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A different multi-extrusion approach - UM tool / printhead changer


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Posted · A different multi-extrusion approach - UM tool / printhead changer

@neotko guess what I just ordered yesterday noon :D

Btw, that motor probably weighs 80g, not 50g. It says 50g on the page, but 80 on the datasheet...

Still I think it's a good model, and comes at a very attractive price, too.

You will need some gear ratio - direct drive with this motor will not deliver enough torque. I'll get a set of Misumi's polyacetal gears (#GEAB) to try with this setup.

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Posted · A different multi-extrusion approach - UM tool / printhead changer

Im also going to keep an eye on this, once again foehnsturm is leading the innovations! I could event go back to e3d perhaps (seems direct drive 3mm works way better than Bowden 3mm).

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    @ultiarjan this might (or maybe not) be interesting for you? No idea..

    I just downloaded the new cura... New 'legacy'? wherever the name, the new, old cura. From Lulzbot 17.10 (they ofc have keep pushing the number like anyone would do instead of going for date)

    What's new? NO IDEA. But, on dual, this it's interesting (since they are programming more where it was left)

    5a3312c5b9776_Capturadepantalla2015-10-21alas9_47_48.thumb.png.7478a0a16352a28cb5716fcf45fd1b2b.png

    Also yesterday tested the new beta cura, the UI it's a mess...

    5a3312c5b9776_Capturadepantalla2015-10-21alas9_47_48.thumb.png.7478a0a16352a28cb5716fcf45fd1b2b.png

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Well electrical engineering was my minor subject at the university. But I hardly remember a thing ... The fan I'm using on the UMO has a start voltage of 8V (max 12V). Does this mean anything regarding the controllability?

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Yes, it means the fan should start turning when you power it with 8V DC.

    BUT, if you have an adjustable DC voltage (for example a laboratory power supply), then you can "kick-start" the fan by supplying 12V DC for a few seconds. Then, you can lower the voltage which will also lower the fan's rpm.

    At some point it will obviously stop. But that should be more like 5V DC, maybe even less.

    The fan needs a certain amount of power in order to overcome the rotor inertia. Once the rotor is moving, you can lower the power.

    Now, an adjustable DC voltage is not the simplest thing to achieve.

    Mathematically, a PWM'd voltage is the same as adjusting a DC voltage.

    12V DC, with 50% PWM, is effectively (mathematically) 6V DC. But in reality the voltage switches between 12V and 0V rapidly. Many fans don't like that and may be damaged when you apply a PWM'd voltage to them.

    But there is a way to "actually" convert a PWM'd voltage into an adjusted DC voltage: By adding a low-pass RC-filter that flattens the PWM signal away, leaving a "more or less" DC voltage. There will be some ripple left in the voltage, but that won't matter to the fan.

    This is the simple part. Now you want to know the correct values for the resistor and capacitor. I have to admit I've never actually done this before, and there are quite a few things to consider even for something as simple as an RC filter.

    I can try putting together a little experiment at lunchtime. I'm not really the type to try and find a mathematical solution. I'd rather just put it together and see what happens. Then (maybe) derive a formula from that...

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Thanks a lot. Would be definitely worth a try. I just connected the fan (conrad.de, brand x-fan) to an adjustable power supply. In fact, it runs from 12V down to 3V and even starts with a voltage as low as that.

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Tried conducting that experiment. Sadly, I couldn't get it to work because I don't have a suitable PWM generator. PicoScopes are really useless for these kinds of things :(

    I'll need a battery powered PWM generator. Makes taking measurements and experiment set-up a lot easier...

    I'm ordering one from ELV, but it will take a few days for it to be delivered.

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Ok, this pancake stepper definitely needs a fan. But the whole print head would become quite bulky then. So I made my own drive wheel / gear combo. The new gearbox will be 18 mm instead of 30 mm in thickness.

    mk8-gear2.thumb.jpg.0a863381a519878ea546bf8ca69877c4.jpg

    mk8-gear.thumb.jpg.2933f982172030c86a2f1ea6f05d7fe2.jpg

    mk8-gear2.thumb.jpg.0a863381a519878ea546bf8ca69877c4.jpg

    mk8-gear.thumb.jpg.2933f982172030c86a2f1ea6f05d7fe2.jpg

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    Posted (edited) · A different multi-extrusion approach - UM tool / printhead changer

    Nice drive wheel ;)

    Maybe you could save some more weight by cutting out spokes?

