href="http://www.everythingkitchens.com/toastmaster_range_burner_6420.html">http://www.everythingkitchens.com/toastmaster_range_burner_6420.html</a> ...only you know from a department store and only $10?<br/><br/>Seems like your heater setup is far more complicated than needed. :P<br/>Otherwise the design is awesome. <br/><br/>--Fjr<br/>
The heat source is just that, something that gets hot. If your thinking about building a machine using one of those check out this post <a rel="nofollow" href="http://www.rcgroups.com/forums/showthread.php?t=621858">http://www.rcgroups.com/forums/showthread.php?t=621858</a> This came from dcrash who also has a vacuum former in the in the laser cutter contest. <br/>
Another good choice for a small vacuum former (about 12 x 18 inches) is the $30 Uniflame portable electric barbecue grill from Wal-Mart. One nice thing about the portable grill is that it doesn't have any internal controls under the hot part, so you can put it upside down on stilts right over your platen. You could use two for a larger machine (about 18 x 24 inches). That not only reduces the footprint of your setup, but lets you use different sized plastic with your oven, with no hassle. (With a bottom heater, hot air rises around undersized plastic and escapes, so you need stop the opening down to the size you're using, or use a lid. With a top heater, the hot air rises into the oven instead of escaping, so less-than-full-size plastic isn't a problem.) Any time you use a prefab heater that doesn't put out just the right amount of heat, evenly distributed, you generally need to do something to even out the heat. Links on my web site show how to do that for a two-burner hot plate or a portable electric grill. (Go to www.VacuumFormerPlans.com and see the links in the sidebar.) For a large machine, the best cheap way of making an oven is to string nichrome coil yourself. (You can get enough nichrome coil for a 12 square foot oven for about $30.) That's not actually hard to do well if you know a couple of tricks. There's a bunch of people over on the tk560.com who've built their own vacuum formers that way. If your oven is metal-lined (aluminum flashing is good), you need high-temperature (ceramic or mica) electrical insulators to hold the hot wire, but you can scrounge those from old waffle irons or toasters from Goodwill.
I plan on building my own vacuum former today (most o it anyway). I want to build my hydrofoam racer out of a more durable material than Styrofoam (http://www.zippyvideos.com/4603120202347646/hydrofoam/ pardon the corny music). I found a local supplier for the plastic but I have two questions.<br/><br/>1) My &quot;toy&quot; came in a protective Styrofoam case which I think I can use to make casts for the pontoons by pouring mold material into. Do you know of any fast setting molding material that does not react with Styrofoam?<br/><br/>2) With respect to the plastic sheeting, I need something light. The transparent stuff I bought from the local supplier worked well on my shoebox experiment but I fear it may be too heavy. What is the lightest commercially available sheeting that has the best impact resistance.<br/><br/>Great posts by the way. My remedial experiment taught me some things but I have really sidestepped some unnecessary trial time purely by reading your posts. Keep up the great work.<br/><br/>Regards,<br/><br/>KKB<br/>
I can't really help with the fast setting mold material, I never really used that type stuff to much. As far as the plastic sheet goes look into polystyrene also called High-Impact Polystyrene. This company sells it <a rel="nofollow" href="http://www.professionalplastics.com/cgi-bin/pp.pl?pgm=co_disp&func=displ&strfnbr=3&prrfnbr=85378&sesent=0,0">Professional Plastics</a> You could save weight going with a thinner material but too thin and it will be to weak. You'll just have to find that balance for you application<br/>
yeah i did a quick drive by at home depot and picked up some LePage Poly Plaster of Paris powder. $3.48 for 1 kg mixing ratio for 4:3 (h20). and it's fast drying (60 minutes but I'll leave it in all night). I'll keep updates if your interested.
Just what I'm looking for thank you. For the heater, I think I'll use a bank of light-bulbs with a dimmer switch.

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Bio: I enjoy building things more than actually using them.
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