trunnion table 4th axis alignment HELP

[Jacob79]

Hi Guys

I have a brand new Fanuc Robodrill with a Fanuc Trunnion factory installed.
My problem is when I tilt the table. 
In 0° I align it perfectly, but when I tilt in 90° and 270° and facemilling it, it does not make those sides parallel to each other.
I believe it is some adjustment of the table that is necessary. The 2 points in the bearings of the trunnion is in alignment, so it must be the baseplate or something of the table itself.
How is right way to make a complete alignment of the trunnion? 

Jacob

[nickbe10]

Can you post a picture?

This is often the problem with off the shelf 4 axis systems. You say the "bearings" are in line. Is that the Head and Tailstock/A-frame bearings, or the "bearings" on the trunion (they need to be in line to each other)? If ALL of the above are good and aligned properly are the trunion surfaces parallel and perpendicular to ALL three machine axis? Don't just check at A0, sweep the faces at A0, A90, A180 and A270.

How about your fixture, is it parallel and perpendicular? Anyone of the components being off will throw a spanner in the works......

I always prefer to make my own trunion/beam and leave extra stock on the surfaces. Then with everything aligned I qualify the trunion/beam surfaces to the spindle. then I machine my bolt pattern (or whatever holding system I am using). This assures everything is "square" to the spindle. Have you got enough material on the trunion to requalify it? Don't jump in here, you must confirm that ALL of the above components are in line and square first, or you could make things worse. Time checking now will save 10x (make that 100x) the number of hours of frustration and heartache later. Consult the dealer. Maybe they expect you to qualify the trunion? If it is brand new, get the dealer in to have a look (make sure it isn't your tooling/fixturing first to avoid embarrassment).

And all this assumes the table is flat and square to the spindle. It would be unusual for it not to be, but not beyond the realms of possibility. If there is a subplate check that it is flat and square to the spindle. I'm not usually happy unless everything is square ad parallel </=.001 over 18" - 24". This is achievable with care.

[cncchipmaker]

We always get the backlash out of our rotary tables when indexing. This is the only way you can get your positions right on the money and this may be why you are having the issue.

[nickbe10]

And on cncchipmakers note how does the "index lock" work, is it automatic or do you need to command it in the code?

[Jacob79]

19 hours ago, nickbe10 said:

Can you post a picture?

This is often the problem with off the shelf 4 axis systems. You say the "bearings" are in line. Is that the Head and Tailstock/A-frame bearings, or the "bearings" on the trunion (they need to be in line to each other)? If ALL of the above are good and aligned properly are the trunion surfaces parallel and perpendicular to ALL three machine axis? Don't just check at A0, sweep the faces at A0, A90, A180 and A270.

How about your fixture, is it parallel and perpendicular? Anyone of the components being off will throw a spanner in the works......

I always prefer to make my own trunion/beam and leave extra stock on the surfaces. Then with everything aligned I qualify the trunion/beam surfaces to the spindle. then I machine my bolt pattern (or whatever holding system I am using). This assures everything is "square" to the spindle. Have you got enough material on the trunion to requalify it? Don't jump in here, you must confirm that ALL of the above components are in line and square first, or you could make things worse. Time checking now will save 10x (make that 100x) the number of hours of frustration and heartache later. Consult the dealer. Maybe they expect you to qualify the trunion? If it is brand new, get the dealer in to have a look (make sure it isn't your tooling/fixturing first to avoid embarrassment).

And all this assumes the table is flat and square to the spindle. It would be unusual for it not to be, but not beyond the realms of possibility. If there is a subplate check that it is flat and square to the spindle. I'm not usually happy unless everything is square ad parallel </=.001 over 18" - 24". This is achievable with care

 

 

I have enough stock on the on my baseplate of the trunion to make parallel to the Z axis, and I have done that and my fixture is parallel and perpendicular. If I check the axis in A0, A90, A270 I have a total error of 0,07mm which is way to much.

My problem is that I need to make a rod/shaft that I can put through the center of the bearings ( bearings on the trunion) to check if they are in line with each other. Because the machine can't reach.

I just assumed that they were, but I can see from all of your comments that my problem is probably there.

We bought the machine directly from Fanuc, and you would not believe the kind of trouble we have had. The service are close to non existing so we have been forced to consult others to help us out because we just couldn't wait for Fanuc. Sometimes there has been over 1month wait on a technician. 

 

 

 

[Newbeeee™]

Are each ends of the trunnion definitely in line?

I mean DEFINATELY in line?

And I also mean in BOTH planes?

0.07mm is only 0.035mm out of squareness, because it obviously doubles when you index from 90 to 270 (.035+.035 = 0.07mm)

Early on, I realised the only way to accurately do this kind of work, was to do as much as possible from each setting. ie, A0 face top, toolchange and side profile/finish all faces.

