Retrofitting a 1986 Maho MH400E

I respect his approach, he is much further along than I am. My thoughts to taking a different approach fall in four areas...

- I assume MAHO engineered everything very well. I assume they didn't just choose some Indramat and motors which fit, but designed the moments of inertia of the entire drive system, and ordered Indramat to build what they specifically needed. While the modern drives Stig using have very high speeds, they may result in lower stiffness in the system. Also, he is risking galling the ways, if he runs the machine for extended periods at those speeds.

- Dumping the gearbox for a 1.5kW belt drive is very limiting, as you said. Probably not an issue for aluminium, but these machines should be capable of so much more. I like your approach of combining the gearbox for torque, with a VFD on the spindle motor to allow spindle speed override and rigid tapping. I can see this being a future upgrade.

- In this video, you can see that Stig also gutted the control cabinet and replaced everything.

Given the quality of the big relays and electrical hardware MAHO used, and the nice layout of the 28A1 control relay board which is very easy to interface with, I didn't want to touch the main electrics. As an aircraft mechanic, "Never touch a working system" comes to mind. Seems like a lot of cost to redo something to get the same result. If you went into business retrofiting MAHO's for commercial use, you probably have to make some significant changes to the original electrical equipment, as they are probably not in in compliance with modern safety standards.

- Not using the glass scales. This might be tied in with the decision to use Mach3 which I don't think can support a closed loop system with glass scales, but it won't improve the machine by only closing the loop to drive encoders. I have the original Heidenhain test report for all three scales fitted, and none deviated more than a micron from it's indicated postion. Using MESA cards, interfacing with the Indramat and Heidenhain scales is trivial. I am hoping that getting them tuned in LinuxCNC is also trvial Watch this space.

I hadn't realised there is a fan mounted to the spindle. From Stig's video's it is plastic and has 12 blades.

You could install two optical sensors to read those blades passing, and use quadrature to give a 48 ppr spindle speed sensor. Not super accurate, but maybe enough for rigid tapping? If you ever want to implement an automatic tool changer, this should be enough for spindle positioning as well.

Hey guys,

I'm completely new here, but I read all your comments in this thread, and it is impressive how you work! You are doing exactly this, what I'm dreaming about! Maybe some day I'm also able to do a.retrofit on a Maho. I'm following your work, you already have a fan!
Looking forward to see your machines working, for sure they will do their jobs great!

greetings from Italy!

I installed that 204-264 jumper to replace the S3 Pendant E-Stop, and installed a switch to simulate the NC-Ready circuit between terminals 200-209.



The behavior is exactly as we discussed in this post.
forum.linuxcnc.org/12-milling/33035-retr...00e?start=150#100478

This works fine.
Mark

Bernd wrote: Hey guys,
Looking forward to see your machines working,

Hi Bernd, that makes three of us that are looking forward to getting our machines working
Mark

Hi guys, Bernd welcome to the club.
Good news with the test. This weekend I will check the estop and others circuits to detect any modification from the previous owner. I have found the perfect spot for spindle encoder if the encoder at the motor won’t work for rigid taping. I will put a pulley in there


And I will drive another pulley above with timing belt. This way i can use it for the horizontal spindle too