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Author Topic: Z axis rapid speed control  (Read 887 times)

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Z axis rapid speed control
« on: June 12, 2018, 10:54:56 AM »
My system (Mach 3, Syil X5)  occasionally loses steps on Z axis rapid retracts. Which of course means the tool doesn't clear the work before an XY move and all hell breaks loose. I've gone to G1 retracts but ....

1) What is the right way to control the speed of Z axis rapids without affecting other axes?

2) I already have the acceleration set very low.  But this problem seems intermittent. The machine is quite new. Any suggestions for a good way to diagnose the real culprit?

Thanks in advance - perennial newbie.

/Greg
http://www.blowsmeaway.com
Re: Z axis rapid speed control
« Reply #1 on: June 12, 2018, 11:36:18 AM »
Hi,
the Z axis rapid traverse rate is set by the velocity setting of in the Z axis motor tuning page.
Try reducing the velocity that is already there by half and try again. If that solves the problem try increasing it until such time as the fault recurs
and then back off by 10-20%.

Craig
My wife left with my best friend...
     and I miss him!
Re: Z axis rapid speed control
« Reply #2 on: June 12, 2018, 11:57:49 AM »
Hi,

Quote
The machine is quite new. Any suggestions for a good way to diagnose the real culprit?

Bound to be the governments fault...start a petition...start a movement....Bloody Guvinmint!

Craig
My wife left with my best friend...
     and I miss him!
Re: Z axis rapid speed control
« Reply #3 on: June 12, 2018, 11:58:09 AM »
Thank you, Craig

Am I correct that this will ALSO reduce the G1 speed?
« Last Edit: June 12, 2018, 12:00:48 PM by gheumann »
Re: Z axis rapid speed control
« Reply #4 on: June 12, 2018, 12:02:01 PM »
Hi,
no.

A G0 move is made at the maximum velocity of that axis...aka the motor tuning velocity
A G1 move is made at the prevailing F speed up to the maximum velocity of the axis, ie the G0 rate.

Craig
My wife left with my best friend...
     and I miss him!
Re: Z axis rapid speed control
« Reply #5 on: June 12, 2018, 01:22:12 PM »
Thanks again. Much appreciated.

What's concerning is I already have the velocity turned down a good bit - the Z axis rapids are less than half the speed of the x and y which give me no trouble. And it is inconsistent. But yesterday I snapped 2 1/8" end mills and ruined an hours worth of lathe-turned and polished blank. Aaarrgh. I will follow up with Syil too.

Cheers!

P.S. - When they come out right, they look like this:

Re: Z axis rapid speed control
« Reply #6 on: June 13, 2018, 12:43:27 AM »
Hi,
keep turning the velocity down, velocity and acceleration are almost always the culprits when a stepper
loses steps. Keep turning it down until you find a sweet spot where it behaves. Then you have to ask the
question 'is this right...or is there another underlying fault?'. You will not be able to answer that question
until you have established that there is indeed parameters (velocity, acceleration) for which the stepper does behave.

Craig
My wife left with my best friend...
     and I miss him!
Re: Z axis rapid speed control
« Reply #7 on: June 13, 2018, 12:49:37 AM »
Hi,
can you tell us a bit more about your machine?

What size and spec are the steppers?
What are the drivers?
What is the voltage of the stepper supply?
What current setting have you applied to your drivers?
What microstepping regime are you using?
What is the pitch of the lead screws?
Is there any belt/gear reduction between the stepper and the lead screw?
What are the steps per unit values in the motor tuning pages?
What controller (parallel port/external) are you using?

Craig
My wife left with my best friend...
     and I miss him!
Re: Z axis rapid speed control
« Reply #8 on: June 13, 2018, 02:44:34 AM »
Beyond the fact that it is a 1 year old Syil X5, and I'm driving it form a PC with a parallel port - I have no idea. The syil guys are really good with support so I will hit them up ...
Re: Z axis rapid speed control
« Reply #9 on: June 13, 2018, 02:56:09 AM »
Hi,
this is your machine....you will probably have to find these things out.

I don't know whether you are the sort of person who buys a car and proceeds to learn as much about that car and ALL its workings or whether you just drive
it and take it to the garage when you've got a problem with it.

With hobby CNC the choices are somewhat more limited, there is no such thing as a CNC workshop, or at least there is but they are very specialized and cost a fortune
that all but excludes you from getting help. Therefore you will have to learn to do it yourself.

I'm always of the opinion that the value of a hobby is related to how much you learn in the pursuit of the hobby. It may well be your learning curve is about the specifics
of your machine so that you can diagnose and correct the faults.

Craig
My wife left with my best friend...
     and I miss him!