How to repair/replace very old Microstepping drivers in Torcam CNC - Page 1
Forum section: electronics / repair

author: Langdon
author_rank: Frequent Contributor
timestamp: October 23, 2024, 01:53:23 pm
content: I have an old Torcam CNC router machine that contains 3 microstepping drivers by Tor Computerized Systems Inc.There is one driver per axis.It is controlled by a PC running LinuxCNC on Debian over a parallel port through a PMDX-122 breakout board.The PC, the parallel port card, and the parallel port cable are reliable and fully functional.The PMDX-122 board works without any problem.However, the CNC Machine does not work.I believe the microstepping driver is the problem. Its microcontroller relies on an EPROM chip that has likely become corrupted over the 30 years since the EPROM was written to.Should I replace the drivers?What should I replace them with?The existing(broken) drivers use 2 L6203 full H-Bridge drivers and are definitely capable of delivering substantial current (6A), the replacement drivers also must be capable of delivering at least 6A (in total for both windings) .The 2 L6203 H-Bridges from each microsteppping driver are still fully functional; should I just desolder them and make my own stepper driver board using the existing H-bridges and heatsink?I have connected a smaller stepper motor to one of the microstepping drivers to test the driver and make sure the Router machines's motors are not at fault. However, the stepper motor i wired up does not move. While the stepper motor I am using to the the driver has 200steps/revolution, so it will take a lot of microsteps to move any noticeable amount, it doe not appear to move at all. The motor heats up and make a high-pitched noise, but it doe not move any measureable amount even after running it for 15 mins.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 23, 2024, 07:08:41 pm
content: Hello Langdon,If you suspect the stepper controller/power stage to be defective, try to locate the STEP & DIR signals of one axis. Those should come from the computer.Apart for very specific needs, it's too much work to developp your own microstepping power stage.I would sugggest you to buy such a 7.2 A microstepping driver/power stage and try to wire it to one of the genuine axis motor.https://www.omc-stepperonline.com/digital-stepper-driver-2-4-7-2a-18-80vac-or-36-110vdc-for-nema-34-motor-dm860tThe user manuel can be downloaded from the product page.You should even be able to reuse the mill's genuine power supply when using these kind of power stages.I also found this page about an update of the TORCAM CNC mill :https://makebright.com/2014/11/torcam-cnc-mill-comes-alive-with-easelgrbl/

author: Swake
author_rank: Frequent Contributor
timestamp: October 23, 2024, 07:56:28 pm
content: 1 driver dead, ok, but 3 drivers dead at ones sounds less probable. Could you share the brand and type of the drivers and the steppers?You write that "The PMDX-122 board works without any problem", I assume you see the LED's blinking when you send some command in LinuxCNC. Have you been able to confirm with a scope or maybe a multimeter that the step and dir outputs of that board effectively output something on all axis towards the drivers?As per the previous message make sure that the power supply for the drivers is within spec of those drivers.Other things that might prevent correct functionality are the e-stop (emergency button) and homing switches. If these are not configured and wired correctly the board is never going to send something to the drivers. Cabling in general is actually rather sensitive on these parallel port setups.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 24, 2024, 04:32:34 pm
content: I know the step and dir signals work.The dir led turns on or off depending on the dir.The step LED does not light or flash, however, that is because it flashes too fast to see.If I wire up the step pin to a 4520B CMOS binary counter IC with LEDs connected to the outputs, it counts reliably.If I wire up the stepper driver's step pin to one of the counter's outputs, it still does not work.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 24, 2024, 04:36:43 pm
content: The drivers are very old.They say Copyright 1991 Tor Computerized Systems Inc. on them.They could be 33 Years old.I fear their EPROM chips might have degraded.They were kept in a school that has no A/C for up to 32 hot summers, which could have accelerated their degradation.

author: fzabkar
author_rank: Super Contributor
timestamp: October 24, 2024, 06:32:04 pm
content: If you can dump the EPROMs, we could confirm whether they are checksummed.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 24, 2024, 06:56:42 pm
content: Hello Langdon,Because the mill dates from the early 90' a bigger footprint retrofit might even be wise if the mechanical framework is still in good shape.The genuine steppers might even not be of thehybrid type(= combination of the permanent magnet and variable reluctance type).Featuringclosed loop hybrid steppersor possiblyclosed loop 3 phase servomotors with brake(othermodels) would certainly give a new run to this machine.And don't forget that the Z axis is usually the slowest axis of a mill or gantry router. Adding a weight balancer might sometines help.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 25, 2024, 02:41:43 pm
content: How do I do that?What does "dump the EPROMs" mean?

