<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; ">I'm wondering if the 1000 deg. spec target should really be deg. F and not deg. C.<div><br><div>"Use a heater that develops an element surface temperature<div>of approximately 800°F (not glowing red), and a sheet support</div><div>surface temperature of less than 225°F (water cooled if necessary)"</div><div>(see page 8 of ref: <a href="http://www.plexiglas.com/literature/pdf/135.pdf">http://www.plexiglas.com/literature/pdf/135.pdf</a> )</div><div><br></div><div>Nichrome wire has a melting point of 1400 deg. C</div><div>1000 deg. F is 540 deg. C</div><div><br></div><div><br><div><div>On 2013-07-08, at 11:10 AM, Richard Sloan <<a href="mailto:rsloan@themindfactory.com">rsloan@themindfactory.com</a>> wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite"><div dir="ltr"><div>Just need a high power dimmer as the cheap dimmers are 300-500W<br><br></div>Richard.<br><br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Sun, Jul 7, 2013 at 3:33 PM, Roman Gargulak <span dir="ltr"><<a href="mailto:roman@cncwings.com" target="_blank">roman@cncwings.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
Henri,<br>
<br>
The dimmer switch is a crude idea for this kind of regulation, but
it may work, you will need to try it. It worked for me when I needed
to cut 6ft long wing halves on my cutter.<br>
I would strongly advise against using dimmer switch directly,
without isolation transformer as you will be dealing with mains
voltage and can electrocute yourself.<br>
Your 5V transformer will not work unfortunately with 8ft of wire, it
will not provide not enough voltage to push required current
through.<br>
<br>
1000°C sounds rather high, I think nichrome wire should not be used
above 800°C-900°C. If it is that hot (1000°C) it may break easily.<br>
You will need close to 50V (that's dangerous level already), I have
a 1:2 step down transformer with a dimmer switch that you can borrow
if you want.<br>
Also, I have plenty of 0.009" stainless steel wire, but I am not
sure if it can sustain that high temperature without breaking, on
top of it, it's resistance is higher than nichrome (about 10ohms/ft)
so you will need really high voltage to heat up 8 feet of it.<br>
<br>
In my opinion, your best bet is a guitar string (G), maybe run two
in parallel to reduce resistance.<span class="HOEnZb"><font color="#888888"><br>
<br>
Roman</font></span><div><div class="h5"><br>
<br>
<br>
<div>On 7/7/2013 12:52 PM, Henri Kuschkowitz
wrote:<br>
</div>
<blockquote type="cite">
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" target="_blank">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" target="_blank">roman@cncwings.com</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"> 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>On 7/4/2013 4:25 PM, Michael
Grant wrote:<br>
</div>
<blockquote type="cite">That power supply is also known as an
autotransformer.<br>
<a href="https://en.wikipedia.org/wiki/Autotransformer" target="_blank">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 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" target="_blank">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 href="http://krazatchu.ca/" target="_blank">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 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 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 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 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 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 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 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>
<div style="FONT:10pt arial">----- Original
Message ----- </div>
<div style="FONT:10pt arial;BACKGROUND:#e4e4e4"><b>From:</b>
<a 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 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 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>
<div><br>
</div>
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