    What drivers and current did you use?

    You can probably get it to run cooler with a TMC2100 stepper driver. At least if you use it in a dual toolhead scenario where there are large portions of "waiting time" - the TMC2100 can automatically lower the motor current when it is not in use.

    Maybe a thin aluminum sheet can act as a passive heatsink?

    Edited by Guest
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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    better now :)

    pancake-extr2-2.thumb.jpg.799a65bfd1ddebb092f85fab90b571df.jpg

    pancake-extr2-1.thumb.jpg.19a73ce25ca64d02743847bb3c3fd3de.jpg

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    better now :)

    You can get some Velcro braided sleeve like the one found Here to tidy up your cables. But it also gives you the flexibility to access them at any time.

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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    BTW, for anyone looking for gear wheels with less than 18 teeth (module 0.5) with a 5 mm bore (which I found quite hard to source): link

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    Posted (edited) · A different multi-extrusion approach - UM tool / printhead changer

    BTW, for anyone looking for gear wheels with less than 18 teeth (module 0.5) with a 5 mm bore (which I found quite hard to source): link

     

    Interesting! Misumi only goes down to 15 teeth minimum. Makes quite the difference for the large gear when you need 1:6 transmission...

    The large gear looks pretty heavy though. Why didn't they include spokes in a steel gear o.O

    Do these gears match with any other module 0.5 gears, e.g. the ones from Misumi? (GEABM0.5-50-3-B-5)

    /edit:

    Oh, wait. 10 teeth only has a 3mm bore. :(

    Well, 13 (smallest with 5mm bore) is still better than 15. Will try one

    Edited by Guest
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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    Do these gears match with any other module 0.5 gears, e.g. the ones from Misumi? (GEABM0.5-50-3-B-5)

     

    I strongly suspect that.

    It's a 13:50 reduction now (1:4.6)

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    Posted (edited) · A different multi-extrusion approach - UM tool / printhead changer

    13:50 is ~ 1:3.85, not 1:4.6? Just to make sure I'm not messing up my calculations :p

    Ordered one of these 13 tooth gears. Misumi will have to wait a bit, though. I don't want to bother them with a 1-item-order..

    /edit:

    Gotta love Misumi :)

    You can directly download STL files of their parts from them. Will make a quick mockup gear set now :)

    Edited by Guest
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    Posted · A different multi-extrusion approach - UM tool / printhead changer

    made a mistake it's actually 13:60:O

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    Posted (edited) · A different multi-extrusion approach - UM tool / printhead changer

    Föhnsturm, if you want to "pwm" the fan, here is my advise:

    Just buy a pack of 10 Capacitors, each 10µF and start with one parallel to the fan. If it doesn't start at your desired Voltage, add another Cap parallel again. Rince and repeat till you are happy ;)Cost: less then 5€ with shipping, e.g. something like that: http://goo.gl/KrbvQ4 (ebay.de as I assume you are german as I am).

    I also don't know if your firmware is capable of PDM instead of PWM, PDM is a better signal for cleaning voltage out with capacitors and is just superior than PWM.

    Also, I can recommend you this fan: Lüfter, Titan, 50x50x15mm, TFD-B5015M12B, radial, kugelgelagert http://r.ebay.com/EAHXXU

    This fan works out of the box and down to 4V in my current printer.

    Furthermore, I am, as always, impressed by your designs! Keep up the work!

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    Posted (edited) · A different multi-extrusion approach - UM tool / printhead changer

    @Labern, will do that. The wiring is a mess.

    @Skimmy, thanks! No resistors needed? Smoothieboard only does PWM as far as I know. However the frequency is adjustable. But as the corresponding variable is measures in milliseconds, I doubt it will do more than 1 kHz.

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