[Lab] Plastic Bending Strips

Roman Gargulak roman at cncwings.com
Thu Jul 4 22:36:23 EDT 2013

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.
The wire itself has very little mass so slow switching will not work as 
wire will cool off quickly.
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.

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.
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.

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 ;-) )
If you can not find variac, you can always try to use regular step down 
transformer and dimmer switch on the primary side.
Or since you will need low voltage, you can try just regular bench top 
power supply.


On 7/4/2013 4:25 PM, Michael Grant wrote:
> That power supply is also known as an autotransformer.
> https://en.wikipedia.org/wiki/Autotransformer
> Care should be taken with an autotransformer, while the voltage can be 
> set low, there is no, none, zero galvanic isolation.
> Meaning the full current of the service is available (20amps). Treat 
> the output as you would treat 120VAC direct from a receptacle...
> I've never seen one in the lab, but they do have a variable  DC supply 
> that is maybe 3amps and 30v max.
> Depending on the load, the heating element, you might be able to use 
> one of those twisty things for lights...
> Alternatively, an AC thermostat for bang bang control with hysteria 
> should also work if you keep the thermal loop tight.
> The last and best option would be a ~$14 PID controller from ebay, 
> that would give the best thermal regulation.
> Sometimes they come in a kit with an SSR (solid state relay) and a 
> thermocouple for a little more dough...
> Here's one kit for $24...
> http://www.ebay.ca/itm/100-240V-Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Probe-/290825156892?pt=LH_DefaultDomain_0&hash=item43b687b91c
> Michael
> --
> http://krazatchu.ca/
> On Thu, Jul 4, 2013 at 4:07 PM, Henri Kuschkowitz 
> <henri.kuschkowitz at gmail.com <mailto:henri.kuschkowitz at gmail.com>> wrote:
>     So, I am still getting some more costs tomorrow, but I think I
>     might go with this quick/dirty setup:
>     http://www.youtube.com/watch?v=wVEf7PfuKxo
>     What do you guys think? This leads me to my next question, would
>     anybody know if the lab has an item similar to this:
>     http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner%2BAd&utm_campaign=Variac%2BTVT001
>     <http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner+Ad&utm_campaign=Variac+TVT001>
>     Cheers all,
>     Henri
>     On 2013-07-04, at 7:54 AM, Alex <alexbarbour at bell.net
>     <mailto:alexbarbour at bell.net>> wrote:
>>     Henri
>>     Angle iron is a common name applied to steel angles. some are
>>     extruded in the heavier sections and have a sharp outside corner.
>>     Some are bent from flat stock and have a radiused corner.
>>     These are better for use as formers for plastics.
>>     Home depot. Hardware dept.
>>     CTC ect.
>>         ----- Original Message -----
>>         *From:* Henri Kuschkowitz <mailto:henri.kuschkowitz at gmail.com>
>>         *To:* Alex <mailto:alexbarbour at bell.net>
>>         *Sent:* Wednesday, July 03, 2013 9:12 AM
>>         *Subject:* Re: [Lab] Plastic Bending Strips
>>         Hey Alex,
>>         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?
>>         Cheers,
>>         Henri
>>         On 2013-07-03, at 8:03, Alex <alexbarbour at bell.net
>>         <mailto:alexbarbour at bell.net>> wrote:
>>>         On the other hand they do produce an acrylic sheet that can
>>>         be bent cold .
>>>         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.
>>>         Alex B
>>>             ----- Original Message -----
>>>             *From:* Henri Kuschkowitz
>>>             <mailto:henri.kuschkowitz at gmail.com>
>>>             *To:* lab <mailto:lab at artengine.ca>
>>>             *Sent:* Tuesday, July 02, 2013 3:09 PM
>>>             *Subject:* [Lab] Plastic Bending Strips
>>>             Hey guys,
>>>             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 bending strip
>>>             heaters
>>>             <http://www.briskheat.com/p-152-rh-plastic-bending-strip-heater.aspx> 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
>>>             Cheers all,
>>>             Henri
>>>             ------------------------------------------------------------------------
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