Retrofitting a 1986 Maho MH400E

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18 Oct 2017 20:06 #100529 by drimaropoylos
I now understand what the 7S1 switch is doing. When one terminal switch on an axis is triggered, the machine is disabled and the indramat can’t move the axis, but the L1 and L2 going into the Indramat with the 1.5mm² wires, gives the necessary power for the brake to release when the 7S1 is energized manually.

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19 Oct 2017 06:11 - 19 Oct 2017 07:20 #100536 by RotarySMP

you probably have removed the maho pendant, and the estop on it is not closing the circuit to activate the K1. So the circuit for 7K1, 7K2, 7K3 can’t activate.
John


Thanks. Good call. I should have caught that, since I only just pulled that 19X5 terminal block a couple of days ago. Mine had no pendant, but that jumper was on the terminal block. Looks like I need a jumper between terminals 204 and 264 until I build a pendant.



Thanks also for the explanation of the 7S1 brake release circuit.
Mark
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Last edit: 19 Oct 2017 07:20 by RotarySMP.

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19 Oct 2017 08:04 - 19 Oct 2017 08:06 #100539 by RotarySMP
John, have you been following Stig's MH 400E conversion to Mach3? Very different approach in that he ripped everything out, and is not using the gearbox at all.

www.youtube.com/user/StigOveRuud/videos
Mark
Last edit: 19 Oct 2017 08:06 by RotarySMP.

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19 Oct 2017 08:57 #100541 by drimaropoylos
I have seen the video, I have even made comment on the video

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19 Oct 2017 09:07 #100542 by drimaropoylos
This approach makes sense if he is going to only mill aluminum with small cutters, and he don’t need the horizontal spindle. The spindle is rated at 1.5Kw, but this is what a true 1.5Kw spindle servo drive looks like.

www.aliexpress.com/item/Economical-1-5kw...arch0204.8.69.s9AoJl

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19 Oct 2017 09:24 #100543 by drimaropoylos
This is one way to fit an encoder in the spindle.
John

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19 Oct 2017 09:28 #100545 by drimaropoylos
Or even better mounted on top of the spindle fan, so I can keep the quill too

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19 Oct 2017 09:45 #100546 by drimaropoylos
He has made a really nice control panel.
John

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19 Oct 2017 14:13 - 19 Oct 2017 19:33 #100554 by RotarySMP
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.
Last edit: 19 Oct 2017 19:33 by RotarySMP.

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19 Oct 2017 14:22 - 19 Oct 2017 14:25 #100555 by RotarySMP
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.
Last edit: 19 Oct 2017 14:25 by RotarySMP.

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