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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Sat Feb 04, 2012 9:38 am Post subject: |
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I've used PP before and found that it is also very sensitive to variations in mold density. For example, the mold was made from about 6 stacked layers of 3/4" MDF and each layer telegraphed through the .187" PP as a large scallop. Places where bondo had been used telegraphed through. The mold was perfectly smooth so all of this was a total surprise to me!
Hope the heating situation with your oven works out. _________________ 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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spektr Master
Joined: 07 Jan 2008 Posts: 425
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Posted: Sat Feb 04, 2012 3:57 pm Post subject: |
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The problem isnt the coils, the issue with polypro is the RATE you heat it. If you dump a ton of BTU's/Second at it, it gets unhappy. You need to heat it up at less than the rate you are using. Throttle the oven back if you have controllers on it, or increast the distance to the oven face by not raising the shuttle all the way up on a protoform style carrier. |
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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Sat Feb 04, 2012 5:04 pm Post subject: |
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I tried having the plastic a few inches lower than the first attempt and it did help, but still burned through on the edges. I will try it even lower next time and see how it goes.
I don't have any controllers on my oven. It's either on or off. It's been great for ABS over the years though, but was hoping to make something that has controlled areas like hotter center and cooler outer edges or vice versa if I need to.
Everything else on my machine works perfectly, but now I want to use PP and need to get it to heat properly. Funny thing is I got it to form when my oven was under the plastic before I made the over head design. It wasn't perfect though and I got a thin spot in the middle due to the plastic sagging into it (or I didn't pull it early enough). |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Sat Feb 04, 2012 9:18 pm Post subject: |
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My experience with PP is a bit limited but was the same as yours on the sagging. It didn't need to sag nearly as much as ABS. I started going by feel instead of sag and when it felt about the same as ABS then it was ready to pull. I probably only did 8-12 test pulls though.
dn _________________ 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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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Sun Feb 05, 2012 1:10 pm Post subject: |
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What kind of heater did you use and was it over or under the plastic? |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Mon Feb 06, 2012 7:52 am Post subject: |
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ANH trooper wrote: | What kind of heater did you use and was it over or under the plastic? |
Proto-Form with the heat on top. Modular oven with nichrome wire and hardibacker. Oven uses range top burner controls but it's been long enough that I don't recall what the settings would've been.
dn _________________ 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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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Tue Feb 07, 2012 2:45 am Post subject: |
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Sounds good.
Do you have a link to your build thread or oven design? |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Tue Feb 07, 2012 8:38 am Post subject: |
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ANH trooper wrote: | Sounds good.
Do you have a link to your build thread or oven design? |
I don't have anything on my vac former on the internet. However, the ProtoForm design and modular oven in this thread are the same as what I did except that he used the ProtoForm oven kit which, to me, is a good idea. http://www.tk560.com/phpBB2/viewtopic.php?t=1162 _________________ 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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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Wed Feb 08, 2012 4:10 am Post subject: |
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Thanks for the link
I remember that build now...really nice!
I also have the build plans on a CD from Doug but there was no mention of building the oven yourself (at least I don't recall there being) with this modular oven. I really like the design and could pull that off on my 2' x 2' oven if I knew the coiled lengths needed and resistance for each section? |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Wed Feb 08, 2012 8:17 am Post subject: |
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ANH trooper wrote: | Thanks for the link
I remember that build now...really nice!
I also have the build plans on a CD from Doug but there was no mention of building the oven yourself (at least I don't recall there being) with this modular oven. I really like the design and could pull that off on my 2' x 2' oven if I knew the coiled lengths needed and resistance for each section? |
Yes, that is a really nice build by TD1035. I have the Protoform plans but couldn't afford the oven kit at the time. It's not hard to reverse engineer the modular design. _________________ 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 Master
Joined: 21 Mar 2007 Posts: 251 Location: Kingdom of Nye Area 51
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Posted: Wed Feb 08, 2012 7:41 pm Post subject: |
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ANH, you could still configure your oven same as a tj oven if you went to a three segment oven. If you isolate the third segment from the first two, you have control of the center third of the oven. Go to the oven calculator and enter, say 4800 watts,240 volts, [same power level as proto-form] , 3 segments, 24x24 oven base, now you have the amount of coiled wire you need and the spacing. The spacing changes, but that isn't a problem. http://www.tk560.com/ovencalculations.html You can select the watts you want, I used 4800 as an example................Fredo
PS Make the changes in the first column, the third column wont show the floor layout. _________________ 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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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Thu Jan 02, 2014 6:36 pm Post subject: |
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Hi guys,
It's a new year and I want to tackle this oven again. I have the oven wired in 2 segments and I am looking to try infinity switches so I can have the centre section hotter then the outer section of the oven. I believe I have found what I am looking for here: http://www.ebay.co.uk/itm/140546738082?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
Can you more experienced guys take a look to make sure I am buying the right controllers please? |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Thu Jan 02, 2014 7:51 pm Post subject: |
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ANH trooper wrote: | Hi guys,
It's a new year and I want to tackle this oven again. I have the oven wired in 2 segments and I am looking to try infinity switches so I can have the centre section hotter then the outer section of the oven. I believe I have found what I am looking for here: http://www.ebay.co.uk/itm/140546738082?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
Can you more experienced guys take a look to make sure I am buying the right controllers please? |
I'm certainly not the most experienced electrician around here but here's my .02. The voltage and amperage look okay. It may take some doing to figure out the purpose for each terminal unless it's supplied with a diagram. Are you thinking this controller will provide variable heat or is it a percentage controller that controls heat by being on part time then fully off part time? _________________ 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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ANH trooper Master
Joined: 20 Oct 2005 Posts: 305 Location: UK
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Posted: Fri Jan 03, 2014 1:02 pm Post subject: |
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I am looking to control the heat with these switches. They are designed for oven hobs so I think they should work. I am hoping there will be a wiring diagram for the terminals or it could be fun trying to work them out (not!)
I believe these are the UK equivalents of infinite switches since all my searches have come up blank looking for them here. I really want to be able to regulate the heat better than just having my oven constantly on hot. |
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jdougn Guru
Joined: 18 Mar 2009 Posts: 714 Location: Louisville KY area
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Posted: Fri Jan 03, 2014 6:20 pm Post subject: |
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These simmerstats appear to be a percentage timer based on information on the net: http://en.wiktionary.org/wiki/simmerstat
The oven on my vac former uses this type of thermostat and it seems to work fine with ABS plastic varying from around 1/16" up to almost 1/4". I'm not sure how well it'd work on thinner plastics or more difficult plastics. This thermostat will simply cycle the heating element on then off to maintain an average temperature. Real interested in seeing how your build works out! _________________ 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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