Well, a little more progress. First of all, I remembered that I have 1 more gear - something like this, although I paid $4 for 5 of them. So I did another attempt with the motor and after 30 minutes of filing and press-fitting I was able to put the gear onto the motor. And it works pretty OK. Now, I printer the original STL, but due to my printer's "qualities" it was quite tight - I had really prby rklauco - General
Yep, looks like - I de-soldered the burned cap, replaced it with ad-hoc through-hole 10uF and everything seems to be ok.by rklauco - General
QuoteipcalitDid you have any luck with the sensor on the outside of the motor casing? 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. I went shopping again and had another no-luck situation with the 5-to-3mm shaft. Out of desperation I bought aluminium rivets. They are not exactly 5mm wide (something likeby rklauco - General
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.by rklauco - General
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 (extremeby rklauco - General
Well, this was fun. I identified 3rd gear in the gearbox that would be a potential candidate for any sort of optical tracking - it's located at an accessible part of the gearbox and has some room above it. So, I tried to hook up additional TB6612 and tried to drive it slowly so I can see if how fast does the gear spin comparing to the output shaft. Let's say not all went according to plan. I haveby rklauco - General
Quoteipcalit If anybody has one of these, it would be great to compare the diameter of the drive gear with the Mk7 or Mk8 commonly in use. Seems like a run-of-the-mill 18T gear, which could be replaced by one brass insert for M3 and some epoxy. No bearings are used on the shaft of the motor, which could lead to premature failure. Wow, that could be interesting. I wonder how the plastic gears forby rklauco - General
Quotebobc I had a look at the schematic here and P1[20] is connected to LED3, and P1[23] is spare, both are routed to headers. Might need to sacrifice an LED but it looks doable. I'm not really sure I follow. As I see the capabilities of the chip, it can only read 1 encoder. You will need 2-4 (depends on which axes/extruder do you want to modify). One quadrature encoder in HW will not help youby rklauco - General
Unfortunately, there was no 5mm tube available in the shop today I have to check a different shop tomorrow evening...by rklauco - General
QuoteipcalitAnother possibility is to engage a larger rubber-coated wheel/gear in a similar way with the belt-driven designs that recently circulated. I don't like adding other wheels, but this could to drive the filament without compression (see attached). The drawback is a more complicated design and parts that are hard to source. Interesting - I've never seen drive like that. I have an idea hby rklauco - General
It's a waste of time these calculations. First of all, inertia only applies to moving objects. Therefore you only have to account the weight of the rotor, not the stator part of the motor. And, in the small DC, it's magnitudes smaller - like 2 orders of magnitude. Also, the inertia by design applies to the shaft, BUT the shaft has a serious breaking force introduced by the gearbox right to it. Thby rklauco - General
The problem with the ones from aliexpress os that their shaft does not extend to the other side of the motor - therefore no encoder can be used on itby rklauco - General
Check Diamond Hotendby rklauco - Mechanics
Not that I'd like to disagree, but your calculation is a bit wrong - NEMA17 shaft radius is 2.5mm (5mm diameter). However, it can spin (tested) up to 4000rpm. For me, the biggest problem here is the price of the motor+encoder - I've got 5 of the motors for $7, but with no encoder. And that seems to be the major difference here I'll do my tests - if a simple hall-effect sensor on the outside of tby rklauco - General
You mean speed? Well, with the current setup (8mm threaded rod) and 9.08V of power supply, the Z axis moves 97mm in 18 seconds.by rklauco - General
LOL Today I measured the physical resolution. The system does 350.000 steps per 94mm of movements. Therefore the resolution is 0.000268571mm per step I think this is beyond any practical usage, so I'll introduce 10x multiplier to step input...by rklauco - General
I think you misunderstood tge goal here - to huild a brand-new controller bottom up would bee probably too much. That's why the goal here is to provide drop-in replacement for current stepper circuits only. And yes - the code wull probably be similar to Misan's, but I don't think that it is a disadvantage.by rklauco - General
