The Craftmans Shop > New from Old
The Sequel - Oh Blimey I bought a CNC Lathe (Beaver TC 20)
cnc-it:
M3 spindle anti clockwise looking from the tailstock end..and the tip facing down to the floor..basically a manual lathe with the tool post rotated 180 degrees around the chuck..a throw back from when early cnc lathes which were modified gap bed lathes..the swarf could then be fired down into the trough so it was easier to leave the machine running without the operator needing to clear the swarf.
The Hitachi Seiki 4nE11 was this same configuration.
cnc-it:
As the Beaver is running clockwise in M3 upward facing tools all the way.
awemawson:
SOLVED :clap:
The post processor is producing a positive depth of thread not a negative one. I have manually altered the produced program shoving a minus sign in and produced a decent thread.
I've not worked out yet why the PP is doing this - it might think it's doing an internal thread - I'll investigate after lunch
russ57:
I'm the furthest from an expert in cnc. But as someone suggested above, in absolute terms, the x direction would need to be reversed for a rear toolpost.
Either that, or you have the southern hemisphere model...
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awemawson:
--- Quote from: russ57 on September 07, 2018, 08:48:03 AM ---I'm the furthest from an expert in cnc. But as someone suggested above, in absolute terms, the x direction would need to be reversed for a rear toolpost.
Either that, or you have the southern hemisphere model...
--- End quote ---
No Russ I don't think that is the case - remember that your frame of reference has rotated. Minus X travel is into the work piece in each case. In all cases the work piece diameter decreases as the tool approaches the axis of rotation.
So the test piece passes the 'will a nut fit' test with flying colours, and also the repeatability test.
As for altering the post processor, when the cycle for threading is generated, the PP doesn't know if it is threading internally (so positive thread depth) or externally (so negative thread depth) and I can't logically derive which case is in operation from the parameters passed from the program. You can't even enter a negative depth of thread where you define the feature, as it slaps your wrist!
One comfort from all this is I'm more than ever convinced that the M19 spindle Orientation issue has to be a software / enabling bit, as this threading is using spindle orientation at a great rate of knots quite satisfactorily.
All this testing is producing masses of swarf - I need to get the covers back asap not only to contain it, but also to allow me to use coolant.
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