Bridgeport VMC760 retrofit

How does a person manage to lift 2" thick steel?

Did you finish the machine yet?

Nope!

Mesa cards and servos are on there way though1 Ill make a more detailed post of my progress in the next day or two.

To answer your question. With a forklift.

Nice welds on your control panel.
Mark

Cheers Mark.

I don't get to do as much ally as I'd like.

Bit of a progress update from the last couple weeks:

Control panel is at the powder coaters. I choose a dark matt charcoal. Mainly as my coater runs this Dulux colour often and Im impatient at the best of times! Should have this back on Tuesday.

The custom control panel buttons are now 3d printed, along with the MX switch carriers. All wired up. These run into a DB25 breakout board and then will travel back the Mesa cards in the cabinet. I appreciate this isn't the nicest way to execute it, but I only require the 7i97t and 7i84u for all IO, and most IO terminates in the cabinet. I got cold feet on flashing the 7i97.... Pics below.

PC has been setup with linuxcnc. I chose a Coofun CK41 miniPC, which The Feral Engineer made some tests on YouTube with seemingly good results. Fingers crossed it works out. It's very compact and so was the price tag. Took me a few nights to get MesaCT and an updated Mesaflash running correctly to recognise the 7i97T. This is honestly due to my lack of unix (or IT in general!) skills. We got there in the end - I'm now able to run a draft linuxcnc config and toggle a coolant assigned output on the 7i97t with no dramas. I'll take that as a win. Yet to hook up the 7i84u.

Have to thank JT for the great MesaCT package!
I was and still am very daunted by the task of editing lines in the Hal/ini files.

The servo drives are currently on their way from China. I went with Leadshine EL7 drives in the end. The price was decent and they're offered in 380-400v 3ph. Opted for analog/pulse control as these control methods appear to be well documented here, especially by Tommylight's guide. Ethercat looked appealing, but given my lack of IT skills I thought it safe to stick with the aforementioned.

This weekend I started drafting the wiring diagrams between the Mesa boards, original Bridgeport control/distrubution board and new servo drives. The free schematic cad on DigiKey.com ist great btw! Would recommend.
Which brings me to my next question:

I assume I can run the enable controls from the 7i97t to drives without a relay? I believe I've drawn this with the correct polarity directions, but any insight are most appreciated.

More updates to come!

Cheers,

j

 
 
 
 



 

Alrighty!

Drives and motors arrived. Setup a bench test rig. 

I've made it as far as getting the encoders to read in LCNC (scale seems right). Unfortunately I'm getting following errors when I try enabling the drive. I can hear the drive enable relay latch very briefly. 

I've followed Tommylights guide, but can't get too far when it errors straight out of the gate. Im also getting a "could not switch machine on, is limit switch activated". I currently have no IO assigned. 

I suspect my wiring is at fault or I'm really missing the mark with my initial PID numbers - I've tried a bunch so far, even with giant max f errors.
Schematic below. Any thoughts would be greatly appreciated!

Thanks,

J



 
 

Perhaps configuring LinuxCNC to invert the fault input will work?

For some reason, powering the enable input on some drives disables the drive (Ask how I know).

You need to set large min-ferror and ferror limits (an inch / 25mm or so) so you can see
the motor behavior (you have about a 50% chance of the wrong feedback direction and
runaway so of course this needs to be addressed first.)

Also make sure you have working drive enables or motors disconnected from linear axis
as a runaway linear axis can be dangerous/destructive.
 

Thank you for your replies PCW and langdons,

You were on the money PCW! I had my MIN-Ferror set way too small - this made sense in my head, but clearly didn't work. Also swapped my A,B and Z polarities at the mesa. Thank you greatly for the tip!!

I've got the test motor running now, and am able to tune it with Tommylight's guide on the bench within 0.003mm ferror. Couple of questions for the next stage though:

- I assume I would get a baseline tune on the bench for all motors. Then instal motors, run the inertia calculator in the motor software (adust these parameters where fit), then finally re-tune/adjust my position tuning with motors under real loads?

Regarding wiring - I plan to use twisted pairs on the ANOout/GND control and each encoder channel. Can I have the 3 encoder twisted pairs in one shielded cable and the analog control in a seperate one? Or can I put them all in a common shielded cable?
Or do all encoder pairs need to be in seperate shielded cables as well?

Currently I'm just using some CAT6 cable for the encoder link and some shielded twin core audio cable for the analog voltage on the bench. However, I'd like to order the right stuff for the next stage of wiring.

Many thanks,

J

 

Digital connections probably won't need shielding.

You might be able to just use cable with one wire and a shield for the analog signal.

Expensive turntables (cheap ones too) have the needle connected directly (electrically) to the 2 wires of the audio cable, the shield and the internal wire.

Upon reaching the amplifier, the shield is connected to "ground", while the wire connects to the amplifier circuit.

The NTI Ti100 boiler that is a part of my house's in-floor heating system uses a flame probe, which is connected via a shielded cable to the FENWAL, with the shield eventually connecting to ground upon termination.