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audioandy
01-06-2010, 09:15 PM
Hi All

This one has me stumpped!

Last week my computer that I have been using to control my machine died on me,because it was a fairly low spec
1Ghz processor 1gig of ram I decided not to spend anytime trying to repair it, but built a new one with some bits I had laying around. The new spec is Dual core 2.4Ghz 4 gig of ram 160 gig sata 2 hard drive complete clean install of windows XP with all latest updates and a clean install of Mach3.

This is where problem begins, I loaded my original xml file, my machine did what ever I asked while jogging it around, so I loaded a simple engraving file and set it to work. Not long into the job I noticed that the engraving was getting lighter until eventually the tool was not touching the job, so I stopped the machine and homed all axis and sent it again, the Z was spot on at the start point but the same thing happened the tool height was changing as the job was running.

I removed the tool and fitted my plunge guage and loaded some G code moving the Z axis up and down at full speed with varying heights from 90mm to 0.1mm and finished at Z zero the guage was bang on no sign of missing steps so I have come to the conclusion it must be something to do with the pulse train from the PC when all axis are moving.

Has anyone else had this or can anyone come up with any ideas to what I can do to sort this damn problem out?

Thanks

Andy

irving2008
01-06-2010, 09:49 PM
your problem is that the step rate specified in the Mach 3 XML is related to the machine clock speed - not the value you entered on screen, so it is likely MACH3 is not sending wide enough pulses and so your driver is missing some step pulses under 3-axis load. Go back into the MACH3 setup, and change the pulse width setting to 5 or 6 and resave the XML... it might be worth checking the MACH3 kernel speed settings...

audioandy
01-06-2010, 10:03 PM
Hi Irving thanks for the reply.

The Kernel speed is set to 35KHz the same as before, I have tried changing the pulse width but only on the Z axis I will go and give it try on all axis and saving the XML.

One more thing I have noticed is the Home LED's on the MACH diagnostics screen, when my home switches are made they are flashing randomly but the LED's on my breakout board are solid and the home switches work fine?

audioandy
01-06-2010, 10:32 PM
Irving I have just tried your suggestions but no difference.

I can feel my hand going in my pocket and bringing out a smooth stepper!

irving2008
01-06-2010, 11:24 PM
Shouldnt be necessary Andy...

Check the grounding of the parallel port. Whats your BOB & driver(s). The MACH3 home 'LEDs' should be solid, if they are flashing but the BOB is solid then this sounds like a grounding or isolation problem... and whats causing that one way is probably having a similar effect the other way...

John S
01-06-2010, 11:27 PM
Go to Config > General Config and in the top right set the debounce to about 1,000.
Try that and if necessary up the debounce further

irving2008
01-06-2010, 11:31 PM
but that wont address the stepping issue will it?

audioandy
01-06-2010, 11:31 PM
Irving

The breakout board is a CNC4PC 11G and the drivers are Gecko's 212's

I will check the earthing tomorrow and report back.

Thanks

Andy

John S
01-06-2010, 11:34 PM
but that wont address the stepping issue will it?

No but the flashing homes could be noise.

irving2008
01-06-2010, 11:38 PM
How are you providing the +5v for the BOB?

John S
01-06-2010, 11:48 PM
How are you providing the +5v for the BOB?

Good point and is this an early C11g that requires 12v and 5v for logic [ forget the speed part ] or the later one that only requires 5 volt

audioandy
01-06-2010, 11:52 PM
Ok

Debounce I did yesterday didn't make any difference, the 5v is from a regulated power supply and is a steady 5.3v

audioandy
01-06-2010, 11:53 PM
Just the 5 volt John

irving2008
01-06-2010, 11:53 PM
Hmmm... assume thats what it was on before you swapped PCs...

audioandy
01-06-2010, 11:58 PM
Yep

I have purchased a video card for my old pc in the hope that will get it up and running again, should be here Thurs.

But I need to sort this out as I know the old PC won't last for ever, a friend has a smooth stepper and has offered to bring it over and try that but I would like to think the PC is more than upto the job without the smooth stepper.

