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Another guy from Illinois!
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Hot_Wheels
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Joined: 19 Sep 2014
Posts: 22

PostPosted: Thu Sep 25, 2014 10:48 pm    Post subject: Another guy from Illinois! Reply with quote

Hey guys my name is Rick and i'm new to the site. My interested are automotive I love cars and have my very own project vehicles which i'm wanting to make some custom vacuum formed parts for it. I have recently built a machine but i'm not having much success yet. I'm hoping I can get some help! Tons of info on this site to start with! Here is a picture of my unit. Its currently set up as a 2 stage system.

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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Fri Sep 26, 2014 6:30 am    Post subject: Reply with quote

Hey Rick, looks like your vac former is off to a good start. What seems to not be working right? I'm not the best guy on here to answer stuff but we can probably get started.
Doug N
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Hot_Wheels
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Joined: 19 Sep 2014
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PostPosted: Fri Sep 26, 2014 10:24 am    Post subject: Reply with quote

Thanks for the quick reply! I seem to have 2 issues. First off it does not seem like i have very much suction. I was using a check valve for the 2 stage system and i could barley keep a thin piece of plastic to hold to the planton when i turned the machine side ways. I removed the check valve and it seemed like i got a little better suction. Is there a way to test suction or how will I know if i have a enough?

On my first and second pull i was getting bubbles in the plastic. I was using .094 acrylic which i got from homedepot. I have since ordered some .060 from eplastics. I heard the bubbles maybe from moisture but i really think its boiling because you can see a outline of the heater where the bubbles are at. I am not pre heating oven, I wonder if I should try that? The other think i was thinking is maybe to raise the plastic higher from the element? I orderded the heater kit from builders workshop but its only a 12x18 and my planton is 18x18, so im not sure if it will be adequate enough. I have yet to assemble the heater.





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Hot_Wheels
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PostPosted: Fri Sep 26, 2014 10:26 am    Post subject: Reply with quote


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Hot_Wheels
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PostPosted: Fri Sep 26, 2014 10:39 am    Post subject: Reply with quote

Fat man burning him self with vacuum former: http://youtu.be/YxWnmY8Sel4
[/code]
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IMMark
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Joined: 18 Nov 2010
Posts: 189
Location: Columbus, Ohio

PostPosted: Fri Sep 26, 2014 6:21 pm    Post subject: Reply with quote

Hi Rick
For checking the vacuum, I would put a vacuum gauge in the line.
For your bubbles, I doubt that it is moister (although moister will cause it).
Since you got the plastic from Home Depot (they turn it over pretty fast) and if it is covered (with the plastic cling) that reduces absorption of moister too.
I would try moving it farther from the heat source, you could also try using some screening to reduce the heat. One last suggestion, since you are just getting started you might want to get some HIPS to practice with. It is cheaper and easier to get a good end result.
And quit burning yourself Laughing
Best of luck
Mark
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Hot_Wheels
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Joined: 19 Sep 2014
Posts: 22

PostPosted: Fri Sep 26, 2014 6:40 pm    Post subject: Reply with quote

Mark thanks for the advice! I have a gauge but its plumbed into the second stage with the surge tank and gast pump. I didn't understand why in the plans they have 2 suction nipples a 1 1/2 and then next to it is a 1/2 barb which is piped to the 2 stage. I was thinking of plugging that hole and just run the 1/2 barb into my 1 1/2 elbow before the check valve so all the vacuum would be coming from the center and my gauge would be able to measure all vacuum. Any thoughts on why they would want it separate? When i pump the tank down and run the pump i was able to maintain -5in hg on the table with nothing on it, not sure if that's good or not? Are there any big box stores where i can find HIPS locally? I found my ace hardware has garage sale signs i think someone mentioned using them but there a little thin. My final project needs to be clear because im making a headlight but i defiantly agree i need something cheaper til i get it all dialed in.


