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Wavy cut on Byspeed 4400

Wavy cut on Byspeed 4400

Wavy cut on Byspeed 4400

Hi All,
Has anyone seen small occilations in he cut finish on a Bystronic
Byspeed 4400, 31,000 hours on time. It maybe it needs new ballscrews although they dont appear to have obvious signs off wear. With the power on if you try to push the machine off position with the power on the machine comes back to withing 0.03 mm both directions
with a dti on the cutting bridge which of course it should do because its reading off the the linear scale rather than an encoder on the motor.The optical tacho mounted on the main servos is not full of excess grease from the ball screws.
The wavy cut is most noticeable on 5mm and under and when 2 axis are moving together
The servo drives are the old analogue type just before the byvison cnc.
With the power off I can not feel any play if I turn the leadscrew nut/motor and watch a dti on the bridge and pushing it by hand sounds ok and feels smooth.
Turning down dynamic factor and accel and brake factor may reduce the problem slightly
but does not remove it.
It does not appear on 10mm thick oxygen cut plate at all but does appear on 3mm nitrogen and oxygen cut part quite bad. It not just a simple case of occilation after changing direction. and the strangest thing we think it appears in minus x direction
and on the right hand side of the cut.
It is fine and most parts are still okay but nowhere as good as a new machine
Our service tech did test cuts of triangles parrallel to the axis on different materails
and could not firgure out if it is a mechanical problem or not.
Bystronic drives do not seem to have tuning options like typical servo drives and motors
Is there any setup cnc settings that may help or way I can at least figure out the
exactly where the problem is.


RE: Wavy cut on Byspeed 4400

Has the encoder strip been cleaned at all or replaced? I have seen this in the past with the first batch of Byspeeds. The issue was the Dynamic factor in the parameters were way too high and had to be dialed back. Did they provide you with any updated parameters since the problem was reported? The applications department would be responsible to provide new parameters.

RE: Wavy cut on Byspeed 4400

Hi Henry,
Yes the encoder strips were replaced with the new non optical type when the machine was about 2.5 years old at no charge
even though they now say no cleaning required we have clean the tapes , removed the reader head wiped clean and set the gap to 0.15 - 0.20
with he supplied green plastic strip.
I have been sent a copy of the setup Parameters so I will compare all of these today to make sure nothing has changed
The machine rapid traverse setting was reduced to 100 metres per minute when installed so should of lasted well.

Have you had to replace many or do most companies replace whole about this age?


RE: Wavy cut on Byspeed 4400

Run the z axis down near the material and then open the door, grab it around the nozzle area and see if there's any play, z bearings break in this machine. Is the grease on the ballscrews discolored or dried out? Shut the machine down and push the x and y axis by hand, it will take a little effort but it should move smoothly. make sure the poscon cards are zero'd out before adjusting the drives.

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS

RE: Wavy cut on Byspeed 4400

The z axis has almost no play as the the leadscrew and linear bearings were replaced with the upgrade kit 6 months ago
and now has remote greasing points, The x and y moves smoothly when pushed but requires some effort ( not really easy
like a well worn leadscrew). The greasing cycles do complete and there appears to be new grease on leadscrews afterwards
I will try to retension the leadscrews to see if it helps. I don't have a TI on how to adjust the drives but was told the other day
that some service techs are not aware the the older machines drives are set to .7 volts and the newer ones are .9 volts even though the
drives are more less the same ones and this adds to the problem if the old one are set to the higher setting.
I really don't know why TI sheets are private and not for owners - are Trumpf the same?
Could you please explain "zero poscon cards" in more detail


RE: Wavy cut on Byspeed 4400

Is it MMC or byvision. What you need to do is shut the 3ph power off to the drives, this makes it so they can't move, then turn the machine on, the voltages should read 0. Also you can force maximum signal to the drive by slowly turning the jog button for the respective axis, the poscon voltage should slowly rise, mqake sure the max values in each direction are the same ie if you go - you should see the poscon max out at like -.995 then + value for same axis should be same +.995

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS

RE: Wavy cut on Byspeed 4400

Hi Jetray,

Don't shoot me for saying this but have you tried clamping the sheet? We have seen this improve the cut finish. It does sound like the bearings within the nut, are there any strange sounds from the axis when moving them at lower speeds, say 2000-2500mm/min?
It may well be worth checking the zero volts once the drives have stopped, given that the feedback should be zero then. Another thing you could try (depending on how experienced and happy you are) putting a 'battery box' or manual input to the drive.
Hope this helps a little.

RE: Wavy cut on Byspeed 4400

@jetray, were you able to resolve your issue with wavy cuts? if yes, can you please advise what fixed it?

RE: Wavy cut on Byspeed 4400

on these machines the ballscrews wear out and cause a wavy cut in one axis. Anyone who owns a byspeed needs to turn the acceleration down so the machine doesn't beat the crap out of itself for a few % more production.

Chris Krug http://krugtech.com/
Maximum Up-time, Minimum BS

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