<html><head><meta http-equiv="Content-Type" content="text/html charset=iso-8859-1"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hey guys,<div><br></div><div>It might be good to clarify what I want/need. After some more research I think I also have a better understanding in general of my requirements. I (will) have various cuts of acrylic, max 7' long, 1/8" thick that I need to bend at a straight angle. As such I require evenly distributed temperature. I similar idea to Roman's foam cutter is probably to closest example. Just to be sure, I am trying to have a setup with a max 1000deg C heat wire. The video I posted earlier seems to do the trick easily if i use 22 gauge Nichrome wire across 8ft and just a dimmer switch for 110V and 15Amps (12Amps). I do have access to a 5V 60Amp transformer, but with my limited skill set I am worried about breaking it. Could someone give me some pointers how I would calculate if I can reach the temperature I am looking for?</div><div><br></div><div>I have used the formula on <a href="http://www.heatersplus.com/nichrome.html">this</a> page to get some details about what I would need for my setup and am currently looking through some more. I am trying to see if I can use the "G" string idea Roman pointed out since Nichrome wire is nowhere to be found in the area and shipping will take a bit too long for my taste.</div><div><br></div><div><br></div><div>Cheers all,</div><div>Henri</div><div><br></div><div><br></div><div><br><div><div>On 2013-07-04, at 10:36 PM, Roman Gargulak <<a href="mailto:roman@cncwings.com">roman@cncwings.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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I do not think that particular PID controller will work with this
application as it is not meant for fast switching, it is meant for
relatively slow processes.<br>
The wire itself has very little mass so slow switching will not work
as wire will cool off quickly.<br>
You really do not need closed loop with feedback for this, the
variac is good solution but maybe a bit overkill, if your heated
wire is only 3-4 feet long.<br>
<br>
On my CNC foam cutter I use 0.009" wire which has quite high
resistance and I need only about 18-20V to heat it up.<br>
With 20AWG wire (which has over 0.030" diameter) you will need lower
voltage and higher amperage, which variac will provide, just be
cautious and treat it as mains as someone wisely pointed out
already.<br>
<br>
If you can not find wire, you can always use steel guitar strings,
"e" string is 0.009", "G" string is 0.016" (talking about guitar G
string here, just to be clear ;-) )<br>
If you can not find variac, you can always try to use regular step
down transformer and dimmer switch on the primary side.<br>
Or since you will need low voltage, you can try just regular bench
top power supply.<br>
<br>
Roman<br>
<br>
<br>
<br>
<br>
<div class="moz-cite-prefix">On 7/4/2013 4:25 PM, Michael Grant
wrote:<br>
</div>
<blockquote cite="mid:CAPvOnTvGRz2k5Luo3HiVp3M-+f6Pj4wR25QS9ix6MPnf5HqkQQ@mail.gmail.com" type="cite">That power supply is also known as an autotransformer.<br>
<a moz-do-not-send="true" href="https://en.wikipedia.org/wiki/Autotransformer">https://en.wikipedia.org/wiki/Autotransformer</a><br>
<br>
Care should be taken with an autotransformer, while the voltage
can be set low, there is no, none, zero galvanic isolation.<br>
Meaning the full current of the service is available (20amps).
Treat the output as you would treat 120VAC direct from a
receptacle...<br>
<br>
I've never seen one in the lab, but they do have a variable DC
supply that is maybe 3amps and 30v max.<br>
Depending on the load, the heating element, you might be able to
use one of those twisty things for lights...<br>
Alternatively, an AC thermostat for bang bang control with
hysteria should also work if you keep the thermal loop tight.<br>
<br>
The last and best option would be a ~$14 PID controller from ebay,
that would give the best thermal regulation. <br>
Sometimes they come in a kit with an SSR (solid state relay) and a
thermocouple for a little more dough...<br>
Here's one kit for $24...<br>
<a moz-do-not-send="true" href="http://www.ebay.ca/itm/100-240V-Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Probe-/290825156892?pt=LH_DefaultDomain_0&hash=item43b687b91c">http://www.ebay.ca/itm/100-240V-Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Probe-/290825156892?pt=LH_DefaultDomain_0&hash=item43b687b91c</a><br>
<br>
<br>
Michael<br>
--<br>
<a moz-do-not-send="true" href="http://krazatchu.ca/">http://krazatchu.ca/</a><br>
<br>
<br>
<div class="gmail_quote">On Thu, Jul 4, 2013 at 4:07 PM, Henri
