Re: [CAD_CAM_EDM_DRO] re:welding linear shafts

You have some really good points there are really good points Ballendo.

I, for one wouldn't trust epoxy mounted shafts....especially on the vertical
shafts. Those wouold be bound to break loose in accordance with Murphy's
law and all its corollaries.

The machine was designed "in a hurry" for those who'd like to get busy
building and not waste any more time talking. The machine was designed
around THK bearings and shafts if that helps any.

The "production versions "I'm working on (using castings) will use box ways,
in case anyone wants to wait that long.
Please don't ask how long....I have no idea and it takes time to complete
the engineering, make detail drawings, send those out for quotes, get parts
cast and actually made and ready for sale.

Smoke

>Quite a few, actually! One of the reasons we see less of
>the "thomson" style shaft and bearing in high-load (read machine
>tools) situations is that this system, by design, is point contact.
>And this point contact wears "grooves in the shafting. Yes, even
>hardened shafts!
>
>Two circles will meet (theoretically) at a single point, tangent to
>both circles. Actually, the metal used in the ball bearings of the
>linear ball-bushing and the shafting, will "deform from roundness"
>under the load and provide additional points of contact and load
>carrying.
>
>But this is still no match for the current generation of linear
>bearings (thk, and others) which use precision grinding to achieve
>contact over much more of the ball bearings' circumference. Equaling
>higher loads/ longer life/ less deformity(which equals less heat),
>etc.
>
>Depending on the loads/life you calc for your proposed machine, none
>of this may actually come into play. But do be aware that thomson
>shafts in the woodworking industry are regularly replaced on CNC
>routers and point-to-point machines (the woodworking equivalent of a
>VMC). Also on autimatic saw stops, which have nearly no load; just
>the pre-load of the bearings on the shaft is enough to wear the
>grooves into the shafts.
>
>Hope this helps.
>
>Ballendo
>
>
>
>
>
>
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