Retrofitting a 1986 Maho MH400E

I read about your gearbox HAL Code in this thread,
forum.linuxcnc.org/38-general-linuxcnc-q...ntrol?start=10#81876
I wasn't really sure how relevant it would be to my case. Yes you are right about need to auto select the appropriate gearbox ratio when an M3 or M4 command is issued.

The MAHO 400E spindle drive system is rather complex.

The 18 speed gearbox...


has three shifters, each positioned by a reversing geared 24VDC motor.


A total of 8 relays are involved in actuating the shifter motors...


with feedback to the controller through 12 micro switches activated by cams mounted on each of the shifters.


If that wasn't enough, there are also relays to twitch the main spindle motor CW and CCW during gear shift, so the gearbox doesn't bind (shown in the second to last diagram above)

And finally to ensure utter complexity, the 2.2kW 3 phase drive motor is reversable, has Star/Delta switching for no-overload starting, and a motor brake for good measure. Here is the power circuit...


My plan is to leave the power circuit untouched. The control electrics will also be controlled by the existing MAHO relay board. So the hardware interface is simply connecting all the existing I/O pins to a 7i84.

The hard part for me is I don't really know where to start with the LinuxCNC control of this gearbox. Tying MESA 7i84 to HAL Pins seems straight forward enough, but is it better to use the Classis ladder to build up the control logic, or create a software widget. If a widget is better, then I'd prefer to use python as I have done a course in it . The system does not need to be real time as I assume you only change gear ratio on a stopped spindle. Even a rough plan of attack of how I should get started on this task would be greatly appreciated.
Mark

You might be able to do the gearbox with standard HAL components.

Each gear corresponds to a pattern of relay and motor positions.
A U32 HAL pin consists of 32 bits that can encode positions.
A mux component can choose one of 18 bit patterns depending on the gear chosen. Then each bit of the u32 number can be turned into a HAL pin with the bitslice hal component You probably also want to turn off the motors and enable the spindle once the selected pattern matches the microswitch feedback. You can use the weighted-sum component to convert the microswitch feedback to an integer. Then check for equality with the comp component

Thanks Andy, that gives me some reading to do. I have to get the machine working under the Phillips control, to see how it does the timing. I don't know if constantly twitch CW/CCW, or just once etc.

I appreciate your support.
Mark

Hello,

switching this gearbox is a little bit more complex...
Important is the timing and the order of single steps.
You have to take care of the transitions between the gearstages.
For example: You can not move in one Step from the right to the left position, yoú have to switch on the center relais
wait at the midle (Spindle motor alternating a litte bit) an then go to the left. Important is also the Richtung of the little
gear shift motor, otherwise the thoots of the gears will not get together.

in attachment some measures i taken from the original PLC.

I have coded this two years ago and finished 90%. Only the evalutation of the 5 bit Gear selection switch is not ready yet. Its the machine from an neigbhour an we stopped because of an broken Axis Spindle....

I will take a review of the code, and publish if its understandable... At the moment i have many jobs, so it will take some time....

attachments

attached schematic of the transmission,
please check if they identical. There have to be 3 variable Resistors in the cabinet, they are for reduction of the stages switching motors, to not overshoot the center position.