Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: hpghost on September 16, 2012, 01:56:47 PM

Title: strange behaviour / offset
Post by: hpghost on September 16, 2012, 01:56:47 PM
I have a JCUT CNC with the USB interface.

from time to time, I get the machine not going to the requested coordinates input in g code. for example if I do z50, it may go z51. this happens very little but in the middle of long machining this is a big pb (see pics).

mach 3 shows the right coordinates. If I pause the machine and start again then if catches back the right coordinates.

any idea?
Title: Re: strange behaviour / offset
Post by: Hood on September 16, 2012, 05:01:01 PM
If Mach is showing the correct position then it is likely an issue with the JCut plugin or hardware.
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 16, 2012, 11:52:41 PM
hep...I am thinking of that UAB being the pb... I got few times USB link crash.

also crash are random. was using mach 3 with parallel interface on a previous machine and never got such pb...

which breakout board would you guys recommend to me?

I have 3 axis to drive, 3 home switches, one vfd spindle.
Title: Re: strange behaviour / offset
Post by: Hood on September 17, 2012, 02:49:56 AM
I would say either look at the CSMIO-IPM or a Ethernet SmoothStepper.
The SmoothStepper would also require at least one breakout board and I think the PMDX ones are hard to beat, you would also need a spindle controller.
The CSMIO would just require the extra connection kit they sell as it already has analogue outputs to control a spindle..
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 17, 2012, 03:13:39 AM
I have this driver.

http://www.leadshine.com/ProductList.aspx?Type=9

the CSMIO-IPM looks good to me. I guess it would just work fine with the driver. correct?

Title: Re: strange behaviour / offset
Post by: Hood on September 17, 2012, 03:38:50 AM
That page covers quite a few drives but as long as they are Step/Dir capable then they will work fine with either CSMIO or ESS.
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 25, 2012, 05:03:11 PM
hi,

just received the Ethernet card as recommended.

my dirvers are leadshine:
http://www.leadshine.com/UploadFile/Down/MA860Hm.pdf

on the USB card I used to have, puls+ and dir+ connected together to Vcc.

on the new CSMIO I have output pin for Dir+/Dir- and Pulse+/Pulse- this is why I do not see how it can be...

The overall machine stability is ok and repositionning sound ok.

when running 10hrs project, I found out that Z would go up sd machine (very slighty but after 10hrs I have about a Cm difference)

How shall I perform the connection? shall I insert the recommneded resistors?
Title: Re: strange behaviour / offset
Post by: Hood on September 25, 2012, 05:42:07 PM
You have differential outputs on the CSMIO/IP-M and your drives can accept differential Inputs have a look at this document and connect as per the differential input diagram.

You could if you wanted connect single ended, if you did then you would not need resistors as your signals are 5v, the drive manual states you only need a resistor for voltages higher than 5v.

However as you have differential signal output from CSMIO and Differential inputs on your drive you would be much better to use them as they are much more noise immune and will give you less problems than connecting single ended.


http://www.cs-lab.eu/en/upload/pdf/CSMIO_IP%20EN%20differential%20outputs_rev2.pdf

Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 26, 2012, 04:42:55 AM
I actually did connected the inputs in differential mode and for some reason that I can not understand, I am getting some issue with the Z axis that loose it's position toward the +.

I did a test as follows: up and down at 4000mm/min for 15 min and it comes back perfectly. however when I launch my milling code for the part, after few minutes it is already offset by few mm.

on x and y, there is no position loss, only on Z.

the stepper in x and y are setup a 10000 steps per rev and the z to 5000 steps per rev which bring all of them at 1000 value in motor setup. I put acceleration to 350mm/s2 which seems fine.

kernel speed (not sure that it affect anything with the RJ45) is set at 100khz.

any clue on what is going on?

hope we can solve this crazy situation...
Title: Re: strange behaviour / offset
Post by: Hood on September 26, 2012, 07:03:14 AM
What is in your code, is it faster than the previous 4000mm/min commande speed you did?
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 26, 2012, 08:50:40 AM
no it is a 3d milling at 1600mm/min 2mm deep pass on 6mm tool at 15000rpm

I even tried at 1000mm/min and same...

could it be at the 100khz are too much when several axis are in motion together??
Title: Re: strange behaviour / offset
Post by: Hood on September 26, 2012, 10:03:33 AM
Kernel has no effect with external devices, any limiting of frquency is done in the plugin.

Could be your Z is losing steps due to the short fast moves that 3D usually contains.
Have you tried reducing the acceleration for the Z axis?
Do you have the step pulse set to the correct state for your drives? ie active high or active low as some drives are particular about that.
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 27, 2012, 03:19:41 PM
Pulse is at 5

Signal is active high And configured as such.

