728VT really unhappy!

[Archer60x]

Here is a video on how this mill works. It does not have a knee.

 

[woodchucker]

I forgot, I didn't read all the way back to remind me what was going on.

 

[Eddyde]

2 weeks ago we set a 728VT in my garage, spent this weekend installing the power feed, traming in the vise, ect.....
Got around to firing the machine up and making chips....went thru the square up the blocks routine, will not square up (in Y ) I tried everything (including getting my text book out from when I served my apprenticeship) finally bolt a 2-4-6 to the table & in the vise....using Z run an indicator up & down the blocks......0055 in 3 inches, the head in nodding at me, crap, call PM.....got thru the details with them, new Kurt vise, new Lyndex collets, used interapid indicator, and started my apprenticeship in 1986....been running machines since then.....3 hours on the phone, try this, they that, thy this.....short answer I get to pull the column loose & shim it....$5722.16 for new machine & I get the privilege of fixing it.....feeling very cheated

I don't blame you for feeling cheated, I'd be pretty ****** off too. I'm also kind of surprised as for the past 9 years of being on this site, I have heard mostly praise of PM machines. Did you get a chance to talk directly to Matt, the owner? He's got a reputation for making things right.

 

[Larry$]

Stefan Gotteswinter has a video on shiming the column. Probably the best info on the subject you can find.

 

[verbotenwhisky]

I am new to this machining stuff. Would pumping the oiler improve head nod?

I have an old dial test indicator and i have a new one on the way, but my head nod seemed to go from top of 2-4-6 block .000 (top) to .010 (bottom) (moving Z up to down). This same .000 to .010 was also shown in the spindle going up and down also. I locked each axis with the hand locks after the movement.

I made two changes like a dummy . Moved my strap clamp to the middle of the 246 block and pumped the oiler 3 or 4 times. Now my head nod goes from .000 to .001 Same with spindle... could be my DTI also.

So my test is in-conclusive until i learn more and get a better DTI i can trust. THis is my setup

View attachment 472896

I worked for an Aerospace Company (which is now long gone) in 1998 that was designing a new launch vehicle (I was the mechanical ground support designer). One of the things I learned from that job was, regardless of how much time it might cost never make more than 1 change at a time then test the change record the differences and make the next. I watched the propulsion guys tediously make a change put the engine together test it then pull it down inspect and put it back together making 1 more change which I remember thinking was dumb; so, one afternoon I asked the dumb question, "why don't you fix the things you see which are causing the issue then test". They smiled at me, then explained that "when you are chasing an issue if you make 2 or 3 changes and it gets worse how do you know which change(s) made it worse and how do you know that one of the changes might have fixed it and the other(s) caused you to chase a different issue which did not exist previously". I have since adopted that philosophy and although it might seem strange but it actually alleviates a lot of stress and reduces time spent.

 

[woodchucker]

I worked for an Aerospace Company (which is now long gone) in 1998 that was designing a new launch vehicle (I was the mechanical ground support designer). One of the things I learned from that job was, regardless of how much time it might cost never make more than 1 change at a time then test the change record the differences and make the next. I watched the propulsion guys tediously make a change put the engine together test it then pull it down inspect and put it back together making 1 more change which I remember thinking was dumb; so, one afternoon I asked the dumb question, "why don't you fix the things you see which are causing the issue then test". They smiled at me, then explained that "when you are chasing an issue if you make 2 or 3 changes and it gets worse how do you know which change(s) made it worse and how do you know that one of the changes might have fixed it and the other(s) caused you to chase a different issue which did not exist previously". I have since adopted that philosophy and although it might seem strange but it actually alleviates a lot of stress and reduces time spent.

That's the same in programming and bug fixing. You work on one issue, make sure it didn't cause some side issues.
Then you go to the next. A sure way to wind up creating a lot of new or , new old issues is to do a lot of fixes at once.

 

[qualitymachinetools]

2 weeks ago we set a 728VT in my garage, spent this weekend installing the power feed, traming in the vise, ect.....
Got around to firing the machine up and making chips....went thru the square up the blocks routine, will not square up (in Y ) I tried everything (including getting my text book out from when I served my apprenticeship) finally bolt a 2-4-6 to the table & in the vise....using Z run an indicator up & down the blocks......0055 in 3 inches, the head in nodding at me, crap, call PM.....got thru the details with them, new Kurt vise, new Lyndex collets, used interapid indicator, and started my apprenticeship in 1986....been running machines since then.....3 hours on the phone, try this, they that, thy this.....short answer I get to pull the column loose & shim it....$5722.16 for new machine & I get the privilege of fixing it.....feeling very cheated

No way, and I am going to find out who told you that. Shimming is fine to perfect it, but not .0055 over 3". They are way better than that. Are you sure the head gibs are tight and its not moving there, or where the head mounts to that plate? Make sure to check that first, but the factory spec is way tighter than .0055 over 3", so I am going to find that tech ticket and explain to our tech people that no, it is not acceptable on this machine.

 

[55fairlane]

No way, and I am going to find out who told you that. Shimming is fine to perfect it, but not .0055 over 3". They are way better than that. Are you sure the head gibs are tight and its not moving there, or where the head mounts to that plate? Make sure to check that first, but the factory spec is way tighter than .0055 over 3", so I am going to find that tech ticket and explain to our tech people that no, it is not acceptable on this machine.

@qualitymachinetools I sent you a pm .

 

[55fairlane]

No way, and I am going to find out who told you that. Shimming is fine to perfect it, but not .0055 over 3". They are way better than that. Are you sure the head gibs are tight and its not moving there, or where the head mounts to that plate? Make sure to check that first, but the factory spec is way tighter than .0055 over 3", so I am going to find that tech ticket and explain to our tech people that no, it is not acceptable on this machine.

I redid the test with an 8 inch angle plate and got .0075 /.008 in 7 inches.

 

[LVLAaron]

I redid the test with an 8 inch angle plate and got .0075 /.008 in 7 inches.

What direction? Z? (up and down)