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Jay-J
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Joined: 19 Jun 2011
Posts: 17
Location: US
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 Posted: Sun Jun 19, 2011 5:06 pm Post subject: Just bought Proto-Form plans, want to alter heating elements |
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Hi everyone, I've been wanting to make a vacuum/thermo forming table for awhile now so here starts my journey!
I just bought Doug's plans and want to know if anyone has done this or sees any problem doing it...
What I want to do is adjust the plans to make a 4' x 4' (or settle for a 3' x 4') machine that uses the same amount of nichrome wire as a 2' x 4' machine according to the Proto-Form plans. So the idea is to buy the precut engineered wire from Doug and stretch it a bit more to fit either 6" x 4' element panels or 6" x 3' panels. Is this idea feasible? I'm assuming if this would work, it would increase the time it takes to heat the plastic which I'm not concerned with. I really want a 4' x 4' machine without having to draw an insane 80 amps is what it boils down to.
Also, I wanted to express how happy I was to stumble upon this community and forum! It took some time to find this site but you guys have the best info available on the web! Thanks! |
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area
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| Posted: Mon Jun 20, 2011 7:56 am Post subject: |
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Hello Jay-J & welcome to the forum!
My suggestion would be to call or PM Doug Walsh (kayker43). For anyone that has purchased his plans, he is very helpful and informative. When I last talked to him, he has not come out with plans for a larger vac former yet because of technical difficulties inherent in the larger size. For one, the plastic carrier gets rather heavy. He can fill you in on the details.
I don't believe it would be practical to resize the ProtoForm oven kit since it comes with pre-cut panels for the oven. The larger vac former will probably require a custom built oven. Not really too difficult at all, just takes a bit more effort and understanding of the vac former oven system.
An important consideration to your vac former build is the type of projects you plan on doing. What type & thickness of plastic do you intend to use for your projects?
hth, DougN
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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Fredo
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Joined: 21 Mar 2007
Posts: 251
Location: Kingdom of Nye Area 51
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| Posted: Mon Jun 20, 2011 9:09 am Post subject: |
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Your not the first one to want to bump up the size of the proto-form. Ask Patternmam how his 3x4 is working out for him. Better yet, read the thread... http://www.tk560.com/phpBB2/viewtopic.php?t=1598 He's the only one I've seen who really finished a larger machine and posted pics of it. The bigger the vf the more power it's going to eat. Cheat the piper and pay the price. Some things you can change and get away with, some you can't. You find out after the fact. The problem with being a trail breaker is that you're the first one to find the crevasse.............Fredo
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If someone has a gun and is trying to kill you,
it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001 |
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Jay-J
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Joined: 19 Jun 2011
Posts: 17
Location: US
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| Posted: Mon Jun 20, 2011 3:38 pm Post subject: |
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I haven't been able to find any definitive answers regarding adequate watts per square inch. I know that the Proto-Form elements are producing somewhere around 8.3 theoretically but they are also called "fast heat." So is that to say they simply reach operating temp faster than calrod (or whatever you might use) or does that mean they heat the plastic faster than other heating sources?
I also understand that the equation is not just simply watts per square inch. I know I must consider the distance between the material and heat source, shielding around the heat source, type and thickness of plastic, etc... But is there any consensus on the minimum watts per square?
Last edited by Jay-J on Tue Jan 03, 2012 7:14 pm; edited 1 time in total |
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jdougn
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Joined: 18 Mar 2009
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Location: Louisville KY area
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| Posted: Mon Jun 20, 2011 7:46 pm Post subject: |
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Nice looking sink! What are the general dimensions?
ABS might be a good choice for the moulds since it is relatively inexpensive, fairly easy to form, and is somewhat flexible.
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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RRK4
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Joined: 17 May 2011
Posts: 58
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| Posted: Mon Jun 20, 2011 9:29 pm Post subject: |
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Nice sink. I have considered making a few small basins myself but never tried. Do you spray those forms or just do a standard pour? Also what do you seal them with?
Why no drain? |
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Fredo
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Joined: 21 Mar 2007
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| Posted: Tue Jun 21, 2011 8:57 am Post subject: |
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Talk about seeing two different things in a picture....When I looked at it, I saw a space across the front of the sink that I took to be the drain. The inside far corner, top, isn't in the right place for that to be a wall. There seems to be a gap, at least to me... But then, I've been known to see things that aren't there.....................Fredo
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If someone has a gun and is trying to kill you,
it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001 |
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RRK4
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| Posted: Tue Jun 21, 2011 9:52 am Post subject: |
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| Fredo wrote: | | When I looked at it, I saw a space across the front of the sink that I took to be the drain. The inside far corner, top, isn't in the right place for that to be a wall. |
That would be a cool drain but I don't really see how you could make it with a one piece, or even multi piece mould. Wouldn't that require a hollow chamber of some kind to funnel into a standard drain pipe? I suppose you could suspend a styrofoam negative and then melt it out with acetone? I believe the most common way that the concrete countertop guys do it is to glue a rubber negative of the drain into the mould so that it leaves a standard sized hole and recess for the drain cover. |
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Jay-J
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Location: US
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| Posted: Tue Jun 21, 2011 3:34 pm Post subject: |
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So back on topic, what about all those questions? Watts per square inch and all that?
