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IMMark
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PostPosted: Thu Jan 27, 2011 11:20 am    Post subject: Hi new guys with questions : ) Reply with quote

Hi
New guy on the block, although I have been lurking (and reading) for quite awhile now. But the time has come for me to try and jump into this great hobby!!!

I will try to outline what I am hoping to accomplish, what ideas I have...but want to stress that I am open to hear all input, thoughts and better ideas!

Here is what I am shooting for;
an overhead oven design, capable of handling a sheet of plastic 33" x 48". What type of plastic, well my thought is to build as versatile machine as possible.
Able to handle the biggest variety of material, thickness, etc. (If I need to narrow down more specific, let me know and I will).
What I have available is about 85amps of power, to accommodate the heating and vacuum system. From what I have read, I should run 220volt (so that is my plan, again unless I hear otherwise from the experts)!
Heating elements, again my thought is nichrome wire (is 22 AWG best or is there advantages to another gage? (but again, if there is a better way to go, even would consider LP...please let me know).
If the nichrome wire is the way to go, I plan on making the modular panels.
I would be using the 3 5/8" metal wall studs for the frame of the oven, with the drop ceiling rails to support each panel.
Is there any consideration to the distance between the coils and the plastic (in other words do you get as close as you can without touching?) I could make the frame deeper if needed, if the approx. 3" will be too close?
I have read how the hardy board is not good because of cracking over time, but I have also read that it may be ok in the modular design because each part is fairly small? My panels would be 8" x 33". Do you think that would be ok?
I thought 8 zones or panels (I hope I am using "zone" correctly, as I have also seen segments?).
I plan on having a controller for each zone, I have 2 thoughts for them here (again, if one is better or another approach is better...please chime in);

1st type of controller;
http://www.bakatronics.com/shop/item.aspx?itemid=597

2nd type of controller;
http://auberins.com/index.php?main_page=product_info&products_id=14

if the 2nd works, I prefer it...looks way cool : )

I think that will be a good start. If I can get any feedback or thoughts it is greatly appreciated.
If I haven't given enough information (or too much), let me know and I will make adjustments!
If anyone is open to chatting about a few things, that would be appreciate as well. I would be happy to pass on my email address or phone number (sometimes a few minutes of talking can make a world of difference).
Thanks in advance for your time and thoughts!
Mark
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spektr
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PostPosted: Thu Jan 27, 2011 1:25 pm    Post subject: Reply with quote

Hi mark. If you use nichrome, and I dont really see a reason not to, Id use the bakatronics controller. The other needs a feedback unit like a type k thermocouple or something. I have no hardibacker opinion. Scott
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IMMark
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PostPosted: Thu Jan 27, 2011 3:02 pm    Post subject: Reply with quote

spektr wrote:
Hi mark. If you use nichrome, and I dont really see a reason not to, Id use the bakatronics controller. The other needs a feedback unit like a type k thermocouple or something. I have no hardibacker opinion. Scott


Hi Scott
Thanks, I figured Nichrome would be the best all around way to go...but just keeping an open mind. I see the 22 AWG is the only size listed in the oven calc. chart, but see it is available anywhere from 15 to 24 for purchase. Do I need to consider other sizes or is 22 the standard that works best?
Also thanks for the input on the controller, although if the 2nd is also functional, the type K thermocouple is only an extra $5 .....so hope to keep that as an option?
Thanks
Mark
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jdougn
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PostPosted: Thu Jan 27, 2011 5:32 pm    Post subject: Reply with quote

Hey Mark,

Welcome to the forum. From reading your post you've done your homework and are headed in the right direction. You might consider getting the ProtoForm plans from build-stuff.com. The plans saved me a lot of time & energy on oven design, wiring controllers, vac systems, carrier design, and parts sourcing.

Since you're going a bit outside the 'box' you might consider testing some individual components before making a serious commitment to the total system. For example, get one of the temp controllers you'd like to use and see how it works for your application. The digital controller may give more precise control and yes, it looks cool too!

Especially since you're using heat controllers, your vac former will be able to handle a wide range of plastics & thicknesses. The modular oven design is the absolute best IMO. It has worked great in my oven and is so easy to control.

What types of projects are you planning?

HTH, DougN
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IMMark
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PostPosted: Thu Jan 27, 2011 6:22 pm    Post subject: Reply with quote

jdougn wrote:
Hey Mark,

Welcome to the forum. From reading your post you've done your homework and are headed in the right direction. You might consider getting the ProtoForm plans from build-stuff.com. The plans saved me a lot of time & energy on oven design, wiring controllers, vac systems, carrier design, and parts sourcing.

Since you're going a bit outside the 'box' you might consider testing some individual components before making a serious commitment to the total system. For example, get one of the temp controllers you'd like to use and see how it works for your application. The digital controller may give more precise control and yes, it looks cool too!

