Fehlmann Picomax 51 CNC 2, reference info, pictures - Page 2
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  1. #21
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    It think it triggers several seconds after the drive is energized.

    When I power up the machine with the main switch it does the following:

    -"Speichertest" (Memory Test) This takes some 10 seconds
    - After that I press the CE switch and hear that the drive is energized (some big relays switching). Approx 3 seconds after that, the RCD is triggering and cuts all power.

    Only solution I have upto now is temporary: Disconnet PE of the machine and connect trough a resistor to limit the error current through PE. Whith that everythin works fine.
    But that cannot be the solution, as this also lowers the protection of the PE wire.

    If I let the drive energize with PE disconnected, and wait 10 seconds and then reconnect PE, the RCD still triggers after 2 seconds. So it does not seem to be an inrush current problem.
    I get arround 40mA of current through PE, which is enough to trigger the RCD.

  2. #22
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    This is interesting, now I'm tempted to put ammeter on the PE wire of my machine

    I will not claim that this is how it should be on all of these machines, because it may vary depending on the PLC program, but on my machine, after power up:
    A) it does the memory test
    B) then I need to press the CE, just like you do
    C) then it powers up X/Y axis servo drives (the spindle drive is NOT powered at this time)
    D) then TNC wants the X/Y reference to be done
    E) then it goes into manual mode (hand icon)
    the spindle drive is still not powered on my machine at this point (all the leds on the drive are dark), I must do it manually with the M3 button on the console (this is when the leds light up on the Stromag drive), or it can be done in program execution modes via code

    so if your machine is acting like mine, and RCD is tripping as after C step, then I'd start the investigation with the X/Y servo drives, because the main drive is not even turned on at the moment, all the current draw (apart from powering the TNC itself), should be related to holding position of X/Y axis via servo motors (there are no brakes on these servos)

    unfortunately Fehlmann didn't include any electric schematics of the machine when they emailed me the PDFs and machine parameters, so I doubt I will be more of help to you at this time, I hadn't have any problems with X/Y servos, didn't even do the tachogenerator maintenance on them yet (which I should...)

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    Hi!

    I stand corrected!

    You are very right, as the RCD tripps probably not because of the spindle drive, but has something todo with the x/y servo drives.
    I checked again the sequence, and the it is identical on my machine, as you have described it.

    RCD tripps shortly after step C.

    I will focus my investigation on the servo drives then.

    I assume I cant just disconnect the servo drives and or the servos, without producing an error, which does prevents the drive from being energised...?

    I wish a good day.

    I think I will buy the the documentation stuff from Fehlmann. Could save me some time..

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    Just want to let you guys know, what I found out:

    These (old) types of X/Y Axis drives and also the Spindle drive produce residual currents, flowing back to the source through the PE conductor.
    This is due to capacitve coupling and the design of the drive filter stages. This is completely normal behaviour for such a machine.

    I measured an RMS current through PE is 18mA when the drive is in powered steady state.
    When X/Y or spindle drive is powered up, current spikes up to 50mA can occur, which is also normal. This will trip an RCD device.

    The solution for this is easy: Don't use an RCD device in your elecrical panel

    Unfortunately where I live, these RCDs are mandatory for all outlets. The only way is, to have the machine directly connected to the breaker, without a plug.
    This allow to have no RCD. This is what I finally did and the machine is working great, so far!

    Thanks alot!

    I now have the full manual of the machine, the servo drive and also the electrical schematic of the cabinet. If somebody needs it, let me know.

    Back to the machine:

    I read you did some measurments on the spindle runout?
    My spindle has a runout of arround 0.012mm (directly in the taper), which is out if spec. But i dont thik that this will be a problem for me.

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    TIR on the bottom part of the spindle taper on my machine was about 0.003mm

    0.015 sounds like a good reason to remove the spindle and at least get a hand feel of how it rotates, before it deteriorates more

    I was planing on doing preventative maintenance on mine, clean, new grease etc, but I don't have detailed enough drawings of the quill to figure out how to proceed with taking it apart, and since mine sounds and works well, I just don't want to go in there just yet

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    Ok, thanks for the info.

    Did you use a testbar to check the true TIR?

