New PM-727V arrived today, Happy ??

[Buffalo21]

Damn 5000 rpm!!

My Rockwell mill does about 6650 rpm, at max gearing, I ran it there long enough to get a speed reading after the mill transmission build, according to the original speed tag, 6300 rpm was the original max speed. I hopefully never need that speed, the mill did it, but it did not sound happy doing it. About 2 weeks ago, I did a job at roughly 3100-3200 rpm, I had no issues, but the overall mechanism sound was a little too busy for me. I did a job today at roughly 1500 rpm and everything sounded good.

 

[macardoso]

@macardoso holy moly! 5K rpm's? Is this the stock setup? Yes Kluber is the grease I used but couldn't remember the name...it's crazy expensive but for a spindle bearing replacement, you don't need much. I really don't think GTPI needs new bearings at this point, but if he's just gathering info for someday, I get that, this place is invaluable for that.
Your 5k versus (well my PM only gets up to 1750 prm, OP's goes to 3 k?) I'd expect much higher temps. But again, I don't believe he has any issues to worry about. His purchase has had plenty already, I think he's a bit shell shocked, don't blame him.

No, not stock at all. I have a 5000 rpm servo belted 1:1 to the spindle. I also have the quill disabled since my CNC used the column for Z axis motion. I started talking about my spindle modifications on posts 4 and 10 here. Perhaps the info might help others. When I ran the spindle stock, the bearings gave me no trouble. I wanted to comment above to just say that if my bearings survive for a long long time at 140*F, I don't think there is any issue with 115*F.

With the design, there isn't any reason I couldn't change the pulleys to get 7.5-10k rpm but I like the low speed torque.

G0704 CNC AC Servo Rebuild (Picture Heavy)

Hi All, About 5 years ago I completed a CNC conversion of a Grizzly G0704 milling machine. Like everyone at that time I chose to go with the Hoss Machine style conversion as there were not many options on the market. I was not comfortable designing my own system at the time since I was just...

www.hobby-machinist.com

The kluber is expensive, but I found a place selling small $30 tubes which is more than I need. I got some dosing syringes from out cats' vet to measure out the grease, and used free space data from NSK bearing catalog to calculate the grease fill for my bearings.

Feel bad for OP on his luck. I kind of expect that if you are buying a machine under 10-20k, you're going to have something broken or not well made on it. Some are easier to fix than others.

 

[GunsOfNavarone]

@macardoso not to lead this too far off topic, but is that the main consideration that is limited on how much speed a spindle can handle? The reason I ask is, I changed my lathe to VFD and I can now get over 4k now, for some reason that doesn't feel safe. If I were able to source very good, angular contact bearings, does this now make this achievable? (in your opinion?)

 

[macardoso]

@macardoso not to lead this too far off topic, but is that the main consideration that is limited on how much speed a spindle can handle? The reason I ask is, I changed my lathe to VFD and I can now get over 4k now, for some reason that doesn't feel safe. If I were able to source very good, angular contact bearings, does this now make this achievable? (in your opinion?)

Bearings have a factor called the DN factor. It is complicated to use, but it determines the maximum application speed, base oil viscosity, and bearing life time at a given load, speed, and temperature.

Good taper roller bearings with appropriately selected oil/grease can give performance into the high 1000s or even 10k+ rpm. You don't need angular contact bearings just because of that. You can probably run your bearings that fast, but you might need to select a different oil, and you will wear them faster. AC bearings will run faster, but also will reduce the spindle rigidity compared to a taper roller unless very carefully designed (additional bearings). I can't say for sure if it is appropriate to run your lathe that fast. I would be very concerned about the max speed of your chuck! They can explode if you exceed their rated speed.

 

[mksj]

Thanks for the info. I never found the cause of the surging , I went over all connection, it only did it the first time it ran and never again. Maybe it was a bat in the bearings, I'll check the oil.
I did notice that the advertised max rpm is 3000, this machine will run smooth at 3500 rpm. Maybe the motor swap? sure it's OK.
What I noticed is that it will operate from 0 to the max rpm stated for each gear, the low speed in each range is just recommend startling point correct ?

Surging as well as elevated bearing temperature are not uncommon with a new machine because everything is tight, it is always recommended that you slowly break in the bearings/gears by running the machine for a period of time starting at the lowest gear range and then successively go to the next higher speed. Running each for 20-30 minutes at each range first in forward and then in reverse, and if the bearings get hot allowing them to cool. Wanking a machine out at top speed out of the box is not a good idea. I had a gear head mill in the past, would go to 3000 RPM, the bearings/spindle head would get so hot you didn't want to put you hand on it for more than a few seconds. When I changed the gear head oil to a synthetic, it made a significant difference in head temperature and top speed. In reality, you rarely need more than 2000 RPM, unless you are running a small cutter with coolant and//or CNC. I now have a VFD knee mill with a direct drive, can't recall ever going past 3000 RPM even though it will go to 5K.

You have a speed pot to adjust the speed but it does not mean the usable speed is from 0-100. A reasonable speed range is 50-100% depending on the design and motor specs, factory VFD mills and lathe are usually 2 or 3 speed with a usable speed range of 20-100% with the 3 phase motors being run at 3X their base speed. So it is a matter of Hp and design, as well as the work load.

Glad you are up and running, DOA machinery does occur or early electronic failure, but once everything is working electronics should go for many years without issues. When I had issues with my gearhead mill, I waited for 6 months for a basic replacement part and had to jump through hoops to prove it was defective. The distributor closed up shop later on, so warranty did ot do me any good, and parts if something else went out I would have been toast. Buying subsequent machinery, service and parts availability played an important part in my choice of machines. It is often a waiting game if a part is not on the shelf, in particular during these times.

 

[BGHansen]

Curious what PM has to say about your experiences with this new mill. Replacing spindle bearings on a brand new machine? Reading posts here regarding PM machines (I don't own one so have no personal experience), they seem to be the best for customer service. Matt doesn't spec out junk components to save a few bucks.

Bruce

 

[GTPI]

Curious what PM has to say about your experiences with this new mill. Replacing spindle bearings on a brand new machine? Reading posts here regarding PM machines (I don't own one so have no personal experience), they seem to be the best for customer service. Matt doesn't spec out junk components to save a few bucks.

Bruce

My mill is up and running after a new motor controller, speed control, new motor and some poorly done electrical connectors replaced.
The answer to your question , absolutely nothing, I called last week with a question and was told to ask my questions by email. I sent the email and got no reply. No follow up to see if the parts worked, nothing. This board has been much help and I thank everyone here. Times have changed.
I know, There's a pandemic !
Seven week ago I became sick, tested positive for Covid-19, I'm also 64 and lucky have made a full recovery . I'm rethinking what's really important . Maybe this week I'll make some chips!