On Tuesday 25 September 2018 07:46:44 Les Newell wrote: > > I am talking in terms of a > > light cut on a stiff aluminium bar between centres. > > That assumes your tailstock is dead nuts on. If not you're going to be > trying to compensate for a mix of tailstock + bed errors. If you use > the bar unsupported there are flex issues. Having said that you always > get some flex in the work so maybe it is a good thing that the test > bar flexes slightly... > That too, Les. For long cuts, cut light and measure. That almost calls for a compensating file. Unforch I have not figured out how to use that as it seems to be intended as a per screw, screw compensator, with no way to cross couple the z location to the x offset that I could deduce.
Thinking out loud here: Ideally, a pulldown menu item to select the file to reload a lincurve according to the material being worked would be handier than sliced bread or bottled beer. Hint hint hint. Or perhaps a slider to adjust the gain between the lincurve output and the offset module in could be used to compensate for machine flex under heavy cutting loads. Wear is consistent, where flex is dependant on cutting forces. So that implies 2 lincurve modules whose outputs are summed together before being presented to the offset module. That way if we had the gain slider, one could even raise the comp on a dynamic basis to compensate for a dulling tool. Not useful for one offs like most of my stuff is, but production quantities where you are making thousands of an item, the out of tolerance scrap could be reduced. Heck, the gain slider could even be put over in the pyvcp portion of the screen, and that could be done right now. I'll do that bit of gui stuff after I've actually matched the taper on the od of the 5c, with the id taper of the spindle. I am still increasing the taper per inch by about .0002 per pass right now. Getting closer, but not there yet. I should put a dial on the shoulder, and measure how far I can move in in the mouth of the spindle as it rocks on the small end, and add about 40% of what I measure to the ramp/inch in the gcode thats re-carving that taper. Right now I need a way to turn off the comp so I am measuring the raw machine and this would be one way to do it without needing to edit the hal file and restart LCNC and rehome the machine. > When I was playing with the head alignment on my Colchester I used a > large chunk of Delrin bar and a very sharp cutter. The bar was pretty > stiff and cutting forces were low. > > Les That too sounds like a great idea, Les. Suggested OD of the Delrin to get that stiffness? At about 30" between centers... Tailstock isn't deadnuts on. The last 4 or 5 thou seems very difficult to achieve as the tightening of the adjustment screws seems to move it in reverse. So I have been experimenting with less and less tension on those screws, depending on the central holddown to lock it. I think the adjusting screws are flexing the base, tipping it slightly as they are snugged up. And I am not convinced the barrel is pointed dead at the center of the spindle, but perhaps a few thou above, so the rear of it needs some Reynolds Wrap shimming? Stuff Yet To Be Determined. > On 25/09/2018 12:19, andy pugh wrote: > > On Tue, 25 Sep 2018 at 11:15, Gene Heskett <[email protected]> wrote: > >> This is also true. But that test bar costs money too. > > > > It can stay in stock as useful material. I am talking in terms of a > > light cut on a stiff aluminium bar between centres. Thanks everybody. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
