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Post Info TOPIC: head shake-Flow IFB


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head shake-Flow IFB
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I have been running this machine for over a year now, Not new t waterjet cutting, or flow waterjets.

We got the machine used, from a tile shop across the street from our shop when they upgraded.  It was a little bit abused, my job has been to try and get the machine to a good running condition.

The problem we have is our X axis.  The head has a noticeable shake to it, which effects our edge quality when cutting with the x axis.  

SInce i have been operating it, i have replaced the ball nuts in both axis. (they had about .020" backlash in all directions) and i have replaced all 4 of the runner blocks on the linear guides on the x axis.  

 

The result is the machine is better, but its not up to par.  There is visible kerfing on our finished products and our holes on thinner gauges .1875" and less tend to be out of round due to the head shaking.

 

The entire bridge shakes, not just the cutting head.  I have dropped the Z axis all the way and made sure everything is tight.  It is most noticeable when traveling -X, but also is noticeable occasionally in the +X.  When travelig -X and the head starts to shake, if i stop traversing, and start again, it will go away.

 

I can take video and pictures if neccesary.

 

Any help would be greatly appreciated, ive tried everything, im not sure what else to do? flowtech has not been very helpful.  We have had a tech out to look at it, and he didnt have any suggestions other than (replace the ball nuts)

 

thanks for the help

Gaven



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FLOW IFB 6X12 with 50is pump


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Linear guides worn from lack of maintenance?

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replaced all 4 of them

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FLOW IFB 6X12 with 50is pump


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Put something non-flexible straight across the top of the linear rails on the base section and see if the machine has been properly leveled. With the flying bridge machines, the systems are weighted so the center of gravity is over those rails, however if the machine is not leveled properly and tilted forward even a bit, the weight transitions outside of those rails and towards the front of the Y axis. This can cause the vibrations you are talking about.


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I will check that, but wouldnt that cause it vibrate in both the X+ and the X-? Ours only shakes in the -x.

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FLOW IFB 6X12 with 50is pump


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i checked front rail, to back rail with a transit (most accurate thing we have) we are within a 1/32" of level on 4 points of the front rail to 4 points on the back rail.

I also checked our perpendicular of the x and y with an 8" machinist setup block. we are within .005" (flow manual states .0005" is acceptable) so that means we would be out 10X the acceptable amount, but i would thing that would only affect how square squares and rectangles are, not cause the entire bridge to shake and oscillate.

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FLOW IFB 6X12 with 50is pump


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Figured out what our problem was, after 18 months.

Decided to tear the machine down again, and broke the motor loose from the bridge and moved the bridge manually by hand, No shake, problem isnt in the rails or linear guides.

Next spin the ballnut and pulley over by hand, smooth in one direction, ratchety feeling in the other. Getting closer!

I break the ball nut loose and spin it on the screw by hand, feels good, Problem isn't in the ball nut.

Whats left? The box that bolts to the bridge that the ball nut bolts to.

I call flow because i cant find an assembly drawing for that component. They need serial numbers, i cant find one, so i thank them for their time and decide to just open up the box and see whats inside.

So i do, and i find grease seals, rotating nuts, a machine shaft with a bolt pattern on one end (ball nut bolts to this) and 2 bearings, hmmm....

So i pull eveything apart, clean it up and look at my bearings, 2 different brands, a FAFNIR, and a NSK. Same part number, but i doubt flow ships their machines with 2 different branded bearings.

I start doing some research on these bearings, "angular contact bearings" apparently only good in one direction, must be preloaded and must be mounted opposite each other in pairs. Now we are really getting somewhere. Both bearings were installed facing the same direction!!! Which would cause it to not thrust properly in one direction

I take the bearings, put them in opposing each other, assemble everything, index the ball nut to .0005" and low and behold, MACHINE RUNS FANTASTIC!

As far as i can tell someone, at some point went into the machine, replaced one, and put it in backwards, i doubt it came from flow that way. The point is, its running great and it only took me 18 months to get it to this point haha

Thanks for all the input.

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FLOW IFB 6X12 with 50is pump
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