CNC Plasma Table

[doubleboost]

Looking very nice
The use of a timing belt for a rack is a very clever idea
Timing belts do not stretch to the extent that would make any difference (as long as they were secured nice and tight)
John

[f350ca]

(05-24-2013, 04:07 PM)doubleboost Wrote: Looking very nice
The use of a timing belt for a rack is a very clever idea
Timing belts do not stretch to the extent that would make any difference (as long as they were secured nice and tight)
John

John
The timing belts are for a reduction between the stepper motor and the pinion that will ride on a conventional metal rack. Thought about using timing belt instead of a rack but decided to go with metal.
The jig was made to drill the holes accurately in the material I will cut the rack from. another jig for the shaper will use dowels in those holes to position the material while I cut the teeth.
The jig will also hold the metal for the rails while I mill a 90 degree face for the wheels to run on.

[f350ca]

Stole a little time to work (play) on the plasma table rails/rack. Using the same jig I built to drill the material I started milling the 90 deg rail edges. Using a C clamp to hold them tight against the back shoulder of the jig they are snugged down with 4 cap screws.



Pardon the horrible photo , the best an I phone can do at macro. The small flat between the bevels seams consistent, how would I measure it.

[f350ca]

Needing a break from my present grind or guess its just polishing on the counters now, I cut a few teeth.
Need racks for the linear motion, and why buy something thats readily available, when I can spend days building it my self. Have three pieces stacked in the shaper.
After a few different tool grinds with different rakes and clearances we tried a larger 3/8 tool blank with no tool holder as was suggested on one of the other forums. Seams to be cutting nice now with reduced chatter.



Still a lot more teeth to cut.

[Mayhem]

Looking good Greg. I do like your "vise"

[DaveH]

Sure is a lot of teeth - looking really good

Just wondering Greg how often do you have to dress/sharpen the tool?

First time I have seen DRO's on a shaper - great idea

DaveH

[stevec]

(05-29-2013, 11:16 PM)f350ca Wrote: Stole a little time to work (play) on the plasma table rails/rack. The small flat between the bevels seams consistent, how would I measure it.

Greg, if you just want to verify the milled surfaces are equal/consistent could you use a small square and a small drill that would just fit in the triangle formed by the square placed against the milled surfaces.
BTW the finish you're getting on those milled flats looks beautiful.

[f350ca]

Thats a good idea Steve, will give it a try, if I'm deep or shallow anywhere the gantry would move sideways, probably less than the resolution of a torch cut but can't hurt to check. The finish is partly the shiny camera at work, its good but to as shiny as the photo shows, cut it with a two insert indexable end mill.
The cutter is holding up really well Dave, I cut most of these teeth with only a couple of light dressings with a fine diamond hone. I'd cut a few teeth with a 1/4 cutter in a tool holder but was getting horrible chatter and the resulting digging in. The DRO works great, the scales on the Logan are useless, scribed on about a 1 inch cylinder. Just hope the error in these Chinese wonders is good enough, but I'm guessing as good as the accuracy I'd get from Chinese made racks. Now I need to CNC the shaper and let it do the repudiative work.
The vice gives good support Mayhem, but more important indexes the racks. I drilled and reamed the holes in the racks with a jig on the mill to give 8.000 inch spacing, must be close as I can flip one of the parts and still get the dowel pins through all three parts. The plates on the table have reamed holes 8.000 apart, after i've cut 8 inches of teeth I can index the racks on the dowels, move the table back 8.000 inches and rezero the DRO

[f350ca]

Finished the racks, 363 teeth.





Haven't figured how to measure them for overall accuracy but if I turn one end for end they mesh down the whole length, so at least they're consistent.

[awemawson]

Well if they are consistent, the actual accuracy isn't important as that can be accommodated in the scaling factor of the software.

Looks superb. You may already have covered this but if so I missed it, how many strokes to cut a tooth?

Andrew