Well, I suspect the whole project will be a big success now I used parts of 2 old Canon printers - paper feeders for the both Z axis, belt from one of its printhead and DC motor for the paper feeder, too. I re-purposed the tensioning mechanism from the printhead, too. I had to do that - without the dynamic tensioning, the axis started VERY slow. However, the circular strip has a VERY high resoluby rklauco - General
Wow, just now I noticed the chip you are using to drive the motor - A4953. That's a fantastic idea - looks way better than the old L298 or even the one I'm using now - TB6612FNG. The TB is a dual H bridge, but for the pin compatibility 1 H bridge is better.by rklauco - General
QuoteB4MeIts kinda sad pid tuning is hard.. but then again, a good guide can help A LONG way ! Check the code of Misan on github - he made a simple processing script, that can help you visualize the approach curve and tune PID using 6 keys. I made a small adjustment (ability to store current values on keypress), but that's just nice-to-have. This helped me to set working (I am not stating idealby rklauco - General
But the gearing is quite serious with the little motor (so is the torque), so 12 impulses per revolution should be plenty...by rklauco - General
Interesting, although I do not fully understand the mechanics here. Why is the middle bearing flanged? What shaft is it you used? How did you connected the shaft to the motor?by rklauco - General
What I don't understand is inkjet printer. If you sum up the components - 2 dc motors, 2 optical encoders, one long strip and one rotary strip, power source, usualy a hardened rod, too, you end up with a bill of cca. 70-80 eur (if you find encoding strips this cheap, of course). However, the whole inkjet, including electronics, mechanics, a lot more rods for paper feed, ... costs 40eur. You can eby rklauco - General
QuoteTraumflugHow about reducing motor current? A printer design isn't at fault if you don't adjust such things properly, nor is the concept of having stepper motors. Of course I did that first. But the steppers were simply too weak to move the gantry then. I'd suggest you first look at the steppers used within ToyRep to get the ideaby rklauco - General
Quoteo_lampe I agree with your torque theory, but in certain moments you need this huge torque ( immediately ). At turning points of a move ( inertia ) or when you start to move you have to deal with more friction. My current solution to this is to limit the jerk movement distance, provide safe acceleration and feedrate speeds. However, if I succeed to get the planner part working ok, I think thiby rklauco - General
This is 100% true. That's the reason I've spent last week or so trying to read repetier firtmware code to identifgy propper routines in planner, hal and printer.cpp. But my cvodingb skills are veru limitedby rklauco - General
Quoteo_lampeHow does "51mNm starting torque" translate in Ncm? Is it 5.1Ncm? Then the "9.8mNm rated load" is only 0.98Ncm, which IMHO is very low. What is the weight of this motor? We have seen steppers with 50grams and 7Ncm holding torque.... Your numbers are correct, confirmed by this site Yes, I admit the torque is low. But, there is a huge difference to steppers. In stepper, you don't knoby rklauco - General
QuoteLoboCNCHow are you testing the servo performance? Is your printer printing yet? A good overall measure is to print something like a GT2 pulley and then seeing how well a GT2 belt fits. Printing pulley teeth produces the sort of small back & forth motion that really tests how well your servos are working dynamically under a load. Could be that your inertial loads are really light as coby rklauco - General
While I agree with the theory, I have to question why all the inkjets use encoder out of the motor only for both the print head and for the paper feed. Nasty issues are probably true, but I have to say one thing. I actually built the device already - I modified the X axis of my ToyRep to the DC servo and it works - even with loosened belt (due to some plans to extend the footprint in future I donby rklauco - General
QuoteLoboCNCReading the specs on motors sold on ebay or aliexpress is really tricky because the people selling them often don't know that they have and fail to give you pertinent details (like encoder resolution, number of channels, etc.) Exactly my experience. Different topic - do you consider it better to have the encoder on the motor? From my perspective the belt still can slip and cause problby rklauco - General