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3d profile problem
« on: June 10, 2013, 07:06:33 PM »
Your fellow machinist is in trouble my friends, so I have been practicing machining some 3d profile; I using steroform as my material and trying to machine simple 3d geometrical shapes like pyramids, cones etc. So I have tried machining this pyramid cone file a couple of times; 4 times specifically. I have succeeded only one time with no mistakes, and other 3 times with a simple error cut on the top of the cone.(@ different place every time neither the same size or lenght).
In your opinion what could be causing this: :(
Some other information that might be helpful  :-\; My zaxis was behaving badly prior to this and the motor usually slows down while I was machining and lose its positioning, while the other two axis worked fine. Thus resulting in improper cuts on a big scale. I have got a new driver for z axis; but seems like the problem has only been minimized to a very large extent. Expect these small mistakes that the machine is making.
Also was running at 45000 kernel speed which took me to 250 to 300ipm @medium accelration, the for the step pulse & dir pulse i got [1 - 0] for all axis (don't know what that means).
I have took the kernel speed back to 25000 and machined @ 225 ipm for the last piece i machine, but still got a error in the machining piece (a small cut at the top).
Z axis mechanically seems to running fine.

Offline ger21

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Re: 3d profile problem
« Reply #1 on: June 10, 2013, 09:09:59 PM »
Increase the step and dir pulse width to 2 or more.

What acceleration and velocity settings are you using for the Z axis? Try reducing the Z axis acceleration by half.
Gerry

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Re: 3d profile problem
« Reply #2 on: June 11, 2013, 02:08:41 AM »
Increase the step and dir pulse width to 2 or more.
Could you explain the set & dir pulse width a bit more? what its purpose and what difference does it makes?

Offline ger21

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Re: 3d profile problem
« Reply #3 on: June 11, 2013, 07:38:31 AM »
It's the duration of the step signal sent to the drives. Most drives require at least 2us for reliable operation. Some require 5 or more.
I've seen many cases with Gecko G540 users, where a weak parallel port requires 15us pulse widths to get reliable operation.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
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Re: 3d profile problem
« Reply #4 on: June 11, 2013, 01:59:02 PM »
where a weak parallel port requires 15us pulse widths to get reliable operation.
I will definitely bump it up to 5 or even more to see if that made a difference; but do you think that will add more time to your machining because let say I have 6000 pulses per min with each pulse staying high for 2us, but now it staying up for 5us, this add 3us to each pulse (could you explain the science behind it just curious )
Mean while as before i was machining @ 250inch for xy @ medium acceleration, and z at limited to 150 plung of 40
Now i simply changed machining speed to 100 in the mach software I got no errors
In your experience what would a reasonable max speed i should expect out of my machine (interested in machining engraving, 3d profile, high reliefs etc)
Specs are:
x z =nema 23 460oz
y = nema 34 600 something oz
lead scew= 5 start 2 turn per inch
backlash nuts on all axises

Offline ger21

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Re: 3d profile problem
« Reply #5 on: June 11, 2013, 05:37:06 PM »
Quote
I will definitely bump it up to 5 or even more to see if that made a difference; but do you think that will add more time to your machining

No, because the pulses will still occur at the same time, they'll just last longer. There's still plenty of time between them.

What is "medium" acceleration? What are your motor tuning numbers?

There are many factors that determine what your maximum speed should be set to.

What drives are you using?
What voltage power supply?
What are the specs of the motors? (Current, voltage, inductance)
What type of machine is it? How much weight are you moving?


Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html