New here with questions

[whitehedr]

If I go with a 1:1 belt design for X&Y axis resolution remains the same as it would with a direct drive. Correct?

Accuracy could suffer with a 1:1 belt drive if backlash is introduced by the belt. Correct???

I am concerned about coupling in direct mode. Currently I do not have a lathe so getting the couplers machined properly.

Maybe I should be about concerned about a belt drive system as well but right now I think that I will be able to do what
I need to do to make a belt drive system work with just my mill. I do need to research motor shaft size and pulley bore size.
It is possible that I will not be able to do anything without first purchasing a small lathe.

RWW

[hoss2006]

You are correct sir.
I can machine the ballscrews to whatever length is needed and make the tip diameter
fit the bore of the flexible coupler if you want,
no need to machine them on your part.
You can order them SDP/SI and McMasterCarr with different bores as well as the timing pulleys whichever route you take.
Would imagine you want to use a belt system to be able to tuck the motors in under the table
to give the mill a more compact footprint.
Hoss

[philbur]

How would you "turn" the motor on a mini mill x-axis without having interference with the base or having it hang a long way out to the side.

Phil

Originally Posted by HawkJET When Bridgeport made their Boss 3 CNC with steppers (I have one), they had a 1:1 ratio and the motors were turned so they did not stick out - they were under the table. Also, there are potential challenges with a direct drive and coupling arrangement. Care needs to be taken to get shafts to align and couplings can also be problematic (although with hobby machines there is far less demand on them). Plus there is the added cantilevered length to handle. The bearing consideration you mention is minor if it even exists. Most commercial CNCs use belts. IMO, I'd rather deal with a belt than a coupling because there is more design flexibility.

[HawkJET]

Originally Posted by philbur How would you "turn" the motor on a mini mill x-axis without having interference with the base or having it hang a long way out to the side.

I dunno... it would depend on the size of the motor, the length of the belt, the mill geometry, the clearance of the table, etc., etc., etc.

It's an opportunity for the designer to be creative, right?

[MechanoMan]

Originally Posted by whitehedr My intention is to build a CNC machine with the stepper motors not hanging straight out from the end of the X&Y axis. I think that I will do a 1:1 ratio. Hawkjet, I think that doing a 1:1 I will not need to be concerned with the resolution/accuracy issue that you mention. Correct me if I am wrong.

Please clarify what problem you're intending to avoid. There is no problem with a stepper "hanging straight out" from the end of the axis. A belt-drive servo would hang off the edge the same way too, unless you're talking about replacing the whole leadscrew with a very long belt (which is possible).

They are typically not exactly direct-coupled. We use a flex coupler between them to isolate the motor from misalignment and leadscrew vibration forces.

[whitehedr]

Here is a link to a YouTube post that shows a belt drive on the Y axis. At a minimum this is what I want to do. If I can figure out a way to tuck a motor in between the frame and table for the X axis I will do that as well.

I do not know who the YouTube poster is. Just want to show what I am trying to accomplish.

RWW

YouTube - Test run of my CNC machine

YouTube - Test run of my CNC machine

p.s.

Hoss, I will be in touch with you to discuss machining of the ball screws after I get the motors and make the mounting plates. I am going on a roadtrip next week to Myrtle Beach. Be gone for a week.