Tormach Driver Failure


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    Default Tormach Driver Failure

    A couple of weeks ago, I was running a part on my PCNC770 when there was a strange loud noise during a z axis move. The noise only lasted a second and the program continued. There was a second strange noise and the head dropped about 1/4" further than programmed. A 1/4" carbide end mill plunged about .080" into my 5C collet chuck and cut a 1/2" long slot in the nose of my collet chuck, a 7/8" collet, and my workpiece before the E-stop killed the program.

    I reset the controller and using the jog shuttle, I confirmed that the x and y axes were still live. When I opened the control panel, the red warning LED on the z axis driver was lit. When I pulled the motor connector there was a very obvious burn on pin 5.
    Tormach Driver Failure-leadshine-driver-jpg

    I switched the motor and control connectors to the y axis controller and verified that the z axis stepper and controller signal were good. I then pulled the driver and removed the cover. A resistance check of the output transistors showed that Q14, an IRF540 MOSFET transistor, was shorted between the source and drain leads. I removed the transistor and confirmed the it was shorted.

    I placed and order with DigiKey for five replacement IRF540's and two pairs of the Phoenix connectors. Two days later, the parts arrived. I installed the new transistor and the new connectors. I installed the repaired board and powered up with the green LED on the z axis driver now lit. I reset the controller and homed the machine with the z axis now behaving normally

    The next day, I talked with customer service at Tormach. They have been aware of a problem with the connectors on the Leadshine controllers for some time and made a production change in 2014. Part of the change was using a dielectric grease on the motor connections to prevent oxidation of the contacts.

    A postmortem of the Leadshine 3ND883 suggested the following scenario. The bifurcated phosphor bronze contact and brass pin are tin plated. The contacts are rated for 15 amps. The pin has a square cross section so the entire current through the connector passes through two opposing lines across the pin. The integrity of the connection is also highly dependent upon the spring force of the contact. When oxidation of the tin plate occurs, the resistance of the connection increases which gives rise to heating. The increase in temperature of the contact will eventually burn the surrounding insulation. Raising the temperature of the contact can also destroy the spring temper of the phosphor bronze, weakening the contact pressure and further increasing resistance. Eventually, the connection becomes intermittent which has the effect of adding extra steps. In addition, Leadshine states that making or disconnecting the connection under power can create transients which can destroy the driver. Failure was most likely due to a chain of events which began with oxidation of the tin plate and ending with destroying the output transistor, shutting down the driver.

    A few suggestions about a repair and replace.
    1. Both halves of the connector should be replaced if burning is evident. While the board connector may not be damaged, it most likely will have oxidation and surface pitting from the subsequent arcing. There is possibility that the product from the burning of the housing have coated the surface of the contact pin resulting in a thin insulating layer.
    2. There are static sensitive devices on the board so it is prudent to take proper antistatic precautions.
    3. The connector is soldered in plated through holes and it can be very difficult to remove without special equipment. If the special equipment isn't available, it would be a good strategy to cut the connector apart so each pin can be removed separately.
    4. Heat sinking of the output transistor depends upon positive contact with the thermal pad. Insert the transistor on the board and bend the leads slightly to hold it. Then mount the board to the heat sink and solder the leads and trim them. This prevents the new part from biasing the mount and possibly decreasing the thermal conductivity of the other transistors.
    5. There is a temperature sensor which is thermally connected to the heat sink with heat sink compound. Make sure that there is sufficient heat sink compound on the surface where it contacts the heat sink.
    6. Use of a dielectric grease or antioxidant gel on the connector contacts is highly recommended. Legrand sells a copper to copper antioxidant , OR-AJCC, in 1/2 oz. tubes. Harger HCAJC1/2 is another brand. Tormach recommends a straight silicone dielectric grease.
    7. The OEM connectors were made by Degson, P/N 2EDGK-5.0-02P-14-00AH and the mating connector is 2EDGRC-5.0-02P-14-00AH. The Phoenix numbers are 1754504 and 1754494 for the plug and socket.

    As a preventive measure, it would be wise to pull the motor connections on a regular basis to check for any burning. If burning is evident, the best practice would be to replace the connector. Removing and reinserting the connector several times will also serve to wipe any oxidation from the contacts.

    On a related note, early Tormach machines had a setting of on,on,on for the 1,2, and 3 positions of the Leadshine driver dip switch. This corresponds to a drive current of 8.3 amps. The latest 770 manual shows on,off,on for the switch setting, corresponding to a drive current of 6.6 amps. Tormach verified today that 6.6 amps is the correct drive current for all three axes on the 770.

    RJ

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    Default Re: Tormach Driver Failure

    I had this happen to me on my X driver, caught it in time and it didnt destroy the mosfet?? I had a thread on it a few months back, I had the same connector burning problem. I cut the connector in two and replaced the bad half of it with some push on connectors, no problem since.

