Hi, I am a beginner with motors in general, but I have 2 questions. Question 1 I would like to ask what the most common way is to attach a flat metal plate to a motor shaft. I have only seen harmonic drives that have additional screw holes, but they can be really expensive. I saw example like these, but they do not have any possibility to screw or connect flat metal plate to it, that must rotate together with the motor shaft. Question2 I noticed that OpenBuilds sells a lot of parts for Nema23 sizes. Can Nema34 be attached to these linear actuators that are designed for Nema34? In general, for hobbyist applications, are certain Nema motor sizes more popular than others? Should I, for instance, only use Nema23 and not Nema34? Thank you.
You can screw into the pre-threaded front holes of a Jog Knob but its its for attaching to our 8mm leadscrews, sadly not a direct fit onto the motor shaft. You could look for a 8mm to 6.35mm reducing bush on McMaster perhaps to make it work Different shaft diameters, different mounting dimensions - both require custom parts just to make them fit in the first place They are more expensive, and usually way overkill. NEMA23s are by far the more popular size in this market
Thank you for the answers. It is really hard to find one except of Jog Knob. Do you think having a metal plate and gluing it to the shaft using "Loctite" is also a good solution? I also would like to ask about achieving an accurate rotation with these motors. From Teknic I see that steppers resolution is 0.45 degrees. If I understand correctly for CNC machines use Lead or Ball screws to move in a precise manner down. But what about rotary movement, not linear one? Is there cheaper options than 500 Eur for harmonic drives or other reducers?
200 steps per rotation - with a microstep driver you can interpolate somewhat. In your rotary application, you would have to use math to take 1.8deg full step and determine based on shaft length or similar what that results to in distance. I don't think it'll last long, but what is the intended use case? Very odd use case, may need to get something custom made
I am trying to make a 5-axis motor head. For the 3 xyz axis, the linear guides are typical. But for to achieve the 3D motion i need to connect rotary movement to get a 3D angle. The issue is that there is plenty of option for linear actuation but nothing really for rotation actuation. Any advice would be much appreciated.
Depending on your shaft size, you could drill out a Mounting Hub (5mm) to fit but I wouldn’t trust that on a nema 34. Best bet would be getting a large diameter GT2 (or similar) timing pulley that matches your shaft size and drilling a mounting pattern in the face. With a motor that large with an expected use of repetitive reversals of motion you might look into keyed shaft and pulleys
Rotational torque would be an issue there. I'd use a large bearing setup to carry the tool weight for the rotational axis, with a reduction pulley system to drive it. Your bearing would need to accomodate thrust and rotational forces.
you mean something liek this? Doughty Drive The 4th & 5th Axis solution there is a belt between the motor and the axis. The motor bearings are not able to take the weight and cutting forces, and you need the reduction to achieve the resolution and accuracy you want. note that some microstepping drivers promise very high microstep rates, but those numbers are not real life, beyond 8x microstepping the positions can become quite inaccurate so you don't really get the resolution you are looking for unless you use Clearpath type devices with real absolute position feedback. so the microstepping gives you 'resolution' but that doesnot equate to 'accuracy'.
or this? https://www.aliexpress.com/item/100...b16916543737551983ea01e!12000018133703040!btf again note the belt reduction, giving more power and accuracy and allowing the motor bearing to avoid carrying the workpiece.
Direct drive for multiaxis isn't a great plan unless you have some beefy (NEMA34+ or ring motor) servos or a fairly narrow diameter of actual cutting area (or you're only cutting foam or something). Holding torque vs cutting force away from the axis of rotation is the main fight here, in addition to sheer resolution; obviously as you move outward from the axis of rotation, your rotational resolution remains constant but your linear/spatial resolution falls off, so you have to design your drivetrain to support the minimum resolution you want at the widest cutting diameter. Harmonic drives are a good option, I have a couple of CSG-32-80s or something for 4th axes though I'm procrastinating on actually doing anything with them (intermediate project has been putting C5 ground screws as X/Y in the mill... Now there's something I should have done years ago ), but here your better bet, assuming softer working materials, is to build a strong but shallow spindle- a pair of appropriately-sized tapered roller or angular contact bearings tightened against each other using a threaded tube through the middle, and then drive that tube with a belt reduction. The wiring for your 5th axis goes directly through the spindle bore of your 4th axis. The only hard part is boring the exact same size and location of bearing seat in opposite sides of the same metal plate, though you could cheat and mount them in a hole with a shim tube between the outer races and then locate them with screw-down flange covers. Not quite as elegant, but it would do the job for a simpler project.
