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Maximum feedrate on my setup?
« on: January 03, 2012, 08:42:00 AM »
Hello There javascript:void(0);

How can i find out the maximum feedrate that my setuo can handle?

for example - if i set the feedrate on a wizard to let us say 1000- then how can i tell if the
stepper motor is able to reach that speed?

( I am using feed per minute)

regards
fred
think of the trees-- use both sides of the computer paper

Offline Graham Waterworth

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Re: Maximum feedrate on my setup?
« Reply #1 on: January 03, 2012, 09:07:23 AM »
The maximum feed rate is set in motor tuning for each axis when the machine is calibrated.

Graham


Without engineers the world stops
Re: Maximum feedrate on my setup?
« Reply #2 on: January 03, 2012, 02:44:59 PM »
thanks--

( and that java thing was supposed to be a smiley)
think of the trees-- use both sides of the computer paper

Offline RICH

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Re: Maximum feedrate on my setup?
« Reply #3 on: January 03, 2012, 05:26:23 PM »
Feed rate as it applies to machining is calculated and you will find info on how to do it here:
   
http://www.machsupport.com/forum/index.php/topic,20045.msg138970.html#msg138970

For material other than metal you will need to experiment for desired results.

How fast your machine can feed a cutter is dependant on your systems design, such as HP,  velocity/acceleration / steps per unit which is part of the motor tuning, etc. Now if you are referring to Feedrate for G0 / rapid positioning, then easily found by trial and error and then adjusted for
material you are going to cut.

RICH
Re: Maximum feedrate on my setup?
« Reply #4 on: January 05, 2012, 01:01:18 PM »
Hello chaps-- i guess i asked the wrong question.
I understand feedrate and machine power,depth of cut etc.

What i want to establish is the maximum speed that my steppers will be able to
achieve in turning the lead screw.

Graham you gave me a clue- so please let me bounce this off the forum
If I set the machine on a long traverse along the Y axis and measure the time
it takes to cover a known distance i will then know what the current feed speed
is.
Is it right that if i then use motor tuning to set the velocity to say 20% higher then time
the same distance again the timed speed should be quicker on the same distance

If i do this over and over again always increasing velocity in motor tuning - i will surely
get to a velocity which does not change the actual time any longer - this will then be
the "terminal " velocity that that stepper is able to achieve oin that load ????

Then when I am running a program i will usuallly but not always use the fastest feed that
is practical and adjust the finish required by changing the speed of the chuck or the depth of cut ??

 
think of the trees-- use both sides of the computer paper
Re: Maximum feedrate on my setup?
« Reply #5 on: January 05, 2012, 01:03:23 PM »
Also rich thanks for the link to cleveland
regards fred
think of the trees-- use both sides of the computer paper

Offline RICH

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Re: Maximum feedrate on my setup?
« Reply #6 on: January 05, 2012, 05:27:08 PM »
Quote
What i want to establish is the maximum speed that my steppers will be able to
achieve in turning the lead screw.

Set a low velocity setting, lets say 10 IPM and an accel of 1. Now keep doubling velocity until your motors skip. Set the velocity say 10IPM
below the velocity that which made it skip. Now start doubling the accel and see where the stepper starts to skip. That is the max velocity at max acceleration. I will add that that is also a very unreliable setting. Depending on the computer used, and your system, you may need to change your kernel setting as that will limit your velocity depending on the steps per unit.

Velocity and acceleration is limited by the motors capability to account for different forces....that said .......What you should be looking for is
POWER. Fast axis and no power is useless and is asking for trouble when applied to actual machining.

RICH

Re: Maximum feedrate on my setup?
« Reply #7 on: January 06, 2012, 12:53:22 PM »
thanks rich-
I am not near the machine now but i will try this on monday.

So what i had in mind fleshes out to this.

I read somewhere that the use of available energy should not be on the maximum
so that there is always some reserve for overloads etc.

so when i have done exercise that you suggest i will know the maximum.

the article suggested that i punt for about half of this as my "prefferred" speed range to be working in.

Using motor tuming i would then set this as the default 'TOP' speed ?
In your experience is my logic correct??

regards and thanks
think of the trees-- use both sides of the computer paper

Offline RICH

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Re: Maximum feedrate on my setup?
« Reply #8 on: January 06, 2012, 05:54:06 PM »
If you were to look at any stepper motor curve you would see that as motor rpm increases the torque starts to drop off.
A general rule of thumb, I often state to set the velocity down 30% from the max you found for starters.
Since power is speed x torque you would probably  increase the power available.
Then one should try some machining of different materials using different feedrates and depth of cutting to gain experience.

Yes your on the right track.

RICH



Re: Maximum feedrate on my setup?
« Reply #9 on: January 08, 2012, 11:59:35 AM »
Thanks Rich--


fred
think of the trees-- use both sides of the computer paper