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missing steps ?
« on: April 29, 2006, 05:04:19 AM »
Hi
Please help if you can!!
I have had a problem with 2 of of the last 3 jobs i've milled with mach3. The cutter has gouged my part during machining. After stopping the program and moving the cutter to x0y0 the work datum has moved position. It looks like it has moved off only in the y axis by about 4mm. The last time it was the xaxis.

I should say I ran the mill last night for 4 hours and there were no problems. I started it up this morning and the error occured after 30minutes - so it appears intermittent.
 
On the last job it gouged after 1 hours cutting. I started again and it cut for 7 hours with no problems.
 
My machine is a Denford Easimill. I have ditched the original driver boards and have fitted gecko201’s and a campbell breakout board in the original controller housing. All wiring is the manufacturers  original shielded cables.The spindle runs from an inverter which is fitted in a steel box at the rear of the machine. However the power to the inverter is taken from the cnc control unit - I have not changed this from the manufacturers original layout. Although i have replace the original inverter.
 
I have pulse frequency set to 25khz and step & dir pulse set to 9. I am working in metric units. My programmed feed rate was 300 and  i was overiding this at 510 - so I’m not going fast. My mach pc is an amd sempron 2600 1.6Ghz with 512M ram. The driver test passes no problems.
 
Thanks in advance
 
David

Offline Graham Waterworth

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Re: missing steps ?
« Reply #1 on: April 29, 2006, 05:34:38 AM »
Hi,

is it always 4mm out?

is 4mm 1 pitch of the screw?

is it belt driven on the axis?

are you doing lots of small rapid moves?

Graham.
America gave us powered flight, England the steam train and Germany the car.  Who invented the first boat?
Re: missing steps ?
« Reply #2 on: April 29, 2006, 05:40:02 AM »
I clocked up the part again and the erroir was nearer 5mm on the yaxis which is the pitch of my lead screw and it is belt drive on all axis. The previous error was about 2.5mm on the x axis.
Thanks
David

Offline Graham Waterworth

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Re: missing steps ?
« Reply #3 on: April 29, 2006, 05:47:08 AM »
It could be that the acceleration needs turning up a bit i.e. give it longer to accelerate.

or

Have you got belt slip?

Graham.
America gave us powered flight, England the steam train and Germany the car.  Who invented the first boat?
Re: missing steps ?
« Reply #4 on: April 29, 2006, 06:07:58 AM »
You could be onto something - the error last week was approx 2.5mm and my drive ratio is 1:2. I dont think i have belt slip. How can i check ?? I can retension the belt drives. How tight should they be ? The toolpath strategy i have used on the gouging programs does use short rapid moves and the successful programs i have ran do not.

I have motor velocity set to 800mm/min and accel set to 200mm/sec/sec.
Thanks
Re: missing steps ?
« Reply #5 on: April 29, 2006, 06:14:09 AM »
It may be a coincidence but the 5mm error is my stepover so it may have failed to do the rapid stepover move ?? Come to think of it the gouging program last week mat have had a 2.5mm stepover ??? Any thoughts

Offline Graham Waterworth

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Re: missing steps ?
« Reply #6 on: April 29, 2006, 06:31:22 AM »
I would drop the accel to 50/sec/sec and work up from there, 200 sounds high to me.

Graham.
America gave us powered flight, England the steam train and Germany the car.  Who invented the first boat?
Re: missing steps ?
« Reply #7 on: April 29, 2006, 10:37:03 AM »
I think i have the answer thanks to you all and Art and Gerry on the mach forum. I was using FRO of 160% which also overides the motor tuning settings for rapid movements. Although my settings test okay in motor tuning tests if I multiply the values by 160% as I was effectively doing by using FRO of 160% the motors lock up.
Thanks
David
Re: missing steps ?
« Reply #8 on: May 01, 2006, 06:29:04 AM »
This is a macro and screen set that I made to fix this problem http://machsupport.com/forum/index.php?topic=509.0
Fixing problems one post at a time ;)

www.newfangledsolutions.com
www.machsupport.com