IMMark wrote:
Hi Rick
For checking the vacuum, I would put a vacuum gauge in the line.
For your bubbles, I doubt that it is moister (although moister will cause it).
Since you got the plastic from Home Depot (they turn it over pretty fast) and if it is covered (with the plastic cling) that reduces absorption of moister too.
I would try moving it farther from the heat source, you could also try using some screening to reduce the heat. One last suggestion, since you are just getting started you might want to get some HIPS to practice with. It is cheaper and easier to get a good end result.
And quit burning yourself Laughing
Best of luck
Mark
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Hot_Wheels
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PostPosted: Fri Sep 26, 2014 6:46 pm    Post subject: Reply with quote

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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Sun Sep 28, 2014 12:25 pm    Post subject: Reply with quote

You're system is off to a good start. Let's see if we can get it working for you. What type of vacuum pump (not shop vac) is plumbed into the system? Also, how air tight is the platen?

Mark is helping with the plastic and I agree with what he's saying. Also agree with the idea of increasing the distance from the element to the plastic. Let me toss in a few ideas on getting the pull to work. First off, keep in mind this is based of my personal experience and what you're doing is at least a little different. I form .236 (1/4") thick ABS, which has a wider heat up/cool down window than acrylic.

Anyhow, the shop vac maxes out at around 5 inHg which seems to be pretty typical. The acrylic you're using evidently needs more (probably lots more) vacuum than 5 inHg so my suggestion would be to completely eliminate the shop vac from the system. (The ABS I run likes over 25inHg.) Here's why, the vac pump doesn't have enough time to create adequate vacuum when staged with the shop vac.

So, how many cfm/inHg does the vac pump are you using have? I see the air hose but didn't see the pump it's attached to. Hopefully the big green tank is a vacuum reserve which is perfect. That tank will provide more than enough vacuum for the size of your former. Also, the gauge on the tank is what matters for where you're at. The gauge on the platen is nice but you need to know how much vacuum you've got to start with.
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Hot_Wheels
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Joined: 19 Sep 2014
Posts: 22

PostPosted: Sun Sep 28, 2014 6:29 pm    Post subject: Reply with quote

Doug the pump is a gast pump oil less carbon rotor type. The previous owner was using it for vacuum bagging limbs. I'm not sure on the cfm but I'll look at the tag tonight. The tank is hooked to the pump there appears to be a check valve and there's a ball valve from the tank to the plantton. I was able to pull the tank to 20/25 inhg I'm not sure how long to run the pump. There is no switch to shut the motor off so I didn't want to burn it up. I know there has to be a leak on the tank or I'm betting it's the hose from the pump to the tank due to it won't hold a vacuum very long. I tried to replace the hose but I couldn't match up the threads at ace hardware. I may have to contact a hydraulic line company to make me a custom line. I ordered the nichrome heater from build stuff. I decided to cheat a little. I had a 300 watt incubator heater which I think is 12x18 it seems to be the perfect size but not enough output. I took the frame with porcelain insulators and strung the nichrome wire I got from build stuff. It appears to be the perfect length and it has a nice zig zag which I feel should give even heating? I want to add a fuse and I think I'll wire it to a extension chords and see how it goes? I know doug engineered his heater but it's dimension is just to small for my 18x18 planton.
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Hot_Wheels
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PostPosted: Sun Sep 28, 2014 7:51 pm    Post subject: Reply with quote

the pump is a gast 1023-V131Q-SG608X

according to the spec its a 10 cfm at atmospheric pressure?
FREE AIR CFM @ 0 VACUUM (IN HG) 10.00
it appears the cfm drops with vacuum .

Here is a picture of the hose i was trying to replace. the inlet of the pump is 3/8 npt. I'm not sure what size the check valve was maybe 1/2 MIP? I think it would be a better idea to have the check valve plumbed directly on the tank so if the hose is faulty at least you can maintain the vacuum at the tank and not worry if there is a small leak in the line. How they currently have it, i feel as if there is a leak in the line that check valve is not doing anything?


So here is a picture of my rewired chicken incubator frame. The platform i feel is the perfect size but i don't know how changing the lay out of the wiring will affect the designed out put of the heater? Should i bolt the frame right down to my sheet metal box? Or let it sit on this insulation board?


if i get rid of the insulation it will drop the heater about another 1/2 lower in to the box, this would give me 3.5 inchecs from the plastic, is this good enough or should we do lower? If i go lower i will need to make a new box.
in the picture from the top of the frame to plastic is 3in. as i mentioned if i remove the insulation board we can make it a total of 3.5 inches.


