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Kev2960
04-06-2017, 05:44 PM
Hi there, I have a problem with the Y axis on my 6040 machine, i'm machining a square as a test and each time the gantry moves to the Y it's out of position be 0.3302mm and this accumulates each time.
Can anyone shed some light on what the problem could be ?

Nickhofen
04-06-2017, 08:47 PM
Are you using mach3? If yes you, can calibrate your axis thru mach3 program.

Kev2960
04-06-2017, 09:03 PM
Yes i am using mach3 and have calibrated the axis over 300mm of travel, it repeats pretty much bang on

Neale
04-06-2017, 09:11 PM
I am one of those people that does not believe in using Mach3 calibration - if you can't calculate the settings and get it right, then you might be covering up a more serious problem. But I'm probably in a minority here...

Back to the original problem - can you describe a bit more exactly what you are doing? Given that you are quoting dimensions to .0001mm, I'm guessing that you are taking these figures from the Mach3 DRO?

Kev2960
04-06-2017, 11:47 PM
No, it's the conversion from an imperial dti that's all

m_c
05-06-2017, 12:15 AM
How many steps does that distance work out as?

Kev2960
05-06-2017, 08:32 AM
To be perfectly honest I have no idea, is there a way to work that out

m_c
05-06-2017, 10:04 AM
What's your step/unit setting?
And are you using metric or imperial?

Kev2960
05-06-2017, 10:33 AM
I'm using metric and the step per rev is set to 320 the same as the X axis

Kev2960
05-06-2017, 10:39 AM
I should just add the velocity is set to 1500 and the acceleration 400
Both step Pulse and step direct are set to 5

Neale
05-06-2017, 11:03 AM
If you are using a dti to measure travel, you should be able to measure backlash, if any, and eliminate that as a cause. Set up the dti so that it is at mid-travel, then move the axis a couple of mm in one direction and return to starting position. Note dti. Then do the same in the opposite direction. Difference in dti readings is a reasonable estimate of backlash. Could be as simple as badly-adjusted ballscrew angular contact bearings.

If the error were rather smaller (of the order of 0.005mm) but increased by the same amount each time you repeated the movement, I would suspect a step pulse polarity problem. I'm a bit sensitive to this one as it bit me in the bum on my machine, and it's a bit subtle to detect as it doesn't show up very easily except after many repeated direction changes. However, your error is many times larger - which is why I asked exactly how you were doing your test. Over what distance, at what speed, does the error show up after one movement or after many repeats, etc. If you can fill in the details, it might let someone spot a likely problem and/or eliminate red herrings.

JohnHaine
05-06-2017, 11:04 AM
Do you have backlash compensation turned on and if so is it set to the correct value?

Kev2960
05-06-2017, 01:17 PM
The llead screw is a ball screw,
And I haven't got backlash elimination on. As for the test it's a square 30 x 30mm. Set machine to the centre 0,0 0.2 deep, cycle start, matches ok
Cycle start = error of 0.3
Cycle start = error of 0.6
And so on
Hope that makes sense

Kev2960
24-08-2017, 10:43 AM
Can anyone shed any light on my problem. I know it's not the program because the square shape machines perfectly on my machine at work

Robin Hewitt
24-08-2017, 11:22 AM
An accumulative error, sounds like fun. Off the top of my head I have 3 guesses... excessive acceleration/deceleration causing a motor to stall/overrun, excessive acceleration/decelleration causing a loose mechanical connection to slip on a shaft, excessive microstepping so you don't reach the minimum up/down times on the driver step pin.

Kev2960
24-08-2017, 01:11 PM
Thanks Robin, I see where your coming from, but the feed is only 200 mm/m and the rapid to position is 1500 mm/m. Could it be a driver fault ?

Robin Hewitt
24-08-2017, 01:48 PM
You need to mark the motor shaft, do the cut, return to the start position, see if the mark has moved. That will tell you whether the fault is before or after the motor.

Kev2960
24-08-2017, 10:54 PM
Hi Robin as you suggested mark the motor shaft do a cut return to start position. the motor shaft is about 1/8th of a turn out of position when cutting a circle 40mm dia

Clive S
25-08-2017, 12:47 AM
Hi Robin as you suggested mark the motor shaft do a cut return to start position. the motor shaft is about 1/8th of a turn out of position when cutting a circle 40mm dia

There you go then loctite the pulley or coupling on then

Edit. My bad I thought he meant shaft had moved in the coupling

Neale
25-08-2017, 10:00 AM
If the motor shaft is out of position at the end, doesn't this sound more like an electrical problem?

1/8 turn is about 0.6mm error - is that about right?

I think you said 320 steps per mm, which would be x8 microstepping with a 5mm lead ballscrew - sounds about right. So, 1600 steps per rev. 1/8 turn is 200 steps - that's a lot! Does this happen with air cutting? If so, can you slow the max speed and acceleration right down to remove the chance of it being missed steps? Is the error always exactly the same each time you test it, or does it vary quite a lot? Does it happen with the spindle running and spindle stopped?

Out of curiosity, where does the gcode come from? As I mentioned earlier, I had a similar problem when I first started setting up my own router, although in my case the error was much smaller (although still cumulative) and I'm trying to think through a logical sequence to try to narrow down the problem.