Last edited by Jay-J on Tue Jan 03, 2012 7:16 pm; edited 1 time in total |
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jdougn
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Location: Louisville KY area
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| Posted: Wed Jun 22, 2011 8:35 am Post subject: |
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| Jay-J wrote: | .............
So back on topic, what about all those questions? Watts per square inch and all that?
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Hey Jay-J, did you get a chance to talk with Doug Walsh yet? Frankly, I don't feel I have enough experience to address the question. You may find some interesting information here:
http://www.tk560.com/phpBB2/viewtopic.php?t=1419&highlight=watt+density
http://www.tk560.com/phpBB2/viewtopic.php?t=1690&highlight=watts+per+square+inch
Look for comments made by Spektr & Kayaker43 since they have the most experience. Although, they don't agree at all times for sure. You can also do a 'search' using terms like "watt density" or "watts per square inch" to see what turns up.
My opinion, is that there are too many variables to say whether a certain watt density will work, or not. You want to heat thick plastic so more heat will be needed. Just a thought, but you may be ahead figuring out a way to get the amps needed instead.
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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Jay-J
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Posts: 17
Location: US
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| Posted: Wed Jun 22, 2011 5:03 pm Post subject: |
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| Thanks jdougn, haven't talked to Doug yet. I did read his opinions about size expansion on this forum and in the supplemental info that comes with his plans. I'm going to contact him to get clarification on few things. I think I'll just go with 8.3 watt/sq in. I trust that Doug has experimented enough to conclude that is an optimum number. I'll start a build thread as soon as I get going. Thanks again! |
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spektr
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Joined: 07 Jan 2008
Posts: 425
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| Posted: Thu Jun 23, 2011 8:50 am Post subject: |
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| It's not the optimal number, but it works fine, there ISNT an optimal number. There are enough variables in the process to make many combinations work. I've run anything from 3 watts to 20 watts. It is entirely dependent on the material youre running. IF you are plannning on running a lot of 3/16 or 1/4 inch, I'd be looking at upper and lower heat.... Scott |
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Fredo
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Joined: 21 Mar 2007
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Location: Kingdom of Nye Area 51
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| Posted: Thu Jun 23, 2011 12:49 pm Post subject: |
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This manual has general info that has helped me understand, somewhat, ovens that work with radiation alone, without convection heating. http://www.infraredheaters.com/page1.htm Some seem think oven air temp. is at work in a IR oven. The temp. of the emitter is the only temp that is important. Change the temp. of your emitter and your watts/sq in go up or down. The only time you need to maintain an exact oven temp. is when the plastic goes in the oven and the door is closed. That's why some use a kitchen oven for simple forming, not a good idea.........Fredo
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If someone has a gun and is trying to kill you,
it would be reasonable to shoot back with your own gun...The Dalai Lama..Seattle 2001 |
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Jay-J
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Joined: 19 Jun 2011
Posts: 17
Location: US
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| Posted: Thu Jun 23, 2011 8:21 pm Post subject: |
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Thanks for the suggestion Scott,
Are there any posts on this forum pertaining to upper and lower heat? Maybe design ideas or actual machines people have built? I am planning on doing a lot of pulls in thicker (3/16" - 1/4") material so exploring that option now would be a good idea. As far as watts/sq in. goes I have gathered that the numbers are all across the board. I guess it's just gonna take more reading and experimentation when the time comes. Thanks again.
Thanks for the link Fredo, I will definitely read that info. I don't you if you guys are aware of this already but I found this,
http://www.thermoformingdivision.com/thermoforming101/index.htm
It has an amazing amount of info on the topic, much of which I don't understand but none the less... |
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jdougn
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Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area
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| Posted: Fri Jun 24, 2011 7:46 am Post subject: |
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| Jay-J wrote: | Thanks for the suggestion Scott,
Are there any posts on this forum pertaining to upper and lower heat? Maybe design ideas or actual machines people have built? .... |
Hey Jay-J, I can offer my experience with building and regularly using a double oven. My vac former is a 2'x4' Protoform design with modular ovens. The top oven has heating controls and is based on the Protoform 8.3 w/in2 but is built with hardibacker and 22g nichrome. The lower oven uses the same modular design, is only on/off, and runs around 4 w/in2. The bottom oven obviously runs at 100% capacity. However, the top oven temp settings vary some.
I almost always run 3/16" black ABS and have run 1/4" ABS just as easily. In general, the top oven runs at around 30%-45% capacity. The top oven is generally adjusted so that the temps on the top of the plastic sheet being heated are very close to the temps on the bottom of the plastic sheet.
The use of the bottom oven is simple. There is a rack behind the vac former that supports the bottom oven. The rack allows the bottom oven to slide onto the vac former table and stradle the platen. After the plastic carrier goes up the bottom oven slides underneath. The bottom oven has camed legs that hit stops and raise the front of the bottom oven around 3"-4" into heating position. The camed legs rotate out as soon as the bottom oven starts moving backwards which allows the front of the oven to clear the sagged plastic.
Cycle time to heat 3/16" HC black ABS with the double ovens cold is 10 minutes. By the third pull, with everything nicely heated up, the cycle time is down to around 5 minutes.
hth, DougN
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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