Retrofitting a 1986 Maho MH400E

The inside of my machine was filthy. The cooling fan system sucks through a filter panel on the far side of the cabinet from the fans. Since the cabinet has gaping holes all over the place and the filter clogs,  the suction simply bypasses the filter and all the dirt and dust from the surrounding workshop covers everything. So I've reversed my fans to pressurize the cabinet instead. I've added a simple wooden box on the outside over the fan intakes and fitted a washable cabin filter from a modern car air conditioner to ensure the incoming air is filtered. I've removed to old incoming filter and left the metal mesh from it in place to stop accidental fingers poking etc. So the old inlet is now the outlet, plus all the other gaps and holes. I had some RCD trip issues previous to doing that. Another saga I'll get to later.

David

Sydney generally is humid. Most of the time it's somewhere in the 65% RH range. But around February/ March it can be much higher. Recently I've been measuring 88% RH outside.
About this time last year there was a lot of rain and severe flooding in the western part of Sydney and elsewhere throughout the rest of the State.
Fortunately my house is relatively high, about 50 meters above sea level. Nevertheless the rain was relentless. Here is a photo of my shed entry during a downpour.
About that time the Maho was just beginning to run correctly. But it started tripping the RCD protection on the main incoming 3 phase GPO for the mill. I noticed a cooked plastic smell so I opened the contactor cabinet and to my amazement there was an arc crackling it's way down between the 1K1 and 1K2 spindle motor contactors, presumably to the DIN rail.
Since I just spent several months tracing and removing maybe 100 meters of redundant wiring and put the rest back neatly it was a bit demoralizing.
The wiring on these is all black for the high current contacts and red for the auxiliary contacts, so easy to mix up. In the end I removed everything one by one, labeling every cable with their standard IEC contactor numbers with my labeler.
All the main contactors were covered in dirt and some sort of crystalline deposit.  All were stripped down and cleaned, the metal parts in alcohol and the plastic in the dishwasher. By accident I noticed that may hands were acidic whilst doing so. So I touched the crystalline stuff with the tip of may tongue. Acid as all get out! Hard to remove even after the dishwasher. A lot of work. So my guess is that the machine has spent some time where there are acid fumes, maybe a plating plant. you can see a bit on the photo before cleaning, but it was mainly down the sides.
There various contacts that were a bit burnt. Fortunately the are some contactors that only use the auxiliary contacts and others that only use the power contacts, so I was able to reassemble most of them by swapping contacts around and getting mainly good for the ones in use.
But I also managed to source some identical contactors being made by Siemens? in China. So I bought a bunch and eventually set up all good ones. The Chinese ones are parts compatible but the moulding parting lines are a bit different so they are made on different tools. And I have a few spare new ones.
The 11K1 and 11K2 contactors were the most burnt. They are the ones the do the nid-nod on the spindle motor for gear change.
So it's been relatively trouble free since then with no RCD trips. But you can see why I changed the cooling fan filtering and pressurization.

David

And now for something a bit odd. I've fitted my Maho with a frog warmer! And no it doesn't have a problem with frogs. It's actually a humidity control system. As you may have seen the rear of my house is basically underground. The concrete roof has a garden on it. You can see from a previous post, on occasion it can look more like a submarine. In the lifting crane post you can just see the front of the house, which has window for its full length which faces the sun (north in the southern hemisphere). So i have a situation where the rear of my shed, through the glass work, faces a cool sandstone wall the is usually damp and stays around 18 degrees C all year round. I can pull damp air along between the glass and the wall to an air conditioner radiator yet to be fitted. Nice and environmentally friendly... eventually.
The awning on the front of the house shades the front rooms from sun in summer and allows it in in winter. Nice. So I currently balance the house temperature by having a set of small fans circulating house air though into the rear shed and back. There is also in water heating tubing throughout the concrete floor including the shed. But here is the downside of all underground houses. If you take warm air from the house and circulate it to that colder zone near the underground part, the absolute amount of moisture stays the same but the relative humidity goes up. And of course dew forms when that cooler air gets to the dew point. In Sydney that can happen even in summer on a high humidity day. So that glass wall sometimes gets wet with dew and puddles of water on the sills. Being right next to it, the radiant temperature of the cold glass can form dew in the contactor cabinet. Expletive deleted here!
So I've fitted this relative humidity controller. I've just set it to give 70% relative humidity and it turns on 40 Watts of the "frog heating" elements. It's currently runs the heating pads about 1/4 of the time, so not expensive. 70% set point gives about 5 degrees C distance from the saturation line on the psychometric chart. I've fitted some 15mm rigid foam to the inside of the cabinet doors and to the inside roof of it to reduce the heat loss which makes a noticeable difference to the on off ratio. When the machine runs this system simply gets overwhelmed by the cooling fans, but it's not really worth switching it off. The elements look like sheets of Mylar with resistive material fused between them. I've simply slipped them up the gap between the contactor mounting panel and the cabinet wall. The mounting panel standoffs give a 15mm gap for them. Perfect place for them. The humidity sensor is on the cabinet roof.
For a few bob extra I got the one with WiFi so now I can check if my "frogs" are doing okay from anywhere in the world!
Note on the side of the mill photo, the air exit mesh as mentioned in a previous post. It now has a Mylar flap over it that stops the humidity system losing warmth. It swings out a bit when the cooling fans run.

