Gallery, Projects and General > How do I??

Relay timing - MAHO MH400E - gearbox control

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hanermo:
Everything electrical has delays, spikes and sparks related to voltage, current and coils in the circuit.

Some old stuff was very costly, very well made, and can resist some forms of abuse for a long time, or forever.
Most older expensive high end electrical stuff for milling machines was like that, at that time.

I would think the Maho relays are similar to that.
Overbuilt, robust, etc.
But they were almost certainly not expecting to be switched at 1 ms intervals or less via modern sw.

Since itīs a gearbox and the usage is likely to be very sporadic and sparse ..
I would very much prefer a robust enforced delay of some kind.

There could be inductive kicks, emf driven spikes, whatever, otherwise.
E.
My servo drives live and work for quite a long time on power-out, about 1 second as a tlar.
I think due to emf and caps and servo motor coils.

My wag is about 0.5 secs delay would be a good start.
Comparing it to VFDs and other std power electronics.

My servo drives can do 20 ms stops at 7.5 kW / 3 secs (300%) + whatever they dump (I suspect over 20 kW momentarily) but they are specifically built for that and I think they dump into the grid.

If you are going to switch fwd/reverse, fast, I would suggest some caution.
The spindle motor + hw has huge power and momentum.

I used to sell Haas machines.
The acceleration took about 30 kW to get to top speed, in 1-2 secs.
Cutting took mostly 3 kW or so.

I think that running a machine at speed, and reversing it electrically, fast, will blow the relays in a colourful way.
And probably all sorts of other stuff.

My servo spindle refit 2.5 kW has about 30 kW sustained power belts, and the mounts are over 50 kg in mass.
My WAG is that stops are over 20 kW in peak power.

RotarySMP:
Thanks for the inputs. It was not the 1.5kW main spindle motor I was talking about sequencing, but just the little 24V 0.8A gearbox shifter motors.

We decided to implement 200ms delay between energising relays. It seems to work really well:



Mark

hanermo:
Nicely done !

RotarySMP:
Thanks. Now I am troubleshooting two Heidenhain LS-403 linear encoders with are making trouble.
Mark

RotarySMP:
Turns out the Y axis linear encoder was fine. The PSU I added to power the Mesa 7i77 and the encoders was only set at 4.7V, whereas the Heidenhain manual specifies 5V +/-5%. Turned up to 5.1V it is stable.

The Z encoder was also okay. It was the third channel of the EX which is dead. I just bought a single channel 602D EXE off ebay and installed that. Now it works fine.

Today I made the first chips.


there is still a fair bit of work to finish wiring up all the buttons and functions of the user interface panel. The bellows covers on X are scrap, so they will need to be replaced before the enclosure goes back on. As it is it flings chips everywhere, so I don't want to use it too much before that enclosure is on there.
Mark

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