Especially since you're using heat controllers, your vac former will be able to handle a wide range of plastics & thicknesses. The modular oven design is the absolute best IMO. It has worked great in my oven and is so easy to control.

What types of projects are you planning?

HTH, DougN

Hi Doug
I am still a newbie for sure, just trying to take it all in.
I think that may be a great idea, building 1 module and see how it goes.
I will still need a bit more help before I get there though.
As for projects..initially, I want to do some pinball/arcade related things. I am a big pinball guy, so this hobby should be a great fit.
But there seems to be a ton of things you could do...it would be cool to have a storm trooper soldier stnading in the gameroom : )
Mark
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crashmann
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PostPosted: Wed Feb 02, 2011 7:55 pm    Post subject: Reply with quote

Hi Mark, and welcome to the platen!

I'm using 22 gauge nichrome on my new 220 volt oven and with 8 hours of use on it (to heat my freezing cold garage since the baseboard heater is broken), the wire has held up very well. The oven pulls 24 amps on a 30 amp circuit breaker, and generates plenty of heat. I don't have any controls on the heat, so I can't render an opinion on the two you've posted.

You don't want the plastic too close to the heat source. You'll scorch the plastic and have uneven heating. Dr. Crash recommended a little distance to allow the convective heat and infra-red energy to diffuse before striking the plastic. If you only heat one side of the plastic, you'll be limited to a thickness of 3/16" Heavier gauge plastic will need two sided heating. I would imagine the bottom oven on drawer sliders that you would roll into position once the plastic is raised to the upper oven. Look on YouTube for some fancy industrial designs.

I would also recommend shaving one inch off your plastic dimensions. You can get 3 pieces of plastic 32" x 48" from a single 4' x 8' sheet. 33" would result in a ton of waste unless you're having it custom extruded - then you're looking at a large order from your supplier.

I used to spend all of my quarters on pinball machines in the arcade. One day I'm going to visit the new Pinball Museum that just opened in Washington DC. There's nothing like experiencing real physics with the shiny metal ball rolling across the playing field!

Charlie
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IMMark
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Location: Columbus, Ohio

PostPosted: Fri Feb 04, 2011 2:21 pm    Post subject: Reply with quote

crashmann wrote:
Hi Mark, and welcome to the platen!

I'm using 22 gauge nichrome on my new 220 volt oven and with 8 hours of use on it (to heat my freezing cold garage since the baseboard heater is broken), the wire has held up very well. The oven pulls 24 amps on a 30 amp circuit breaker, and generates plenty of heat. I don't have any controls on the heat, so I can't render an opinion on the two you've posted.

You don't want the plastic too close to the heat source. You'll scorch the plastic and have uneven heating. Dr. Crash recommended a little distance to allow the convective heat and infra-red energy to diffuse before striking the plastic. If you only heat one side of the plastic, you'll be limited to a thickness of 3/16" Heavier gauge plastic will need two sided heating. I would imagine the bottom oven on drawer sliders that you would roll into position once the plastic is raised to the upper oven. Look on YouTube for some fancy industrial designs.

I would also recommend shaving one inch off your plastic dimensions. You can get 3 pieces of plastic 32" x 48" from a single 4' x 8' sheet. 33" would result in a ton of waste unless you're having it custom extruded - then you're looking at a large order from your supplier.

I used to spend all of my quarters on pinball machines in the arcade. One day I'm going to visit the new Pinball Museum that just opened in Washington DC. There's nothing like experiencing real physics with the shiny metal ball rolling across the playing field!

Charlie

Hi Charlie
Thanks for the post!!!
This is a great site...with lots of information...but I wish there was more discusion going on. It looks like there was at one time, I see lots of posts that of 5 & 6 pages long, mine is 5 posts long (and 3 of them are mine : )
Also BIG thanks for pionting out my table size. I made a math error and never double checked...it is suppose to be 32' x 48".
As for the 22 gauge nichrome, I see that is what is always used...I guess a heavier gauge would be used if you needed more resistance?
As for the controllers, I have been going back and forth with myself...I think either is doable..but the digital temp seems to have some advantages and really won't cost much more.
I will have a few more questions coming up, so if you are around (and willing) please keep an eye ....your help is very much appreciated!
Also, if there are any other newbies reading this...I will try to help out any way that I can.
Thanks
Mark
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crashmann
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PostPosted: Sat Feb 05, 2011 12:42 am    Post subject: Reply with quote

IMMark wrote:

As for the 22 gauge nichrome, I see that is what is always used...I guess a heavier gauge would be used if you needed more resistance?


