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New to me Bridgeport TC22

arsenix

Aluminum
Joined
Jul 28, 2011
Location
Milpitas, CA
During pandemic I bought a few "new" machine tools, including 1997 Bridgeport TC22. I was hoping to tap into some other owners here as I dig through it. I've been slowly working through servicing it and getting it running. Although "fully running", it is an old machine and a number of little things have needed attention before I start running parts on it. Lots of cleaning ancient crud... replacing o-rings and seals.

I decided I should likely change the gearbox oil as it looked a little low on the sight glass. When I drained it, only about 3/4 of a quart came out. Post draining the sight glass was the same level... ie it was likely lower than it looked. There is a fair bit of red goo around the shot pin actuator (ie it seems to be leaking there). It also looks a bit wet around the base of the motor. The "cavity" around the main spindle belt was certainly filled with a lot of goo. Makes me think the lower seal on the gearbox is likely leaking.

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Was wondering if folks had any suggestions. I was hoping to NOT have to pull the motor/gearbox... but maybe it is inevitable at this point. Does anyone know offhand about how much gearbox oil these are supposed to take?

I'll likely have more questions! The list of things I've already done is long, although I feel like I am getting close to chip time!
 
Have been working my way through the machine. Got the pneumatic system all sealed up. Rebuilt the rotary drive and replaced every o-ring in all the nylon hose junctions!

I redid the lube lines to the head and have oil flowing up there. I cannot figure out how to get to the lubrication manifold under the table though. Is there an access hatch I'm missing? Any TC22 owners have a trick to share? Still cleaning all the swarf off down there too so many areas remain deadly to bare hands!
 
After jogging the table back and forth to get all the side covers removed, and sopping up a lake of old way oil (which had been obscuring the manifold), I uncovered it. It is about 10" in from the side though. I can just barely touch it jamming my arm in there. I suppose I could undo the ends of the ball screw and move that out of the way but that seems like a fair bit of work and maybe take some setup to get it aligned again?
 
I can’t provide any input, but I’m watching this tread. I just bought one of these too, and I’m starting the cleanup too.
 
I ended up removing the X axis thrust bearings and screwing out the ballscrew to give more clearance to remove the lubrication manifold in the table. With that removed it wasn't too bad to remove the lube manifold and clean it all out. All back together now. Getting close to making some more chips with it.

I ended up making some custom wrenches to remove and reinstall the ball screw nuts. I listed the extras if you need a set: Bridgeport CNC Milling Machine Ballscrew Nut Service Tool Wrench Set TorqueCut | eBay

Will post some photos of the process later.
 
As long as you're going through it, I would replace the proximity sensors / cables for the tool changer. My first machine was a TC22 and I got it cheap because the tool changer would intermittently fault out...found two cables that were old and brittle and new ones were cheap.
 
Thanks for that tip! Did you just buy the cable from bptparts? I haven't looked at the tool changer much yet other than checking to see if it worked.
 
It doesn't appear that my bijur is lubricating. I can pull the lever and it pumps, but doesn't seem to be running automatically. Is the machine supposed to apply power to the bijur only when the spindle is running or all the time? I don't seem to be seeing power to the power terminals at the pump (even when spindle is on), so maybe the control has a fuse blown or something?

EDIT: I hooked the pump directly to 115v and confirmed it works fine.
 
After wasting a fair amount of time troubleshooting I realized that the machine only runs the lubrication pump when it is running a program. So it was working perfectly all along! I'm sure I missed this somewhere in the manuals.
 
Spent the last few days running parts on the machine. So far works great! The software is a tad quirky and has a few bugs (like don't press another button after pressing quill up until it is finished raising the quill!) but they are easy enough to work around.

Only issue I had was that the Z axis way cover caught the table at one point and was damaged. It rolled up during a part of the program where the table was all the way to the rear corner and the rolled up guard caught the table... bent/slid/etc. Not sure I can repair it. I guess this is why many of these machines have this guard cut short. I had just bought and installed a nice nearly new one too. Ugh. I'm not too inclined to invest in another one since it seems like a hokey design. Has anyone fashioned anything better? Maybe some of the standard rubber/fabric way cover bellows that are common on machinery?
 