Andy

irving2008
02-06-2010, 12:02 AM
can you retry your G-code test with some x & Y thrown in as well?

audioandy
02-06-2010, 12:14 AM
can you retry your G-code test with some x & Y thrown in as well?

Yes can do Irving will have to be tomorrow now

Andy

John S
02-06-2010, 12:16 AM
What version of Mach ? because this is two reports of jittering i have seen.
can you go back to a known older version ?

Older versions are here.

ftp://machsupport.com/

audioandy
02-06-2010, 12:20 AM
Yes can do John again will have to be tomorrow off to bed now up at 5.30 for work

Thanks for the help

Andy

audioandy
04-06-2010, 12:29 AM
Bit of a Red Herring!

I have managed to get my old PC back up and running by fitting a new graphics card, so I thought my troubles were over for the time being, but it was not to be I have the same fault with the old computer that I had with the new one!

So this weekend will be taken up fault finding hopefully with the aid of a scope.

I have checked the grounding Irving and that seems to be ok so at this moment in time I am still a bit lost how I can go from a fully working machine to this overnight?

It all adds to the fun...............not

I will keep you posted with my findings.

Andy

irving2008
04-06-2010, 01:38 AM
Could be the BOB itself is causing a problem? Although i cant see how for the moment... unless its a power supply issue under three axis load...

audioandy
04-06-2010, 07:14 AM
Hi Irving

I have a C10 BOB so the first thing I will try is changing over to that. The C11G that I am using at the moment has the two supplies 12v and 5v (I thought it only had the 5v its that long ago since I fitted it) the 12v is reading 11.88v and the 5v is reading 5.5v the only thing I have'nt checked yet is the 24v for my home and limits this circuit also has 24v opto relays to switch the 5V so alot still to check.

I will be back!

Regards

Andy

audioandy
06-06-2010, 11:06 AM
Well I feel a right plonker!

Saturday morning I started my quest to find out what was going on with my machine, first thing moved my home switch wiring to another BOB only to find the the LED's were still flashing on the diagnostics screen.

So another check of the voltages and everything checked out ok until I checked the opto relays I was using to switch the 24v to 5v, 5 volts going in 2.3volt coming out ! So straight to the BOB removed the wires from one of my home switches and linked it out, solid LED on the screen.Removed the opto's replaced with some 24v relays problem solved.

Now the missing step saga,all the time I have been checking the problem I have been using the same G code program, I had checked the code and everything looked good, when I was running the tests with my plunge gauge(different g code) there was no sign of any missing steps, I went back to my cam program I had used for creating the code and found that I was trying to move the tool 17mm a sec! I know the machine would only achieve it's max that is set on the motor tuning page, but never the less I thought this might be the problem,I adjusted my toolpath paramaters and created the G code loaded it into the machine, NO MORE MISSED STEPS :dance:

It just go's to show how a series of events can send you down the complete wrong track, I had convinced myself it was the new computer. I will look on this as part of the very steep learning curve we all embark on when we set out down the home cnc route.

Thanks for all your help Irving and John.

Andy

John S
06-06-2010, 12:16 PM
You can now sew your CNC badge onto your uniform, dib, dib, dib....

audioandy
06-06-2010, 02:06 PM
I have nailed the badge to my head as a reminder not be such a plonker! lol

audioandy
06-06-2010, 08:21 PM
17mm per sec= 1.2 meters a min that aint that fast and my machine rapids at just under 5 meters a min?

A friend has been up this afternoon and brought along his smooth stepper we connected it up,took about 5min, loaded the code I was having a problem with and ran it at 4.4 meters a min with no missed steps its nice to have it confirmed that there is nothing wrong with the machine.

The smooth stepper is a great bit of kit so if anybody reading this is thinking of getting one I can highly recommend them.

andy

der_fisherman
17-08-2010, 10:12 PM
What a great and interesting blog. I would like to thank all contributors.
Andy