Help with 5th axis trunion table.

[classic9mm]

Hello, maybe someone has some insight on this problem I am having. I recently started a new programming position. This company just got 2 new Okuma Vertical Machining Centers with Nikken 5th axis tilt and rotate tables. I am using Delcam Partmaker. I am working on a 3+2 axis project that requires me to rotate up to 270 degrees and tilt no more than 90 degrees. The Nikken Table is sitting along the Y axis of the Machine. The problem I am having is that when the part is tilted at 90 degrees the tool path seems to be shifted about .015 from where it should be. It is shifted in what would be the X axis when the part started at A0 C0 when it is cutting the part is at C90 and A90 and laying along the Y axis it Is short the same amount when it is at 180 degrees the other way C270 and A90. I have a feeling that whomever got the starting work offset for the Nikken table might have been off. What I cant figure out is are the center lines of rotation off from A and C when tilted 90 degrees? Does that happen a lot with these 5th axis Trunion tables? If so do I modify the output in the posts? I have already built the post from scratch because Partmakers support is non existent. Any Thoughts? I will doing extensive experiments after this run for now I have jut changed the geometry to correct the errors . Thank You.

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[lcvette]

Hello, maybe someone has some insight on this problem I am having. I recently started a new programming position. This company just got 2 new Okuma Vertical Machining Centers with Nikken 5th axis tilt and rotate tables. I am using Delcam Partmaker. I am working on a 3+2 axis project that requires me to rotate up to 270 degrees and tilt no more than 90 degrees. The Nikken Table is sitting along the Y axis of the Machine. The problem I am having is that when the part is tilted at 90 degrees the tool path seems to be shifted about .015 from where it should be. It is shifted in what would be the X axis when the part started at A0 C0 when it is cutting the part is at C90 and A90 and laying along the Y axis it Is short the same amount when it is at 180 degrees the other way C270 and A90. I have a feeling that whomever got the starting work offset for the Nikken table might have been off. What I cant figure out is are the center lines of rotation off from A and C when tilted 90 degrees? Does that happen a lot with these 5th axis Trunion tables? If so do I modify the output in the posts? I have already built the post from scratch because Partmakers support is non existent. Any Thoughts? I will doing extensive experiments after this run for now I have jut changed the geometry to correct the errors . Thank You.

The first thing I would check is to be sure your centerline's of rotation are true. If those are of at all is going to stack. Then your location of those centerline in relation to the X, Y, Z coordinate system. Then make sure it's correct in the cam software for is kinematics calculations. Finally, make sure your fixtures are correctly defined.

If you have a precision block you can mount and probe to verify everything is correct it is helpful to prove your setup is programmed in properly this of course is easier to do with at least a true 180* twist in the 4th and full 360* rotation on the 5th.

Once you verify the centerline's are correct, you will need to verify that the command movement and actual movement of each axis on the trunnion is being achieved. Make sure there isn't any backlash in the rising acid as this will definitely show itself in stacked error as you move out from the rotation centerlines!

Let us know what you find!

Chris

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[classic9mm]

Yesterday after a week of suggesting that it was not the setup in the cam software and that the zero position of the 5th axis trunnion was off we milled a cylinder into a aluminum block with the c axis rotating. Sure enough the x axis was off. From now on we will use the xyz zero from the machined cylinder center. I know there is alot more that we need to take in to account to make everything perfect. The centerlines at a 90 and a 0 seem like they are perfect. My only other concern was a few thou difference along the x axis at a 90. I feel a little vindicated now that I proved everything was ok in the cam software. I also an very conserned because whomever set the fith axis up origionally didn't seem to do a very good job l.

[lcvette]

Yesterday after a week of suggesting that it was not the setup in the cam software and that the zero position of the 5th axis trunnion was off we milled a cylinder into a aluminum block with the c axis rotating. Sure enough the x axis was off. From now on we will use the xyz zero from the machined cylinder center. I know there is alot more that we need to take in to account to make everything perfect. The centerlines at a 90 and a 0 seem like they are perfect. My only other concern was a few thou difference along the x axis at a 90. I feel a little vindicated now that I proved everything was ok in the cam software. I also an very conserned because whomever set the fith axis up origionally didn't seem to do a very good job l.

I'm glad you figured it out, finding any minor variances can be tricky because so many variables come into play with 5 axis setups. Honestly you would want to start with ensuring X, Y, Z are all square to each other as that's your foundation for accuracy. Remember to check your column run-out prior to your tram.

If those are all true and squared, move to the 4th being square and true to the X, Y, Z.. then once confirmed, move to the 5th axis. If the spindle and head is true to the table through full Z travel and tram is good, you can run a tram test on the trunnion table surface. You may need to shim the 4th and 5th trunnion assembly on the table to achieve correct alignment. Obviously you hope it is machined perfectly square and won't require shimming. I like to stone for any burrs that could cause it to be off before getting in to shimming.

after that you should only be faced with the margin of error of the measurement tools used for all of the alignment and the only way to improve that gets ridiculously expensive.

Hope that helps. There is a reason most have a dedicated machine for trunnion setups, going through setting it up takes a while if anything is off it can take alot longer..lol. Once it's setup and dialed in most don't want to have to go through it again..lol

Glad you are getting it there!

Chris

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