Light Machine Corp. Benchman XTr (retrofit)

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10 Dec 2015 11:05 #66726 by cncbasher
your not the only one Andy ,

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23 Dec 2015 19:31 #67270 by steve_a
Ok I have made many hard decisions and the hardest is to abandon the servo motor power supply. I labeled all my connectors on the two boards sandwiched on the left side and went to town with a meter. The output from the toroid /choke goes to the bottom board where the two big caps and resistors finish the smoothing. It is then distributed to the motor controllers. I decided I didn't want to make a board to finish off the regulation and opted just to order a 72V unregulated PS from CNC4PC. Yep, a $200 decision. However I have used one of these supplies before on another project and I feel confident it will do the job and save me the time (and worry) of producing the board for the resistors and caps. I also noticed that there is a transistor on the bottom board that taps into the power supply... Could just be for a power supply valid signal of it might power something else. Anyway, that was pretty much the last straw for me... I am already behind and I don't plan to spend time chasing traces. I think MAC might have some way of using the installed toroids but as I just made a personal decision and chickened out.
I also need a 5V and 24V power supply. I know the door and air control solenoids use 24V and I think the motor brakes are 24V. I will need 5V for the logic systems. I also plan to tear out the solenoid logic board and probably replace it with something like an Arduino or a Rasberry PI. I MIGHT still use the 24V supply. Last time I powered stuff up it worked... but it depends on what I see as control for it but I think it is self contained and will still be useful as a supply. I did a quick look at digi-key power supplies. If I can get a 24V for $25 or so I might just replace that just for ease of wiring, besides, my original idea for this machine was to gut the controls and give it a fresh start so I'm kind of returning to Plan A.
For safety control I ordered a solid state, zero cross relay so I can delay the servo motor supply from powering up until I have valid control signals. I believe this is what the relay on the bottom board did so I'm just duplicating that idea.
Christmas break coming up, so this is a good time to order supplies and hit this again in the new year!

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23 Dec 2015 20:13 #67271 by andypugh

steve_a wrote: I also need a 5V and 24V power supply. I know the door and air control solenoids use 24V and I think the motor brakes are 24V. I will need 5V for the logic systems.


Once you have one DC supply the most expedient (and easy to debug) way to get the other DC voltages is with the LED display DC-DC converters that you can find on eBay:
www.ebay.co.uk/itm/291571630825

As an example of what I mean. There are higher-current ones, and also step-up varieties.

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23 Jan 2016 05:59 #68955 by steve_a
Does anyone know if the brakes on the motors are just to hold the motors when the machine is powered off or are they supposed to be engaged to hold position while cutting when there is not supposed to be movement in that axis? Seems like a waste to just have brakes to prevent movement when the machine is off.... might make sense to have a more complex role as a dynamic hold for added rigidity.

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02 Feb 2016 12:02 #69428 by andypugh
They are generally just to hold the axes when the power is off.
This can be especially useful for the Z axis if there is a danger of the head dropping on to the table.

Brakes can also prevent position-loss when the power is off and the encoders are not counting.
(this works better with absolute single-turn devices like resolvers, though)

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14 Jul 2016 01:34 #77420 by steve_a
Ok I am Back. After a long robotics season and reworking a plasma table I can finally give much needed time to this project. I AM using the kflop and I am suffering for it, but I believe the mechanics of this machine will still be useful to anyone working with one of these in Linux with a Mesa. SO far, I delivered 24V to the z axis brake, and the spindle started to drop rapidly until I pulled the 24V and it locked up. Pretty cool!
I tried to leave as much of the wiring intact as I could so I am using what's there to make my connections so as not to disturb the original wiring. Because there are smoothing circuits on the original control boards, I elected to buy a 72V power supply and just gut and replace the main toroid 72v supply and the main control PCAs when that time comes. Right now, I just have the power supply sitting on a work table behind the Benchman. I ordered some male ribbon cable connectors and used the ribbon cable to breakout the encoder signals and wire them into the Kflop/Kannalog unit. I WISH I had a Mesa, but the wiring seems to be the same in terms of what the signals are. I used the Copley amplifier manual and wired the X axis in the torque mode ( more on that in a minute) and used the 1.5V battery suggestion... MOVEMENT!
A quick note... the Kflop/Kannalog documentation STINKS! I've been stumbling through it all, but today, Success! I can control the x axis and the encoders are actively giving position and I am able to control the movement. Next comes tuning. If I can get this X axis to work, the others will be easy.
Got a question for you gurus out there. Something strange. I THOUGHT the Copleys were set up in Velocity mode... but I don;t see where they are getting a Tachometer reading. Is it the index pulse from the encoders? Did I miss an actual brush tachometer? Also, the Manual defines component values (appox) for Torque and Velocity modes.... these seem to be set up as BOTH. CH11 has a zero ohm resistor (a short) that you would see in torque mode instead of a small cap... and CH9 is supposed to be blank for torque mode but instead has a 220PF cap installed like you would see in Velocity mode. Coupled with the missing Tach I'm totally confused. Anyone have any ideas on this? My first thought is to convert the Copleys to Torque mode to avoid a conflict with the controller that thinks it is controlling everything.
I will post drawing of my connections as soon as I actually draw them.