David

Here is the coolant pump after a lot of paint stripping and painting. Note: the plastic impeller just unscrews, but left hand thread.
I replaced the ball bearings in the motor with new double sealed ones.
The pump shaft I linished on the lathe.
There was a coolant thrower on the shaft but it was just a rubber grommet that someone put there. I replaced it with a Vee ring seal. I smoothed the face of the pump casing so the lip of the seal can run on it. I've dry run it mounted on the tank. It runs so smooth I had to put my finger on the shaft to tell if it was running. If anyone knows where I can buy a small 415 Volt plug and socket for a 300 Watt motor so I can shorten the very long cable to it I'd like to hear.
The tank I had sand blasted with a bunch of other stuff. it was a nasty mess inside. It's leak testing in the photo, with a bit of detergent to lower the surface tension for leaks. It has a new level indicator as the old one was smashed. The cover plates blanking the holes for it were my first CNC part off the Maho.
There is a new linear grommet around the perimeter for the lid to sit on.
That little bucket on the side of it by the sink tap goes into the foot of the mill and catches the coolant returning to the tank. It means the tank must be put in that position which is awkward. I've placed some big plastic slides underneath it so I can slide it out for cleaning. It needed raising anyway as the whole mill is sitting up on rubber mounting pads and the side bucket wouldn't fit otherwise.
David

This is near the end of the saga. I thought I'd add a little on the lube oil mess these machines make. I'm using oil lamp wicks to help direct the bulk of the lost lube from the various slides etc.
Starting with the little moat at the base of the Z jacking screw: Much of the knee's lost oil ends up in the moat. On mine is unevenly cast and ends up with puddles of lube oil in it. To drain that oil, I've simply put a wick of the type used by old oil lamps in it. The end of it goes down the drain hole in the casting where it is caught in an old sandwich tray. I threaded that drain hole and put a bit of brass tubing down below for fear that the wick might get caught in the Z axis drive belt as you see. The tray is actually a bit full. I'd prefer that the wick wasn't touching the oil, not that it's important. The thing that makes it work is the head drop down the wick to that point. It will actually cause concave menisci in the wick laying in the moat from that suction head. So the puddles get sucked empty, not dry unfortunately.
Along the X axis on mine is a rather hopeless piece of sheet metal that is pretending to catch oil running down the face from the slide way above. I'll probably improve that at some point, but currently I've simply used gasket cement to seal against the casting face. It has drain hole at each end back into the casting but the oil from them drops on the shed floor out of other casting holes. It's not clear in the photo but I've  threaded the cross drillings in them and attached plastic tubing. The tubing arcs around back into the casting and drips onto the shield spring cover of the Z axis jack screw. But again, I've put a wick in them. In this case there is a bootlace that runs a bit along the tough formed by the bend in the sheet metal oil catcher, into it's drain port and some distance down the plastic tube. The same capillary action as above sucks the oil from the trough and deposits it down the tube. I can say that there is a lot of oiling on that spring shield. Cheap and cheerful and easy to do. Noticeably saves mopping the oil off the floor, but it's not a magician.
Also,unless you machine is very stable and level, that sheet metal trough will flood at one end. My whole machine is on rubber mounts so it can flood.

David

I had another look at my gear change system just to be sure I had things in a row.

First thing I should add is the relay board on mine is hardly fit for purpose. The 3rd PCB, that I removed as redundant, is clearly marked "LUBRATRONICS 4 ACHES". So it's for lubricating 4 axes, not gear changing in particular. On who knows what. I can see why the later Mahos have a much nicer looking board.

My tracing drawing didn't make much sense to me. Some while back, after a while thinking about it, it seems this is how mine works:

The Izumi PLC on mine never actuates 11d9 relay. I've just checked every gear change to make sure 11d9 never actuates. That means the forth cam on each change motor is bypassed as is the voltage dropping resistor.

The result is my gear change motors run full speed at 24 volts and full power. Note my gear change motors seem to be Bosch windscreen motors repurposed. So the later machines may have more suitable ones.

The redundant track notes on my drawing are incorrect. Sorry, I forgot to remove that. What happens is that the normally closed contacts on 11d5, 11d6, and 11d7 short circuit the motor winding when they aren't energized. That also means the motors are dynamically braked by the motor back EMF short circuiting through the motor winding when the the relays turn off. So the motors stop faster.

I guess the previous Philips controller had some strategy to use 11d9. But these boards were like that everywhere. I took me ages to figure out what was redundant and how whats left actually worked. A nightmare. The wiring diagram of the later board looks like Maho cleaned it up and made their own.

David