Hello Guest it is October 14, 2019, 12:32:31 PM

Author Topic: accel and velocity  (Read 13445 times)

0 Members and 1 Guest are viewing this topic.

accel and velocity
« on: January 26, 2012, 01:28:16 AM »
is there a formula to know what the accelleration and velocity need to be set at? when i set it to 20ipm feedrate, not sure if its right or not. and its not cutting correctly in arcs, circles, or engraving. seems to be gaining steps. also i have servos but not sure why encoders arent recognizing that it is out of position. im hoping it can be fixed by getting accel and vel correct. Thanks

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: accel and velocity
« Reply #1 on: January 26, 2012, 03:20:40 AM »
With Servos you should be able to work out the velocity easily assuming you know the voltage you are supplying and the v/1000rpm of you motors and what the max RPM of the motor is. Acceleration is just a case of trying and seeing. If you are getting out of position then your servo tuning is bad and if it does not fault then the drive has the following error set too large.
Hood
Re: accel and velocity
« Reply #2 on: January 27, 2012, 01:29:30 AM »
I am going to get a voltage and ohms reading on my power supply tomorrow.  I have been debating on getting a laptop to run my machine on. If it meets system requirements will I be able to use it?

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: accel and velocity
« Reply #3 on: January 27, 2012, 03:04:28 AM »
If you are using the parallel port then a laptop may or may not work, if using an external controller such as the Smoothstepper then a laptop should be fine.
Hood

Offline RICH

*
  • *
  •  7,367 7,367
    • View Profile
Re: accel and velocity
« Reply #4 on: January 27, 2012, 06:50:42 AM »
Quote
is there a formula to know what the accelleration and velocity need to be set at?

Yes and no, by that I am meaning that it is not straight forward calculation since acceleration, velocity, steps per, and other parameters need to be considered and they all
are relative to a specific machine and what you are going to do with it. For the typical user it is just easier to do some testing and use the values found. But in my opinion that
is not giving the user an understanding of what it all means, how it relates to Mach configuration, and thus the same questions will continue to be posted.

In light of the above, I started a writeup that eventualy will be put in Members Docs providing a discusion of the big picture.

RICH

 
 
Re: accel and velocity
« Reply #5 on: January 27, 2012, 09:14:17 AM »
Is there a certain factor that would make the laptop not work? Or is it just a gamble? Thanks

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: accel and velocity
« Reply #6 on: January 27, 2012, 09:23:34 AM »
The newer the laptop the less chance it will work but some old ones wont either so its just a chance you would take. It is mainly the power saving features of laptops that cause issues with the drivers timing and also the onboard graphics. As said this should not be a problem if using an external controller with the laptop, in fact Artsoft only officially supports laptops if using an external controller.

Hood
Re: accel and velocity
« Reply #7 on: January 30, 2012, 04:19:37 PM »
I found someone that retrofitted the same mill I have to mach. So the hardware on the machine is identical. Only difference is the drives, Bob,  and encoder count. Since the same servos, belt reductions, lead screws and all of that is the same, will my steps per unit, acceleration, and velocity be the same?

Sent from my DROIDX using Tapatalk

Offline Hood

*
  •  25,855 25,855
  • Carnoustie, Scotland
    • View Profile
Re: accel and velocity
« Reply #8 on: January 30, 2012, 04:29:48 PM »
No, drives, power supply to them and  encoder count etc can all make a difference.
Hood

Offline RICH

*
  • *
  •  7,367 7,367
    • View Profile
Re: accel and velocity
« Reply #9 on: January 30, 2012, 05:03:21 PM »
The input input values in motor tuning change.

There are three parts to the total system, and to keep it simple, they are:

Mach - used loosely here, it includes the PC ( which includes how well the pc will function for using the controlling software, namely Mach ), controller ( which includes drive type, power supply ) , and all the rest of the items which touch the generated pulse stream

MACHINE - Its does the task and is made up of mechanical items (all those items which make up an axis) and electromechanical ( motors which must provide power to do work).......which in this case is identical....but adjustment of the machine can influence preformance.......so lets assume identical

MACHINING- is the task to be done which requires that the software and machine are capable of providing for it.

All the parts are interelated, changing one part affects the other parts of the total system.

RICH