LPKF Protomat S42: Machine "shock absorber"/"stroke limiter" tuning

[rsaxvc]

I've bought a Protomat S42 from a college that changed their curriculum. The machine configuration disk was long ago lost. I've been able to reinitialize the machine to learn its limits and approximate a new home position, I can warm up the spindle and drill holes. It's time to create a "New Reference Hole System", and I'm working through those steps in the manual, but when I go to drill the hole using the 2.95mm reference bit, it just barely doesn't touch the reference strips.

It seems the component known as the "shock absorber" or "stroke limiter" is preventing the drill bit from drilling deeper than roughly the height of the aluminum bed / reference strips. Preventing drilling into the machine bed, sounds like a great idea, but I bet I've got to disable that safety while drilling the reference holes. I've attached an image showing the rough location of the limiter and a diagram of the right-side of the head where it is located. I was hoping you could help me with any of the following questions:

• Is the shock-absorber's purpose to prevent crashing the drill into the machine?
• Is there a way to temporarly bypass it, without affecting the height it is set to?
• If I need to adjust for reference hole drilling, how do I set the appropriate height so the holes are a good depth?
• If I need to adjust for reference hole drilling, what is the right height for resetting it afterwards, and how do I do so?

[DiodeDipShit]

The bumpers are there to prevent shock to the drive motors in case of over limit travel.  The machine should never get to close the the bumpers. It seems that Your tool bit may be the wrong length. Try holding the a tool slightly further out of the collet/holder then tighten. Be cautious as You could drive right through Your work and into the table. Make sure the 'Z' start is above Your work and the 'z' feed is reasonable, 5-10 inches per minute.  Protomat may have proprietary bits and You are coming up short. Contact them for new tooling or look in McMaster-Carr for equivalent length carbide bits and adjust Your 'Z' depth accordingly in the program. The machine should never get to close the the bumpers. There are parameters in the bios that set travel limits. These are hard to find in the general program. If in doubt, read the Program manual thoroughly. Then read it again. Also second hand generic software is OK, but can leave out many options.
This is the link for the software for the machine: https://app.lpkfusa.com/products/pcb_prototyping/software/circuitpro_pm/

[rsaxvc]

> It seems that Your tool bit may be the wrong length.

That is such a a better explanation! I think I was thrown off because my machine came with a 2.95mm bit, but perhaps it is not "the" 2.95mm reference bit, which could long enough to drill into the reference strips without undoing the Z stage stroke limiter.

Say, is there any chance you would mind dimensioning an LPKF "special drill for reference drilling" bit if you've got one? I couldn't find it in LPKF's catalog.

> Adjust Your 'Z' depth accordingly in the program.
> This is the link for the software for the machine.

I believe S42 was of the last to be used with the older Boardmaster software I have, and even has manual Z stage adjustment via a large screw that adjusts the bit relative to a plastic foot, and no software Z controls other than down-time.

Thank you for your help with this.

[DiodeDipShit]

This seems to be the bit You are using, it is 36 mm long:   https://app.lpkfusa.com/Store/pages/ProductDetail.aspx?cat=11%2f39&cid=39&pid=221
LPKF offers slightly longer endmills that are 38mm in length, but not 2.95 in diameter.
Here is an alternative source with many 38mm lengths to choose from:  https://www.mcmaster.com/products/end-mills/system-of-measurement~metric/mill-diameter~3-mm/
This particular choice will not let You down, it may outlast 10 standard carbide bits, it is about a third way down the above link:
Diamondlike Carbon (DLC) Coated
4 Flute
3mm   3mm   15mm   38mm   Equal   33°   Carbon Fiber, Fiberglass, Graphite   Center Cutting   Part # 4119A815   $33.60

[rsaxvc]

I'm afraid I may not have explained my challenge accurately enough. I'm trying to drill reference holes in the plastic strips the non-camera S42 uses for PCB registration. Once I'm able to do so, I should be able to install a pair of reference pins in the strips, then fit PCB with corresponding holds over the pins, mill one side of a PCB, flip it, and mill the other, then drill and slip a bit of wire through, solder on both ends.

The bit for drilling the reference specified in the manual and software, as a 2.95mm drilling bit I couldn't find on LPKF's website. My machine came with two 38mm 2.95mm drill bits, but they're short enough that the Z-stroke-limiter just barely prevents contact with the bed or reference strips.

You've got me thinking that a longer 2.95mm drill bit is probably what the machine originally came with from LPKF, and I'd like to replace it, but I'd need to know the length required for the right depth. Too shallow and the pins are likely to loosen prematurely, too deep and it might drill fully through the reference strip into the aluminum bed.

I've attached a photo of my machine that I hope shows this better.

[rsaxvc]

I think I found it! Stashed away in a different bit-box, there was one unmarked drill bit with a pink ring around it, 43mm long, 2.95mm diameter. The reference strips are 4.5mm thick, the reference strip slot is 5mm deep past the bed surface, so if a 38mm bit is almost touching the bed, a 43mm bit would leave at least .5mm clearance from the bottom of the slot, without adjusting the Z-stage-limiter. I've also found a short piece of old reference strip with a hole in it! What a find! A short bit of plastic! But the hole in there is ~3.4mm deep, and when I drilled with the 43mm bit, I got a ~3.3mm deep hole that matches the reference pin well. I think I'm all set. Thanks!

[DiodeDipShit]

Hi RSAXVC, I am glad You rectified the situation. Sorry I wasn't able to interpret some of Your details. I was about to suggest putting a spacer board or shim stock underneath Your work. It is a good idea to do so when working so close to the table in case Your tool slips out of the holder. Shims will also add a degree of safety while You are getting used to the machine.
https://www.mcmaster.com/products/shim-packs/color-coded-shim-stock-sets/