    I think I dont trust myself to dismantle the spindle, just yet..

    How much TIR do you have, when a tool is inserted, on the toolholder?

    FYI:
    Fehlmann offered to make a spindle service for 4k CHF.

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    I don't have a SF32 test bar, I indicated on the spindle taper directly

    regarding TIR with tools, I mostly use ER25 collet holders, and tap in the nut on each tool to get it under 0,01mm, the only holder I have that could be indicated is the face mill holder, but not much point measuring that

    there are probably ultra precision bearings in that spindle, which is 1.5-2+k for the set at least, so that 4k isn't totally unreasonable Chiron asked a little more than that just for a set of 2 1m long 45mm linear guides with carriages

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    Hi!

    I also thought this is quite reasonable.

    BTW: A question on how to best use the machine, when milling:

    As the Z-Axis is not controlled automatically by the controller, how do write programms for this?
    I mean, for example,if you want to mill a piece out of thick material and you need multiple passes.
    So you would programm the outline of the piece, manually adjust the Z-Depth, then let the programm run, then re-adjust the Z-Height and so on, till the piece is milled out.

    Are you doing it also like this? Or is there a better way?

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    I have only used it to mill plastic and aluminum, and when milling aluminum, I use al specific ZcN coated 3fl end mills, 10mm (22mm cut length), and I've programmed adaptive toolpaths with ~1.2mm step over with 0.05-0.08mm chip load at around 7k rpm, and with these parameters I could cut up to 20mm deep in one pass (6082 aluminum), it sounded good, no vibration, no squeeling, there is deflection of course, which results in some roughness on the bottom face, but finishing pass to final depth takes care of that

    so to apply this strategy I would drill a hole to nearly bottom of the pocket (or through, if the part allows), and then in the milling program just go to the drill hole location, manually lower to the full depth and mill it out in one pass, then finish pass at final depth if needed

    one note regarding built in cycles for rectangular and round pockets, formula for step over is k=K*R (R=tool radius, K=machine parameter 176), individual cycle definitions do not include that parameter, and factory default MP176 was 0.5 on my machine, which would work for plastics, but not so much for aluminum, I reduced it to 0.1, which again allows me to use those cycles at full depth, and probably, with some tweaking, could be used for manual helical ramping if you can't or don't want to use predrilled holes like I described earlier

    you could also use column M codes to drop into a predrilled hole (the manual column height button on the lower control panel must not be lit for this to work automatically, else you will need to press START for each column height adjustment in the program), one of the column stops has a fine adjustment, I haven't used that yet, but I have a part to make soon where I may try it out

    then there is the rotating quill stop to the left of the spindle which could be used to quickly set Z depth, and the central height stop with vernier scale for some finer control

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    Used your technique (drop into hole with the column) with great success.

    I read thaty ou have connected your machine to your PC.

    How did you set it up? Are you drip feeding it or sending the whole programe?

    Where did you find the Pinning? And COM settings?

    Cheers

  11. #31
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    I had problems setting up serial connection between the TNC and PC, I wrote about it earlier, serial signal level from the TNC wasn't full +12 for a "1", it was at +2~3V range, on top of that, default machine parameters had zeroes in where the settings for serial port should be, which led me into thinking that perhaps the serial connection was a payed option which my machine didn't have, I don't know

    I put together a very crude amplifier from an ATX power supply (+/-12V source) and an opamp to boost the low voltage up to the required +12, which together with the required machine parameters allowed me to use Heidenhains TNCremo server to upload/download programs, drip feed also worked, but I had some weird problems with couple programs where the program wouldn't work in drip feed mode (TNC would complain about error in line xx), but would upload and execute normally from the machines memory, might have been something to do with the post processor I edited and used with F360, hadn't have time to debug it fully

    I don't have the notes with me right now, I'll post the exact MPs for serial settings on the TNC and on the PC side in the evening, when I'll get back home

    here is a pic of port settings on the PC side:
    capture.jpg

    on the TNC:
    MP 71: 515
    MP 218: 17736
    MP 219: 16712
    MP 220: 279
    MP 221: 5382
    MP 222: 168
    MP 223: 1
    MP 224: 4

    cable diagrams can be found here:
    https://product.heidenhain.de/JPBC/i...56-02-A-02.pdf
    Attached Thumbnails Attached Thumbnails capture.jpg  
    Last edited by jz79; 11-26-2019 at 03:42 PM.

