Retrofit MAHO MH700c with Philips 432 control

Hello,

I remeber the encoders are mystic analog stuff....
The User Sascha (ethercat) has already retroffited some of these machines, with an special interface board. Try to contact him.

Dominik

These could be 11um or 1vpp analog sinusoidal signals.
They can be converted with heidenhain products (or others)

are they philips brand? any other info ?

Chris M

You can get some converters on ebay look for heidenhain exe100...101 or you can buy new ones called "heilig und schwab sk111" look for the heilig und schwab homepage.

IFAIK Heidenhain EXE converters are only for 11 micro amp SIN wave encoders.
Are you confirming that is what is needed?

Heidenhain IBV converters are for 1 volt peak SIN wave encoders.

Chris M

You can search for Müllernick or mullernick. He had converted a Maho7000 iirc withphilips 432 control, some years ago and
know everything about the strange philips linearencoders.

Sorry to say you have the "bad" encoders on your Maho.

It's true that Nick Müller did something with these encoders, but I don't remember if he was successfull. I think he (and everybody else with this kind of scales) ended up replacing them with new scales. They are not possible to interpolate the same way the Heidenhain ones (the 11 uA/pp sin/cos ones) are either as the signals out of the read heads are already digital. And apparently they suffer from contamination as well since the scale is in the open.

I think you can find a lot of info about this in my thread over at Practical Machinist forum called "The fix your Maho thread". It's quite long by now, so I didn't have time to read through it all to find the relevant info. But from what I remember Nick gave some comments on his work on this in there somewhere.
And replacement parts are almost impossible to get. Or at least very pricy if you can find them. Your best bet would be to try to ask the others who have taken their Philips scalse out of their machines if they can sell you their old scales for parts. Again, there are a few in the above mentioned thread.

I also suggested one way to read them in that thread, but it involves sactrificing original Philips controller cards (that are somewhat valueable as spare parts). But you do need the correct version! And there is 2 read chains on each card so you need 2 cards for 3 (or 4) axes. Look in the thread for the details.

You do have good iron though (providing there is no extensive wear) in that machine, so it's a good candidate for retrofitting (better than mine!). But you do have your work cut out for you!

I'm planning on making a propper "how to retrofit a Maho with LinuxCNC" thread soon. I think I have all the info I need to get it done by now. I only need to find the time to get the machine done and make the documentation on how I did it. So it will be some time yet I'm afraid.

Anders

Well, these encoders are not so "bad" at all. I had a lot of fun to discover the old technology and adapt it to LinuxCNC (with help from Nick Müller about schamatics and signal analysis). It's long time ago (in 2011 if I remember right) and I have not created a lot of documentation, but I've uploaded the stuff to GitHub . So please have a look if you like.

Basically the scales consists of an photo diode array which analog output is multiplexed and PWM encoded. I have created a FPGA based decoder with pulse width measurement and sincos correlator in hardware and convert the sin/cos values to angle (within the 0,635 mm cycle) in software.

The machine is still in usage today and works fine. I have planned to create some detailed documentation in the wiki, but time is always a tight resource

Hehe, by "bad" I meant there are no support and spare parts to get, unlike the Heidenhain, where there are loads of available spare parts for cheap. From a technical point of view I'm sure the Philips scales are just as good as the Heidenhain ones. Possibly except from the fact that they are using an open design which is prone to contamination.

I wasn't aware someone had done a serious job of making these work, and I'm impressed you did go through the effort of doing that. If you have a working unit and would be willing to share it I urge you to share what you already have on the PM forum. I know there are several others out there who will come across this problem in the future too.
Maybe you can even make a readily available product for sale and be able to get a little return for your time spent. But you shouldn't expect to get rich though

What interpolation factor are you able to get out of these BTW. It would be interesting to know how accurate they are compared to the Heidenhain scales.

Out of curiosity, do you think it would be possible to use any of the iC-Haus read heads or something to read these scales? They do much the same as you seem to be doing.

Anders