Kev2960
25-08-2017, 10:42 AM
Hi yes the error is cumulative while air cutting, I also thought the G code from mach 3 might be the problem so I took a circle from my mazak at work but that still had the same effect. I'm a bit stumped as to what it might be

Neale
25-08-2017, 11:05 AM
again, sorry for asking simple questions, but it does help eliminate the obvious!

This also happens if cutting a square? Have you tried typing manual gcode into the MDI window? Something like (assuming you are starting at (0,0)):
F100
g1x100
G1y100
G1x0

That's about as simple as it gets and you have control over reversals of direction - circles have a lot more in them so less clear exactly what is happening.
G1y0

Kev2960
26-08-2017, 12:14 AM
I've done the test you suggest all ok. I've also done rapid to position over a distance of 400mm to zero and zero to 400mm and it's right every time. Back to a circle and it's out of position again. Also used a wizard rec pocket and that was ok.

magicniner
27-08-2017, 01:16 PM
There will be no magic involved and finding situations where the error doesn't occur rarely helps to narrow down what's causing it where it does. Assuming you have some matching drivers in your system swap one over with the Y and see if the fault stays with the axis or follows the driver, ditto the motor. You can test your break out board by swapping X and Y outputs and swapping pin out config in Mach3 and seeing if the fault stays with the axis or moves with the BOB output.
If the fault isn't in the electrics then it's mechanical.

- Nick

Kev2960
13-09-2017, 07:13 AM
I think It's the driver so bought a Hy-DIV268N-5A from eBay to see if that might work, the wiring is not the same so can anyone help
My machine has these;
DC DC BB AA GND V+ P 5v Dir
The driver from eBay has these;
DC DC BB AA EN EN PUL PUL
DIR DIR
Where do the V+ and 5v wires go ?

Boyan Silyavski
13-09-2017, 09:19 PM
The way i see it:

1.Nobody said the obvious: the rising edge of the signal is not right most possibly. Just change it and try again. That 99% is the problem. /just saw Neale pointed you/ . Did you do something about it?

2. Mach3. Clean install and try again. Hve been there a couple of times

Kev2960
14-09-2017, 12:38 AM
Hi thanks for your reply, what do you mean by the rising edge of the signal? If I reinstall mach3 will that affect my license

Boyan Silyavski
14-09-2017, 01:01 PM
Hi thanks for your reply, what do you mean by the rising edge of the signal? If I reinstall mach3 will that affect my license

What is your stepper driver exact name and model? Normally there is a jumper on the driver / controller to change that. Also is explained in controller user manual. Normally mistake is seen on the z axis as it makes more movements, if all is not set right. Check it anyway.

No. The Mach3 license file is called Mach1Lic.dat , so just go into Mach3 folder , find the file and save it somewhere else. If you don't have original manufacturers Set file open Mach3 and take snapshots of "general " , " motor tuning"/for each axis/ , "inputs outputs" , "homing limits" setting tabs. Uninstall mach3. Delete folder mach3. Restart. Install Mach3. Restart. program all setting. SAVE SETTINGS. CLOSE MACH3. Open mach3 and check how all is working. Once you are happy and all works well make a copy of your screen for further use, so you dont have to input every detail again and again.

Close mach3 when its doing something, power down the PC without closing Mach3 and its f%%$d up 101%. Did i tell again how much i dislike it for that little details and behaviour...

Clive S
14-09-2017, 01:18 PM
The way i see it:

1.Nobody said the obvious: the rising edge of the signal is not right most possibly. Just change it and try again. That 99% is the problem. /just saw Neale pointed you/ . Did you do something about it?

2. Mach3. Clean install and try again. Hve been there a couple of times

Again Boyan you are jumping in and have not read the post from the beginning, If you read post #13 there is no way that a rising edge problem would be 0.3mm out on such a simple cut. In this case you are muddying the waters.

Clive S
14-09-2017, 01:43 PM
I think It's the driver so bought a Hy-DIV268N-5A from eBay to see if that might work, the wiring is not the same so can anyone help
My machine has these;
DC DC BB AA GND V+ P 5v Dir
The driver from eBay has these;
DC DC BB AA EN EN PUL PUL
DIR DIR
Where do the V+ and 5v wires go ?

A picture of the wire connections to the drive would help or a link to it.
But basically DC,DC,BB,AA are the same. EN (enable) may not be needed but the PUL and PUL etc with have a +ve or -ve and which way you connect them can vary.

Kev2960
15-09-2017, 05:03 PM
Hi Clive I've got a couple of photo's for you. The one on the left is the one i bought off ebay that i want to try in place of the existing one, the other two are from my machine. P 5v DIR go to the Y axis on the bob--dip switch--24v input--BB AA for the stepper motor. So basicly i just want to connect up the one on the left

Clive S
15-09-2017, 05:36 PM
Kev I would connect 5v +ve to the pulse +ve and dir +ve on the new drive and connect the pulse -ve and dir -ve to the controller.

You will also have to probably set the dip switches to the same as the original drive

Kev2960
15-09-2017, 05:38 PM
Thanks Clive