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Author Topic: Z Axis Ball Screw Pitch  (Read 5474 times)

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Offline olf20

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Z Axis Ball Screw Pitch
« on: May 31, 2010, 10:09:25 AM »
For those of you who have converted your Z axis to ball screw, what
diameter, pitch, and grade did you use. I'm looking on EBay and find a
wide range.
Hood was kind enough to send me some pictures of his sometime back,
so I have a good idea of how to go about the construction.

Thanks for any help!!!

olf20  / Bob
Mach3, Atlas Knee Mill, 4th Axis, VcarvePro, ESS, Super PID.
Been Heating with corn since 1998

Offline Hood

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Re: Z Axis Ball Screw Pitch
« Reply #1 on: May 31, 2010, 10:30:12 AM »
I used 25mm but you could likely get away with a bit less, suppose really depends  what you are going to be doing with it.
Normal pitch of 5mm/0.200" would be fine but depends on gearing you will use, if any. My Beaver Mill has 32mm Dia and 10mm pitch but its a bigger machine and with the 2000 line encoder that gives a resolution of 0.00125mm.

Hood
Re: Z Axis Ball Screw Pitch
« Reply #2 on: May 31, 2010, 10:44:58 AM »
Quote
2000 line encoder
are you use servo motor ?
if yes DC or AC ?
if you use AC ,SmoothStepper work well ?
**Even a clock that does not work is right twice a day**

Offline RICH

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Re: Z Axis Ball Screw Pitch
« Reply #3 on: May 31, 2010, 11:43:55 AM »
Like Hood says depends on what your going to do with it.
For my engraving / light weight milling machine, using steppers, I used a 16mm dia x 5mm pitch ball screw which has an adjustable nut to take out the backlash and  2.5 gearing.  Overkill, but i used what was available. The steps per unit are 25000 / resolution 1/25000=.00004", but ....., in practical use i can hold the depth to 0.0005 which is fine for the engraving work i do. The screw is rolled.

One of these days i will change the Z on my Atlas mill to be ball screw driven and will use the same ball screw for it.
You need to consider how accurately you what the movement to be, the torque required for the machining, how fast you want to move the axis,  have an axis system appropriate for the machine, and then design / pick the appropriate components for what you want to do ( within the cost restraints you place on the system ). So there are trade offs to made.

So do thinking / homework before you buy so you won't be sorry later on.
You may want to take a look at my Lathe conversion in Members Docs since it provides some design considerations before i started.

Rich

Offline olf20

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Re: Z Axis Ball Screw Pitch
« Reply #4 on: May 31, 2010, 01:27:54 PM »
I have been using the Atlas Mill for a couple of years, with the rack and
pinion. I'm making mostly wood products with it but do some metal.
The machine currently has steppers and I have had no problems. I don't
push the IPM as I just like to set it up and let it run.
It's funny that my mill is also a Atlas with a offset router motor attached.
Rich
I will have a look at your conversion.
Thanks for the information!!

olf20 / Bob
Mach3, Atlas Knee Mill, 4th Axis, VcarvePro, ESS, Super PID.
Been Heating with corn since 1998

Offline Hood

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Re: Z Axis Ball Screw Pitch
« Reply #5 on: May 31, 2010, 03:07:01 PM »
Quote
2000 line encoder
are you use servo motor ?

Yes

if yes DC or AC ?
AC

if you use AC ,SmoothStepper work well ?
Yes because my servo drives accept Step/Dir inputs

Hood
Re: Z Axis Ball Screw Pitch
« Reply #6 on: June 01, 2010, 03:47:43 AM »
then your drive is digital .but i have Yaskawa(analog, SR15BC)
them are Speed control. for cnc machines are suitable?
in addition ,SmoothStepper can drive them ?

Amir
**Even a clock that does not work is right twice a day**

Offline Hood

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Re: Z Axis Ball Screw Pitch
« Reply #7 on: June 01, 2010, 07:59:12 AM »
then your drive is digital .but i have Yaskawa(analog, SR15BC)
them are Speed control. for cnc machines are suitable?
in addition ,SmoothStepper can drive them ?

Amir

My drives can do analogue as wel but for Mach you need Step/Dir.
The SmoothStepper is only Step/Dir but the DSPMC, K-Flop(with K-Analogue card), Galil can all be used with analogue drives and there is another which I cant recall the exact name but its something like Yaps.

Hood