[Lab] Plastic Bending Strips

Mon Jul 8 11:10:00 EDT 2013

Just need a high power dimmer as the cheap dimmers are 300-500W

Richard.

On Sun, Jul 7, 2013 at 3:33 PM, Roman Gargulak <roman at cncwings.com> wrote:

>  Henri,
>
> 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.
> I would strongly advise against using dimmer switch directly, without
> isolation transformer as you will be dealing with mains voltage and can
> electrocute yourself.
> Your 5V transformer will not work unfortunately with 8ft of wire, it will
> not provide not enough voltage to push required current through.
>
> 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.
> 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.
> 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.
>
> In my opinion, your best bet is a guitar string (G), maybe run two in
> parallel to reduce resistance.
>
> Roman
>
>
>
> On 7/7/2013 12:52 PM, Henri Kuschkowitz wrote:
>
> Hey guys,
>
>  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?
>
>  I have used the formula on this<http://www.heatersplus.com/nichrome.html> 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.
>
>
>  Cheers all,
> Henri
>
>
>
>  On 2013-07-04, at 10:36 PM, Roman Gargulak <roman at cncwings.com> wrote:
>
>  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.
>
> Roman
>
>
>
>
> 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> 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> 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 <henri.kuschkowitz at gmail.com>
>> *To:* Alex <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> 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 <henri.kuschkowitz at gmail.com>
>> *To:* lab <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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