I ended up tracking feed rate for turning too. It ended up being easier. The jog buttons do not but they run a totally different movement engine without distance as part of the equation.
The ELS was designed originally for a single axis carriage motion control system. The X axis was added on later and is slaved to the Z. In other words you can't turn X faster than Z. But you can run the entire system with one axis powered and it tells you how much to manually move either the cross slide or compound on each pass for threading. For many people that's more than enough. I'm really looking forward to doing something with hardware as simple as the Xylotex DB25/26 and BBB. I haven't tried yet but hopefully the 4.3" LCD cape will also function with the cape. If not I have a Manga LCD/Touch screen on a kickstarter order. Mind you it was 3x the price of the 1280x1024 LCD used display I bought on Friday. But smaller. Just a tad... John > -----Original Message----- > From: Dave Cole [mailto:linuxcncro...@gmail.com] > Sent: October-16-17 10:32 AM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] MachineKit on the BeagleBone Black > > John, > So you are talking about always tracking the spindle even during normal > turning. > Thus gearing the carriage to the spindle. > That is not normally done on a CNC lathe even if you are doing feed per > rev.�� If you are doing feed per rev, you don't normally > need anything more than one pulse per rev.�� IE, Mach3.� That is > normally a velocity ratio.��� Traditionally, the only time you need to > "gear" the tool to the carriage is threading. > > Dave > > On 10/16/2017 12:11 PM, John Dammeyer wrote: > > Hi Andy, > > Yes and no. A turning operation is actually just a very fine pitch > > threading > operation although ideally you don't actually want the tool bit to enter the > work > at exactly the same point. A tad bit of randomnous on each start is nice to > shave the crests from the previous pass. > > > > In either case though, at the 3000 RPM or even 6000 RPM that a small Unimat > DB-200 or Sherline can turn, you want to know the RPM and you need to track > the turns per inch; which granted may only 0.001 for a nice smooth finish but > is > essentially still threading. Just the tip of the tool is so round for smooth > turning > that there is no root or crest cut. > > > > For example my Machinist toolbox calculates for turning 1/8" brass: > > MATERIAL= Brass > > SURFACE SPEED= 91 MPM > > CUTTING TOOL MATERIAL= HSS > > NOMINAL STOCK DIAMETER= 0.125 inches 3.175 mm > > DEPTH OF PASS= 0.1 mm > > SPINDLE SPEED= 9419 RPM > > FEEDRATE= 32.44734 IPM 0.00344 IPR 824.1625 mmPM 0.0875 mmPR > > MATERIAL REMOVAL RATE= 0.04859 in�/min > > MATERIAL POWER CONSTANT= 0.5 > > REQUIRED HORSEPOWER= 0.02858 > > > > You still have to know when to stop turning so you are tracking 9419 RPM > (157 RPS). > > > > Assume a small lathe has a directly coupled stepper with 1600 steps per rev > and 20 TPI lead screw (0.050/per turn). Divided by steps/turn we find we need > 108.8 steps per spindle rev to create 0.00344 IPR. Doesn't matter how fast > the > spindle is turning yet. > > > > The spindle is turning 157 RPS so to keep up we turn the stepper at 17,081 > steps/second. My ELS would then throttle that max stepper speed of say > 10,000 as would MachineKit based on the number in the ini file. But wait, > the > lathe can't do 9419. Max RPM on this theoretical Unimat is 6000 RPM or 100 > RPS so now steps per second is 10880 which is within range more or less of the > torque capabilities of the stepper. > > However, turn only a 0.25" length for that miniature model part and the > stepper may not even get up to speed before it has to decelerate to the > shoulder you are turning. > > > > We went through all sorts of those types of scenarios on the E-Leadscrew > group during the development of the ELS. > > > > John > > > > > >> -----Original Message----- > >> From: andy pugh [mailto:bodge...@gmail.com] > >> Sent: October-16-17 5:29 AM > >> To: Enhanced Machine Controller (EMC) > >> Subject: Re: [Emc-users] MachineKit on the BeagleBone Black > >> > >> On 15 October 2017 at 18:58, John Dammeyer <jo...@autoartisans.com> > >> wrote: > >> > >>> Anyway, back to the Beagle and the QEP. A 1000 line encoder on the > spindle > >>> and 1000 line encoder on the lead screw motor results in 4000 PPR for > each. > >>> To turn a 1:1 thread they both have to be turning the same rate. Say you > >>> are doing high speed threading of leadscrew pitch (8TPI) at 2400 RPM. > >>> That's 40 RPS or 25mS per turn. If the Beagle PRU cycle time is 10uS then > >>> it's there to read the QEP counter 2500 times per revolution. (25mS/10uS > >>> = > >>> 0.144 degrees of spindle rotation) . > >> > >> It's worth bearing in mind that you typically wouldn't thread 8tpi at > 2400rpm. > >> Even if your counter can't manage maximum spindle speed you may still > >> be able to use the lathe perfectly happily. > >> > >> -- > >> atp > >> "A motorcycle is a bicycle with a pandemonium attachment and is > >> designed for the especial use of mechanical geniuses, daredevils and > >> lunatics." > >> ? George Fitch, Atlanta Constitution Newspaper, 1916 > >> > >> ------------------------------------------------------------------------------ > >> Check out the vibrant tech community on one of the world's most > >> engaging tech sites, Slashdot.org! http://sdm.link/slashdot > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > > > > ------------------------------------------------------------------------------ > > Check out the vibrant tech community on one of the world's most > > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