I feel it work for normal 2mm step over passes but not for the 0.2 ones...

 I tried to reduce and increase and same...
Title: Re: strange behaviour / offset
Post by: Hood on September 27, 2012, 03:28:00 PM
Pulse width has no effect when using an external controller so thats not the problem. The CSMIO controllers have 50% duty cycle on the pulse outputs.

Only thing I can think of is you could try swapping drives or motors from other axis to see if it could be one or the other that is the issue.
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 28, 2012, 02:29:19 PM
what about the microstep resolution setting in the drives...anything special to be aware?
Title: Re: strange behaviour / offset
Post by: hpghost on September 28, 2012, 02:56:02 PM
I increased motor acceleration to 400 and it seems better... will see after the 9 hrs of milling but so far it did not seem to loose steps...

any logics on that?
Title: Re: strange behaviour / offset
Post by: Hood on September 28, 2012, 04:13:36 PM
According to most people the optimum microstepping for a machine axis is around 10.

Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 28, 2012, 11:54:04 PM
then I should maybe reduce it to 10...it is currently 50
Title: Re: strange behaviour / offset
Post by: hpghost on September 29, 2012, 02:34:51 AM
ok... did further test. have not yet switched the drives or motor but:
- I set all drives to 10 microsteps and adjusted motor settings accordingly. which means that I divided by 5 the number of steps per rev compared to before.
- I created a program of 4 hole of 5mm deep positionned on rectangular way. after each hole the machine goes up to 10mm above the part surface.
- Then I offset the z to 50mm to have safe distance and runned the program.
- after completion I go back down and the zero is no more 50mm it is approx 44mm. which means a shift of approx 6mm. which is strange because in my previous test on the large 3d part, it was doing positive offset.

obviously by reducing the microsteps, I increased the shift...

any good idea following that test? I will shift the drives now...
Title: Re: strange behaviour / offset
Post by: hpghost on September 29, 2012, 02:37:25 AM
forgot to mention something really strange.

if I run a simple program like:
g1 x0 y0 z0 f4000
g1 x5 y5 z5
g1 x0 y0 z0
...

it comes back in position quite well...
Title: Re: strange behaviour / offset
Post by: Hood on September 29, 2012, 03:21:14 AM
The last test sounds like its missing steps on the Z positive moves but as you say its opposite to before then it could be a drive issue.
Hood
Title: Re: strange behaviour / offset
Post by: hpghost on September 29, 2012, 05:24:43 PM
ok... so did more test and here are the results

- exchanged the drives and same result.
- re-done the wiring between drives and interface board (to avoid misconnection or inverted pulse)
- changed feedrate of the test program and noticed that x and y where also getting some shift at some feedrate.
- the did a test full speed (5000mm/min). result is no visible shift
- so basically the lower the steps per min are and the more drift I get.this is why at 50 microteps it was not as obvious as now.

previously with the original JNC-40 USB interface card, it was crashing a lot but at least there was no shift like now.

could it be the CSMIO interface card? if so why?

i have no more idea on what is the issue...

thanks.

renaud



as a summary of my setup:
my motor specs:
http://00353cf.netsolhost.com/motors/Stepper_Motors/Hybrid_Steppers/85_110mm/86BYGH450.pdf

my driver specs:
http://www.leadshine.com/UploadFile/Down/MA860Hm.pdf

my interface:
http://www.cs-lab.eu/en/upload/pdf/User_Manual_CSMIOIPM_EN_rev1_2.pdf

Title: Re: strange behaviour / offset
Post by: hpghost on September 29, 2012, 05:32:46 PM
With the jnc USB interface signal was not in differential mode. Could it be that the driver does not work in that config?
Title: Re: strange behaviour / offset
Post by: Hood on September 30, 2012, 05:14:47 AM
The drives say they are differential input, you could try connecting them single ended if you wish, info is in the CSMIO manual I linked to.
However you said things got worse when youdecreased the microstepping, did you ever try that microstepping on the other controller?
I cant think what could be causing that but if you attach your xml I will look at it to make sure there is nothing wrong in it that could possibly cause something like your problem.
Hood
Title: Re: strange behaviour / offset
Post by: TechCNC on October 01, 2012, 03:08:51 AM
Hi,

Please check 'config/ports&pins/motor outputs' settings. Try to change 'Step Low Active' setting for Z axis. Let me know if it helped.

BR
Andrew
Title: Re: strange behaviour / offset
Post by: hpghost on October 01, 2012, 12:29:46 PM
as surprising at it might be, indeed it seems to work... ???

will do further tests in the next days to confirm