For my IDEX (independent dual extrusion) printer I need to use 2 motors for the X axis, one on each side. Can I use the the motor shafts for the bearing idler as well? I know it’s kind of weird but it would save about 50 mm in the X axis and ~$70. I feel like as long as the idle X motor is locked it should be fine.
Yes! indeed! This is how I designed my last printer. I don’t remember the kind of bearing that I used for the idler. I can find it out next week if you are interested.
@Diego_Viejo thanks! I’ve got the part in mind already: https://us.misumi-ec.com/vona2/detail/110302651360/?Inch=0&CategorySpec=00000045557::a,d 00000029797::af
yeah, I also considered something similar, but the idler pulley of this kind that i got was to wide to be secured to the motor shaft. Here, the limit factor is the shaft length. I finally choose to put just two fanged bearings as idler pulley.
It’s going to more than double the load on the motor shaft bearings. Idlers see higher shaft loads than motor pulleys because they see up to preload+accelForce on both legs while the max motors see is preload+accelForce on one leg and preload on the other leg. (The exact shaft load depends on the belt length and direction of motion.)
Can the motor handle it? Probably?
@Ryan_Carlyle I would think so but here’s the motor I’ll be using:
http://kysanelectronics-com.3dcartstores.com/42BYGH101-26AWG_p_624.html
Belt length will be about 920mm. I guess I’ll just have to be careful not to over-tighten the X belts.
Interesting idea, I too worry about the load on the stepper shaft. In my printer (also idex) I have a support bearing on each stepper shaft, so I don’t have to worry about deflection.
Well it seems my question has become moot; the longest shaft I can find on a usable Nema 17 motor is only 25 mm. This barely gives enough room for a press fit pulley and idler, and I’m worried a pulley with no set screw will come loose.
Or would the press fit pulley keep its hold fine? I’m just worried it’ll slip
Why would you want to use press fit? A set screw or clamp hub pulley can hang off the end of the motor shaft.
Yeah but there’s like no room. Hold on I’ll post some screenshots of the design with the set screw one and you can let me know if it’s an issue or not.
The blue is the top surface of the motor shaft. This is the configuration with the idler on top and pulley on bottom. 0.1 mm clearance between all parts.
missing/deleted image from Google+
What’s all that space between the motor and older?
The pulley is on the bottom, the long shaft is for the set screws, I’m not sure why the screws weren’t added into their model. The shaft is 22 mm long, the pulley is 18 mm, and the idler is 10.3 mm. With the 0.1 mm clearance between moving parts, the distance between the end of the motor shaft and the end of the idler is 6.5 mm, more than half the thickness of the idler. This setup is for 6 mm belts, I think 4 mm would be too small.
Put the idler adjacent to the motor and put the drive pulley on the outside. The drive pulley should work fine as long as the set screw hub is on the shaft.
Yeah that’ll work fine on one side, but it has to be swapped on the other. Otherwise one belt would have 2 idlers, one belt would have 2 pulleys.
Unless you flip the motor around on one side.
Yeah that’s what I was just trying to figure out. It’ll work but it won’t be as pretty.