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14 Jul 2016 02:03 #77421 by wrightsh
So on my ProLight (which I think is pretty much the same machine) there's a board that takes the encoders as an input and runs through several logic chips to produce a tachometer output. At one point I tried tracing out all of these components and found datasheets for them and got a schematic but if I remember correctly I would have needed a few more supply voltages then just +5 and +24. I think each of the LED's below and to the left of this tachometer board correspond to each of these supply voltages which are fed from the box that houses the computer. I ended up just getting rid of that board and running the servos in torque mode and have been happy with it. I can look up the tuning values that I used if you want.

-Shawn
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The following user(s) said Thank You: steve_a

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14 Jul 2016 02:58 #77423 by steve_a
Thanks Wrightsh! That board is similar but I think there are some differences. It IS pretty close though and I'm sure your explanation is the right one. I have the original tuning values, they are listed in an earlier post on this thread but if you have other values I would love to see them. Tuning is supposed to be the hardest part and I suspect the values I should use for this new controller are either the same or some numeric ratio. Anyway, if you can post those without too much trouble I would appreciate that.

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14 Jul 2016 03:30 - 14 Jul 2016 22:03 #77426 by wrightsh
So my X & Y run pretty well with this but I do need to do some more work on the Z because I recently added a plate between the spindle and the carriage that the spindle mounts to in order to shift the Z axis up by a couple inches & the added weight needs some compensation. At least on my ProLight if you bring the Z all the way down the spindle nose is basically in the table. Which isn't very helpful if you only have 9" of Z travel and are always going to have at least ~2" of tool holder and tool + however tall your vise is
#********************
# Axis X
#********************
[AXIS_0]
TYPE = LINEAR
HOME = 6.0
FERROR = 0.001
MIN_FERROR = 0.001
MAX_VELOCITY = 2.00
MAX_ACCELERATION = 40.0
P = 14000
I = 0
D = 13
FF0 = 0
FF1 = 15
FF2 = 0
BIAS = 0
DEADBAND = 5e-05
MAX_OUTPUT = 0
ENCODER_SCALE = -40000
OUTPUT_SCALE = 10
OUTPUT_MIN_LIMIT = -7
OUTPUT_MAX_LIMIT = 7
MIN_LIMIT = 0.0
MAX_LIMIT = 12.0
HOME_OFFSET = -0.1
HOME_SEARCH_VEL = -0.2
HOME_LATCH_VEL = 0.01
HOME_FINAL_VEL = 1.00
HOME_USE_INDEX = YES
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 1
COMP_FILE_TYPE = 1
COMP_FILE = xscrew.comp

#********************
# Axis Y
#********************
[AXIS_1]
TYPE = LINEAR
HOME = 3.0
FERROR = 0.001
MIN_FERROR = 0.0005
MAX_VELOCITY = 2.0
MAX_ACCELERATION = 40.0
P = 14000
I = 0
D = 13
FF0 = 0
FF1 = 15
FF2 = 0
BIAS = 0
DEADBAND = 5e-05
MAX_OUTPUT = 0
ENCODER_SCALE = -40000
OUTPUT_SCALE = -10
OUTPUT_MIN_LIMIT = -7
OUTPUT_MAX_LIMIT = 7
MIN_LIMIT = -0.0
MAX_LIMIT = 6.0
HOME_OFFSET = 0.00000
HOME_SEARCH_VEL = -0.2
HOME_LATCH_VEL = 0.01
HOME_FINAL_VEL = 1.00
HOME_USE_INDEX = YES
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 1
COMP_FILE_TYPE = 1
COMP_FILE = yscrew.comp

#********************
# Axis Z
#********************
[AXIS_2]
TYPE = LINEAR
HOME = -0.1
FERROR = 0.002
MIN_FERROR = 0.001
MAX_VELOCITY = 2.0
MAX_ACCELERATION = 30.0
P = 14000
I = 0
D = 13
FF0 = 0
FF1 = 15
FF2 = 0
BIAS = 0.6
DEADBAND = 5e-05
MAX_OUTPUT = 0
ENCODER_SCALE = -40000
OUTPUT_SCALE = -10
OUTPUT_MIN_LIMIT = -7
OUTPUT_MAX_LIMIT = 7
MIN_LIMIT = -9.0
MAX_LIMIT = 0
HOME_OFFSET = 0
HOME_SEARCH_VEL = 0.2
HOME_LATCH_VEL = -0.01
HOME_FINAL_VEL = 1.00
HOME_USE_INDEX = YES
HOME_IGNORE_LIMITS = YES
HOME_SEQUENCE = 0
COMP_FILE_TYPE = 1
COMP_FILE = zscrew.comp


You'll also need to put the amp into torque mode
Last edit: 14 Jul 2016 22:03 by BigJohnT. Reason: add code tags

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14 Jul 2016 22:54 #77468 by steve_a
Thanks for the numbers wrightsh. I played with mine today but they are pretty different by the time it was all said and done.
I have two axis running and have decided that for E-Stop I will disable all the Copley Servo Amps. There is quite a bit of residual power stored in the smoothing caps of my DC supply SO I think the motors will continue to move a small amount after an E-Stop. I have to supply ground to pins 11, 12 and 13 and by disconnecting the ground I can completely stop any movement. Making some pretty good progress.

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