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Maho MH400 P hydraulics


Oct 17, 2004
Shady Cove, OR
I am getting a Maho MH400 P* (s/n 41 983), to convert to what I call "electro-manual" use. It had some flavor of point-to-point controller, that was removed during decommissioning / prior sale. Some of the electrical / electronic parts remain, but seems most are gone. I don't have the machine yet, but my friend who is selling it to me is making some mods before shipping it (from ME to OR).

I am trying to prepare for the electro-manual conversion, and the next thing on my list is figuring out how to get the hydraulics to work, mainly for the toolholder release, but hopefully also for clamping the axes for feeds.

This machine was supposedly used in a school (I'm guessing in MI), so I think some of the electrical was modified for US import. I don't have a nameplate photo of the hydraulic system yet, so I don't know the electrical requirements (any guesses for me? what was "normal" in these?). A copy of the hydraulic schematic is attached. It looks like a single phase motor ("M 1~"), but that's all I know right now.

My initial questions are:

1) Have other people gone this route, converting these old "point-to-point" CNC-ish machines to electro-manual use?

2) Can I just hook up electrical power and a (momentary?) switch, to release the toolholder(s)? Is it that easy, or am I barking up the wrong tree?

3) Likewise, will it be somewhat straightforward to hydraulically clamp the axes for feeds? (Once I sort out the servo motor of course... that'll be my next thread.)

4) The specs for this machine suggest it has 3 automatic quill feed speeds (0.02 / 0.06 / 0.12 mm / rev), but I didn't see any indication of what I thought might feed the spindle when I was looking at the machine. Is that what the "O" on the axis selector switch on the panel might do? Nothing on the hydraulic schematic hints to the spindle feed. Or is this just a less equipped model that was sold to a school? Any clues?

5) Is the clear button on the panel, just above the emergency stop, the toolholder release?

I will get the old switch panel, and that is sorta what I'm hoping to use / modify for my electro-manual controls of the hydraulics and feeds.

Any hints / suggestions / direction / ideas are more than welcome.



HydraulicSchematic.jpg SwitchPanel.jpg VerticalFront.jpg VerticalRight2.jpg

P.S. The "P" version has acme screws, which I think is ideal / fine for a manual machine. From what I have read, the "E" model was more CNCed, and had ball screws. But the whole Maho world is new to me, so I'm kinda drinking from the proverbial fire hose.
So some guessing here on the hydraulic sertup which should be confirmed when looking at the actual machine....
Appears that the hydraulic pump is tied to a pressure switch...when the machine is powered the pump gets power and pumps up the system till the switch cuts out....
It stays in that state cycling as needed to maintain the set pressure.....(Looks like 140 BAR)

There are four solenoid valves shown i am guessing one per axis and one that releases both the horizontal and vertical tool grippers.
Three of the valves are tied to hydraulic cylinders that if i read the print correctly are applied normally(axis held) and released when powered....So with no hydraulic pressure the axis are held via a brake
on each..
Looks like there is also a hydraulic accumulator in the system that applies compressed gas (nitrogen) over the hydraulic system...Gives smooth pressure , evens out the pump strokes,

Any manual feed would need to keep the pump activated (likely via a relay)
The pump becomes automatic, starting when the pressure drops when activating a cylinder, and stopping once the set system pressure is reached....

Cheers Ross
This is similar to my Hermle. The hydraulic pump is powered up whenever the control power is on and shuts off with a pressure switch.
So all you need for the tool changer is to connect the pushbutton to the valve.
Same for the axis clamps. However, there is an interlock that disengages the axis locks when feed is engaged.

The servo for the feeds engages a clutch for each axis. The button to the left of the axis selector is for rapids.

Ah, ok Ross, that adds some clarity to what I was seeing, but not understanding fully.

Attached are a couple photos of the way the hydraulics were hanging on the back of the column. Since fixed, my friend added a support bracket. The four solenoids are easy to identify, and correspond to the schematic (posted right side up this time), for the 3 axes and the vertical and horizontal spindles in parallel.

I now recognize the nitrogen accumulator in the schematic, and the tank in the photo, next to an oil fill.

One circuit board is in a box, and it it loaded with relays (like any CNC-type machine control is), so maybe when I have that in hand I can decipher the "relay logic" a bit. I wasn't really sure on these types of systems whether the hydraulic clamping on the axes was on or off by default. I assumed, looking at the switch panel, that each could be selectively clamped / released.

From what I've been told, the toolholders are held in mechanically, and the hydraulics only used to release them, hence asking if that is a momentary switch to activate them.

Any guesses on what the normal power to the hydraulic pump might be? 220V single phase, if it was shipped to the US? Could I be that lucky? I think I read somewhere that power in Germany used to be 460V / 3phase standard. But I don't know on these types of machines if they used some sort of lower voltage for secondary equipment (like pumps). There is a huge, multi-tap transformer, but I didn't pay too much attention to it, since I only had a limited amount of time to look over the machine.

Here are some more pics of the hydraulics and appendages, in case anyone has other insights.



Version 2.jpg HangingHydralics.jpg HydAccumulator-Fill.jpg HydSolenoids-Reservoir.jpg HydSolenoidsTop.jpg
Thank you Chris.

The hydraulic pump is powered up whenever the control power is on and shuts off with a pressure switch...So all you need for the tool changer is to connect the pushbutton to the valve.

So it sounds like as soon as I know the power requirement for the pump, I can at least do a basic tool change test.

Same for the axis clamps. However, there is an interlock that disengages the axis locks when feed is engaged.

Sounds like the interlock is going to take some more logic and probably relays to manage it.

The button to the left of the axis selector is for rapids.

Ah, thanks. Do you know what the two looped figures below the selector are for? The enclosed "|" symbol and the enclosed zig-zag?

I have been assuming the "+" and "-" buttons on the right side are for jogging?

And I am guessing the top right knob is a range multiplier... 1:1 and 1:100?

I breezed through the manual and don't recall seeing any explanation of the buttons. I hope that is just my memory and it will all become clear when I have the machine in front of me and manual in hand (even if nothing is working yet).

Not run one of these machines , but i can speculate.
Think the button with the rectangle above the black button is for continuous feed ,or cycle. The red button below cancels that/turns power off
The button with the wavy line is the rapid...in this case it over speeds the servo motor.
The white button below i am guessing is a power on switch.,looks to have been illuminated which would make sense.
Looks like there are selectors to have the brake applied an any axis, and i would wager that the logic overrides the brake when the axis is engaged even if the brake is "on".
You would wish to have a manual off for the brake to allow hand wheel operation of any axis.

Cheers Ross
Your machine has no powerfeed on the quill I think
I do not see a selection knob/handle for the feeds
Here is a pic of a 400P with powerfeeds on the quill

and another one
From a 600P

Hey do you have the electric diagram, if you do could you take a picture of it and sent them to my mail maybe. I have some problems with my maho mh400p, but i dont have the diagram