Hurco BMC30 Retrofit

Next I mounted and wired the pc, mesa boards, servo drives and motors.
Here is a video of the machine moving after initial tuning of the drives:

It ended up around £800 when I added the filter I needed for it.
I keep pushing ahead on the project because I need it but it did take me almost 6 months to make a start

Not a lot more progress on the machine over the last month. I have been pulling my hair out trying to get to the bottom of the noise issue.
Its currently driving me insane! I have pulled all my wiring out several times over. I have isolated the issue to the DMM servos and drives.
Everything is wired as per manufacturers spec but as soon as power is applied to the servo drives the noise appears. All power into the drives is through line filters and the control lines are twisted pair with shielding which is earthed as per the DMM manual. I realised yesterday I may have overlooked something: there are two power inputs the control logic circuit and the main input circuit.

-The control logic circuit is 110-240v single phase which I have wired within spec.
- The main circuit is spec'd as the following in the manual "Single-phase or Three-phase 110~240VAC ± 10% 50/60Hz 300VAC Peak"
I'm using the original 3 Phase transformers in the machine, possibly naively I assumed the 3 phase power to be spec'd as a line to line voltage. The original yaskawa servos were 200v however the transformer to them actually outputs circa 180v. Im wondering if the power requirements are actually a phase to 0v measurement, if so I would be out of spec for the main circuit input. I have contacted DMM to clarify.


Other than that I have been doing some test parts, everything seems to work reasonably well so far.
I built a brake for the VFD from a couple of oven elements wired in parallel to give me the correct power/OHMs rating. I have played around with the VFD settings , I can now brake from 6000 rpm to stop in around 4 seconds, I can actually stop in less but this keeps it safe. The VFD also has DC injection braking which I can set to hold the spindle in place for 10 seconds after it stops. I'm hoping I can use this feature to lock my spindle after I do a spindle orientation for tool changing.

I also played around with gmoccapy, I really like it, I have a 17" touch screen which I plan to build my control panel with so gmoccapy will work out great.

Andy,

The noise was bad enough to glitch out the control computer (inside one of the control panels) and/or PS2 keyboard and mouse. A USB keyboard was not affected though.
I had tried to use as much of the original wiring as possible but there were so many ground loops and absolutely no shielding that I just decided to start from scratch. Pulling all earths to a single star point stopped 80% of the noise. I also used shielding tape at the servo end of the control-servo drive cables. The last and surprisingly least effective thing I did was to swap out the old VFD-Spindle motor cable to CY cable.

I still have a little bit of noise which I can see from a flicker in my screen however it doesn't seem to have any effect on the workings of the machine. I guess those old 80's electronics were pretty resistant to noise!


My next issue was spindle wear. Over the years of tool changing the spindle had ended up out of round. I could measure 0.03-0.035mm runout on the inside of the spindle. After blueing a couple of holders I could see where the issue was. Sending out the spindle for a regrind and new bearings wasn't an option considering what the machine is worth. My other option was a homebrew grind in situ using a boring bar, I wasn't overly excited about the thought of this though. With nothing to lose, I decided to blue up the inside of the spindle and carefully touch the high spots with a die grinder. I then removed the drive lug. With the spindle running @ 150rpm I firmly held a new bt40 holder (no pull stud) that I lathered in valve grinding paste in the spindle. I did this with x6 brand new holders to ensure I was always using a proper taper. Basically, I did a regrind on the fly. The die grinder marks were removed. Success! Runout measures circa 0.0025mm in the spindle and clocking the inside of a BT40 ER32 holder (not one I used for grinding) I measure 0.01mm of runout which is the spec'd tolerance for the holder. I attribute the success of this to the fact that with the high spots removed the taper acted as a guide for itself. Although not perfect or close to a new machine I'm happy with the runout considering its almost a 30yo machine. It should hold good enough tolerance for anything I will need it to do.
I thought I had made a bollocks of it at the start as although runout was acceptable tools where very hard to remove from the spindle. Turned out grinding/honing the spindle had left it so smooth that every tool was creating a vacuum effect just the same way slips do. A very light touch with a piece of sandpaper on the inside of the spindle instantly solved the problem.

As of now I'm running the machine and just doing manual tool changes to see how it's running. So far so good, its holding tolerance well. I would like to play around with the backlash settings a bit more and also the settling tolerance on the servo drives.

Next on the list is to reinstall flood coolant as I only have the mql system running. After that, I need to get the spindle chiller back together and then the final job will be the tool changer.

Picture of the machine in its current state except I now have my sliding guards fitting.

Andy,

I have done both of these. All remaining noise (and most of the original noise) seems to be coming from the servo drives. The noise only appears when the drives are powered on.

Regards,
Andy

Genius idea to fix the runout! Have you tackled your tool changer yet? The spindle orient step is giving me a lot of grief in my retrofit.

I've been following you on IG - keep up the good work!