Question on X2 Mill CNC Ballscrew upgrade X axis

[truckeic]

I basically have done the Hoss CNC conversion and i used his Ball screw dimensions. so here is my problem, when the table is far left in the Machine ZERO location the ball screw is unsupported at the end and when I fast jog the table the ball screw wobbles due to be unsupported. The length of the ball screw does not protrude the left side of the table. has anybody done a fix for this or am i just being to OCD?

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[dazp1976]

I basically have done the Hoss CNC conversion and i used his Ball screw dimensions. so here is my problem, when the table is far left in the Machine ZERO location the ball screw is unsupported at the end and when I fast jog the table the ball screw wobbles due to be unsupported. The length of the ball screw does not protrude the left side of the table. has anybody done a fix for this or am i just being to OCD?

I had exactly the same which is where my high backlash was coming from initially. The table didn't move until the screw had gone up/down at that end first it had that much wobble.
Fortunately I had used a standard BK end machined 450mm 1204 screw that stuck out of the end so could see it plain as day.

I decided to bodge up an extension to the end of the table from some off cuts to be able to fit a BK bearing support onto it to hold the screw in place. It's rough round the edges but it'll do for now.

As soon as I did this it made the screw feel nice and rigid and my backlash went down to a tiny 0.003mm.
I could've prob got away with using a 400mm screw so it didn't stick out as much but it works so I've left it as-is.

If it's not causing an issue then leave it, it's likely due to a bendy screw. However if it is causing a problem like mine was then maybe you need to get another longer screw and have a re-think.
I've not looked into it but I'm wondering if a needle roller bearing & casing that fits the O,D of the ballscrew could be somehow fitted in the table cavity just to support it.

[truckeic]

Did you use the stock thrust bearing on the x axis? I did the same thing Hoss drew up but cant find the ballscrew dimensions (machined down dimensions) i think i am just going to order a longer ballscrew. do you have the ballscrew dimensions?

thanks

I had exactly the same which is where my high backlash was coming from initially. The table didn't move until the screw had gone up/down at that end first it had that much wobble.
Fortunately I had used a standard BK end machined 450mm 1204 screw that stuck out of the end so could see it plain as day.

I decided to bodge up an extension to the end of the table from some off cuts to be able to fit a BK bearing support onto it to hold the screw in place. It's rough round the edges but it'll do for now.

As soon as I did this it made the screw feel nice and rigid and my backlash went down to a tiny 0.003mm.
I could've prob got away with using a 400mm screw so it didn't stick out as much but it works so I've left it as-is.

If it's not causing an issue then leave it, it's likely due to a bendy screw. However if it is causing a problem like mine was then maybe you need to get another longer screw and have a re-think.
I've not looked into it but I'm wondering if a needle roller bearing & casing that fits the O,D of the ballscrew could be somehow fitted in the table cavity just to support it.

[cncuser1]

If you can actually see a wobble or see that the ball screw is drooping then it is a good idea to support it, especially at higher speeds.
You should only have bearings capable of thrust at one end, the other end is radial only support.
If the ball screw isn't long enough then attach a shaft to extend it into whatever bearing you need. Just make sure the engagement between new and old shaft is enough to do the job.

Just be careful that the ball screw axis is parallel to the axis of the way, otherwise you will stress the ball screw ( that is a problem I have now)

[truckeic]

so would like some pipe work to catch thee end of the shaft and get secured to a mount at the opposite end from the thrust bearing?

Thanks

If you can actually see a wobble or see that the ball screw is drooping then it is a good idea to support it, especially at higher speeds.
You should only have bearings capable of thrust at one end, the other end is radial only support.
If the ball screw isn't long enough then attach a shaft to extend it into whatever bearing you need. Just make sure the engagement between new and old shaft is enough to do the job.

