Re: Pololu geared DC motor 30g prototype extruder May 19, 2016 06:14PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 19, 2016 11:57PM |
Registered: 7 years ago Posts: 78 |
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rklauco
Well, I had another night of fun
I have got the motor working with L298N and tried to paint a bit of a black line on the gear I wanted. I found that it has a gear ratio ~1:31 with the final shaft. So that would have worked.
However, for the love of God I was not able to glue anything to the gear. It's so smooth that no glue stick to it. I tried superglue, rubber-like glue, even hot glue (extremely thin layer due to the space constraints) and, as expected, none of them works.
So I gave up and I'll try to contact China sellers for some price quotes. I'm not buying the one from pololu - I have 5 of these with no encoder for $15. I'm not willing to pay $15 for one with encoder.
If I can't get anything reasonable from china, I still can go to i2c ASM sensor - I'll glue the magnet to the end of the 5mm shaft (as soon as I'm able to get my hands on one) and I'll measure the magnet rotation as Misan did with his servo-driven extruder.
Re: Pololu geared DC motor 30g prototype extruder May 20, 2016 12:39AM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 20, 2016 11:10AM |
Registered: 7 years ago Posts: 78 |
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rklauco
Honestly, the problem with the ir led is the size - try it and you'll see
Magnetizing seems more plausible, but the gearbox i have is pressed together - I was unable to take it apart.
Re: Pololu geared DC motor 30g prototype extruder May 20, 2016 04:10PM |
Registered: 8 years ago Posts: 181 |
Not yet - to read it, I'd need oscilloscope. And I ordered it already, but it will travel from China, so I expect it in like 4 weeks or so.Quote
ipcalit
Did you have any luck with the sensor on the outside of the motor casing?
Re: Pololu geared DC motor 30g prototype extruder May 21, 2016 02:44AM |
Registered: 7 years ago Posts: 78 |
Re: Pololu geared DC motor 30g prototype extruder May 21, 2016 01:59PM |
Registered: 12 years ago Posts: 972 |
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rklauco
...
I have no idea what mistake I did, but I burned 2 TB6612 drivers - their capacitors blew directly upon connecting 12V.
Re: Pololu geared DC motor 30g prototype extruder May 21, 2016 02:28PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 21, 2016 07:14PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 21, 2016 11:39PM |
Registered: 7 years ago Posts: 78 |
Re: Pololu geared DC motor 30g prototype extruder May 22, 2016 03:25PM |
Registered: 8 years ago Posts: 9 |
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ipcalit
Funny as I was looking today into doing a similar thing. Found a tiny 683 bearing and old Meccano brass gear 10T that I drilled to ~3mm and then made a groove with triangular file. Heated the gear up on the stove then quickly press-fit it on the shaft - solid like a rock now. I adjusted the size of the extruder to fit the new parts and guess what.... 15g total and it works like a champ. The evolution of the design is rather nice (v1-v2-v3) with strong torque and minimal parts count.
New parts:
1x 683 bearing (3x7x3)
1x brass bushing (3mm inner, 5mm outer, 7mm outer flange, 2.5mm thick)
1x 10T brass gear
1x N20 gear motor 1:100 (30rpm)
1x M3 screw 10mm
Attached are two STL files for the extruder, one including a guide for the filament and the other without it if your printer cannot handle fine details.
Re: Pololu geared DC motor 30g prototype extruder May 22, 2016 05:32PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 22, 2016 10:14PM |
Registered: 7 years ago Posts: 78 |
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rklauco
So - I started to re-design the thing based on the original shape.
I was thinking about using 4-screw bearing hold with springs to provide sufficient grip for the gear.
So I printed the file attached.
And then I found I do hot have screws long enough to hold the bearing holder AND the spring.
Just out of curiosity I tested it without spring - and IT WORKS!!!
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rklauco
The 5 screws used now have some impact - the weight of the full device is now 44 grams, instead of 30. But that's also due to the fact that I over-engineered the extruder and used unnecessary thick walls.
I think I'm gonna invest and pay the ~$16 for the version with encoder - I'd love to see this working.
Re: Pololu geared DC motor 30g prototype extruder May 22, 2016 10:30PM |
Registered: 7 years ago Posts: 78 |
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nallar
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ipcalit
Funny as I was looking today into doing a similar thing. Found a tiny 683 bearing and old Meccano brass gear 10T that I drilled to ~3mm and then made a groove with triangular file. Heated the gear up on the stove then quickly press-fit it on the shaft - solid like a rock now. I adjusted the size of the extruder to fit the new parts and guess what.... 15g total and it works like a champ. The evolution of the design is rather nice (v1-v2-v3) with strong torque and minimal parts count.
New parts:
1x 683 bearing (3x7x3)
1x brass bushing (3mm inner, 5mm outer, 7mm outer flange, 2.5mm thick)
1x 10T brass gear
1x N20 gear motor 1:100 (30rpm)
1x M3 screw 10mm
Attached are two STL files for the extruder, one including a guide for the filament and the other without it if your printer cannot handle fine details.
That looks awesome! How much force can it apply to the filament?
Re: Pololu geared DC motor 30g prototype extruder May 24, 2016 02:16PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 24, 2016 05:11PM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 24, 2016 06:01PM |
Registered: 7 years ago Posts: 78 |
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rklauco
This is AMAZING.
Not only it has a great grip on filament, it is also unexpectedly fast.
It works great and on 12V it runs through the filament like a knife through a butter.
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rklauco
Tomorrow I'll test direct connection to my fake e3d-v5 to see how it performs in real life situation.
The current version is 25grams only.
