[kmagyoyo]

I've started with some practical modifications. Added aluminum plate to cover the hole left by the OE interface. Mounted the display, keyboard and mouse on top of the console. Ideally the display would have mounted flat to the top of the console, but the display I have has some of its guts inside the base.

I was hoping to put the PC inside the console, as the cabinet is somewhat sealed from dust. Unfortunately I couldn't find anywhere it would fit, so I think I will mount it to the back or side of the console. My last CNCPC sat out in the open, and I never had any issues, although I did blow it out regularly.

[kawfree]

Any update on the Acorn Machdrives wiring. I just received my Acorn and Machdrives a few weeks ago for re-wiring my Gerber Sabre 408. It's always better to follow a tried and tested procedure than adventure into the unknown.

[kmagyoyo]

I decided to save the card frame from the original drives, it holds the high-current rectifier board and I was able to modify the slots so they hold the Machdrives in fan-cooled comfort. Plenty of room in there for a Z-axis drive if needed.



Then I mounted the Acorn board to the face of the card frame. This might not be ideal since I'll have to unscrew it every time I need to access the drive cards.



Wiring the Acorn to the Machdrives seems pretty straightforward per the diagrams provided by Centroid. I'm a little unsure about how to connect the encoders, there are two for each axis, one on the motor and one on the ball screw. Plus I have no idea if they are compatible with the Acorn.

[skrubol]

Wiring the Acorn to the Machdrives seems pretty straightforward per the diagrams provided by Centroid. I'm a little unsure about how to connect the encoders, there are two for each axis, one on the motor and one on the ball screw. Plus I have no idea if they are compatible with the Acorn.

The encoders would connect to the Machdrives, not the Acorn. Looks like the models you have only support a single encoder (the significantly pricier BRA does support dual encoders,) so you probably would want to use the encoder on the motor as it can be tougher to tune the further away the encoder is from the motor.

[kmagyoyo]

The encoders would connect to the Machdrives, not the Acorn. Looks like the models you have only support a single encoder (the significantly pricier BRA does support dual encoders,) so you probably would want to use the encoder on the motor as it can be tougher to tune the further away the encoder is from the motor.

Good advice. Yeah, one encoder should do it, this machine won't be making any aerospace parts...If I can get +/- 0.005 I'll be thrilled.

[Krlerma]

I have the same machine that i want to convert into a cnc. It has different motors. I have not done any research on them yet




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[kmagyoyo]

Krlerma your motors appear to be identical in specs. Probably made in the same factory but sold to Masterwood by a different vendor.

[kmagyoyo]

I got the computer hooked up and running the Acorn. It's not really much progress but it was exciting to see it looking like a real machine. My next step is to hook up the drives to the servos and see if the tuning software will run.

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[kmagyoyo]

So I picked up a nice little Hitachi oscilloscope on fleabay, smells like stale cigarette smoke but hey it was $125 delivered. I hooked up the power supply board and poked around, all I can find is 100 VDC. The motors didn't appear to be rated for 100V, so I am confused. Voltage measurement was verified with my DMM.

The MachDrive BRB are only good for 80 VDC. There is nothing on the power board that resembles a voltage regulator. There are a couple rectifiers and electrolytic filter capacitors, not much else.

[kmagyoyo]

I'm unclear on connection of the encoder. Machdrive's manual seems to think my encoder will have at least 4 wires (0V, +5V, A out and B out) but I only see 2 wires.

Anybody know what type of encoder this is and how it can be connected?

Worst case, there is another encoder on the ball screw with the right connections, though @skrubol tells me it will be harder to tune.

[skrubol]

I'm unclear on connection of the encoder. Machdrive's manual seems to think my encoder will have at least 4 wires (0V, +5V, A out and B out) but I only see 2 wires.

Anybody know what type of encoder this is and how it can be connected?

Worst case, there is another encoder on the ball screw with the right connections, though @skrubol tells me it will be harder to tune.

