Machining the DMM Technology servo motor flanges - and a peek at the encoder (again)

When I made the X and Y axis motor housings, I didn't get carried away ensuring that the features that mate with the servo motors were made exactly to spec. Sure enough, the bores are slightly too tight for the motors. I was expecting this and was planning on having to machine the flange registers on the servo motors.

It's simple enough - remove the 4 bolts that hold the flange plates to the motor bodies and machine them down on the lathe.

The registers were about 0.15 - 0.2mm undersize. I suspect a second finishing pass might have helped but it's no big deal right now.

The flange plate comes off easily enough, taking care not to damage the encoder assembly at the other end of the rotor, whatever that looks like - I'll take another look later.

Not sure what the 4 extra holes were for but they were bunged up with 4 nylon screws to keep the insects out.

4 jaw chuck to get it concentric within a thou or so - it's not critical here.

Hmm, about 0.16mm undersize:

...an 0.37 undersize at the worst location. I suspect the calipers were a little off square:

I used a carbide boring bar with CCGT06 tip to clear the jaws.

There you go: 

Motor reassembled:

"Made in Canada". Haha - yes and I'm Mary Poppins!

Let's have a look at the encoder. I looked at it about 3 years ago but I forget what I found. Under the main cover, there's a secondary plastic housing. Note that nothing so far includes any form of sealing as such.

I got the cover off, nearly destroying the electronics in the process. The funny black thing is just a plastic moulding...

...that locates a series of sensors. I didn't bother looking any closer but I assume they are Hall effect sensors. Not sure if they are linear or digital but it's not a massive concern.

I don't like tantalum caps. There's no justification I've yet seen for their use. Their failure mode is short circuit and they have no unique properties to justify their cost and unreliability. Anyway....

Note also that there is a resonator (8MHz?), which suggests some form of micro or at least a transceiver.

And this is the target magnet for the sensors. It seems to be magnetic, judging by my simple screwdriver test.

This is the external cover and cable entry. As mentioned, there is no attempt at sealing. I suppose they may argue that a magnet / Hall sensor solution doesn't need much but I'd disagree. But I've previously looked at the servo drives themselves and they are clearly not of "industrial" construction so much as "hobby" grade. No disrespect intended but let's be clear what we are looking at.

There.