LPKF ProtoMat S42: removing Z-axis assembly with spindle motor

At the end of June 2010 the collet was not holding in drill bits or mill tips. The initial suspicion was that there was dirt in the collet. After clearning with a very small (dental) brush - one of the 0.370mm drill bits would hold, but not tighly. Milling bits were not held at all.

Initially it appeared that the whole machine (43 kg) would have to be shipped back for repair. However, the local distributor Solectro AB called on Friday 9 July to say that we could simply remove the Z-axis head and ship that to them for repair. So that afternoon I started to remove the acoustic cover to get to the milling head. On Monday I got a note from Sven Ems at the LPKF factory with a nice guide to removing the motor assembly block. This document is called "Exchanging the milling spindle of the ProtoMat S 42" dated 2 July 2008. It had the file name "PM_S42_Exchange-milling spindle - both versions-e.pdf"

This page attempts to describes what I did, but only for informational purposes. It is only for use by those knowledgable in such repairs. Many of the pictures were taken out of order, but the description is hopefully clear.

I used a parts box with bins to place the various screws and other parts in as I removed them. Each bin was assigned a number of the for Bn, where n is an integer.

  1. The zeroth step was to turn off the power and disconnect the power cable from the ProtoMat S42.
  2. Remove the 8 Torx T20 flat head screws from each of the left and right plastic parts of the acoustic cover. Place these screws in bin B1.
  3. Remove vacuum hose - lifting up the hose from the metal tube at the milling head.
  4. Remove 3 Torx T20 screws from the top of the back cover. Place these screws in bin B2.
  5. Remove 2 Torx T20 screws and lock washers from each side of the bottom vertical brackets holding up the plexiglass & metal top. Place these screws in bin B3. Remove the plexiglass & metal top.
  6. Remove 3 flat head Torx T20 screws from ach side of the plastic covers of the machine. Place these screws in bin B4.
  7. Loosen top metal T25 screws - that act as a hinge for the top metal cover of the ProtoMat. Remove black plastic push pins from this top cover. Rotate cover back this reveals the cables that run to the Z-axis head. Place these screws in bin B5. See figure belows side
  view of machine with cover removedview from above after removing the two push pins
  8. Remove the metal cover over the circuit board for the Z-axis. See two Torx T10 screws in the figure below. Note that you also have to remove the two screws on the front side (as seen facing the head) - to get the cover to release cleanly - note that these screws simply hold the cover together. In the figure these have been replaced into where they were screwed into (beneath the cover) {so as not to loose the screws). Note that there is a slot along the top of this cover for the black ribbon cable and black round power cable to the LED. View of milling head, showing location
  of the screws that hold the cover on the small circuit board
  9. Remove the two Philips screws undered the black ribbon cable - to separate the cable chain from the Z-axis head. See figure below. Location of screws attaching the cable chain
  10. Remove the ground cables from the ground connection on the top of the Z-axis controller board using a T10 screw driver. Note that from the screw head coming inward there are two washers, then the lug for the round green ground cable, then another washer, then the lug for the grounding strap. See figures below. view showing grounding cables
  connected to the circuit boardGrounding point on the circuit board
  11. Remove the two Torx T10 screws holding the heat sink into place. See figure below. Location of screws holding the
  headsink to motor assembly
  12. Remove the cables from the Z-axis controller board.closeup view of the incoming control cable closeup of cable connection to the motor
    Note notch on top of motor connector cable. See figure below. very tight closeup of notch in the
connectors for the motor cable
  13. Remove collet lever. See figures below. (Note this picture was taken before the removal of the heat sink.) Collet leverend view of collect lever.
  14. Remove the three T20 fixing head bolts from deep in the block of the Z-axis milling head. See figure below. Place these screws in bin B6. (Note that this picture was taken before removal of the collet lever.)
    Z-axis mount after the heatsink is removed
  15. Z-axis mount after removal of motor and controller assembly.
    View of Z-axis mount after removal of
the motor and controller assembly
  16. Remove the Torx T10 screws holding circuit board fixture to block. Carefully slide the motor cable out of the slot. Place these screws in bin B7.
  17. Remove circuit fixture (taking care not to get thermal paste on your hands). The block will look similar to the figure below.
    view of motor assembly after removal of
  circuit board
  18. View of the back of the circuit board fixture.
    back of circuit board - showing thermal
  19. Remove T20 screws that attach the depth limiter to the milling head. See figure for the shapes of these two different small blocks. Note that the bottom one can easily be reached from below. But getting to the top one requires removing the controller board! Place the lower depth limiter block in bin B8 and the upper depth limiter block in bin B9.
    View of the two depth limiter mounting blocks
  20. View of where the top depth limiter attachment is connected.
    close up of depth limiter after the top
  attachment block is removed
  21. The removed motor assembly. See two views below.
    view of motor assebly from spindle point
of viewview of motor assembly from the side
  22. The depth limiter by itself. Note that the wire is soldered to the LED, this limits the ability to work with it attached to the motor assembly. Note that the wire is still connected to the light in the depth limiter. Be careful not to break this wire.
    view of the depth limit by

On Tuesday 10 August 2010 the replacement motor mounted in its mounting block arrived, and was installed on Wednesday 11 August 2010.

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Latest update 23 August 2010, small fix 22 January 2015
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