[Roar]

Hello

I have a problem with the X axis, when I cut something in plastic i get wavy edge.
When I use the y axis,i get no wavy edge. (y axis is the longest axis on my cnc router)
I control the cnc router manual and use the arrow key on the keyboard.

I use the same speed and feed on y and x axis.

Can it be something with settings in Mach3? (motor tuning,acceleration)
Can It be that Z-axis is not stiffness?
Z-axis have only two Hiwin HGH20CA (one on each side) X-axis have four HGH20CA
I use the 2.2 kW Plug and Play Spindle/VFD System from cncrouterparts and 4-Axis Digital Plug and Play NEMA 34 System.

Wondering if I should create new z-axis with four HGH20CA,will be more stiffness?

I am quite newbie on cnc router.

[Jon.N.CNC]

You could be compromising your gantry end plate rigidity. What depth of cut, bit, feed & speed, x & y motor tuning settings?

[Roar]

You could be compromising your gantry end plate rigidity.

The end plate of gantry is 20 mm aluminium,Hiwin Linear Rails is bolted to this 20 mm plate on back,so it should be enough stiffness.

If that is the problem,i must do something on the top/bottom or buy a 20mm steel plate.


Motor tuning settings, look at the pictures


depth of cut, bit, feed & speed


Machine cutter perfect with y axis with this setting:

spindel 13000 rpm
feed speed 1000/Min
end mill 3 flute 8mm
depth of cut 10mm (outside cut,so only 0,5mm will be remove from plate)

But on the x axis I get wavy edge?

very strange

[Jon.N.CNC]

You could be compromising your gantry end plate rigidity.

The end plate of gantry is 20 mm aluminium,Hiwin Linear Rails is bolted to this 20 mm plate on back,so it should be enough stiffness.

If that is the problem,i must do something on the top/bottom or buy a 20mm steel plate.


Motor tuning settings, look at the pictures


depth of cut, bit, feed & speed


Machine cutter perfect with y axis with this setting:

spindel 13000 rpm
feed speed 1000/Min
end mill 3 flute 8mm
depth of cut 10mm (outside cut,so only 0,5mm will be remove from plate)

But on the x axis I get wavy edge?

very strange

Sorry forgot to ask, which plastic? 20mm aluminum plate is not alot tbh (enough to cut plastics but your going at all wrong i feel) 10mm doc is quite deep. Try say 4mm doc and see if you still get it. The bit is that a spiral, end mill or straight flute?

You're acceleration is far too high, try 100-200mm/s/s, not that i think that is the cause of your issue but it does help if you start the cut with some acceleration curve.

Could also be work holding, you're attacking it with a 10mm doc and extreme acceleration and its going to put a lot of vibration into the stock.

The gantry plates are the plates attached either side to the left and right of your x plate. The rigidity of these could be getting compromised. The rigidity in the x axis plate being compromised would be more evident when cutting in the y direction.

do you have a picture of the wavy edge?

[ger21]

He's taking a 0.5mm finish pass, so 10mm is not too deep.
Actually, higher acceleration is better. The problem is that most machines can't handle it.

Is the waviness the full length of cut, or just after turning a corner?
Are you using ballscrews on all axis?

[Jon.N.CNC]

He's taking a 0.5mm finish pass, so 10mm is not too deep.
Actually, higher acceleration is better. The problem is that most machines can't handle it.

Is the waviness the full length of cut, or just after turning a corner?
Are you using ballscrews on all axis?

Is he using a finishing pass. he hasn't said. 10mm doc with 8mm bit in say acrylic is more than his machine is capable of doing well.

edit: yes he has sorry, misread what he was saying, hmm still if its acrylic or other hard plastic 10mm it could still be too much for the machine.

[ger21]

Here's what he said...

(outside cut,so only 0,5mm will be remove from plate)

[TitaniumProcess]

I'm kind of a newbie in this area, but when mine would get wavy, my friend just helped me speed it up and adjust the tension.

Sorry I'm unfamiliar with how to tell you how/if you can do it with your machine, but good luck!

[Roar]

I have now try adjusted acceleration to 200 but is the same,i have set all to 500

Is the waviness the full length of cut? yes,all the way.

