Retrofitting a 1986 Maho MH400E

19 Jul 2017 08:31 #96034 by db1981
19 Jul 2017 08:47 #96035 by db1981
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.
19 Jul 2017 13:03 - 19 Jul 2017 13:28 #96064 by RotarySMP
Thanks for the inputs. In the HAL.Oszi screen shots, what are the Red line at the top, the purple in the middle and the blue line near the bottom please? The legend is not legible.
I am not sure if I understand what the HAL-Oszi is displaying. Is it the open/closed status of the gearbox feedback swtiches in response to the individual motor relays being activated, with the file name giving the selected motor and direction? eg m_r.png = Midrange motor (Mittelstufe) relays powered and with the change direction (Drehrichtung Umkehr) in direction RH? What is l_r.png?

The 400E gearbox schematic seems similar, although differently drawn to the MH700 you sent. I'll have to trace through in more detail to see if they are significantly different. I noted that my schematic has an extra "Start" relay in the gearbox control circuit which the MH 700 didn't have.

The three 100ohm 20W variable resisters are located at the top of the 28A1 Relaisplatine 11R1-11R3 on mine.

To try and keep all the relevant information together, here is the manual positioning of the gear shifter positions with the resulting spindle speeds.

I appreciate your offer to share the code you have already written for this system. It seems that the topic of retrofitting MAHO's comes up often on all the forums, and some have successfully integrated the gearbox control into LinuxCNC, but the knowledge is not easily accessible in one thread or location. I tried searching the IRC archive, but it also have found little info on MAHO gearbox control.
Last edit: 19 Jul 2017 13:28 by RotarySMP.
19 Jul 2017 13:39 - 19 Jul 2017 13:40 #96067 by RotarySMP
A basic question, if you can do the complicated control of this gearbox with it's 8 relays and 12 feedback switches plus timing and twiching the spindle directly in the HAL, what is classic ladder used for?
Last edit: 19 Jul 2017 13:40 by RotarySMP.
19 Jul 2017 13:49 #96070 by Todd Zuercher
For some people graphical ladder logic is easier to program than hal logic, especially when it gets complicated. There isn't much (if anything) that can be done in Classicladder, that can't be done just in Hal.
19 Jul 2017 13:55 #96073 by andypugh
Ladder is rather better for sequences than HAL. It is also a lot easier for experienced ladder programmers.

But I don't know Ladder, so always end up using HAL (often with custom components)
19 Jul 2017 13:55 - 19 Jul 2017 13:59 #96074 by db1981
your start relais seems to be for switching to low speed for the alternating left/right turning. On the Mh700 this is done with an 70V transformer output.

Hal Oszi:
I Used Hal Oszi with an input card to record what happens when the original PLC is switching gears, my real Oszi has only 4 Channels.

the png are named as the movements : L_R = Position left to Pos right switching.

links,rechts,mitte,richtung are the four cams of on transmission stage (left,right,center,an one switch witch tells the siemens plc, in which direction the motors turns last and if it has to start in opposite direction) If you start in wrong direction the motors has not enough power to lock the gear in. Also its important from the timing that the gear motor starts with the right direction from the main spindle turning.

K7Richtung, K3 Motor, Wahlmitte, Bremse are the Outputs of the PLC to the Relais. (direction Motor, Motor Power, the relais witch enable the center switch, Spindle Brake)

there have been some solutions in the past, but only for the 2 stage Transmission with Frequency driven Spindle motor. This Transmission has only 2 Positions (Left/right) per stage, without the hole Center Position part.

My component is finished an i will share it. the things i thought which were unready have to be in the control panel part.
I only need a little bit time, to do some coments and optic....
Last edit: 19 Jul 2017 13:59 by db1981.
19 Jul 2017 14:01 #96076 by db1981
I have not used ladder (hating...) or special hal programming.
Its an real time C component.
19 Jul 2017 14:07 #96077 by Todd Zuercher
Ladder Logic is often easier for me. But I've had to spend some time browsing through the enormous PLCs of several other large commercial CNCs trying to fix problems.
19 Jul 2017 15:53 - 24 Jul 2017 13:37 #96083 by RotarySMP
Thanks for the feedback to HAL verses Ladder.

Your start relais seems to be for switching to low speed for the alternating left/right turning. On the MH700 this is done with an 70V transformer output.

So that would mean that 11K8 "Start" relay sets the main spindle motor power to star so when the twitch relays activate it only get 240V per winding right?

Since my machine is not currently operating, I have never actually seen or heard a MAHO do it's gear change, except for M├╝llernicks you tube videos of the simpler 4 speed MH700. Does the control command all three shifters motors concurrently or is gear changing done sequentially?
Last edit: 24 Jul 2017 13:37 by RotarySMP.
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