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Home Forum General General LinuxCNC Questions Heavy Duty Plasma - Ball Screws

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TOPIC: Heavy Duty Plasma - Ball Screws

Re:Heavy Duty Plasma - Ball Screws 11 Jul 2012 17:15 #21810

  • ocpistol
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Ok so I was thinking would it be better to mount a low watt laser next to the plasma instead of a router? We would use it for cutting insulation and engraving serial number/part numbers.
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Re:Heavy Duty Plasma - Ball Screws 11 Jul 2012 21:50 #21814

  • jmelson
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ocpistol wrote:
My company is looking at making out own cnc plasma table because non we see on the market are what we are looking for. Unless they go over a 200k machine. We are a family business we work with stainless steel and brass, we make beer towers.
Anyways what we want to do is have 2 x axis motors powering ball screws, 1 y axis and a Z. We want to be able to cut a 5x10 area and im wondering what kind of motors I will need to be able to travel at least 325imp cut speed. Also if it is possible to do this with emc2.
Are you sure you want ballscrews? Many plasma machines have been built with rack and pinion drives.
The large sizes typically used as well as the high feeds make ballscrews a poor choice. You need either
huge diameters of very coarse thread pitches to keep the long screws from whipping.

Probably servo motors are a good choice as you get more power per weight and sustained high
speed operation. But, lots of these machines have been built with modern steppers, too.

Jon
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Re:Heavy Duty Plasma - Ball Screws 12 Jul 2012 03:59 #21818

  • BigJohnT
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I used timing belts on my design but sized them one size too small so unless the slide rails are spotless clean I get chatter. In hind sight linear rails would have been used and a bigger less stretchy belt. I really like the idea of the dual belt drive with one belt bonded down to the rail...

John
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Re:Heavy Duty Plasma - Ball Screws 14 Jul 2012 06:50 #21934

  • doug6949
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BigJohnT wrote:
I used timing belts on my design but sized them one size too small ...............

John

I commend you for recognizing the real problem. Most builders blame the concept and abandon belts altogether. The two most common mistakes are inadequate belt width and trying to use fabric reinforced buna-n instead of steel reinforced urethane belts. The other mistake is using a closed loop belt which effectively doubles the stretch problem.

I repaired three 10 foot traveling head surface grinders that each used a single 50mm wide belt to pull a 10HP spindle. The machines run 60-100 hours a week. The belts last 3-5 years.

No industrial plasma table that I am aware of uses ball screws. Every one I have seen or worked on had belt or rack and pinion drive. The better quality systems use double preloaded pinions on each rack to eliminate backlash.

Doug
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Re:Heavy Duty Plasma - Ball Screws 14 Jul 2012 06:54 #21935

  • BigJohnT
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IIRC, my belts are fiberglas cord.

doug6949 wrote:
The better quality systems use double preloaded pinions on each rack to eliminate backlash.

Doug

Do you know how they preload the pinions?

John
Last Edit: 14 Jul 2012 06:57 by BigJohnT.
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Re:Heavy Duty Plasma - Ball Screws 14 Jul 2012 06:59 #21936

  • andypugh
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BigJohnT wrote:
IIRC, my belts are fiberglas cord.

doug6949 wrote:
Do you know how they preload the pinions?

Springs, I think:
www.hpcgears.com/products/anti-backlash_gears.htm

I think there is a simple groove half in each gear, with offset ends.
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