    The X and Y driver connectors were both discolored, the Z driver was OK.

    edit: this is the thread, post #7 has pics
    Stepper driver connector

    My X axis became erratic today, upon checking the 5 pin connector on the driver, it is toast!
    I thought I saw a post on this in the past but I cant find it now, I would think Mouser or digikey would have one if I knew the ID number of the connectors involved. Anyone have any information on these?

    The connectors on both X and Y drivers are discolored, the two lower pins are the worst, they appear to be a bit small to carry the current required?

    Any insight on this would be much appreciated..........


    Last edited by popspipes; 11-07-2017 at 01:18 AM.
    mike sr


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    Default Tormach Driver Failure

    Countrysmith - Thanks for this wonderfully detailed and clear post.



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    Default Re: Tormach Driver Failure

    Mike,

    I had seen your post and it was a great help in understanding what was happening.

    The connector chosen by Leadshine is not the best for this situation. Requirements for the connector are high current capacity and a clean connection. An intermittent is disastrous both to the machine operation and to the Leadshine driver, as I found out.

    A better solution would be to replace the connector with the same type as on the controller board. The inconvenience of having to undo five screw terminals when changing out a driver is small compared to the potential damage from a faulty connection.

    My research into antioxidants brought up the fact that British Telecom has gone away from silicone grease because they found that it was creating intermittent contacts in their communications switches. The theory was that with light pressure contacts, the grease would create a thin dielectric film which would provide an insulating layer between the conductors. This was a case for make/break connections and some of the contacts that I have seen in telecom relays are very flimsy but it is a point to ponder.

    On the other hand, some of the conductive greases have metal powder in their formulation. Not a problem where you have screw contactss which are capable of displacing metal but for light pressure contacts could be a problem in high current situations.

    the third type of antioxidant compound is the petroleum based grease mentioned in the post. It or something similar has been used for a century for equipment like TV tuners with success but again, not high current situations. There is a similar product used with toggle switch contacts but I am not aware of its formulation.

    For now, I will use the silicone grease and be extremely wary of any potential problems.



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    Default Re: Tormach Driver Failure

    Country,

    I wanted to get rid of the corrosion as it makes a high resistance joint, I cleaned and soldered the wires on to the board connector, its just a bit of a jury rig fix but will conduct away the heat better I hope. I liked your detailed explanation of the problem and a proper fix, and to find out that the transistors and connectors are available.

    I check mine often now for any signs of burning on the Z driver as its still original. That connector in my opinion is really not up to the job.......

    mike sr


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    Default Re: Tormach Driver Failure

    Thanks for that RJ, a very useful and detailed write-up. The plugs on my axis drivers are starting to show signs of charring on pin five. I've ordered some replacement Phoenix plugs. I don't have the same electronics capabilities as yourself so it could have been an expensive driver replacement.

    Phil



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    Default Re: Tormach Driver Failure

    This post got me to thinking I should check the connections on the drivers. One of them (Z axis) was replaced about a year ago due to failure just like indicated here. What I found this morning is while I've caught it in time, the Z axis is again burning the connector. I'll dig through my stash of various plugs here and see what I can come up with for a solution - like some Anderson Power Poles because I know where a big box is from back in the RC days. Anyway, thanks for sharing. Had you not - I might not have looked and would be ordering/replacing a driver again.

    WW



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    Default Re: Tormach Driver Failure

    Quote Originally Posted by wildwhl View Post
    This post got me to thinking I should check the connections on the drivers. One of them (Z axis) was replaced about a year ago due to failure just like indicated here. What I found this morning is while I've caught it in time, the Z axis is again burning the connector. I'll dig through my stash of various plugs here and see what I can come up with for a solution - like some Anderson Power Poles because I know where a big box is from back in the RC days. Anyway, thanks for sharing. Had you not - I might not have looked and would be ordering/replacing a driver again.

    WW
    The problems I had was not only the female connector was mostly burned up but the male connector that is soldered to the board was corroded as well hence the fix that I chose. Replacing bothe male and female connectors would be the best fix......

    mike sr


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    Default Re: Tormach Driver Failure

    So, is the issue "arcing" because of bad connections, and then it burns through?



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    Default Re: Tormach Driver Failure

    Quote Originally Posted by syscore View Post
    So, is the issue "arcing" because of bad connections, and then it burns through?
    Yes, tha is what was happening here.


    Personal opinion is the connector is too light duty for the job, a bit of corrosion not enough spring tension, equals a recipe for failure.
    arcing will destroy the output transistors, they dont tolerate the voltage spikes produced by it.

    I caught mine early enough that no damage was done to the driver, I only had to repair the connector.

    mike sr


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    Default Re: Tormach Driver Failure

    Quote Originally Posted by popspipes View Post
    The problems I had was not only the female connector was mostly burned up but the male connector that is soldered to the board was corroded as well hence the fix that I chose. Replacing bothe male and female connectors would be the best fix......
    I ended up soldering a pig-tail to some anderson power poles. Soldered the machine end connectors too, thereby eliminating the Phoenix connector entirely.

