[mflux_gamblej]

Hey guys, my VH-65 wont cold start. It was working a month ago (last time i used it). I suspect the limit switch inside. I put new oil in it last time I used it, and It seems that some coolant leaked into the gearbox too; the oil was above the level marker on the side of the rotary table.

I use my rotary as an indexer (don't have the PCB for full 4th) with a fadal servo controller model 1 indexer box. When you power on the box you have to align the mark on the rotary table and CS it just like the other axis on the mill. Now it won't find it's index.

Something interesting that I don't understand is that previously if you didn't align the mark right, it would sill 'find its index' and allow you to operate it - it just was offset by whatever distance you were from a proper CS with the marks aligned. I also notice that if you jog the rotary around very slowly you hear it tick/click every few degrees. Maybe there are several index locations on some kind of limit sw encoder wheel?

Another symptom is that usually when it runs it's CS routine it will rotate about 10 degrees CCW, then rotate back about half that CW and it will then have found it's CS index mark. Last night it would only rotate CCW but then not back the other way. The indexer box says 'index mark not found, jog to align marks and press ESC to try again.' This morning with all the machines and compressors shut off, I can hear the motor really well in the VH-65. When you press CS it moves CCW 10 deg like it should, then from some positions, it will actually move a tiny amount back CW but only fractions of a degree. You can hear the coil in the servo motor energized and moving the system minute amounts. It still doesn't find it's CS index, but it does seem better than it was last night at least.

Does anyone know what kind of limit switch is inside the VH-65? I could see that if it were optical or magnetic that my oil over-fill may have messed it up by getting it dirty or maybe shorting? (seems unlikely). For now I drained some oil an am letting it sit. I'll try it again later. I assume that getting to the limit switch in this thing is going to require a full tare down . Any experienced fadal advice would help me out a lot here. Of course I have an indexing job lined up - so as usual in the CNC world time is of the essence.

[DareBee]

Mine doesn't have any switches inside.

[mflux_gamblej]

Mine doesn't have any switches inside.

There has to be some way that the system is 'finding' it's CS index. If not a mechanical limit switch, could it be a magnetic eddy current proximity sensor? Or maybe just some kind of signal from the resolver? The resolver is easy to get to - it's on the back of the motor if you take off the end plate. That being said, I'm not sure what to test or look for once the cover is off.

[mflux_gamblej]

I've been on the phone with a tech who has some experience with this system. He confirmed that there are no limit switches inside the rotary table. So, it must be down to the resolver / encoder or it might be the driver amplifier? Maybe even a bad cable? I'll continue to look around. Has anyone had their VH-65 encoder replaced for any reason? How might it go bad?

[DareBee]

There has to be some way that the system is 'finding' it's CS index. If not a mechanical limit switch, could it be a magnetic eddy current proximity sensor? Or maybe just some kind of signal from the resolver? The resolver is easy to get to - it's on the back of the motor if you take off the end plate. That being said, I'm not sure what to test or look for once the cover is off.

It's CS index is anywhere that you set it.
If you always want it the same place, you eyeball up the arrows (exactly the same as XY&Z)
I never zero my rotary on CS function. EIther am starting with a blank that it makes no difference or I am indicating (tramming) a custom location (which will end up getting a "SET A").

[mflux_gamblej]

Well, a picture is worth a thousand words.

The encoder wheel must have slipped loose off of it's set screw. What shocks me, and what is going to cost me $400, is that the damn wheel was allowed to crash in any condition - what a poor design. You can see that the wheel was crashing into the reflector optics. This also looks like old encoder technology which means it will be $$ to replace.



Also, I can confirm myself that there are no electronics inside the rotary table that would be for any kind of limit switch - only the wires going to the servo and it's encoder (what's left of it in my case).

[DareBee]

Of course it's old.
1995 was the last year of manufacture for the DC servo machines.

I believe that is the same encoder as on the other 3 axis as well

[mflux_gamblej]

I plan to order a modern differential encoder with an index channel from US Digital. They're a good encoder supplier that I've put on some robots in the past. Hopefully I'll be able to find a wiring diagram so I can figure out which pins on the old ENC-0003 / Renco 77822-136 encoder. There are 8 pins. surely its one order or the next of:

supply - red
gnd - black
a+ - white
a- - yellow
b+ - green
b- - blue
index+ - orange
index- - brown

I'll make measurements to make sure that the voltages are TTL level (3 or 5 or so volts) so they won't damage the new encoder. Anybody familiar with, or have a schematic that shows which wires are which on the fadal side of things?

a side note: the 'index' channel allows for just that - it's a mark on the encoder wheel which serves as an index that you can use for whatever purpose. In the case of fadal, it serves as the 'this is zero' marker. Not a bad choice since it would be 1 or less full rotations of the worm in the rotary table, or the ball screws on the main axis.

This explains why my rotary couldn't find its index mark whether it was missing other encoder counts or not - the index marker on the wheel was rubbed off. A good way to fail I suppose. Alternately I may not have noticed and may have delivered a customer part with an angle that is totally wrong.

[mflux_gamblej]

here's a table to translate from the renco encoder to a us digital brand encoder

cable: CA-FC10-SH-NC, 10-Pin Latching Connector / Unterminated, Shielded Cable
encoder: E5-1000-250-IE-D-H-R-1, E5 Optical Kit Encoder



this cost me 1/4th the price of a legacy / obsolete renco part, and 1/2 the price of a recommended replacement from the company that apparently owns renco these days

[Waynno]

I have replaced a couple over the years, Mine usually start giving out when ya do a circular type move
and they can shutter just enough to leave a bad finish, kinda minor imperfection in the work piece
seems per every screw revolution.

They are rather cheap to replace, I think I paid like 100 bucks for one a few years ago

Lucky you have a Fadal, The older Mori Sieki Lathes I own, A used one run about a grand

Wayne

[mflux_gamblej]

I finally got the new US Digital substitute encoder working. Some pins are backwards vs. the old Renco datasheets, and the index pin is backwards vs the modern (newer than my VH-65 rotary table) fadal maintenance manual. The index pin may get read backwards because the rising edge is synced different on my new US digital than it was on the old Renco. bottom line is that the new encoder was way cheaper, and works great. final working pin-out is shown in the screen shot attached. also, I had to machine some 4-40 holes in the existing servo encoder mount.