Just for reference the old heater was about 2.5 in from the plastic.




So my goal this week will to get a new hose, maybe relocate check valve?

possible build a new heater box ( i need to find another source for sheet metal if so =(, trying to avoid this)

wire heater to extension cord and test. bzzzzzzzzzzzzaap (maybe add a 15 amp inline fuse just incase?)

Find leaks, any ideas how to find leaks? a smoke bomb keeps coming to mind but not sure how.
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area

PostPosted: Sun Sep 28, 2014 8:18 pm    Post subject: Reply with quote

That Gast should be a very good vac pump and that will allow getting rid of the shop vac system altogether. That'll get a lot closer to a good pull right there. I wouldn't worry about the check valve for now unless it is the source of the leak.

After getting rid of the shop vac & related plumbing then start looking for major leaks next. What is the platen made from? Make sure it is totally sealed around the edges and the bottom. That much vacuum will pull air straight through MDF and some plywood so it has to be sealed. To test for leaks, cover the platen surface with a heavy garbage bag, rubber shower curtain, or similar. Might have to temporarily use masking tape to seal the plastic around the edges of the platen. Create vacuum in the tank so the pump can be shut off to listen & feel for air leaks.

To permanently seal plywood or MDF I've used silicone caulk or fiberglass resin with success. The silicone withstands direct contact with hot plastic, the resin doesn't as well but it is a lot easier to use in other areas like the bottom of the platen.

Don't know your exact electrical set up but be careful about letting energized wires come in contact with the sheet metal liner. If the current set up leaves the edges of the plastic too cold to form properly it'll need spread out. Generally, the oven will need more heat around the edges than in the center.
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Hot_Wheels
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Joined: 19 Sep 2014
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PostPosted: Sat Oct 04, 2014 3:59 pm    Post subject: Reply with quote

no big updates. I would like to get try out my heater this weekend but i have a few questions. First off i saw someone use a dimmer switch to control the heat, do you think this will work with my coil? any paticular dimmer to use? or should i just plug it right into the wall?
According to one engineer I spoke with at infrared heaters, he suggested based on my desired temperature and size that I would need total of 1920 watts, at 7.5 ohms, 8.53 watts per sq in (i have a 18x18 planton). So the heater coil i got from build stuff is very close to what the engineer suggested. The coil i got from build stuff is 8.2-8.6ohm, per ohm's law using 120 volt puts me at 14.63 amps and 1756 watts. is this to close for a 15 amp circuit? I'm thinking my garage circuit might be 20 amp but my breakers are not labeled but i do know the dryer is a 20 amp so i could pull off there if needed.
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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area

PostPosted: Mon Oct 06, 2014 6:51 am    Post subject: Reply with quote

Hot_Wheels wrote:
no big updates. I would like to get try out my heater this weekend but i have a few questions. First off i saw someone use a dimmer switch to control the heat, do you think this will work with my coil? any paticular dimmer to use? or should i just plug it right into the wall?
According to one engineer I spoke with at infrared heaters, he suggested based on my desired temperature and size that I would need total of 1920 watts, at 7.5 ohms, 8.53 watts per sq in (i have a 18x18 planton). So the heater coil i got from build stuff is very close to what the engineer suggested. The coil i got from build stuff is 8.2-8.6ohm, per ohm's law using 120 volt puts me at 14.63 amps and 1756 watts. is this to close for a 15 amp circuit? I'm thinking my garage circuit might be 20 amp but my breakers are not labeled but i do know the dryer is a 20 amp so i could pull off there if needed.


This all looks fine to me. Check the breaker box for the amperage in your garage but most local codes dictate 20 amp circuits. Even if it's only 15 it should still be okay. The worst it'll do is kick a breaker but make sure that your oven is the only thing using that circuit. Doug Walsh at Build Stuff knows what he's doing and his designs work well. Good to see you're figuring out the math behind your oven. Most importantly, have fun with it!
DougN
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Hot_Wheels
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Joined: 19 Sep 2014
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PostPosted: Mon Oct 06, 2014 2:54 pm    Post subject: Reply with quote

Do you know if I can use a dimmer or not?
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