[sudo-discuss] 3D Printer - needs new heating element
Steve Berl
steveberl at gmail.com
Sat Nov 2 09:55:46 PDT 2013
If it helps, Lasher's is open on Saturdays from 10-2.
Steve
On Saturday, November 2, 2013, Hol Gaskill wrote:
> al lashers is great! they don't stay open late enough for me to go there
> after work though, so i usually get this kind of stuff online.
>
> it is 12vdc so the LED warning is easily done. for AC you could still
> just use one LED at just under 50% duty cycle and it'll block the reverse
> current.
> i don't know about all that empirical stuff - say you want 3V at the LED
> at 30mA, that's a 9V drop over the series resistor and R=V/I=9V/.03A = 300
> ohm resistor. could also just slap a chunk of 12V led strip down and call
> it a day - definitely bright!
>
> i would be curious to know if the problem resulted from simply being left
> on or what. the fan was not running iirc so that could have had alot to do
> with it, will have to check that as part of the repair - for now i'm just
> going to get these
> http://www.amazon.com/Resistor-Heating-Element-Printer-RepRap/dp/B00C44TBPA
>
> jake i'd be interested in learning more about how to tune the PID
> settings. no idea about the temperature sensing status since it stayed at
> room temperature, didn't think to use body heat or anything to test it but
> that'll be an easy enough check. i did not check the thermistor (or is it
> a thermocouple?) for continuity.
>
> cheers,
> hol
>
>
> Nov 1, 2013 05:45:36 PM, g2g-public01 at att.net wrote:
>
>
>
>
>
>
> >
> Yo's-
> >
>
> >
> And/or you can take the existing fried resistor to Al Lasher's
> Electronics on University Ave in Berkeley and they'll find a
> replacement, either exact-same or very close (the tolerances on
> resistors used as heaters are pretty wide). If it's a 3 to 5 watt
> resistor it shouldn't cost more than a couple bucks.
> >
>
> >
> Al Lasher's is an oldschool electronics shop that everyone in SR
> ought to know about: their stock of raw component parts is
> fantastic, and the folks who work there have been around forever
> & know their stuff. You'll probably find stuff there that
> suggests new projects to do.
> >
>
> >
> Chances are if you bring in the heat sink with the resistor glued
> on, they'll also be able to tell you what kind of glue is needed,
> and they probably have it in stock along with the resistor.
> >
>
> >
>
> >
> Re. putting an LED on the heating element:
> >
>
> >
> Good idea and will need a dropping resistor ahead of the LED,
> otherwise the LED will probably fry the first time it's turned on.
> If the voltage used to run the heater resistor is AC, then wire two
> LEDs together, one in reverse polarity with respect to the other,
> and they'll both light up.
> >
>
> >
> To estimate the value for the dropping resistor, measure the voltage
> input to the heater resistor and the current it draws (after you
> replace it with one that works), and compare with the specs for the
> LEDs you're using. If the dropping resistor or the LEDs get warm
> when in use (aside from ambient heat from the heater resistor), or
> the LEDs are excessively bright, substitute a higher value dropping
> resistor.
> >
>
> >
> If I was doing this, I'd just go empirical and use a large variable
> resistor in series with the LEDs, and turn it down slowly while in
> operation, until the LEDs light up to a sufficient degree (not dim
> but not too bright), then measure the value of the setting on the
> variable resistor and find a fixed resistor of similar or slightly
> higher value.
> >
>
> >
>
> >
> Useful tools for these types of purposes:
> >
>
> >
> A resistance decade box, and a capacitance decade box. These let
> you do empirical tests by switching-in progressively different
> values of resistors and capacitors into circuits until you get the
> desired result. Lasher's probably has at least a resistance decade
> box in stock. The reason these are called "decade boxes" is because
> the traditional version has selectors with ten positions each, and
> the values of each selector increase by factors of 10 relative to
> the next lower selector on the box.
> >
>
> >
> The exception to the use of decade boxes is where a component
> handles a large power level, such as a heater resistor, or an
> electrolytic capacitor in a power supply. I'm guessing that your
> heater resistor handles from 3 - 5 watts, but it may be more. The
> resistors in decade boxes are typically rated at 1/4 watt to 1/2
> watt and are designed for testing signal/control/audio circuits
> rather than circuits that carry higher power levels.
> >
>
> >
> -G
> >
>
> >
>
> >
> =====
> >
>
> >
>
> >
>
> >
> On 13-11-01-Fri 5:20 PM, Jake wrote:
> >
>
>
> >I retract my assertion that you hadn't put any text in
> your email.
>
> >
>
> >
> as for the printer, it seems clear that you and steve are right
> that the resistor is burned out. I wonder what caused this - i
> haven't heard of it happening a lot bu on Nov 01, 2013, Jake
> wrote:
>
> >
> Hol,
>
> >
>
> >
> you forgot to put any text in your post at all! please be
> clear of how
>
> >
> you came to this conclusion.
>
> >
>
> >
> The heating element is a resistor glued into a block of
> metal on the end
>
> >
> of the extruder. It has two wires which go to a connector
> a couple inches
>
> >
> from it, and they go back to the machine.
>
> >
>
> >
> To test the heating element, one can unplug this connector
> and use a
>
> >
> multimeter to measure its resistance. It should be
> something like 8 ohms,
>
> >
> i don't know the exact value but 100 is too much and
> indicates it's bad.
>
> >
>
> >
> it was replaced a little while ago by a technician from
> the corporation
>
> >
> that made it.
>
> >
>
> >
> If the machine is acting up about heating, we need to know
> whether the
>
> >
> problem is with the heating or the temperature sensing. If
> the
>
> >
> temperature sensor is reporting ambient temperature, it's
> probably
>
> >
> working.
>
> >
>
> >
> if the temp sensor is working but the heating element
> isn't making it heat
>
> >
> up, it could be the heating element (see test above) or it
> could be the
>
> >
> connector near it, or the wires from there back to the
> main board, or
>
> >
> where those wires connect to the brain.
>
> >
>
> >
> can you give more information about what you tried and
> what you observed?
>
> >
>
> >
> -jake
>
> >
>
> >
>
>
> >
>
> >
>
> >
>
>
> >
>
>
> >
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--
-steve
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