Sounds like a tachometer rather than an encoder. Probably not useful for the Machdrive. Most modern servo amplifiers just get the velocity signal by differentiating the position signal, but on older analog amps I think it was fairly common to use a tach to get the velocity. I think it makes sense that it's close to the motor, keeps things stable, while the encoder on the screw enables better accuracy.

[kmagyoyo]

The Hohner encoder on the ball screw reads "PRO1310/500". Can't find anything about it on their website. I'm going to take a wild guess that the
"/500" is the increments per revolution. The pinout makes sense if you translate the wire colors from Italian, but I'm not sure what the "O" wire should be connected to. So far I haven't gotten a signal that the drive has recognized.

[__Britt]

Just a guess on my part, but... "O" might be the index pulse?

[kmagyoyo]

That's probably correct, Britt. I should connect the outputs to the oscilloscope and find out.

[kmagyoyo]

Here's the drive output at the axis motor, doesn't change when I jog the control. Motor doesn't move. I would expect it to go to DC? I believe the drive is receiving the step/dir command because it throws a following error after more than a second or two of jogging (due to lack of encoder feedback). Reading is with a 10X probe.

[skrubol]

Here's the drive output at the axis motor, doesn't change when I jog the control. Motor doesn't move. I would expect it to go to DC? I believe the drive is receiving the step/dir command because it throws a following error after more than a second or two of jogging (due to lack of encoder feedback). Reading is with a 10X probe.

What are the voltages and frequencies on that scope reading? Hard to tell from just a pic. Is the motor making noise? (Driving a square wave through a motor would ordinarily make quite a bit of noise at the frequency of the square wave.) Have you checked the resistance of the motor?

[kmagyoyo]

?WE HAVE MOTION...I put the X-axis aside for now and hooked up the Y-axis. Immediately had Y encoder talking to the drive, so there must be a bad connection on the X encoder. Completed the drive config and got the Y-axis moving with the Tuna software wave generator.

Regarding the lack of movement on the X servo, that was related to my hastiness in configuring the drive...the Machdrive won’t output to a motor until config has been completed. David with Machdrive has been very patient with me. Thanks to SEK22Hornet for pointing me toward Machdrive, they make a fantastic product and service is top notch.

Long way to go before I’m cutting any parts but passing this milestone means I can start thinking about the Z-axis. Probably looking for a simple lead screw with a Clearpath servo...let me know if you have ideas.

[skrubol]

?WE HAVE MOTION...

I can start thinking about the Z-axis. Probably looking for a simple lead screw with a Clearpath servo...let me know if you have ideas.

Congrats!
I've read very few accounts of customers who regret Clearpath's. They aren't the best bang for the buck power wise (DMM servos are more traditional AC servos, but very inexpensive and seem to be pretty good quality,) but Clearpath's seem to be so easy to get running they're probably a good investment if you value your time.

[kmagyoyo]

After having trouble getting the x axis encoder to show a signal, I skipped over to the y axis and quickly got it working, and in fact was able to get axis motion via Tuna’s wave generator.

Now I’m confident the x encoder issue is just a bad connection. So I’ve moved on to the z axis. Bought this ballscrew kit on eBay. Seems like a very high quality piece of hardware considering it was only about $40.



Now I need the servo and spindle as these items are going to be located very close together on the y axis car. Might need to do some sketchup to lay it all out.

[kmagyoyo]

Teknic was very helpful in specifying a Clearpath servo for my Z. With cables, a 492 oz-in NEMA 23 servo came to just under $400 shipped. I looked at alternatives like a leadshine stepper with encoder, but after adding a drive it wasn’t much less.

Looks like I’ll need to come up with a 75 VDC supply, the engineer at Teknic said it will take max 90 volts (which I already have onboard) but that doesn’t leave any room for regen and I’ll likely get overvoltage faults. Teknic has an appropriate PS but it’s $200.