Kuschkowitz <span dir="ltr"><<a moz-do-not-send="true" href="mailto:henri.kuschkowitz@gmail.com" target="_blank">henri.kuschkowitz@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word">So, I am still getting some
more costs tomorrow, but I think I might go with this
quick/dirty setup: <a moz-do-not-send="true" href="http://www.youtube.com/watch?v=wVEf7PfuKxo" target="_blank">http://www.youtube.com/watch?v=wVEf7PfuKxo</a>
<div> <br>
</div>
<div>What do you guys think? This leads me to my next
question, would anybody know if the lab has an item
similar to this:
<div>
<div><a moz-do-not-send="true" href="http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner+Ad&utm_campaign=Variac+TVT001" target="_blank">http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner%2BAd&utm_campaign=Variac%2BTVT001</a></div>
<div> </div>
<div><br>
</div>
<div>Cheers all,</div>
<div>Henri</div>
<div><br>
</div>
<div>
<div>
<div>On 2013-07-04, at 7:54 AM, Alex <<a moz-do-not-send="true" href="mailto:alexbarbour@bell.net" target="_blank">alexbarbour@bell.net</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div dir="auto" bgcolor="#ffffff">
<div><font face="Arial">Henri</font></div>
<div> </div>
<div><font face="Arial">Angle iron is a common
name applied to steel angles. some are
extruded in the heavier sections and have a
sharp outside corner.</font></div>
<div> </div>
<div><font face="Arial">Some are bent from flat
stock and have a radiused corner.</font></div>
<div><font face="Arial">These are better for use
as formers for plastics.</font></div>
<div> </div>
<div><font face="Arial">Home depot. Hardware
dept.</font></div>
<div><font face="Arial">CTC ect.</font></div>
<blockquote style="BORDER-LEFT:#000000 2px
solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px" dir="ltr">
<div style="FONT:10pt arial">----- Original
Message ----- </div>
<div style="FONT:10pt
arial;BACKGROUND:#e4e4e4"><b>From:</b> <a moz-do-not-send="true" title="henri.kuschkowitz@gmail.com" href="mailto:henri.kuschkowitz@gmail.com" target="_blank">Henri Kuschkowitz</a> </div>
<div style="FONT:10pt arial"><b>To:</b> <a moz-do-not-send="true" title="alexbarbour@bell.net" href="mailto:alexbarbour@bell.net" target="_blank">Alex</a> </div>
<div style="FONT:10pt arial"><b>Sent:</b>
Wednesday, July 03, 2013 9:12 AM</div>
<div style="FONT:10pt arial"><b>Subject:</b>
Re: [Lab] Plastic Bending Strips</div>
<div><br>
</div>
<div>Hey Alex,</div>
<div><br>
</div>
<div>I have a very particular type of acrylic
we are going to be using that I doubt comes
'bendable'. Angle iron? I haven't seen those
before. Got a reference or suggestion?</div>
<div><br>
</div>
<div>Cheers,<br>
Henri</div>
<div><br>
On 2013-07-03, at 8:03, Alex <<a moz-do-not-send="true" href="mailto:alexbarbour@bell.net" target="_blank">alexbarbour@bell.net</a>>
wrote:<br>
<br>
</div>
<blockquote type="cite">
<div>
<div><font face="Arial">On the other hand
they do produce an acrylic sheet that
can be bent cold .</font></div>
<div><font face="Arial">Have done small
pieces by hand. For larger OR thicker
( say 1/8 inch + )one needs a former
for the edge. Angle iron with a round
egde serves well.</font></div>
<div><font face="Arial">Alex B</font></div>
<blockquote style="BORDER-LEFT:#000000 2px
solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px">
<div>
<div class="h5">
<div style="FONT:10pt arial">-----
Original Message ----- </div>
<div style="FONT:10pt
arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a moz-do-not-send="true" title="henri.kuschkowitz@gmail.com" href="mailto:henri.kuschkowitz@gmail.com" target="_blank">Henri
Kuschkowitz</a> </div>
<div style="FONT:10pt arial"><b>To:</b>
<a moz-do-not-send="true" title="lab@artengine.ca" href="mailto:lab@artengine.ca" target="_blank">lab</a> </div>
<div style="FONT:10pt arial"><b>Sent:</b>
Tuesday, July 02, 2013 3:09 PM</div>
<div style="FONT:10pt arial"><b>Subject:</b>
[Lab] Plastic Bending Strips</div>
<div><br>
</div>
Hey guys,
<div><br>
</div>
<div>I figured it's a good time to
start asking the collective for
some feedback. We are planing on
bending larger sheets of acrylic
(they will definitely not fit into
the laser cutter) and I am looking
at <a moz-do-not-send="true" href="http://www.briskheat.com/p-152-rh-plastic-bending-strip-heater.aspx" target="_blank">bending strip
heaters</a> to build a custom
heating element for our purposes.
Before I go ahead ordering the
pieces I was wondering if anyone
had ever used such a thing and/or
knows of a good local source? For
saving some money, I wonder if
reusing a baseboard heater could
do the trick :P</div>
<div><br>
</div>
<div>Cheers all,</div>
<div>Henri<span style="white-space:pre-wrap"> </span></div>
<div><br>
</div>
</div>
</div>
<hr>
<div class="im">
<div><br>
</div>
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