author: Langdon
author_rank: Frequent Contributor
timestamp: October 25, 2024, 02:51:15 pm
content: I saw the makebright page.the problem is, info is limited and there is no way to contact the person who fixed the Torcam CNC to ask him for more info.Furthermore, my machine has already been replaced.I don't need to wire up the original driver board with GRBL because the original board is long gone.There is a replacement PMDX-122 board that definitely works.It's just those damn stepper drivers!Note: It's technically possible that the motors are to blame.Also, AFAIK, opto-isolators burn out.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 25, 2024, 06:11:17 pm
content: Even if it's not that common, steppers can technically also suffer from asingle shorted turn.Only a ringing test...... of each motor coil will dispel any doubts.A basic check on the optocopler is to verify if the IR emiter led is still healthy.With a vanilla multimeter in 'diode' mode, measure the forward voltage of the diode : should be between 1,1 and 1,7 VDCMaking a dump of an EPROM means reading its' contents.It requires anEPROM programmer.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 29, 2024, 02:14:17 pm
content: I am almost certain that all 3 microstepping drivers are broken.Everything else works.The drivers must be at fault.What would you recommend as a replacement?The motors in the CNC machine are 4.6A DC stepper motors.They have 200 steps/rev.The power supply is 40VAC, 40VDC, or 120VACIf necessary, I can hook up a 24VDC or 12VDC power supply.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 29, 2024, 03:43:54 pm
content: Hello Langdon,As written above, I would suggest those :https://www.omc-stepperonline.com/digital-stepper-driver-2-4-7-2a-18-80vac-or-36-110vdc-for-nema-34-motor-dm860tYou can hook them to the 40 VAC power supply.But maybe wait another day if someone else on the forum might make a better suggestion.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 29, 2024, 04:01:41 pm
content: I am in Ontario, Canada.The seller must ship to me.I am not going to deal with any company that charges $50 extra to ship to Canada.What are your thoughts on these:https://www.ebay.ca/itm/203996840791https://www.ebay.ca/itm/375578234876

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 29, 2024, 04:30:58 pm
content: Quote from: Langdon on October 29, 2024, 04:01:41 pmThe 'DM556' should do it too, just take care that the input voltage span is lower than for the 'DM860T' I suggested above, and it's DC only (18~48V DC power supply).Use small fans to blow on the heatsinks.

author: Langdon
author_rank: Frequent Contributor
timestamp: October 30, 2024, 03:45:21 pm
content: Do you think this driver will be poor quality?https://www.ebay.ca/itm/203996840791Should I buy one first to test if it is cheap junk and then buy 2 more if the first is good?

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: October 30, 2024, 06:20:17 pm
content: Quote from: Langdon on October 30, 2024, 03:45:21 pmIt's a 'DM556' and as stated above, it should work well as a remplacement of the defective genuine drivers.Of course, for C$22, you get probably only a copy of the 'DM566', which was originallymanufactured by Leadshine. User manual V1here.The Leadshine unit, currently in version 3, also features a programmable smoothing filter and other improvements (sertup performed via dip switches SW9 to SW16). User manual for v3here.If you don't want to take an excessive financial risk, it is certainly a good idea to buy only one unit and hook it on each axis motor, to see if it always behaves well.A suitable test is to apply very slow accelerating ramps to identify all of the resonance points.You may also try some fast moves back and forth to check if there's no step loss.In case of resonance, if the motor driver cannot cope with it, some CNC software can be setup to avoid dedicated displacement speeds where this situation occurs (which often leads to bad surface roughness during the milling process).You may also mount the steppers by using dedicated rubber dampers or even use an oil resonance damper directely fitted on the axis.https://www.cnczone.com/forums/stepper-motors-drives/32284-take-stepper-damper-8.html#post534256https://www.cnczone.com/forums/diy-cnc-router-table-machines/103920-cnc.htmlUpdate #1 : contents enhanced by describing differences between ebay motor driver model and genuine Leadshine part.Update #2 : tackling mechanical resonance