Mounting motor under table?

**Rogue** · 01-09-2011

Assuming there are no clearance issues with the table/nut, are there any disadvantages to mounting the motor under the table, parallel to the leadscrew?

Another of my soon-to-be-infamous-for-low-quality example images:

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(not sure if the picture worked, ISP is being a pain today)

I'm hoping that a pulley system of some form would be suitable to belt-drive the leadscrew from that location.

**GTJim** · 01-09-2011

IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

Jim

**Ricardoco** · 01-09-2011

Originally Posted by GTJim

IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

Jim

here! here!

and if you think your drawings are basic i do all mine in paint!!! so you will never win that competition.....

**Jonathan** · 01-09-2011

Originally Posted by GTJim

IMO I dont see any problems with mounting as drawn as long as the spindle protudes enough for a pully, and I think it keeps things tidy.

You could mill a pocket in the shaft side of the aluminium to accommodate the pulley if there is not enough space.

Pulleys are definitely good plan as they will let you change the ratio allowing the stepper motor to be put in the right region of the speed/torque curve. You can also swap them round to get more resolution if required.

**AdCNC** · 01-09-2011

This is similar to what i did with my first machine.

http://www.mycncuk.com/forums/attach...2&d=1269125465

Plenty of pics on my build

http://www.mycncuk.com/forums/showth...tempt-Of-A-CNC

**Rogue** · 03-09-2011

Sorry for the delay in replying. Had ISP issues for a few days and my posts seem to intermittently require moderator approval (though I think it's when the post includes links).

Jonathan: I think I'll be looking at some kind of pocket, but I still haven't started to research the pulley systems yet so I don't know what I will need in terms of size and clearance.

AdCNC: Awesome build. This axis isn't fixed to the main structure though, it will be the X axis unit mounted on the Y axis.

**Jonathan** · 04-09-2011

Originally Posted by Rogue

Jonathan: I think I'll be looking at some kind of pocket, but I still haven't started to research the pulley systems yet so I don't know what I will need in terms of size and clearance.

I used XL pulleys , but HTD 5mm pitch is better. I've found 1/2" wide best to be fine. It's best to use reasonably big pulleys to reduce belt wear. In general minimum 5 teeth engaged with belt.

ADCNC: like the setup with the coolant etc...

**Rogue** · 04-09-2011

Just to prove how slowly my brain works... by 1/2 wide do you mean I need to accomodate a diameter of 1/2", or it will protrude 1/2"(+bit sticking out for setscrew) from the mount?

**Jonathan** · 04-09-2011

I meant the width of the timing belt should be at least 1/2". You can calculate it ... but that works fine for me so etc.

I would want the shaft to stick out as far as you can get it to as it depends on the pulley, where the setscrews are and the position of the other pulley.

**Rogue** · 04-09-2011

Fair enough, so until I settle on a firm number I'll pencil in 1 1/2" clearance from the surface of the mounting block for the pulleys. I suppose judiciously placed idlers would also help with increasing the engagement with the belt.

Is belt something that can be shortened easily, or will I be confined to designing around what is available?