VF-10 Table Flexing

[MICFDI]

Although I read the CNC Forums, I seldom post. However, our shop has run into an issue I thought I would run by you folks. We purchased a HAAS VF-10 approximately 3 years ago. We haven’t had much problem with it up until about 2 months ago.

A little back ground: the VF-10 allows us to build spars for some military aircraft applications. These spars are made of 2024 – T851 aluminum. We machine a couple different lengths but it fair to say they run from 90 – 110 inches in length. The bar size starts out at approximately 4 X 5 inches. It is common for us to use a piece of 6061 approximately 3 - 5 inches thick as a sub-plate in which to bolt the spar material for our various operations.

Here is the problem. It is common practice for us to bolt the 6061 sub-plate down to the bed of the machine and then skim the top of the plate in order to make it flat. I must admit is some cases when we set the piece of material on the table you might see as much a .070 to .090 gap is various places. Using bolts we secure the sub-plate to the machine table. The gap obviously disappears as we bolt it to the table, without much force I might add. We then put the block of spar material on top of the sub-plate and will start our machining operations. We have used this method for approximately two and half years and we’ve had no issues. However, both the previous set up and our last set up have been a nightmare. The table seems to be flexing on the ends a great deal. So much so we can’t even cut a flat surface on the 6061 sub-plate, let alone cut a good spar.

We called our local HAAS distributor who sent the maintenance tech’s out and they did things such as check the machine for level, checked for worn truck and such. Today they come to us and tell us they can’t find anything wrong and we are not using standard machining practices. They want us to machine both sides of the 6061 sub-plate and make it perfectly flat. Then they want us to completely square up our spar material before bolting it down. There theory is the stress in our parts is so much that it is causing the table to flex. As we cut the part it starts to move as the stresses move and thus we can’t cut a good part. I am a point I’m going to humor them but no matter how much I try to tell them they don’t understand even if I make everything perfectly flat the spar material has stress in it, as I machine the part, those stresses are going to move, thus if the table is not rigid enough to hold the part, the part will move.

I would be very interested in your feedback. Is our practice of not milling both sides incorrect? Am I expecting too much in asking there table to hold this type of material without moving? Are we missing something obvious?

[haastec]

Your dealer may be partially correct and partially full of BS. Shocker!!!

I have seen situations where the subplate does not sit flat to the table after some time due to a buildup of the coolant that has dried underneath essentially lifting portions of the plate. As much of a pain this will be with a VF-10 sized plate, remove your subplate, clean and stone the machine table. Verify the table is level and has no twist in it, very important. Then machine both sides of the subplate, just to humor the HFO.

I would probably bet that your parts will come out like they were when you first set up the machine after doing this.

Good luck and keep us posted!

[HuFlungDung]

I would make every effort to machine the subplate flat in its unclamped postion. That means wherever you make the initial clamping, you have the piece up on blocks at the primary clamping points. At every intermediate clamping point, you place a support screw jack, and you use an indicator to watch for deflection as you tighten the clamp. You'd jack the part to neutralize clamping deflection.

Then you machine the first side.

Flip it over onto precision spacer blocks and test that they make contact with minimal gap variation. You might need to shim it here and there again to prevent clamping deflection.

Machine the second side.

At this point, the second side should make a pretty decent flat plane. If you had to shim the piece, then flip it again, but put it down on the table this time. Then take another light pass to flatten the top. You should then be good to go.

I would use the same procedure on the actual workpiece, to flatten it and get it parallel sided before clamping it solidly and directly to the subplate.

[Delw]

did you change material suppliers?

[MICFDI]

No, we have not changed material distributors.

The sub-plate has been on and off numerous times in fact we have used different sub-plates with similar results. The HAAS tech's have even went so far as to bar bar and level the table.

Late last night we just set the sub-plate on the table and the table moved almost .004 on the right hand outer most part of the table. The center of the table where the trucks are seems to be pretty stable.

We are in the process of machining both sides of the sub-plate.

Thanks all for your feedback - will keep everyone posted as we progress.

[Delw]

The table moved just setting the sub plate on? that too me would mean something is definatly loose, Maybe the way its leveled.
I assume you measured off the table and not the subplate?

I do lots of plates on my 40x20 fadal, Obviously I am no were close to the size of a v11 but its the same basic princiable. when ever I put on a new subplate I always cut top and bottom, then when doing the plates I always cut the locating surface. this ensures I am flat and parralle and it also helps reduce the stress that you might put into the part when you bolt it down. pretty mcuh what hungflung posted.

that would ahve been my first reply also, however I read somethign that you through in and thats the part about it worked great except for the last 2 months. reason I asked about material suppliers as something has changed in the last 2 months.
your subplate could be bent? I am assuming you check for burrs or gouges etc etc, bent sub plate is a pretty good possibility.

other things that it could be are loose leveling mounts mayeb when the subplate is in the machine tighten one mount a tad.

if all thats checked out ok it could very well be the table of the machine and the guides it rides on, somehow they are a tad sloppy, however while .004 doesn't sound like alot on that length of a table and with the other things you brought up I am beating on leveling componets.

I would love to see that machine rip through material that big.

Delw

[haastec]

I would hope your technician checked this but is it possible that the outrigger support for that side is out of adjustment? Was the table leveled at both the max and min travel in X?

[MICFDI]

Haastec - they did level the entire machine to include the outriggers. Also, it's my understanding they lifted the entire bed off the ways just to make sure the ways were tight and there was nothing wrong with the trucks.

I'm 99% sure they leveled the table in both the min and max travel for X. I'll ask when they come back tomorrow just to be sure.

[fuzzyracing1967]

Ok I'll give you one more to chew on for your problem.How about the floor itself? Have any cracks developed in the last few months that posabley now the machine is sitting on more then on slab? I only say this as it happen to one of are big lathes,chased are tail trying to figure it out.

[ROBERT TAMEZ]

How did you finally resolve the problem of the table flexing at the ends?

[ToyMaker94566]

mic-6 rather than 6061 makes a better sub-plate IMO. Not as pretty but less stressed like 6061 can exhibit. Also, I will grease the table underneath to slow corrosion. Some shops will even set the plate on standoffs to allow the table to breath and shorten the Z travel. You should pull the sub-plate from time to time just to clean underneath. Things can get funky down there after awhile.