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rklauco
I decided I won't install the encoder for the motor - it's too expansive. Instead, I'll glue magnet on top of the actual wheel and set the AS5600 and use misan's code for i2c communication. The resolution is 12bit, so theoretically I should be able to read 4096 positions, therefore the resolution should be somewhere around 0.08 degree.
I do not plan to go to this detail - even 1024 bit resolution is an overkill according my opinion.
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rklauco
The reason of not using the onshaft encoder is twofold - first of all the size - I would not be able to fit in the encoder as it extends for more than 1mm and therefore the snug fit of the motor body would not be so snug. And the second reason is the price - I can get 5 pieces of the AS5600 including the magnet for ~$18 including shipping - making it less then $4 for single extruder.
Funny thing is that not only will this be significantly smaller and lighter then extruder with stepper - it will be also much cheaper.
Current price list:
- motor N20-12V-100 (1:100 gear reduction, 12V) for $3
- encoder with magnet for less then $4
- gear for $1.5
- bearing mr126zz for $0.14
- M3 bolt 20mm for $0.01
- M3 nut 20mm for $0.01
- ATtiny85 for $1
Total price of the whole setup is therefore less then $10 (not including the 3 printed parts).
See attached photos and the OpenSCAD design.
I have to modify the design a bit - the nut is difficult to insert without heating it up and the nut and bolt "cover" is too thin (printing it on my crappy printer is quite bad), but the functionality is OK.
I printed mine in ABS with 50% infill, 3 top and 3 bottom layers and 3 perimeters.
Now I have to make 3 of them and buy the diamond hotend
Re: Pololu geared DC motor 30g prototype extruder May 24, 2016 06:52PM |
Registered: 9 years ago Posts: 483 |
Re: Pololu geared DC motor 30g prototype extruder May 24, 2016 07:03PM |
Registered: 7 years ago Posts: 78 |
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rklauco
So. My findings from this night:
- It does work.
- The motor is quite strong.
- Actually too strong - when trying to push filament through 0.2mm nozzle the whole extruder assembly torn appart the ABS bond.
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rklauco
Next step - print the extruder including the e3d-v5 holder together to avoid splitting under heavy loads.
Also, another negative finding - my gear is mounted a bit wrong - it has a tiny bit more grip on one part a a tiny bit less grip on the other side - therefore one can hear the sound of the motor being uneven - when the gear has smaller distance to the ball bearing, it has to work significantly more as the resistance from the actual gear is much higher. Then, when it's over the "peak", it starts to go very fast - until another revolution and therefore another bump.
Seems like the coupling of 5mm gear to 3mm shaft will be the most critical part here.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 01:06AM |
Registered: 7 years ago Posts: 78 |
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etfrench
The AS5600 is only 0-360 degrees. Don't you need an incremental encoder like AS5247?
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 02:48AM |
Registered: 12 years ago Posts: 972 |
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 03:55AM |
Registered: 8 years ago Posts: 181 |
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 04:06AM |
Registered: 12 years ago Posts: 972 |
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 08:20AM |
Registered: 14 years ago Posts: 351 |
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ipcalit
Awaiting for encoder and perhaps insights into using QEI with Smoothieboard.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 11:02AM |
Registered: 7 years ago Posts: 78 |
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misan
I like to have at least 400 counts per revolution, but resolution depends of the wheel's radius. I would aim at a filament length resolution of at least 0.1mm.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 11:04AM |
Registered: 7 years ago Posts: 78 |
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arthurwolf
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ipcalit
Awaiting for encoder and perhaps insights into using QEI with Smoothieboard.
You can wire the encoder to the Smoothieboard and the hardware peripheral exists, but the Smoothie firmware has no code to use it at this point.
So you'd need to add support for that yourself.
Also, there is only one QEI peripheral, so this'd work only for one axis.
If you need help with anything, you can email me at wolf.arthur@gmail.com, always love to see folks trying unusual things.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 11:06AM |
Registered: 14 years ago Posts: 351 |
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ipcalit
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arthurwolf
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ipcalit
Awaiting for encoder and perhaps insights into using QEI with Smoothieboard.
You can wire the encoder to the Smoothieboard and the hardware peripheral exists, but the Smoothie firmware has no code to use it at this point.
So you'd need to add support for that yourself.
Also, there is only one QEI peripheral, so this'd work only for one axis.
If you need help with anything, you can email me at wolf.arthur@gmail.com, always love to see folks trying unusual things.
If we use AS5600 as rklauco suggested, perhaps we don't even have to worry about QEI as we'll track the filament directly (precision has to be determined). Then we can use existing I2C or SPI (which is used by the display anyway) libraries. What do you think?
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 11:59AM |
Registered: 8 years ago Posts: 5,232 |
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If so you want as much of the work going on withing the firmware, or you'll meet problems very easily with synchronizatio, precision etc.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 12:02PM |
Registered: 14 years ago Posts: 351 |
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o_lampe
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If so you want as much of the work going on withing the firmware, or you'll meet problems very easily with synchronizatio, precision etc.
What synchronization?
The ATtiny gets the step/dir signal from the Atmega ( or other main controller ) and takes care of one motor in a closed loop. But AFAIK there is no feedback to the planner of the maincontroller that allows to sync the other axes with a skipping extruder. For the main controller it is still an open loop, right?
@rklauko
I'd make an e3d holder with integrated clamping holder for the motor/gear. That way you can easily change the motor when brushes or gears are worn out.
Re: Pololu geared DC motor 30g prototype extruder May 25, 2016 12:03PM |
Registered: 8 years ago Posts: 5,232 |