Question Again with a Z Axix problem

For the past few weeks I have also been experiencing issues with my Z Axis suddenly plunging down. I recently changed my HF Spindle for a small industrial one which was slightly heavier, once fitted I noticed when the Z axis was in use there was a noise and vibration. I cleaned all the machine down with particular attention to Z, and the problem appeared to be cured. Fat chance! 5 hours into an 8 hour tool path the Z axis plunged and trashed the job, but did continue cutting the tool path about 10mm lower than it should!

I have tweaked and tested several times since then. To the point where after inspecting my Z rail and rollers I noticed some scoring and pitting on both. So I bought new rollers and a new Z rail which I fitted yesterday. I made sure the tension on the Z carriage was correct re-greased and tested everything again.

As I started the cut attached below I noticed the Z Axis was once again making a faint noise and vibration after about 2 hours. As can be seen after 3 hours of cutting the Z axis plunged about 10mm straight down with no warning. I now have exhausted all avenues and need some advice on what the problem could be and how to go about rectifying it. As an aside no other electrical spikes or equipment starts took place before the Z went mad!

Fingers crossed.

Regards,

Sonny

Sonny,

In what program do you create the G-code?

And I see a submariners badge, see the code as a target. You know what to do with them

regards

Good morning CNCMiller,

Thanks for getting back to me.

Good catch with the Submariners Badge not many would pick that up, and the use of target too. You know submariners ? I am using Aspire to make the G code Mach2/3 Arcs (mm).

Regards,

Hello Sonny,

Yes I know submariners quite well, after 30 years navy you get to know your mates.

Looking at the picture I assume you are using the "Pocket" toolpath of Aspire.
Does the problem occur in the roughing part or in the finishing part?
And what Feedrate is used in combination with tool diameter and cutting depth?

When I read your problem it seems to me it has to do with:
- or the G-code;
- or USB connection lost during job, resulting in new Z-zero point on current job position;
- or Mach 3 goes to sleep function for a moment, resulting in new Z-zero point on current job position;
- or a Electrical flaw in the mainboard.

I suggest to take the spindle off the machine and run the code without actually milling , just to check if the plunge is coming back ( Can you jump to the code line just before the critical point and start from there?). I don't think you want to wait for 3 hours:)
It will cost you no material.

I'm not familiar with Mach 3 but in windows you must kill the option to switch off the USB connection, this results in loss of code.
Check in all control software that connection stays on, no sleep functions active.

Hope you can find the problem

Regards,
Erik

Hi Erik,

I did 37 years left in 2014 but still involved with the sleek black messengers of death. Were you a Submariner, you didn't actually say?

OK to answer your questions as best as I know.

Yes it was the 'Pocket' toolpath I was using and thinking about it I think the issue has always been on the finishing part. Come to think on it I may try to separate the roughing and finishing tool paths, and not rely on the combined pathing.

The feed rate was on my 3.175em, feed 40mm/sec and plunge 15mm/sec with a speed of 14k/min.

My laptop no longer goes to sleep, I found that snag out a while ago!

I have now started to download my tool paths to the hard drive of the PC and do not run from the USB. Although I do not know where to kill the off switch of the USB connection on windows.

While I understand about taking the spindle off the machine how would I know if or when the plunge happens, or am I being a thick Dabber?

Do you use UCCNC? I assume (you know about the A word) being on this site you use a Stepcraft machine, if so what post processing do you use if not Mach2/3. Would it be worth me using a different post processor if so which one would also work with the Stepcraft 840?

I am very grateful for all your time and effort in helping me out, I do not want to become a burden on your time or good graces, please don't hesitate to let me know.

Thanks again, ATB

Sonny

Hi Sonny,

I never sailed on the "Black sigars" I prefer the sunlight and fresh air. I did 33 year on surface ships but some of my friends are from the subs.

Ok let's look a bit further.
Can you check the combined toolpath (in Notepad) where it starts the finishing toolpath? check for Z-depth in G-code something like
(linenr G01 Z0.000 F25.0 M07) mover Z to zero point or does it look like this (linenr G01 Z-5.500 F25.0 M07) here Z is plunge 5.5 mm deep into the material. If the second line appears there is apparently something wrong in the Aspire toolpath calculation.

Laptop checks out ok (I assume you had a USB cable connected to the 840 and run the code from the laptop?)
USB connectivity was in the earlier versions of windows 10 set by Settings>Equipment> USB connectivity, but I can't find it back in the latest update.

Taking of the spindle is something I do if I want to checkout the running G-code.
But a code that last for 4 hours is almost not done to watch, so edit the code and delete sections that are not necessary for the test.
If you set the Z-zero height at the toolholder at lets say 6 cm above bed, then you can measure the end height of the toolholder when the roughing begins and finished and when the finish pad begin.

In my bottom lines I stated my setup of hard and software.
I use WinPC-NC USB that came with the machine when I bought it, that was the light version and I upgraded it to the full version.
You can find a demo version on: www.lewetz.de/en/service/download
UCCNC did not exist when I bought the machine.
The postprocessor I use for this is "WinPC-NC_ATC_Arcs_mm (*.nc)"

can you attach the toolpath code that creates the problem?

Good luck

Erik

Hi Erik,

General Service eh! I have probable viewed you through the peep stick at some time during our service!

Thanks for your comprehensive reply. I have viewed the G code at the point where it went mad and there is nothing to suggest it is code related. When I said it happened during the finishing run it usually manifests well into the run not at the start. I did wonder whether it was a function of the combined rough/finish tool path in Aspire 10 but I have also had the snag during my finishing run on models that do not have the combined functionality.

I have attached the rough and the finished tool paths.

I had a look at WinPC-NC USB, it looks complicated.

Stay well,

Sonny

Hi Sonny,

General service..... more ASW specialist, detecting and hunting the quiet black sigars

I have looked at your code and can't find any flaw in that, so I don't think that's the problem. what a relief..

Could it be that there is a hick-up in the Mach 3 program after a toolchange or longer period of running?
And you say you have encountered the same plunge on other projects? Are they also a long period of time working?

And don't worry WinPC is not difficult, but very powerful and it's made for Stepcraft all the setup versions of Stepcraft machines are included, so load your machine type at first start and you are ready to go.

Until the next time
Erik

Hi Erik,

Its a small world I was a ASW Specialist also then went SD and did the same job for the rest of my time.

The only thing I can think of is its a time thing, the finish tool path was about 4 hours ish and it messed up about 3+ hours in on my other job.

I will keep you updated.

Thanks for all the help.

Sonny

Are you using a USB cable with ferrite coils on both sides?

I had the same probleme. It came from the dust hose. A lot of static builds up when used. This inteferes with the stepper motor.
Ground the hose by taping som wire with each 100 mm stripped. Tape it where the bare metal is. Connect this wire to the grounding piont in the wall outlet, or some other means of grounding source.
I have newer had the problem again.
Frank Erik Vestly
Norway