728VT really unhappy!

rogerl said:
55fairlane:
Do you think that the problem with the previous machine was because it was sitting on a flimsy base? You have a much more stable base that your new machine is sitting on.

Roger L
Click to expand...
No, there is/was a problem with the machine. I believe the machine was dropped in shipping.
I noticed how flimsy the base is once I had removed the original machine. With how flimsy the base is , there is no way I could have ever gotten the machine "shimmed up" , i.e. shimmed into a true & flat condition
 
Downunder Bob said:
It's good that you have your machine setup to your satisfaction. However please uinderstand that having a machine level is an old argument and is based on a false premise. The machine must be true to itself. As a trained fitter and turner / toolmaker, and now retired marine engineer, I have used many machines, lathes, mills, shapers etc on board many a ship at sea. Now please explain to me how a machine on a ship at sea can be level. There will be individual moments in time when it's level, but a second later it will not be level. What is important is that when the machine is bolted down that all stresses and bowing and twisting are removed from it, then the usual test cuts are made, final adjustments are done, and the machine is good for service. I have used many machines in this way, and found no difficulty in obtaining the same precision that I would expect while on dry land.
Click to expand...
I also am a tool maker by trade, to your argument of a naval based machine, the machine is bolted to the decking of the ship in a true & flat condition. Therefore the yaw & pitch of the ship should not affect the accuracy of the machine tool.
We use the term "level" to refer to a true & flat condition
 
Larry$ said:
It's worth noting that cast iron moves! Ideally it is stress relieved before finish grinding the reference surfaces. Takes time & $ so think about that in relatioship to where the machine came from. There are always stresses in castings, uneven cooling! Over time those stresses relax and may cause the casting to change shape, slightly/or more.
Click to expand...
When a machine spends a great deal of time, i.e. months, bolted to an uneven wooden pallet they can pickup a twist and/or bow. We think of these castings as big heavy and stiff but the stiff part is subjective, they will deform to match the foundation they are sitting on. With time and patients these induced twists and bows can be worked out, they will relax to the new foundation if allowed, it doesn't hurt to provide a little encouragement like 150 pounds of lead if you can.....
 
55fairlane said:
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
Click to expand...
Is that a square column machine? If so I have a square column and I have had to shim it too. From what I have read, shimming is not the best for rigidity. I still chase mine around just about every time the head moves. I hate it. I would return it
 
Pevehouse said:
Is that a square column machine? If so I have a square column and I have had to shim it too. From what I have read, shimming is not the best for rigidity. I still chase mine around just about every time the head moves. I hate it. I would return it
Click to expand...
Yes a "square column " , bolted from the underside.
I feel the column it's self is very square to the machine, the base is twisted, I shimmed under the corner of the machine base. That will not affect rigidity.
Even if the column is out of square and needs shimming, if done properly this should not affect rigidity.
It should be noted, the use of a torque wrench (set at proper torque) is a must when setting the machine, or doing the shimming. A even know amount of torque is necessary.
 
verbotenwhisky said:
When a machine spends a great deal of time, i.e. months, bolted to an uneven wooden pallet they can pickup a twist and/or bow. We think of these castings as big heavy and stiff but the stiff part is subjective, they will deform to match the foundation they are sitting on. With time and patients these induced twists and bows can be worked out, they will relax to the new foundation if allowed, it doesn't hurt to provide a little encouragement like 150 pounds of lead if you can.....
Click to expand...
Yes I believe being bolted to a pallet can cause an out of square condition, the wood doesn't offer much support, there for you will need to correct this.
Our big VMC's at work , those casting will move they are not perfect ridged, in fact I believe they are designed to give a little to keep from breaking up in to scrap.

I added those aluminum plates and that has made a great difference, then in the very bottom of the cabinet there is a 300 pounds of lead and cast iron....should help
 
55fairlane said:
Yes I believe being bolted to a pallet can cause an out of square condition, the wood doesn't offer much support, there for you will need to correct this.
Our big VMC's at work , those casting will move they are not perfect ridged, in fact I believe they are designed to give a little to keep from breaking up in to scrap.

I added those aluminum plates and that has made a great difference, then in the very bottom of the cabinet there is a 300 pounds of lead and cast iron....should help
Click to expand...
My lathe has a twist and since it is not bolted to the floor I could not pull it out so I used 150 pounds of lead in the aft tail stock corner of the cabinet and over a period of a couple months it settled down flat, cuts beautifully now. My mill settled down and I am now doing a final adjustment to it, it is a PM940V.
 
You must log in or register to reply here.
Back
Top