Hi All, I've got a shop that has asked me to make up a PM schedule for their two axis CNC lathes with 10 station turret, and their three vertical machining centers with 20 tool ATC, three axis and an indexer. No manuals. All are Supermax models. Things that have crossed my mind are: Inspect all belts..................how often? Check backlash.................how often? How do you check Z axis backlash? Does anyone clean and re-grease thrust bearings periodically?
I've looked for links for a standard PM schedule for these types machines but no luck. Any ideas? Thanks in advance, Bart
============ Obvious but contact the manufacturer and as for their suggested PM schedule.
Do you have functioning run-time meters on all the machines? Have you considered some sort of computerized program where the total run hours are input at the end of every shift and a maintainence to-do list is printed out for each machine?
Before you waste a lot of time/effort will management schedule the downtime required or is this another "feel good -- thumb drill?"
Been there -- done that (and wasted a lot of time/effort).
Unka George (George McDuffee)
...and at the end of the fight is a tombstone white with the name of the late deceased, and the epitaph drear: ?A Fool lies here, who tried to hustle the East.?
Rudyard Kipling The Naulahka, ch. 5, heading (1892).
I perform pm on over 100 machines in one plant and they are performed.
Monthly Quarterly Semi-Annual Annual
Changing Hydraulic oil Heat Exchanger Fluids Filters on lube pumps clean oil resovoirs Check power supply voltages Check backlash Inspect belts Inspect wipers Back-up parameter data Check all safety devices (door interlocks) Clean electrical enclosure, check for lose wires Ensure documention is kept in the proper location Clean fans in electrical enclosures and filters. Check for loose electrical connections . Replace buttons or any hardware on operator panel that is broken.
Get the OEM'S maintenace manual and look what what they say.
Backlash is determined with a dial indicator placed on the slid then increment the axis (.001 ) direction for lets say .010 then reverse direction, increment the same number of .001 increments and see if the slide had any lost motion.
Thanks Dave, list is very helpful. My inquiry on backlash was for a vertical machining center's Z axis where the head's weight tends to mask any backlash on an indicator. I was thinking of blocking up the head and checking for linear movement at the ballscrew end. Regards, Bart
Thanks George, I contacted the dealer (twice) for documentation but never heard back from them. I like your idea of going straight to the builder. I'll try that tomorrow. I'm open to software, even a spreadsheet that reacts to accumulated run hours, the "maintenance to-do-list" is what I'm after. I understand the "thumb drill". I spoke extensively to this shop about PM, offering to make a list of all perishables such as fuses, belts and bearings, etc. so they could have an arsenal on the shelf for repairs. They liked everything until they saw my quote, then it was "we'll get back to you". That was three service calls ago, all preventable and resulting in additional days down waiting on parts that should have been on the shelf.
============ Like the old ad says "pay me now or pay me [more] later." With a downtime rate of 100$ or more per man-machine hour for the modern cnc shop how they could *NOT* afford to have what they needed to keep things running or was this another case of "things are different this time"?
Sounds like the bean counters are running this particular asylum, so don't invest too much of yourself. Never teach a pig how to sing -- it wastes your time and annoys the pig. My problem was I could not tell the difference between making a pig's squeal and making a pig sing....
While it takes a lot of discipline to start, a log of everything that is done to a machine can be extremely helpful when you have a breakdown or go out of (statistical) control.
More than likely there is some "off the shelf" software that will both log machine changes and generate to-do lists. Any of our readers have some suggestions on this? If you are using this type of software how are you closing the loop to insure that the maintenance activities were in fact done and not "pencil whipped"? Should be a simple database application.
Unka George (George McDuffee)
...and at the end of the fight is a tombstone white with the name of the late deceased, and the epitaph drear: ?A Fool lies here, who tried to hustle the East.?
Rudyard Kipling The Naulahka, ch. 5, heading (1892).
"Bart" wrote in news:330a7$44c7f12a$d84442d4$ snipped-for-privacy@FUSE.NET:
Monthly
Monthly
You are checking for mechanical slop. The book should have a recommendation on method. There are several, probably the most used is a pry bar long enough to get enough leverage to lift the slide, but not long enough that you could do any damage to the ballscrew. The only kludge with this method is you do not know whether the slop is in the screw or the thrust bearings.
No Add in: Change (or clean) pneumatic silencers every 6 months - 1 year, depending on environment conditions, and how well the oilers (if equipped) are set.
CLEAN THE MACHINE - Weekly, if not daily
Change the hydraulic oil, filters and wipe out the tank once per year.
Clean/change the air filters on the electrical cabinets monthly.
DaveB's suggestions are a great start to a "list", but you probably don't want to break preload on thrust sets, or you'll get to throw them away earlier than necessary. When they make noise or get loose; that is when to change them (or when you have to break preload to change the ballscrew, that is also the time).
Check the backlash. But it's true; you won't know whether it is the screw or bearings making the gap. You can inspect screws for wear, and if you see any in the threads, it is time for a new ballscrew AND thrust bearings.
On Z, you can lever on the head with a wood 4x4 and fulcrum. Not hard, but just enough to make it move some, and it will... if it is "too much" (your call on that, as everyone's idea of too much is different) then it's time to fix it. Also be aware that loose gibs can cause sway and movement in this test too.
To check the play in the ball nut you put an indicator right on the ball contact part of the screw and attach the indicator to the moving slide. Any movement is in the nut or the nut housing when you move the slide across its length or back and forth. This method will indicate errors across the entire length of the screw or as much as you can travel with the indicator in position. Use a tenths or better indicator. I use a Federal electronic indicator that goes down to millionths. This eliminates the thrust bearing movement errors.
"Bart" wrote in news:e3ed6$44ca41fd$d8442d4c$24027 @FUSE.NET:
If any are Fanucked, they have fans on top of the controllers (top of monitor) that will give you absolute FITS if they go bad. Serious wierd things happen when that gets hot.
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