You should then have the best job you can have, and for jobbing work, I found it easier to then set datums for A90/A270 because I could then set my Z off the finished face. 

[nickbe10]

So as Newbeee says that is only .0013 inch, and maybe double if you have to work three sides, really not that bad for an off the shelf  product in this category. What tolerances are you having to hit? What material are you cutting? What's your largest endmill you need to run? I ask because this is a pretty lightweight machine. Most applications I have seen with these machines involved parts in the 1"-3 " range, usually from aluminum extrusion and +/- .01" - +/- .03" tolerance. That's a pretty big/heavy fixture for a machine this size . So the amount you are off on your rotation could be easily drowned out by tool deflection/pressure, droop from the weight of the fixture, etc.....

I would agree with Newbeee that the trunion bearings would be my first suspect because they are bolted together so there is bound to be "some" inbuilt error. The axis of rotation is probably sweeping, that is it is not perfectly parallel to the X axis.

If you really need to tease this out can you attach an aluminum block at each end using the outboard holes? Have you got a Bridgeport or some other three axis machine? You need to start with as square a block as you can manage.

Get them attached as far out on the trunion on each end as you can.

Find the Center of rotation in the middle of the table. Use that as your offset in Y and Z

Take a side cut on one face of the blocks at A0 then an end cut at the same Z value as Y on the first cut on the A90/A270 rotation. So Y3.0"  at A0 and then Z3.0 at A90

Make the cuts so they overlap but don't cover each other.

Any step between the two cuts will tell you how far off the center of rotation you are for any particular rotation/plane at that point on the X axis

If you can do this on all three faces of the two blocks at opposite ends of the table you will be able to work out which planes are out and by how much.

But even if you get this far what's the fix? Are the trunion components pinned? If not maybe you could loosen the bolts and tap it closer to square. If they are pinned then you would need to rebore and resleeve the bearing holes. You will need some very good indicators and probes to even get it close, or at least closer than you are.

The last beam (not trunion) I made was 24" long. I ground to adjacent faces square and then put it in a 50T big travel Mori Horizontal (very new machine never crashed) probed the ground faces at each end ( B180 degrees apart) and bored my bearing holes. Then checked with a CMM. And we were still a  few .0001s off, which was fine, our tightest tolerance plane to plane was .003. Do you have access to that sort of machinery?

And with all that maybe you get it down to .0005 - .0008, its never going to be perfect......you might be better off just learning to live with it.....if you can.

Hope that helps......

[coolvdub62]

That looks like a lot of mass on such a small machine. You might want to hire somebody with a laser inferomoter that knows how to use it to check the alignment between the two ends of rotation. The set up looks like it could have many potential problem areas.

Edited December 26, 2017 by coolvdub62
spelling

[Jacob79]

On 26/12/2017 at 1:23 AM, coolvdub62 said:

That looks like a lot of mass on such a small machine. You might want to hire somebody with a laser inferomoter that knows how to use it to check the alignment between the two ends of rotation. The set up looks like it could have many potential problem areas.

I think you are right that it is to much weight on this small machine, but I cannot explain it to my boss. I will check the alignment of the two ends of rotation, align everything again and take it from there.

[Newbeeee™]

I don't think mass is the problem, I think it's as simple as alignment.

These little machines can take one heck of a load, and run and run and run.

How are you going to check the height alignment? If you run a clock along the machined pallet face (A0) and it reads 0, it doesn't mean the bearngs at each end are parallel.

It just means the face has been skimmed on the machine.

But clock at A0, index 90 (mdi not handwheel - think backlash etc) and then clock the face both along in the X and also vertically in the Z

[nickbe10]

1 hour ago, newbeeee said:

But clock at A0, index 90 (mdi not handwheel - think backlash etc) and then clock the face both along in the X and also vertically in the Z

That's the point of doing the end (i.e. end of endmill) cuts + side cuts (i.e. side of endmill) on all three faces of the test blocks. If it is rotating on center of X axis there should be NO steps. Steps and which way they go (end cut relative to side cut) will tell him how far off center he is at that location in X and for all planes concerned, end cut and side cut on each face. This will give a Hard number rather than a relative one from the indicator.

The thing that worries me is the tolerances he is trying to hit (as you mentioned before he is only 0.0013 off at the moment) and the material (unknown quantities at this end).....as it is he could hit +/- 0.01 in Al with no problems.  +/- 0.005 in Ti would be more problematic........They don't call them Robodrills for nothing, they are mainly for drilling and light profiling, and for that I have seen them used extremely effectively. Z clearance looks tight too...........