track roller guide system and ballscrew question

hello all, I am going to build a plasma table, and piecing together what all I need.

I am planning to make the table 4' x 8'. At this size, linear ball bearing guides become very pricey. I was clicking thru mcmaster's and saw these on page 988 http://www.mcmaster.com/ctlg/loadpag...+Motion+Guides

http://www.mcmaster.com/catalog/111/...l/9904kp1s.gif

would these be sufficient for guides?

also what diameter ballscrews would I need for 4 x 8 foot to avoid whip?

i noticed the end mounting blocks for ballscrews are quite expensive as well, is there any cheaper way to get around having to use these?

thanks
tom

Tom,

Hi! I can't speak for or against the guides you've show-no experience. Given that you are talking a plasma table though they very likely would work-your not really pushing off of a workpiece as with a mill. I'd avoid ballscrews for this as its like overkill for what your doing (due to the plasma kerf). Would they work? Sure! Could you get 100% satisfactory results cheaper? Sure! A great many of the plasma tables-even commercial units-use rack and pinion drive. The gear rack lays along the axis. A spur gear is driven by a motor attached to the moving axis and engages the rack. As the motor turns, the axis runs up and down the rack. The ones I've seen driven by steppers had the motor directly turning the spur gear (wouldn't need to be though). With servos you'd need some intermediate gear reduction for sure. Another option might be belt drive using toothed belts and pulleys. What is it your wanting to plas?

Lance

Quote:

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Originally Posted by Evodyne

Tom,

Hi! I can't speak for or against the guides you've show-no experience. Given that you are talking a plasma table though they very likely would work-your not really pushing off of a workpiece as with a mill. I'd avoid ballscrews for this as its like overkill for what your doing (due to the plasma kerf). Would they work? Sure! Could you get 100% satisfactory results cheaper? Sure! A great many of the plasma tables-even commercial units-use rack and pinion drive. The gear rack lays along the axis. A spur gear is driven by a motor attached to the moving axis and engages the rack. As the motor turns, the axis runs up and down the rack. The ones I've seen driven by steppers had the motor directly turning the spur gear (wouldn't need to be though). With servos you'd need some intermediate gear reduction for sure. Another option might be belt drive using toothed belts and pulleys. What is it your wanting to plas?

Lance

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thanks for the info Lance,

I had decided on ballscrews just in case i wanted to do any wood routing.

but mainly the purpose of this table will be to make 1/2" stainless and mild steel flanges for turbo manifolds as well as intercooler endtank pieces from 12 gauge aluminum.

tom

Quote:

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Originally Posted by Evodyne

Tom,

Hi! I can't speak for or against the guides you've show-no experience. Given that you are talking a plasma table though they very likely would work-your not really pushing off of a workpiece as with a mill. I'd avoid ballscrews for this as its like overkill for what your doing (due to the plasma kerf). Would they work? Sure! Could you get 100% satisfactory results cheaper? Sure! A great many of the plasma tables-even commercial units-use rack and pinion drive. The gear rack lays along the axis. A spur gear is driven by a motor attached to the moving axis and engages the rack. As the motor turns, the axis runs up and down the rack. The ones I've seen driven by steppers had the motor directly turning the spur gear (wouldn't need to be though). With servos you'd need some intermediate gear reduction for sure. Another option might be belt drive using toothed belts and pulleys. What is it your wanting to plas?

Lance

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I am searching for spur gears and gear racks and the longest I can find is 6 '. is it ok to line multiple (like two 4' gear racks) together? what is the common tooth size used?


thanks

tom

Tom,

Hi again! You certainly can link the sections together. Thinking about it, you need to make sure that the pieces meet at the same point-you might need to gradually remove some material from the end of one piece till the two mating ends match. Then take a spare length, turn it upside down, and place it onto the two sections you are laying together. The teeth will interlock and position the two pieces correctly relative to each other. Then tighten down the bottom pieces and you are on your way.

As for the tooth size, I can't advise you. I do know there's more to it-there are different angles, pitch angles I believe, involved as well. A little common sense would tell me that teeth too fine wouldn't be appropriate for a 4' x 8' plasma-you want something you can apply a little torque to to get everything moving. But again, I need to defer. I know this has come up before-you might search the site for rack & pinion or gear rack and see what the old posts can tell you. And of course there is our good friend Google. Well, I've had it. I'm signing off and going to bed. Have a good one!

Lance

welll I have decided to scale it down to 4' x 4'.

this should save on cost considerabley I think I am also gonn go with the v-groove style guides as well

http://www.photodump.org/stored/durdurdur.gif

Where did you find a v groove setup like this? its seems perfect for an xaxis

Is that also from mastercarr? Whats product code or something?

Also, what would the cost be on that thing?

Did anyone find out where to get a v-groove guide like this from?

Thanks!

the v groove roller setup posted is from McMaster-Carr yes. I dont have the number on that unit, but do have a catalog here.

Ed

Precision Open V-Groove Track Roller Guide Blocks and Rails

look on page 1017 of the online catalog...or search for part# 71625K21 and that should get you to the page
http://www.mcmaster.com/

Ed

This company has them http://www.cadcamcadcam.com/index.as...TS&Category=16

That looks like Bishop Wisecarver stuff. They less expensive V bearings and track at

http://www.bwc.com/

Tom,

If you will email me, jccinc-at-owc-dot-net, I'll send you pics of my approach to this type of job. I think aluminum rails are a poor choice for rails. Also, there are less expensive and better ways to make economical rails.

Regards,
Jack C.

If you are going to cut 1/2" stainless, you'll need a very, VERY rigid machine to prevent the cutter from chattering. You also need to monitor tooth load very carefully so as not to work harden the material prior to cutting.

Huh?

If you cut too slowly or with too low of a cutter load, the metal will work harden before it cust and you'll do nothing but eat up bits. We learned that lesson cutting 308 and 321 stainless.

What you propose for a plasma or water jet cutter should work fine as cutter axis rigidity is not a major issue. However when you start cutting decent thickness plate, a router might not be the optimum tool - you need something with ballz.

Now if you got them lazer cut by a vendor and then tuned them up with a finish pass with the router, that might be viable. But cutting from scratch from plate might prove to be a bit hard - at least from my experiences.

http://teausa.net/

this place also has the dual vee system and is quite a bit less than I have seen. They are also an advertizer here on the zone, which cadcamcad is also, in a round about way.
Mike