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Author Topic: Machining relief problems  (Read 485 times)

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Offline TPS

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Re: Machining relief problems
« Reply #10 on: August 23, 2019, 04:40:02 AM »
maybe it can be Computer power, you can try to run the program and turn toolpath off (diagnostic page).
anything is possible, just try it.
if you find some mistakes, in my bad bavarian english,they are yours.
Re: Machining relief problems
« Reply #11 on: August 24, 2019, 04:45:44 AM »
Does you Z axis have weight - ie. could a counterbalance or gas strut reduce the mass when it is travelling in an upward direction ?

Hi Tweakie,

Sorry I didn't understand what you were saying at first, I do now and will look into it, I may be able to attach a spring somewhere

Thanks Chuck

Offline Tweakie.CNC

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Re: Machining relief problems
« Reply #12 on: August 24, 2019, 07:20:25 AM »
Hi Chuck,

Stepper motors torque reduces with speed so heavy loads are best lifted slowly. If they loose steps on the way up then, on the downward travel, the axis will move to a lower position and this is the problem I think you are experiencing.

Reducing Velocity and Acceleration is usually the answer but if you can attach a spring (or better still a gas strut) to reduce the weight the stepper has to lift then it may help.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Machining relief problems
« Reply #13 on: August 25, 2019, 03:14:35 AM »
I tried fitting an extension spring to the Z axis with about 5 kg strength, unfortunately it didn't make any difference, this was using a profile that only cut .2 to .5 mm. it still cut at an ever increasing depth.

I have read that someone having the same experience applied more power to the stepper motor and that fixed the problem, what would your thoughts be on that?

Thanks
Chuck

Offline TPS

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Re: Machining relief problems
« Reply #14 on: August 25, 2019, 03:38:09 AM »
have you tryed to run Programm with toolpath turned off (see below)
anything is possible, just try it.
if you find some mistakes, in my bad bavarian english,they are yours.
Re: Machining relief problems
« Reply #15 on: August 25, 2019, 03:46:31 AM »
have you tryed to run Programm with toolpath turned off (see below)

No not yet, I will try tomorrow

One thing I did find though was when checking motor tuning settings, the pulse settings were at 0 for all axis so I set them at 5 and saved, after closing that window and reopening, they were all at 0 again, does that sound normal?

Offline Tweakie.CNC

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Re: Machining relief problems
« Reply #16 on: August 25, 2019, 04:56:48 AM »
Quote
I have read that someone having the same experience applied more power to the stepper motor and that fixed the problem, what would your thoughts be on that?

Hi Chuck

Stepper motors should run hot to the touch (but below 60deg.C) if your Z axis stepper is running cool then you could try increasing the current by one increment.
Ideally, stepper motors have their rated current printed on a label and that is the current that should be set at the driver - a stepper motors rated current should not be exceeded.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Machining relief problems
« Reply #17 on: August 26, 2019, 01:37:21 AM »
have you tryed to run Programm with toolpath turned off (see below)

I tried running with toolpath turned off, unfortunately no change

Offline RICH

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Re: Machining relief problems
« Reply #18 on: August 26, 2019, 06:17:33 AM »
Im using a small Chinese cnc machine and I don't have any trouble engraving shapes and text.

May be true, but when doing 3 axis moves with numerous small axis moves, you really need
to have steppers that can provide the accel necessary. The stepper can skip and you would
not even know it, the dro will show correctly but the actual postition will be wrong. the skipping
may be repeatable or ramdom depending on the gcode your doing.

From reply #8, you ran the following code and there was no Z problem.
You tested for a Z move of 5 mm ( .197")

M98 P123 L100
M30

O123
G90 G1 Z-5 F250
G1 Z0
M99
%

A look at the gcode you posted shows small Z moves approx range from
say .003mm to .050 ( .00011" to .002" ) for example.

I would suggest you see what the machine can do at the feedrate your calling,BUT,
test at Z distances of 4,3,2,1,.5,.1 mm's etc. You may want to just jog those distances and see
what a indicator shows. You will not move .0001" accurately as that is theoretical resolution
of your axis. If you have backlash, and you do, machining of small moves accurately just dosen't work well!

Test with only the Z, down only, then down and up and down movement and if that test is good,
add X & Y moves and test again. BTW, may want to add a pause using G4 so you can do a measurement
post move. Let us know how things go.

RICH
 
« Last Edit: August 26, 2019, 06:24:59 AM by RICH »
Re: Machining relief problems
« Reply #19 on: September 12, 2019, 04:43:58 AM »
Hi guys,

Not having much luck with settings etc. so I thought I would upgrade stepper drives to TB6600 seeing that one of my originals died.

After doing that I face the dilemma of getting them to work, I had no problems getting the "A" Axis to turn, but the others only buzz.

The originals dips where all set the same so I set all the new ones the same, but no that wasn't the answer, I tried all available combinations with no luck.

I tried changing the motor profiles to that of the "A" Axis in Mach3, but no change.

Any Ideas?

I have attached pics of the original and TB6600 drivers to give an idea of how Ive wired them up.

Thanks Chuck