[Lab] Plastic Bending Strips
Roman Gargulak
roman at cncwings.com
Mon Jul 8 14:01:08 EDT 2013
We are talking about 250-300W of resistive load here so standard dimmer
should do just fine.
Roman
On 7/8/2013 11:10 AM, Richard Sloan wrote:
> 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
> <mailto: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
>> <mailto: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
>>>> <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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>>>>
>>>>
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