OZO new hotwire set up - RC Groups
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Jun 04, 2011, 02:34 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
Build Log

OZO new hotwire set up

Hey guys. Been working on a new hotwire power box and fume collection system for my foam cutting. going to do my first official build log of it. Not totally sure to put this here or in the DIY electronics section but since this has to do with foam cutting I think it makes more sense to put it here. If admins feel other wise please feel free to move it.

Ive been doing the hotwire set up for a few years now and each time I've redone my power box to get more and more precises control of the tools I make to do this fun hobby of ours.

My original box was simply a transformer being controlled via a dimmer switch. This worked mostly ok but I always had a very hard time getting the temp low enough to not simply burn a hole in the foam.

My newest box (4th one I think if you count my really crappy first one) combines the power regulation for up to 6 selectable tools, along with an integrated fume collection system and filters.

Why make it so complex? Evolution.... I use a wide range of different tools, each one needing different power needs. My 5 different tools currently range from 11watts to 32 watts of power. My main table uses 11 where as my "knife" needs 14. Not a huge difference but enough that I do have to adjust for.

Why a built in fume collection system? Talk with anyone who has run a hot wire setup for long periods of time. They will tell you that you need good ventilation or you can get really sick or worse. I use a strong blower fan puling the air through several filters including a carbon filter to scrub the air clean.

Now for some pictures.
Last edited by OutcastZeroOne; Jun 04, 2011 at 03:32 AM.
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Jun 04, 2011, 03:02 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
Some pictures of the guts of the power box.

All relays, switches and power plugs are color coded to make it easier to figure out what goes where. I did some test runs on the power supply. The new power board barly gets warm. My old set up only had two larger 5 amp adjustable regulators that would get so hot you could get your hand near them.

The new board has 14 LM317T adjustable power regulators on a custom PCB I made. each IC can handel 1.5 amps of power for a total of 21 amps of power handeling ability. Total power output of the transformers is only 14 amps at 15v ~ 17v but my tools dont go over 8 amps max. Having more smaller IC's rather than a few larger ones has its benefits.

1. Cost, LM317T cost $0.24 each where as the large 5 amp LM338 cost $5.59 each.
2. Heat dissipation. Smaller IC's over a larger area with less load on each IC.
Last edited by OutcastZeroOne; Jun 04, 2011 at 03:28 AM.
Jun 04, 2011, 03:10 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
Details of the filter system.

The fan is out of a '92 Dodge Colt. Got it from my local Pick'n Pull for $26. Nice thing about this is that it was designed to pull air through filters and ducting. The fan pulls about 6 amps of power at full power. Each of the transformers can only do 4 amps of power. So to save them from frying I use two. I did a test run letting it run for 20 min at half power and the transformers never got very warm. Just above room temp.

I still need to finish the lid for the fan along with the valve system to open and close the tools in use or not in use.
Jun 07, 2011, 12:38 PM
Registered User
Wow very cool - you really took some pride in that! Do you have a closeup of the PCB or a wiring diagram?
Jun 07, 2011, 12:54 PM
Foam Av8r
RogueTitan's Avatar
very nice professional looking rig however just a tad too complicated for me to even entertain the thought of building one for my self
Jun 07, 2011, 11:33 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
Originally Posted by HighwayChild
Wow very cool - you really took some pride in that! Do you have a closeup of the PCB or a wiring diagram?
I dont, and it a pain to pull that sucker back out. :P

Originally Posted by RogueTitan
very nice professional looking rig however just a tad too complicated for me to even entertain the thought of building one for my self
Meh, if it was easy everyone would have one . I actually work at a high end car stereo shop so this is nothing to me compaired to some of the systems I've done or had to clean up from hole in the wall hack shops :P. My only real problem is that I keep changing my mind on how I want stuff to be.

Right now Im making the valve cover for the vacuum system. Even made my own valves for it too. Yes, I am the crazy one in the shop.
Jul 21, 2011, 11:35 AM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
Over the weekend I made some hand tools for foam cutting. I redid my hot knife and made a servo cutter (for digging out openings for servos ). They are all PCB based. I made them with small termanel blocks to easily replace the wire should it burn out.

going to make a second servo cutter so that I can ahve two tools, one set up for verticle cuts and the other for laying the servo on its side.
Aug 26, 2012, 11:24 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
a bit late, but heres a quick demo of my custom hand tools for my set up to cut out a notch for wing spars (wire runs, also a tool set to the width of my servos not in video but same idea.) and also cutting a hinge for control surfaces.

Custom Hotwire Hand tools (1 min 45 sec)
Aug 27, 2012, 10:38 AM
Krued Up
snolord1's Avatar
i thought id seen it all,this is too cool...awsome job and def. keep us posted on the progresssion
Oct 07, 2012, 02:30 PM
I ask a lot of questions.
Would it be possible to build in a temp sensor that can auto-control the wattage right at knife PCB? Maybe this way it can micro adjust to make sure the wire is at the perfect temp.
Oct 07, 2012, 02:41 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
yes it is, but it would be difficult since the temp of the wire is different from the start to the middle. It would also require useing totally different regulators since most thermistors work backwards of what the LM-317 needs to auto adjust like that.

New set up will have the adjustment knobs right at each tool. So if there is build up from useage, temp can be adjusted to keep working or burn off buildup.
Oct 07, 2012, 04:36 PM
mlp666's Avatar
Very impressive, makes my Heath Robinson attempts look pathetic
Oct 07, 2012, 06:57 PM
"Fly, yes... Land, No"
OutcastZeroOne's Avatar
looks like it dose a clean job.

The only reason I am making a new version of my set up is simply because of how combersom it is. Ill be combining the table and power supply into a single unit with tool storage along the top for glue and clamps and such. 2' of cutting depth instead of 8", and just taking up less space.

Ive got the new filtration tube and tensioner mostly built. I can only work on it durring lunch breaks so I've got a limited time to do anything.
Mar 23, 2013, 05:30 PM
Registered User
davec921's Avatar
Hey Outcast.
I really like your setup. I was wondering if you had a wiring schematic I could get so that I could make my own. I love to make stuff but Im not the greatest at designing things my self. But Im really good at following a good set of plans.

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