Well it is good to see the images are uploading again!
First and foremost: If anyone out there has a damaged spindle for a 2001'ish DMU eVo (50 or 70) that has a good stator please contact me and let me know what you want for it ASAP. I'm going to be pulling the trigger on getting the stator rebuilt starting later today but if someone has something that will work already I would consider that route too, price dependent of course.
So after a whole bunch of hours with my DMU50 eVolution I now have it powering up and moving around. I ultrasonically cleaned the large heat exchanger cooler for the glycol (massive copper unit that would be very expensive to replace!) and cleaned/rebuilt the entire cooling aggregate on the back of the machine. This took a long time, but at least now it will work as new in terms of efficiency.
Here you can see the rags the previous owner stuffed all over the base of the unit to capture all the leaking fluid going everywhere. The fans were caked with gunk and heat exchanger was almost clogged completely closed. The stuff that came out of the rad has varying consistency between clay and molasses and is extremely difficult to work with. It doesn't wipe off surfaces and I'm very thankful for ultrasonic cleaning technology otherwise that would have been very difficult to get as clean as it now is. I can only imagine what the lungs look like of the people that had to work in the shop this machine came from.
Here it's clean, the entire bottom tray is made from brass as is the cast heat exchanger that is used to take glycol to cool the heat exchanger that is mounted inside the control cabinet. What is nice about this design is the hot air inside in cabinet that rises from convection is cooled by the cooler at the best intake point. This machine they were smarter about mounting the entire control and drives near the bottom of the cabinet so the intake to them would be the coolest air in the cabinet. This is a major improvement over the 50V machines. I still would prefer a dedicated AC unit like the MC800H and my Ultrasonic 10 have, but this is better than before. Interestingly, the MC800H has it's heatsinks for the drives all getting air from outside the cabinet entirely. This is nice as the cabinet doesn't need nearly as much cooling and the electronics themselves (which suffer longevity issues by the higher temps) will last longer. Fanuc started doing this in the late 90's too and I think it is a much better way than the Siemens 611 system that has all the heat staying in the cabinet. One benefit of the Siemens design though is the heat changers and fans stay clean as they aren't taking in shop air. That is until the whole system starts running too hot and the operator starts running the machine with the door open. Anyway, I digress....
So early this morning it was "Arts and crafts" time. The stator on this Kessler spindle is encapsulated in epoxy. I may not do this myself once it is rewound but just in case I do, I decided to cast silicone molds of the original stator epoxy profile since making such molds is much cheaper and faster than if I tried to do this later.
It's funny, I literally looked around my shop/storage until I found parts that would work to seal the stator and not waste too much silicone. What you see there is the exact amount of 2 part casting silicone that I had on hand for another project that I didn't get around to. I took a turned steel part that I had with a profile that worked perfectly and tossed a 3in ABS drain pipe on it. I had some "dum dum" strip caulk that is non hardening that I worked around the interfaces between the parts and this is the result.
In a few hours I'll pull it out and proceed to press out the stator and start destroying that epoxy to remove the thermal sensor. My research has found there have been some great advancements in stator encapsulation so I may invest in some of the latest products to gain the thermal conductivity benefits they provide.
I must say that although I have had great reliability from the older 50V Kessler design (Knock on wood), this spindle is much better designed than the older ones. First, the actual tip of the spindle between the bearings is now cooled, like the MC800H. I always couldn't believe the 50V's didn't have any glycol going to this region, and instead they rely on the thermal comp in the control to keep machining in tolerance. This spindle not only has additional cooling, but it has the thermal sensor placed right near the tip as well. In addition, the spindle is air/oil lubricated instead of grease. Now I know this ultimately is more expensive because of all the air and therefore energy you will spend running this spindle, but what I like about it is that as long as you take good care of the system and your air supply, the bearings are always being "cleaned" while the spindle is run. Also the air/oil provides better cooling and constantly fresh lubricant. Lastly, it isn't as easy to damage the bearings from overheating or contamination like grease spindles. If coolant somehow made it through the three teirs of labyrinth seals, it wouldn't stay there for long enough to do any real damage, and certainly not contaminate like it would grease.
Also, these spindles no longer have two parts. Now this is not really a bonus in some ways. If you damage a taper the older design is cheaper and easier to fix, as you can have spare tapers on hand that aren't part of the motor section. The benefit of the newer spindle design is that the overall assembly is much stiffer, vibrations from cutting will be absorbed better by the spindle mass, and there is one less high precision ceramic hybrid bearing to have to purchase when replacing all of them. The newer spindle has a separate bearing assembly that allows for axial motion only of the top angular contact bearing. It's spring loaded to keep the balls preloaded and therefore less likely to skid and cause premature wear, but the bearing is free to move with almost no resistance so that any thermal growth in the spindle doesn't create any additional force on the bearings. On other machines, like the Kitamura, they used rollers instead because they do serve a similar function but you cannot really preload all of them so skidding would be hard to prevent. This design is much better. When I was researching information on this I came across a Deckel Maho patent that they applied to the later spindles that also allows the cables and bearing assemblies to be released by just a few socket head cap screws. On those spindles you can drop the entire spindle with bearings from the machine without removing the stator. This makes the labour cost of removing the spindle in the event of damaged bearings much less.
Then again, on the older DMU50V spindles, as long as the motor side bearings are fine, you can remove the taper section without even having to drain the coolant or anything. The downside is that you do have to disconnect the drawbar gripper whereas the newer design that can all remain fully installed.
That's enough for now, we'll see how this stator repair goes.
Dave @ Nerv
Nothing like nice parts with fresh powder-coat.
Happy new year and hope the machine will be whole again soon !