I have to get back to other projects for a while. I've disabled the metric checkbox and made it invisible since the conversion to metric and back isn't complete yet. And since the value to use for MAX_ACCELERATION in the INI file is suspect perhaps the whole project is a joke.
I've attached the zip with the Lazarus Source Code. I've compiled and run this on a PC with Windows, BeagleBone and Raspberry Pi. If you are running Linux sudo apt install lazarus should be enough. My first attempt at putting something on GitHub. https://github.com/jcdammeyer/LinuxCNC John Dammeyer > -----Original Message----- > From: John Dammeyer [mailto:jo...@autoartisans.com] > Sent: July-22-20 12:53 PM > To: 'Enhanced Machine Controller (EMC)' > Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with > Bostomatic BD18-2 to linuxcnc > > > -----Original Message----- > > From: andy pugh [mailto:bodge...@gmail.com] > > > > On Wed, 22 Jul 2020 at 19:33, Chris Albertson < > > <mailto:albertson.ch...@gmail.com> albertson.ch...@gmail.com> wrote: > > > > > That said acceleration is related to speed. (acceleration) x (time) = > > > (speed) > > > example: (10 inch per second squared) x ( 0.5 seconds) = (5 inches per > > > second) > > > > Also bear in mind that speed x acceleration x mass = power > > > > -- > > atp > > Let's take step back to the original question > > One has a motor with a plate that says 3000 RPM, 226 oz-in, 7.8A continuous > at 90V. The mill has a 5 TPI lead screw and a table that > weighs 200 lbs. > > So the questions that I think were asked or what the discussion was about was: > > 1. Can you run this table lead screw at 3000 RPM if the Servo Drive can > handle 7.8A at 90V. > 2. If not what reduction ratio is required between motor and lead screw to > run the motor at full speed. > > Jon Elson provided the numbers for linear force created by the lead screw > pitch. (with some guessing at friction) and the form I > created and attached with 1:1 ratio shows 600 ipm and and 2.2G acceleration. > > > > In real life I have the second screen shot with 3:1 belt reduction and as is > logical, speed drops by 1/3, Torque is multiplied by 3 so > Acceleration also increased by 3 to 6.66G. > > > If we divided 200 by 60 we get a speed of 3.333333 in/sec which, if the > LinuxCNC ini file has LINEAR=inches, is used for > MAX_VELOCITY. From the ini file documentation > http://linuxcnc.org/docs/2.6/html/config/ini_config.html#sub:ini-variables > > However the document also says "The maximum acceleration for any axis or > coordinated axis move, in machine units per second > per second." > > There is no way that my motor can do 2556 in/sec^2. In fact 40 is a more > reasonable number. So we can do as Andy suggests and > just get to it by trial and error. But what's the point of any of this math > if all we do is configure by mucking around until it sort of > works. > > So either Jon Elson is horribly wrong with the constant linear force > calculation to determine force required to accelerate or > something else is wrong. I'm just trying to figure out how to calculate, > knowing only the above parameters, what you'd plug into > MAX_ACCELERATION as a starting point. I realize it needs to be tweaked since > ball screw verses acme screw makes a difference. > Static verses Kinetic friction makes a difference. > > So is Jon's calculation of Continuous Linear force correct? Something's > missing but I can't put my finger on it. > John Dammeyer > > > > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