Been working through the gear change system to get that working reliably. It would occasionally switch gears properly but only after a few retries. I rebuilt the Turn-Act although after getting the new seals it seemed apparent that it had been rebuilt somewhat recently. The ones that were in there seemed fine. This was not the primary issue. The solenoid was not engaging fully for one. I cleaned out the solenoid and resealed it which improved flow but still no improvement.

I took the motor off and confirmed that the transmission mechanically shifts quite smoothly. I can easily change gears by hand. No issues there. The issue is that the Turn-Act was not completing the gear change. What was happening was that the turn-act would stop producing torque after moving about 45 degrees. This would happen in either direction. It seems there was just enough leakage that the pressure across the vane was equal at that position. I purchased a used replacement Turn-Act which seemed in fine shape but it behaved exactly the same. I'm not sure if this is normal but my machine has very tiny flow restrictors on both ports of the turn-act. Like a pin hole. I think the internal leakage is overflowing these restrictions at that position, so the actuator stops producing torque.

After working through this I put it all back together with the restrictors removed. It shifts dead reliable now but the shift is pretty... abrupt. I assume Bridgeport put those in to soften the shift. I wonder how much of a problem this will be. I believe that if the "exhaust" was unrestricted there would be no issues with the slight internal leakage. You can buy restrictors with check valves in them so they only restrict in one direction. Wondering if I should try some of those to damp out the shifting but still allow unrestricted venting. I'm really not clear how the system was supposed to work with those tiny restrictors on both ports. Seems like even a tiny amount of internal leakage would cause it to not work. Both of the cylinders I have seem to be in fine shape and make great torque, but even with greasing/oiling they have a tiny amount of leakage at certain positions.

Anyone else witness this same issue?
 
I ended up buying and installing some one way restriction valves from Festo. These have an adjustment to change the flow restriction, and only act in one direction. This let me dial in a little damping into the gear change, but still leave enough flow for the change to be reliable. I dialed in more restriction until it started to retry the speed change, then backed them out a full turn. These are FESTO GRLA-1/8-B, which has the proper threads to drop in place of the existing restrictors. They restrict input flow but not exhaust. Found them for $20 for the pair on ebay. I really can't grok how this system would work reliably with the tiny restrictors it came with. Even a slight leakage in the turn-act will cause it to stick and fail to change gears.

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This machine has been running nicely. I did some checks on it this morning to check backlash and tram. It looks like there is about .0003" worth of backlash in X/Y. I zeroed an indicator, rapid out and back a few inches, then check, go the other direction. About .0003" change in reading. Doesn't seem to bad. Tram varies around .001" over an 18" sweep. The factory spec is +-.001 over a 12" sweep, so I'm within factory spec although this doesn't seem too tight to me.

One issue I'm having is that the machine has a bit of vibration on the Z axis. It varies in intensity but you can clearly see the indicator vibrating around .001" when you are indicating Z. It gets worse when you jog up, goes away when you jog down, constant when sitting. The indicated position in the control does not change. Maybe the belt is too tight/too loose? I did cinch it when I was servicing the machine. Tramming the head any tighter is tough with this vibration present. It doesn't seem to impact surface finish when machining that I have noticed though.
 
As I detailed in this thread on cnczone, I ended up I believe fixing the Z axis vibration issue. Traced it back to a factory defect in the Z axis motor wiring (a bad solder joint). There is a still a tiny bit but I'm satisfied with it. I've been running parts on the machine.

I've noticed a little odd behavior with the tool eject process. Some of my tools just seem to "just release" and some some have to be actively popped out by the machine. I worry that my clamp force is not up to spec. I don't have a clamp gauge handy. Maybe on a machine this age the bellville springs in the drawbar are almost certainly dead/dying? Unfortunately it is a bit of a time investment to just "open up and check"! Once I dig into it I probably just want to have the spring washers ready to swap in?

Anyone done the spring washers on one of these machines? bptparts quoted me $400 for the parts but it seems like mcmaster sells springs in this size for ~$100/set. I won't be sure of the size until I get in there though since I can't find any specs. My Bridgeport maintenance manual does not list a part number for these, unlike the manuals for some other Bridgeport machines.
 
I disassembled the drawbar, which isn't too difficult. Just need to pop off the spindle covers and the drawbar actuator cylinder. Need a 30mm combo wrench for the preload nut, and an allen wrench or some other rod to stick up into the spindle and stop it from spinning at the end of the removal process.

