Heidenhain TNC355, question regarding PLC program
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  1. #1
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    Default Heidenhain TNC355, question regarding PLC program

    I have a Micron WF41 cnc mill with said TNC355 control and would like to have a look at the PLC program to make couple modifications regarding tool changer operation (disable it, and all related error messages with it), and the mill came with a full enclosure which was damaged and discarded, so there are few other door position check and locking routines I would like to edit.

    I have experience of using the TNC155 and 355 and doing some troubleshooting, but not with the PLC program itself, and studying the service manual regarding programming the PLC doesn't really get me anywhere - what I wanted to do is to view/edit/export the current PLC program stored in the eprom, but all I see is NOP in every line when doing the following:
    Turn on the machine:
    - it goes to axis reference screen
    - I cannot currently reference the axis because of few error messages related to (supposedly) hydraulics, enclosure door switches and tool changer arm positioning
    - I then press the MOD, "up button" to enter code:951026, I can access the input/output/marker etc screens, everything seems fine so far, but when I press the "edit" button (used normally for NC program editing), it goes into PLC edit screen, but as I said all I see is NOP in every line, which makes me think that I'm looking at the memory where PLC might be stored, but it isn't loaded from the EPROM into RAM.

    Changing parameter 77 to run the PLC program from RAM yields same results - NOP in every line, a blank PLC program essentially.

    I have electric wiring diagrams for this machine, but there seems to be something missing there, I can bypass the door check error messages by bridging inputs in the control cabinet, but the hydraulics message and tool changer arm messages give little clues as to what is the issue, there are 2 hydraulic circuits in the machine, one for tool retention (wired and operational) and the other, completely separate and not connected at the moment, is for tool changer arm operation, so viewing the PLC program might give me some clues as to what the control seems to be complaining about (in French...).

    In the end I would be fine with running the PLC program from RAM, since it looks from the manual that is quite easy to export/import it if the need arises, but I'd like to view/edit the original program and not recreate it from scratch.

    Any suggestions regarding how to view the PLC program on the control?

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    Been a while but I think you can first transfer it to the eprom. You cannot edit the plc as it is. So look for that command to transfer the program. Been 20 years since I played with it.

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    turns out that reading the manual very carefully helps sometimes, who would have thunk!

    a little bit further after the "For editing purposes, a program can be copied from EPROM into RAM", they did mention that after switching to editing screen (after code:951026, followed by "edit program" button), where I saw all those NOP lines (empty RAM), you have to press "Qdef" button, which in this mode means "copy", a message in German appeared on the screen that translates to "Do you want to copy from EPROM?", pressed "ENT" and there it is, my precious PLC program I can now study and try to edit

    so now, if I were to change the MP 77 from default "1" meaning - run program from EPROM to "0" - run program from RAM, I can edit/run/test my modified PLC program

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    AS I recall, the PLC can be 'dense'

    Inputs and outputs need to be defined, so I ended up finding where the definition for a particular input was then searching for it to see where it came up in the program. It can be tedious, especially if not in your first language!

    I would be kind of surprised if some of these issue could not be resolved via the parameters. I would look for and think about any toolchanger related parameters.

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    I was hoping that I could disable those features in machine parameters, but unfortunately there is nothing even regarding automatic/manual tool changes, just number of tools stored in memory, and changing that to zero does nothing to circumvent the tool changer error checking logic

    I have a reasonably well understanding of hardware logic circuits, so it is not all chinese to me, the one problem I do see now is that the program doesn't contain the error messages in French I'm seeing on the screen, but I think I'll make a list of suspect markers for them, and then create a new empty test program in RAM, something simple, like a push button would activate that suspected marker to display the error message, then just map them out and cross check the OEM program when that message is used to see what input states generate it, time consuming, but apart from bothering Heidenhain asking for decompiled contents of those custom EPROMS, which I suspect they won't share anyway, this is the only way to understand what is going on in there

    I taught myself to program Basic when I was just a kid, then some Pascal, C, Java etc., this will be just another language to learn, I just wish there was an extra day in the week, or couple for this

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    Native language ought to be German, I wonder if you can get those errors to display in a language more useful to you

    I think there have to be parameters related to the toolchanger, starting with what it does at startup, is it an axis? Look for verious feed definitions for a 4th axis you do not have. If it is, disabling it 'might' turn off some of the error messages.
    For instance I was troublshooting a wonky Y axis and disabled it for referencing etc allowing me to look at other things without an error shutting the machine down

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    I get messages in English, German and French on it, even though the language in parameters is set to English

    From reading the installation manual, it did mention that OEM upon completing the PLC program can send it Heidenhain to be compiled and written to EPROM, and that it may include custom event messages as well, that is why, I think, I get French on top of German and English messages.

    I actually got Heidenhain to sell me an English TNC language EPROM (not PLC) for the TNC155 I have on a Fehlmann, the machine came from Switzerland with French language as well, and about 80% of messages are now in English, some are still in German, and machine specific error messages are, just like with the Mikron, in French. Heidenhain sent only 1 replacement EPROM then.

    Good point about the 4th axis, it is defined in machine parameters, but I thought someone had simply ripped it out when the machine went for sale, because the documentation I got from Mikron for this specific machine (they asked for model numbers and serial number) did include 4th axis in the parts list, it was defined in control as "C" though. Will need to keep that in mind if I find a lot of "weird" references to it in the PLC program, thanks.

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    so I mapped the error messages in French to 4 of the possible custom error messages useable by the machine builder, they are markers #2955, #2980, #2925 and #2933, the problem is that when I do a search in the PLC program, only one of those marker numbers comes up, the one related to tool arm position, no clue as to how/why the other 3 are being set/activated yet, back to studying the plc programming manual

    edit: there are 2 memory blocks for PLC program, 0-2047 and 2048-3071, and after setting MP77 to 2, to load both regions into RAM to edit and export, found my "missing" error message markers in the portion of the program that was in the 2048-3071 region
    Last edited by jz79; 02-27-2020 at 02:36 AM.

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    so after a lot of poking the control cabinet with a tester, because some input states were not changing regardless if you put 24V on it or pull it to ground, found a bad 74HC14 chip on the processor board of the control, also a resistor network that pulls 8 inputs to ground was shot and "leaking" a 24V from one input to few others, after replacing those some error messages went away, but to avoid having to edit the PLC program and run it from RAM, had to also pull up X6/12 (input #87, named "release magazine", without this the "feed release" wouldn't engage) and X5/2 (input #85, "swiveling arm spindle side", it just complains that tool changer is not in the right place)

    after these repairs and then fixing the +15 supply rail on the Bosch TR15 feed drive 038035 power supply board (failed LM340-15 regulator) I could finally get the machine to reference

    couple more issues still remain, the electric gear changing to select spindle speeds seems to work but the feedback back to control is failing, and can only job Z/Y axis to one direction, control shows "Limit Y-" or "Limit Z-" when trying the other direction, limit switches themselves seem fine, so might be another bad chip on the processor board, and the control won't stay in the "handwheel" mode, jumps back to "manual" mode instantly, other modes seem to work fine

    weird to see this many seemingly unrelated problems on one machine, when any one of them would make it unusable basically


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