Thread: Homann Designs TM20LV CNC conversion

One thing I'm thinking of changing is to change the mounting of the FK12 bearing block from the other side. That way the inside of the flange will line up with the end of the table and the ballscrew length needed will not be dependant on the thickness of the end-plate.

That way, it would not matter if the endplate material was 12mm or 1/2" plate.

I tried putting the bearing block on the inside but there is not enough clearance to the underside of the table. It's probably less than 1mm but I think I'll just leave them on the out side.

I also made up the other end-plate for the floating bearing block.

It's almost time to order some ballscrews .

I'm not sure on what diameter to have on the end for the timing pulleys. I am tossing up between 10mm, 3/8" or 8mm.

At this stage I'm thinking of getting 3/8" as there seems to be a better range of XL pulleys and also the stepper shafts are 3/8"

Cheers,

Peter.

Hi Peter,
Think about protection for the bearings and motor as you will proably use coolant if only CRC or WD40.
A cover would also prevent pinching if fingers got in the belt/pulley area.
If you start thinking about it now you could incorporate mounting it on your end plates.

Hi Rod,

Thanks for the input. I have some end covers for the motors and the pulley end will be covered by the housing that holds the belts, etc.

I haven't decided yet as to which way the motors will be mounted. I want to fold them back so as to reduce the extension and overhang, but without taking away from the travel.

Cheers,

Peter.

Progress is slow due to all of life's other pressures and demands.

I've been working on ways to mount the Y-axis belt drive set-up and motor. Attached is an image of my planned layout.

I was a bit worried about the belt (XL) length as I'm concerned that it may too long. The length is needed so I can tuck the motor out of the way, rather than it sticking out the front. From a reply on the CncZone I think I'll be ok

The idler bearing is set quite low so that I can use a smaller pulley on the motor and get a 2:1 ratio.

Cheers,

Peter

Attached are images for the ballscrew dimensions. I plan to send these to Chai from linearmotionbearings2008.

Before I send them off, can anyone see any errors or deficiencies with the drawings?

Cheers,

Peter

Drawings look fine. It took a little while to realise you want a flat milled on the end of the shaft (pulley end) so might be an idea to describe that on the drawings.

Hi Rod,

Thanks for the comment. I'll add a note about the flat.

Do you think it's OK to have two negative tolerances on the 12mm shaft for the bearing? Or would it be better to specify the diameter to 11.992 with a single -.009 tolerance?

same for the 3/8" and 10mm shaft ends

Cheers,

Peter

Hi Peter,
OK as is. To be honest I doubt you will get them returned at the tolerance of your drawing. Even a standard screw with BK/BF blocks requires a bit of tweaking on the lathe for a good fit.

Hi Rod,

Yeah I reckon your right. I put the comments "end machined for FK12 bearing support" so that they may machine them to fit.

It will be interesting to see what turns up.

Cheers,

Peter.

Hey Peter,

Just with the idler you had in the first picture, i would also look to keep this deflection in the belt to a minimum as it will take power away from the drive system. (Stepper)

Hi Mike,

Good point, thanks. The idler is there to clear the saddle as it moves out over the pulleys.

For the idler, I'm planning to use 2 of these bearing stacked on top of each other.
10 Bearing 696-2RS 6x15 Sealed 6x15x5 Miniature Ball Bearings
10 Bearing 6x12x4 Sealed Miniature Ball Bearings

Unless thare are better solutions?

Cheers,

Peter

Nothing to contribute, but I'm enjoying your build Peter.

Brad.

Thanks Brad. I wish I was enjoying it a bit more.

All of the nut holders are going to be problematic. I has expecting the mill to be similar to the BF20 mills.

I guess I should enjoy the challenge.

Cheers,

Peter.