Missing steps ?

[DavyD]

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

[daedalus]

what material are you cutting, how big are your steppers, and what type of ways does your machine have? Have you checked that everything moves smoothly by hand?

[dertsap]

ive found that when i used the over ride with mach 2 it got screwy on me and i loss steps , this happened acouple of times now

[DavyD]

I am cutting 6082 aluminium and taking only 1mm cuts with a 10mm cutter 5mm stepovers. I am using the original steppers fitted by the manufacturer I am not sure of their size . The machine uses ball screws and v ways. Everything moves smoothly. The machine is ex university and is mechanically like new.

Thanks David

[DavyD]

On the last job when i reran the programs after the first gouge - all went well with 7 hours machining. I did run the feed at the programmed rate and did not overide. Although last night i cut for 4 hours with feed overide set at 150% and all was okay.

[ger21]

When you crank up the FRO in Mach3, it will also speed up the rapids, actually exceeding the motor tuning settings. It's best to program faster and slow down using FRO.

I can't think of anything else off hand right now.

[DavyD]

I think you are right. Althought my velocity and accel values test okay when motor tuning. If I multiply the values by 160% as I was doing by using FRO the motors lock up.

Thanks

David

[ger21]

In Config>State, if you check "NoFRO on Queue", the FRO won't apply to rapids. The downside is that the response will not be immediate, due to previous moves being buffered.

[mfrank7143]

I have had the same problem with my Boxford 260 vmc, the error always seems to be in the Y axis in the - direction. The machine is running mach2, and I have spent a lot of time trying to get to the bottom of the problem. I thought I had solved the problem by slowing the motors top speed down by 20% but after doing a couple of decent jobs the problem returned!

Mike.

[DavyD]

I have slowed down the acceleration on my motors and have since machined successfully for 30 hours. Hopefully that was the problem. I also only use FRO to slow down the programmed feed.