Are you using ballscrews on all axis? yes, 25mm on x,y and 16mm on z-axis


you can see the wavy egde on the picture,made a movie too.
https://youtu.be/E6bIxJgYmB0

[Jon.N.CNC]

I have now try adjusted acceleration to 200 but is the same,i have set all to 500

Is the waviness the full length of cut? yes,all the way.

Are you using ballscrews on all axis? yes, 25mm on x,y and 16mm on z-axis


you can see the wavy egde on the picture,made a movie too.
https://youtu.be/E6bIxJgYmB0

does it happen if you decrease the depth of cut?

[Roar]

does it happen if you decrease the depth of cut?

I try 4mm,but it is the same

[Jon.N.CNC]

does it happen if you decrease the depth of cut?

I try 4mm,but it is the same

cool, that rules out rigidity. interesting the waves are in the same place on both passes. Is it possible that the x ballscrew locknut is too tight? It wants to just tight enough to stop any play (hand tight).

[ger21]

If you cut the feedrate in half, do the ripples get closer together?

[wizard]

does it happen if you decrease the depth of cut?

I try 4mm,but it is the same

You might be getting a periodic error from something. As Jon suggest above leadscrews bearings could be an issue. Also a bent leadscrews could be an issue. Even linear bearing could be an issue if a bad bearing ball should be recirculating through one of the blocks.

I'd look at the waviness to see if there is a fixed pitch involved. That might give you an idea as to where to look.

[Roar]

Is it possible that the x ballscrew locknut is too tight?

Yes,that was the problem.

I disconnected the ball screw from x-axis and use my hand to sliding x axis,cut was absolutely perfect.

The Ball Screw bearings Support Unit on the end of the 25mm Ball Screw is not centered (made in China)

25 mm Ball Screw is not bent,i have measured with dial gauge is perfect.

I can use the old one,but i can not tight lock nut at all.

i will try to centralize the old one,before I make a new one.
I have metal lathe and milling machine.

[Roar]

I have now centralize the old Ball Screw bearings Support Unit, and is now perfect,locknut is not tightened too hard.

Still there is a little bit wavy edge.

As said when the ball nut,ball screw is disconnected from x-axis and use my hand to sliding x axis,cut was absolutely perfect.

Maybe there's something with the Ball Nut,is not level with the block unit.(maybe i most use shims)

[Jon.N.CNC]

I have now centralize the old Ball Screw bearings Support Unit, and is now perfect,locknut is not tightened too hard.

Still there is a little bit wavy edge.

As said when the ball nut,ball screw is disconnected from x-axis and use my hand to sliding x axis,cut was absolutely perfect.

Maybe there's something with the Ball Nut,is not level with the block unit.(maybe i most use shims)

Could be but it would likely jam up or they make a clicking sound if that was the case. Does it sound as smooth as the y and z? Could have some issue with the nut itself. Or did you check all the ballscrew support bearings spun freely without lumps? Also have you checked that the axis is traveling the same distance as in the dro? the coupling slipping might make a wavy edge.

[Roar]

I have seen at ball nut,ball screw,bearings,measured traveling vs DRO and coupling,everything is okay.
Have greased up ball nut and ball screw too.

I do not use Flexible Coupler, motor is directly connected to ball screw with joint.

will try again to remove the ball screw and sliding x axis with hand.

Tomorrow i will see little more on the issue.

[G59]

I don't know if you tried it yet?, reducing or increasing the spindle speed? Use shorter tool?

[Roar]

I don't know if you tried it yet?, reducing or increasing the spindle speed? Use shorter tool? Have tried it too.


I have now taken some videos,when I measure wavy edge with dial gauge.

I discovered that y axis is not synchronized with slave axis,i use a timing belt so is only loosen the set screw and turning one ball screw. (but it has nothing to do with wavy edge)


I discovered that z axis moving too much,watch the video 3 and 4.

Is that normally on a cnc router?

can this lead to wavy edge?

as I said,Z-axis have only two Hiwin HGH20CA (one on each side)

https://youtu.be/SzKx4GF6hRQ
https://youtu.be/qn5WoFNWNM4
https://youtu.be/fxvdltKHgUo
https://youtu.be/rECBCgZilVw