    Turns out this was the Y axis...I just assumed it was the Z. When I looked back it was just February of this year that the Z failed. Looking closely at all of the stepper lead wires from the controllers, they've all been a bit hot before (the heatshrink label markers are discolored). It's definitely a weak point for sure. Someday I'd like to rebuild this enclosure and move the electronics cabinet entirely.

    WW

    Attached Thumbnails Attached Thumbnails Tormach Driver Failure-img_4322-jpg   Tormach Driver Failure-img_4318-jpg   Tormach Driver Failure-img_4319-jpg  


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    Default Re: Tormach Driver Failure

    Quote Originally Posted by wildwhl View Post
    I ended up soldering a pig-tail to some anderson power poles. Soldered the machine end connectors too, thereby eliminating the Phoenix connector entirely.

    Turns out this was the Y axis...I just assumed it was the Z. When I looked back it was just February of this year that the Z failed. Looking closely at all of the stepper lead wires from the controllers, they've all been a bit hot before (the heatshrink label markers are discolored). It's definitely a weak point for sure. Someday I'd like to rebuild this enclosure and move the electronics cabinet entirely.

    WW
    This seems to be the best permanent solution. I disassembled a scorched plug connector and examined the components under a microscope together with the board connector pin. I couldn't see any corrosion and definitely no arcing, the pin and spring connector were still bright and shiny all over. The plastic around the connector however was blacken and degraded. I think the over heating is due to electrical resistance, suggesting the connector is just not up to the job, so bypassing the connector altogether is probably a good idea.

    Phil



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    Default Re: Tormach Driver Failure

    I'll also add: I checked these connectors maybe 30 days ago, and they all looked good. I was not using dielectric grease (or at least I don't think I was - don't recall and do not see any evidence of such). They were all fine ~30 days ago.

    Thinking a bit about it this morning I realized I've had a few (maybe half dozen) y axis jams, when traveling towards the column and an excess of swarf or a hunk of metal had fallen back there, in the past few weeks. I wonder if this in any way contributed to the obvious burning of that connector...though...I doubt it. I'd guess the current spikes under that situation but heck, I dunno! I ALSO found one of the z axis wires (ferrule crimp that I installed) was less than ideal. Fixed that too. In fact, I think I will modify all the drivers this weekend as I have the Y just this morning.

    WW



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    Default Re: Tormach Driver Failure

    "I'd guess the current spikes under that situation but heck, I dunno!"

    The Tormach mills, lathes and some accessories use stepper motors rather than servos. A servo would draw more current during a stall because the position feedback would try to correct the position. However a stepper motor does not draw more current since it is open loop and the driving currents do not significantly change due to a stall.



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    Default Re: Tormach Driver Failure

    For those concerned about the reliability of the motor connection on the Leadshine driver, here is a direct wiring replacement for the plug in connector. Phoenix P/N 1935349; DigiKey no. 277-1595-ND, or Mouser no. 651-1935349. Access holes for the wires will have to be made in the plastic cover.

    I haven't made the conversion myself yet but plan on doing so with my next order to DigiKey.

    RJ



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    Default Re: Tormach Driver Failure

    I'd like to order some parts and be prepared for potential driver surgery in the near future. Would anyone happen to have a link or specific part number for the IR540's?

    WW



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    Default Re: Tormach Driver Failure

    Link: Google .... search: IR540 price.

    Phil



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    Default Re: Tormach Driver Failure

    Quote Originally Posted by philbur View Post
    Link: Google .... search: IR540 price.

    Phil
    Gee, thanks Phil. I just see there are a lot of options, and not knowledgeable enough to know which specifically I need.

    Is this one sufficient? https://www.digikey.com/product-deta...ZPBF-ND/666094

    WW



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    Default Re: Tormach Driver Failure

    Quote Originally Posted by wildwhl View Post
    Gee, thanks Phil. I just see there are a lot of options, and not knowledgeable enough to know which specifically I need.

    Is this one sufficient? https://www.digikey.com/product-deta...ZPBF-ND/666094

    WW
    The part is actually an IRF540. I ordered from DigiKey. Their p/n is IRF540PBF-ND The IRF540Z is made by International Rectifier and appears to have slightly better characteristics, lower on resistance, slightly higher current capability. both will work.

    Last edited by CountrySmith; 12-02-2017 at 02:03 PM.
    R J


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    Default Re: Tormach Driver Failure

    Quote Originally Posted by CountrySmith View Post
    The part is actually an IRF540. I ordered from Di9giKEY . Their p/n is IRF540PBF-ND The IRF540Z is made by International Rectifier and appears to have slightly better characteristics, lower on resistance, slightly higher current capability. both will work.
    Awesome, and thank you. Would have dug around in my expired driver and the internet a bit more - but I've been stuck at a BSA tree lot all day. Now home - time to make some chips!

    WW



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