Source for Reasonably Priced Ballscrew?

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hanermo
Posts: 44
Joined: Tue Oct 01, 2013 5:47 am

Re: Source for Reasonably Priced Ballscrew?

Post by hanermo » Thu Jul 07, 2016 9:21 am

The mentioned sources are all good.

Making fits is perfectly possible on a lathe.
More rigid is better.

I use a 32 mm D screw on Z, and will use a 20-32 mm screw on new X.
Screw is behind the saddle, so it does not need to fit inside (nuts dont fit).

Current screw is 0.750", from mcmaster (ie roton) and is crap. Dont use these.
(These have spring, once you get to micron resolutions. Terrible consistency.)

My mechanical resolution is less than 1 micron.
Step size is 0.2 microns via ac brushless servos, and belt drives, at 1:2, with 30 mm wide HTD belts.

Taking 1 micron *incremental* cuts, with ccmt 21.51 inserts, in free machining steel, clearly takes off some material, as surface changes visibly.
I cannot, atm, position to 1 micron accuracy. Yet.

Will add glass scales, hopefully submicron, and this will give feedback and hopefully secondary feedback to controller.
This will also allow mapping the screws.
I also plan to (hope to) (when ??) put the screws in tension.
X axis is already in tension, double-preloaded. Its fixed at front and pulled from back (reverse screw thread).

Next screw might be ground, C3.
A custom ground 20 mm D and C3 accuracy (ie very small) rise is available from Hiwin, as custom order, for about 600€.
This is reasonable, for me.
At 3 mm I might direct drive it, via a rigid coupler (no spring, just straight).
This would make it more rigid, and at 10.000 counts I might get 3 / 10.000 == 0.3 microns, plus 0 minus 0-2, or about 0.6 um resolution *and* positioning.

I also sell screws.
20-25 mm screws are about 100-180€ with nuts, if they come with others stuff re_shipping..
Taiwanese TBI made, china agent.

I have some 25 mm and 32 mm screws, in Spain, VAT included.
I usually take about 10-20 of anything, and flog off the extras as time goes by.
Saves on shipping, greatly.

I highly recommend thick screws.
The rigidity is very much greater.

For example a 32 mm (SFU3205) screw is 54 kgf / um rigidity or K value.
A 1605 is about 2x less rigid.
Here is data.
http://www.tbimotion.com.tw/product/detail/168/1/en

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SteveHGraham
Posts: 7115
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: Source for Reasonably Priced Ballscrew?

Post by SteveHGraham » Thu Jul 07, 2016 2:27 pm

Thanks for the advice, hanermo. I can't recall; what size is your lathe? The one I'm doing is 7x14.

I can find thicker screws. I don't know if they'll be cheap enough to satisfy me, though. I will check around.
Every hard-fried egg began life sunny-side up.

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ctwo
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Joined: Tue Mar 27, 2012 12:37 pm
Location: Silly Cone Valley

Re: Source for Reasonably Priced Ballscrew?

Post by ctwo » Thu Jul 07, 2016 2:59 pm

Standards are so important that everyone must have their own...
To measure is to know - Lord Kelvin
Disclaimer: I'm just a guy with a few machines...

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SteveHGraham
Posts: 7115
Joined: Sat Jan 17, 2009 7:55 pm
Location: Florida

Re: Source for Reasonably Priced Ballscrew?

Post by SteveHGraham » Thu Jul 07, 2016 3:21 pm

Not yet. Still looking around, and I want to make the current screw function as well as possible before I upgrade.
Every hard-fried egg began life sunny-side up.

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