The springs aren't broken, but they do look fairly worn. They are the 31.5mm x 16.3mm x 2mm thick size that seems to be commonly spec'd on other Bridgeport VMCs, and there were exactly 100. Mcmaster carries this size: $114 for 9 packs of 12. Mine seem to be worn down to 1.9mm or thinner. I have to say when disassembling the unit I don't think there was nearly enough preload to hit the factory pull force (1687 lbs). If the stacks were worn as I'm measuring that would have reduced preload by about 30-40% from the spec, which may be the only factor. From my calculations of the stroke on this machine and the stack, the springs are not heavily loaded and are using over half the working load limit for these springs. That might be why they are not cracked but just worn and are likely the original units. The stack seems well designed for the loads and travel.

I'm doing a little research into the best lubricant for these. What is in there appears to be a high moly, thick grease of some kind. Some reading folks suggest Kluber NBU 15, which appear to cost about $1/gram. Maybe I should see if I can find some gold-flake antiseize instead? :)

One odd thing is that the engineering diagrams in the maintenance manual show an o-ring at the top of the drawbar. This would provide a seal for the "air blast" and prevent air oil lubricant from spraying around up in the belt area (which it clearly does). There is a pressed in cylinder up there which in the diagram the o-ring sits on top of. On my machine this cylinder is only slightly under the surface of the drawbar, with not nearly enough room for an o-ring. I'm tempted to press it a bit deeper so I can drop an o-ring in there. Some light tapping didn't do much though. It needs to move down about .02-.03" in order for there to be enough clearance for a 1/16" o-ring in there and leave a little bit of a "pocket". The diagrams clearly show it further recessed with an o-ring, which makes sense to me. I'll probably have to put it in the press though for this to happen, which I'm not excited about.
 
I got bellville springs from McMaster (PN 96445K295, 16.3 mm ID, 31.5 mm OD, 2 mm Thick). They match to the dimensions and appearance of the one that were in there identically. Seems to indicate that maybe these weren't worn at all and were just a bit undersized and maybe under-preloaded. I suspect these were replaced at some point with these identical Mcmaster springs. Mcmaster did not have a tolerance for the thickness so I guess they are a tad underthick, although they still meet the load requirements. I elected to change them out anyways since I already had them despite the fact that the old ones seem fine. The old ones were certainly not preloaded to spec, but not radically so.

I preloaded the stack 18.5mm, which should give a preload of just under 1700 lbs which is the spec in the service manual. It was preloaded to something around 14mm previously. Possible the slightly thinner belleville springs were not compensated for when someone repreloaded it.

I did add an o-ring to the top of the drawbar as shown in the service manuals after pressing the "restrictor cylinder" down ~1/16". We'll see if this stays in place after the machine runs for a while. Should keep a little more of the air puff during tool change off the belts and keep oil out of that area. I reshimmed the drawbar cylinder and found all the clearances were sloppier than the manual calls for. The cylinder was also not aligned properly due to this. The drawbar now runs slightly slower (due to the higher preload) but also seems smoother and less clunky since the clearances are all tighter.

Although I increased the drawbar pull force slightly I doubt this is going to make a noticeable change in the machine's running in any way. Mostly peace of mind since I was unsure about the condition of the belleville springs! The changer is now running more smoothly at least!
 
I've nearly finished interfacing a 4th axis 5C indexer to the machine. Excited to finally have a 4 axis CNC to play with. The 4th axis support on the DX32 seems decent so far but as with many things I suspect it somewhat "light". We'll see how it works once I start trying to run parts on it. It is working but I need to play with the gains on it. I interfaced a brushless motor control to the DX32 using a VESC BLDC controller, which so far seems to be working.

One things I've noticed running parts on this machine is that is currently doesn't seem to like my adaptive toolpaths much. With faster paths it seems to just be acceleration limits on the machine (no surprise it is an older machine), but even with slower toolpaths the motion can get pretty jerky. It seems like the machine is stopping between moves. I assume this is just because the control doesn't have many steps of look ahead? I was machining with a small end mill a few days ago at only 2 inches/min and was surprised it was not able to maintain full speed on an adaptive path at this speed. I may look closer at the post to see if I can improve this.
 

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