The first reference for building a custom vacuum forming table came from the Thurston James book "The Prop Builder's Molding and Casting Handbook" where he recommended using 22 gauge nichrome wire. It has worked well for my first vac table 32" x 24"

I would expect the heavier gauge wire to have more resistance, and give off more heat compared to the same length of 22 gauge wire. With the heat that is coming off my new oven, I don't think heavier gauge nichrome would be an advantage. In fact, I would suspect it would be a detriment - you would use shorter loops or segments in your oven because the resistance of the wire is high, resulting in really hot lines, but very cold gaps in between. The 22 gauge would force you to have more coils in the oven, resulting in a more distributed heat pattern.

It's all speculation on my part, but it seems to make sense in my head Smile

Charlie


Last edited by crashmann on Sun Feb 06, 2011 11:41 pm; edited 1 time in total
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IMMark
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PostPosted: Sat Feb 05, 2011 10:36 am    Post subject: Reply with quote

Yea, 22 may be the magic number..I was just kind of curious when I saw the other sizes available.
I won't try and reinvent the wheel....22 sounds good to me!
I have a few questions on the "vac" side of things...not sure if I should start a new thread ??
I'll just keep going here, if it is better to start new threads...let me know and I will.
On the vac side, if I understand things right...
the bigger the CFM on the pump...will just save you cycling time on refilling your tank? That a 1.5 cfm will work...but takes a long time.
6 cfm or higher is more realistic.
And that tank size has to do with the "size" of the mold area to be vacuumed, and not really so much with platen size? Does that sound right? If so, is a 25 gal. a good size to cover most needs?
Lastly, what is the "weak" point of the system usually? By that I mean is it leaking vacuum around the platen, or where do most people have problems?
Sorry for all of the questions and hope they are clear enough.
Also, if anyone is interested..I can post some pics of the building process as I proceed.
Thanks
Mark
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IMMark
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PostPosted: Sat Feb 05, 2011 2:15 pm    Post subject: Reply with quote

One other question, regarding the holding frame going into the oven....how much clearance do you allow on the sides?
I plan on the holding frame moving up and down pretty acurate, so I was thinking about a 1/4" on each of the 4 sides. I assume you want it fairly tight to keep heat loss to a minimum.
Also regarding how close the plastic is to the heat source, mine will be about 3" or so...I hope that will be ok, especially using a controlled heat source.
Mark
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jdougn
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Joined: 18 Mar 2009
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PostPosted: Sat Feb 05, 2011 5:22 pm    Post subject: Reply with quote

IMMark wrote:
On the vac side, if I understand things right...
the bigger the CFM on the pump...will just save you cycling time on refilling your tank? That a 1.5 cfm will work...but takes a long time.
6 cfm or higher is more realistic.
And that tank size has to do with the "size" of the mold area to be vacuumed, and not really so much with platen size? Does that sound right? If so, is a 25 gal. a good size to cover most needs?
Lastly, what is the "weak" point of the system usually? By that I mean is it leaking vacuum around the platen, or where do most people have problems?

IMMark wrote:
One other question, regarding the holding frame going into the oven....how much clearance do you allow on the sides?
I plan on the holding frame moving up and down pretty acurate, so I was thinking about a 1/4" on each of the 4 sides. I assume you want it fairly tight to keep heat loss to a minimum.
Also regarding how close the plastic is to the heat source, mine will be about 3" or so...I hope that will be ok, especially using a controlled heat source.
Mark


Hey Mark, my first suggestion would be to consider getting the ProtoForm plans at http://www.build-stuff.com. Even though you want to build a 33x48 the plans will save you considerable time & money. Many of the most technical questions are answered by the basic design of the Protoform.

You're right on the tank size. For nearly flat pulls the system would use relatively little reserve and may not even need a tank, just a good vac pump. For pulls that have larger voids under the plastic a larger tank is needed. My 2'x4' system uses a 30 gallon tank (because that's what I had) and 10 cfm vac pump. On big pulls with large void areas it is just enough. For most situations, a 25 gallon tank should be perfect. Since you have it, go ahead and use it. You can always add more tanks later.

Keep the fit between the carrier and oven as tight as reasonable. However, the plastic should be more than 3" away from the oven to get a good heat pattern.

hth, DougN
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IMMark
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PostPosted: Sat Feb 05, 2011 7:41 pm    Post subject: Reply with quote

jdougn wrote:
IMMark wrote:
On the vac side, if I understand things right...
the bigger the CFM on the pump...will just save you cycling time on refilling your tank? That a 1.5 cfm will work...but takes a long time.
6 cfm or higher is more realistic.
And that tank size has to do with the "size" of the mold area to be vacuumed, and not really so much with platen size? Does that sound right? If so, is a 25 gal. a good size to cover most needs?
Lastly, what is the "weak" point of the system usually? By that I mean is it leaking vacuum around the platen, or where do most people have problems?