Just be careful that the ball screw axis is parallel to the axis of the way, otherwise you will stress the ball screw ( that is a problem I have now)

[dazp1976]

Did you use the stock thrust bearing on the x axis? I did the same thing Hoss drew up but cant find the ballscrew dimensions (machined down dimensions) i think i am just going to order a longer ballscrew. do you have the ballscrew dimensions?

thanks

Hi chap.
Can't help with the Hoss screw dimensions, just show you how I did my motor side:

Yes I used the stock thrust bearings 10x26x11mm (51200) and used a standard end machined 1204 C7 ballscrew.
Then used a 1" thick block with longer screws on the outside sandwiching the stock bearing block between that and the table. Then 1 of those nema23 motor mounts you can buy from ebay bolted to that:


I could also use 12x26x9 bearings in there (with a washer packer to make them to 11) for fitting a standard 1605 screw in there.

Then you've already seen my support side which has just a bog standard bearing in. I think my table extension piece was 30mm long and my drop down piece with the BK mount attached was 12mm thick.
I used a 450mm length screw and may have got a 400mm to work with just a drop down piece that had a bearing directly in.

[truckeic]

Hi chap.
Can't help with the Hoss screw dimensions, just show you how I did my motor side:

Yes I used the stock thrust bearings 10x26x11mm (51200) and used a standard end machined 1204 C7 ballscrew.
Then used a 1" thick block with longer screws on the outside sandwiching the stock bearing block between that and the table. Then 1 of those nema23 motor mounts you can buy from ebay bolted to that:


I could also use 12x26x9 bearings in there (with a washer packer to make them to 11) for fitting a standard 1605 screw in there.

Then you've already seen my support side which has just a bog standard bearing in. I think my table extension piece was 30mm long and my drop down piece with the BK mount attached was 12mm thick.
I used a 450mm length screw and may have got a 400mm to work with just a drop down piece that had a bearing directly in.

Looks really good. Guess my question was do you know the machined down dimensions are for the stock thrust bearing. I replaced my screws with C7 ballscrews. I am thinking about just buying another X ballsrew a little longer.

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[cncuser1]

Before installing the bearing eliminate the wobble: Is the ball screw bent, is it loose in the ball nut?

If I were in your situation I would want the ball screw to be machined down to a diameter to remove the helix, to just be a pure cylinder. I would make an extra extension-piece that fit over the machined part of the ball screw. The length of the machined section would be 1.5-2 times the diameter of the machined section. Press fit the parts together. If the ball screw is not too hard cross drill and install a pin to keep everything together. The extension piece is long enough to fit the radial bearing.

[truckeic]

Before installing the bearing eliminate the wobble: Is the ball screw bent, is it loose in the ball nut?

If I were in your situation I would want the ball screw to be machined down to a diameter to remove the helix, to just be a pure cylinder. I would make an extra extension-piece that fit over the machined part of the ball screw. The length of the machined section would be 1.5-2 times the diameter of the machined section. Press fit the parts together. If the ball screw is not too hard cross drill and install a pin to keep everything together. The extension piece is long enough to fit the radial bearing.

Ok.. may look into that. My problem is I don't own a lathe to machine the ballscrews.

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[rcheli]

Ok.. may look into that. My problem is I don't own a lathe to machine the ballscrews.

Where are you located truckeic? I have a lathe and would be willing to help with that. I'm in Pittsburgh, PA.

John

[truckeic]

Where are you located truckeic? I have a lathe and would be willing to help with that. I'm in Pittsburgh, PA.

John

Man I wish you were closer.. I am in NC...I sure appreciate the offer

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[rcheli]

Well I am always looking for stuff to make. Particularly on my X3 mill. If you need anything made for your mill I'll make it for material costs and postage. It's hard to make parts for your mill when it's the only one you have. Especially if you have to tear it apart to get good measurements.

John

[truckeic]

Well I am always looking for stuff to make. Particularly on my X3 mill. If you need anything made for your mill I'll make it for material costs and postage. It's hard to make parts for your mill when it's the only one you have. Especially if you have to tear it apart to get good measurements.

John

Well I may take you up on something I need... I sure appreciate the offer!

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[cncuser1]

Well If you cant machine the ball screw then a compromise is to install something on the underside of the table to hold the ballscrew.

Something like a block with a hole to catch the ballscrew. Screw the block to the underside of the table.

But first off find the source of the wobble. If it wobbles at low RPM then it may be bent, possibly the ball nut is loose in the saddle( no that is not a euphemism)