  12. #32
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    So the bad news - Stromag CHA 055.2 spindle motor drive failed on my machine couple weeks ago, sparks, smoke etc.

    Good news - after about 30 hours spent reverse engineering it, I managed to repair it and it seems to work fine now.

    It is a 3 phase 12 thyristor (for active braking and instant reverse) rectifier unit that also powers the DC field winding on the motor, and this DC field winding is powered from a transformer that takes 2 phases on the primary to power field DC generation portion of the drive, and somehow arcing happened from the primary winding to couple PCB tracks under said transformer, nearly all ICs were shot, all power rails damaged. Getting the +/-15V and +12V rails working was pretty straight forward, 7815, 7812 and 7915 regulators had to be replaced with few burnt resistors. The logic board, with all new opamps (RC4136) and few logics (4013/4016/4081/4078/4093) would still error out and not work, TNC kept complaining as well. Zero information about these drives on the interwebs as far as I could find, so had to reverse engineer that logic board to understand what was going on, at the end it turned out that one of the new 4093 ICs was bad, internal short when powered up, as a result it wanted to make the drive power up in both directions, which would mean all 12 thyristors open at the same, which would mean lots of sparks and smoke, and there was even couple leds saying it wanted to do that, marked very clearly as "I" and "II"... anyway, that 4093 got replaced and all works fine now.

    The "problem" with these drives is that they can be customized, the logic board I mean, so one simply can't by a "CHA 055.2" from another machine, plug it in and expect it to work, and on top of that, the ones advertised for sale, listed as - used, working, had missing components on them clearly visible in photos... this is what pushed me to put in the work to get mine back in order.

    this is what the "clean" draft ended up looking like for the logic board:
    20191228_225142.jpg

    I made both the board and schematic drawings public (I used EasyEDA for this), logic board pcb drawing is basically complete, important nets grouped and marked and is probably 99% true, no values for caps or resistors, bottom board schematic is done for only about half of it, same thing with power board pcb, it is about 70% complete and about the same schematic wise, use at your own risk!

    link to EasyEDA cloud storage of the project files

  13. #33
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    Have either of you Picomax owners contemplated installing new spindle bearings ? My P50 is very quiet at the slower motor speeds but at high speed I think it is noisier than it would have been when new. I haven't yet glanced at the parts drawings yet but just wondering if removing the quill spindle is as easy as loosening a max travel quill stop and lowering it all the way ?

  14. #34
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    I was considering doing preventive maintenance on the spindle, but I keep putting that off partly because I have no drawings for it, and mine is producing quite a good finish both on facing and side milling, I simply don't have a good enough reason to take it apart yet, I even tried to undo bolts on the manual quill shaft cover on the right hand side, that looked like the only way in, but they seemed to have been permanently locktited in and I just gave up on it for now.

    I wrote previously that I observed some weird noises that started at around 2,5k rpm and seemed to go away at higher rpm, but those noises are gone now since I fixed the tachogenerator on the spindle motor, overall noise wise it seems ok till about 7,5k rpm, past that it seems to get progressively louder quickly, so I'm just staying under 7k for now.

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    while I was digging inside the control cabinet, decided to look into the TNC to see what the problem with the TX signal was, the low amplitude I mentioned previously (-12V to +3V only, when it should be -12V to +12V), traced the TX wire to the 2nd board inside the TNC and there the culprit was - SN75188 chip, a line driver, TTL to RS232 converter basically, and it shouldn't be putting out a -12V>+3V, replaced it with a MC1488 and problem solved, now it's back to spec

    while I was at it, decided to replace the DB25 connector at the control cabinet side with a DB9 one, so the null modem cable could be omitted as well and the laptops usb to rs232 adapter could be plugged directly into the cabinet making things tidier, tnc to db9 pinout as in the pic below, taken from the heidenhain interface manual pdf

    20200102.jpg20200103.jpgtnc-db9.jpg


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