IMMark wrote:
One other question, regarding the holding frame going into the oven....how much clearance do you allow on the sides?
I plan on the holding frame moving up and down pretty acurate, so I was thinking about a 1/4" on each of the 4 sides. I assume you want it fairly tight to keep heat loss to a minimum.
Also regarding how close the plastic is to the heat source, mine will be about 3" or so...I hope that will be ok, especially using a controlled heat source.
Mark


Hey Mark, my first suggestion would be to consider getting the ProtoForm plans at http://www.build-stuff.com. Even though you want to build a 33x48 the plans will save you considerable time & money. Many of the most technical questions are answered by the basic design of the Protoform.

You're right on the tank size. For nearly flat pulls the system would use relatively little reserve and may not even need a tank, just a good vac pump. For pulls that have larger voids under the plastic a larger tank is needed. My 2'x4' system uses a 30 gallon tank (because that's what I had) and 10 cfm vac pump. On big pulls with large void areas it is just enough. For most situations, a 25 gallon tank should be perfect. Since you have it, go ahead and use it. You can always add more tanks later.

Keep the fit between the carrier and oven as tight as reasonable. However, the plastic should be more than 3" away from the oven to get a good heat pattern.

hth, DougN


Hi DougN
I know that I should consider getting a set of plans...for me, I enjoy going through the learning and designing process, I don't mind some trial and error.
I have looked at several places that appear to be selling the same plans, however the prices are all over the place. Any story behind that, is there an original and a bunch of people just copied it?
Is the link you gave to a member of TK560?

Regarding the vac stuff, in doing more reading...I should have a tank in the 35-60 gal. range for a platen of 32x48. I don't have the 25 yet, I just know where one is.
If the 3" is too close for the plastic I have another "frame" I can install and bring it down another 2 1/2". Perhaps all of this is spelled out in all of the plans?
Mark
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jdougn
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PostPosted: Sun Feb 06, 2011 3:43 pm    Post subject: buy the plans Reply with quote

[quote="IMMark"]
jdougn wrote:
Hey Mark, my first suggestion would be to consider getting the ProtoForm plans at http://www.build-stuff.com. Even though you want to build a 33x48 the plans will save you considerable time & money. Many of the most technical questions are answered by the basic design of the Protoform.
hth, DougN

IMMark wrote:

Hi DougN
I know that I should consider getting a set of plans...for me, I enjoy going through the learning and designing process, I don't mind some trial and error.
I have looked at several places that appear to be selling the same plans, however the prices are all over the place. Any story behind that, is there an original and a bunch of people just copied it?
Is the link you gave to a member of TK560?

Regarding the vac stuff, in doing more reading...I should have a tank in the 35-60 gal. range for a platen of 32x48. I don't have the 25 yet, I just know where one is.
If the 3" is too close for the plastic I have another "frame" I can install and bring it down another 2 1/2". Perhaps all of this is spelled out in all of the plans?
Mark


I should get paid as often as I recommend the ProtoForm plans but they work. Doug Walsh, the designer for the ProtoForm, is Kayaker43 on the TK560 forum. The ProtoForm plans and oven kit will answer all your vac former questions. They'll help your build be fun instead of frustrating. Build a good vac former first then start thinking about design modification.

Some other plans will be based on older technology that doesn't work as well as the ProtoForm or the plans may not be very complete. Without knowing your sources there is no specific answer.

hth, DougN
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crashmann
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PostPosted: Sun Feb 06, 2011 11:51 pm    Post subject: Reply with quote

Having a higher CFM rated vac pump will allow you to evacuate the air much faster - either from the tank, or directly from the platen. A 1.5 cfm pump would probably not be much good without a surge tank, but anything 6 cfm or higher could work without a tank. When I upgraded my platen and added a valve to isolate the surge tank, I accidentally made several large pulls using just the pump Very Happy

My 32" x 24" oven had 6" of clearance between the oven coils and plastic holding frame. That will probably work for your oven as well.

The ProtoForm plans are highly recommended, and result in a very professional machine. It depends on how much experimentation and frustration you are willing to put up with. There's also a couple of good ProtoForm build threads on this forum that show the benefits of having a nice set of plans to follow.

Charlie
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IMMark
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PostPosted: Wed Feb 09, 2011 8:22 am    Post subject: Reply with quote

crashmann wrote:
I accidentally made several large pulls using just the pump Very Happy



Charlie


LOL...I assume you were intentially testing the ability to vac without using the tank Wink

DougN and Charlie,
I did purchase plans from Doug, and will see what that does for me. Not ideal, as it is not the machine I want to build. But I have gotten 2 books, spent countless hours of reading here (and other websites), and now bought the set of build plans....I hope I eventually end up with a machine out of all of this!!!

I will keep you informed...and I am sure, I will still have more questions if you don't mind.
Mark
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