6040 cutting aluminum -> Chatters in one direction

I have a CNC6040 machine.

Yesterday we cut a few small (3x4 inches) rectangular pieces from 1/2 inch aluminum plate. (profile cut... so one site of the cut is climb and one side is conventional)

The machine long axis is X and short axis it Y. Zero of each axis of the machine is at closest point to motor mount.

Cutting was done with 1/4 inch 4 flute carbide bit VERY slowly (1/5 mm depth of cut per pass, feed rate was tried from 200-600 mm/min) RPM was varied from 6000-14000 to get largest possible chips.
The groove of the cut was constantly flooded with WD-40.

On 3 of the 4 sides of the cut we got zero chatter and the cutting was very quite. On the 4th side we got quite a bit of noise and chatter marks on that side of the part.

The direction of that chattery cut was on the short axis (Y) of the machine while the cutter was moving towards the motor.

Later I put a micrometer block and pushed on the motor spindle as hard as I could and there is total of 1~2/1000 deflection BUT it is the same in both directions.
I moved the head several times 50 mm back and forth and the machine has virtually zero backlash.

Also re checked that all the bolts are tight.

What should I do next to figure this out ?

-D

Just to review: on a normal machine the spindle revolves in a clockwise direction, looking down from the top. If the toolpath goes around the outside of the part clockwise, that is climb cutting. If it goes counterclockwise, that is conventional cutting. It sounds like you're having trouble when your machine is trying to cut aluminum in conventional mode. Climb is usually smoother. If you can structure your toolpath so the whole thing is moving in the same direction, rather than changing directions on one side, then your edges will probably look better. Of course, if you're cutting in a slot, the tool is cutting conventionally on one side and in climb mode on the other, which can rock the tool around, dull it, and cause rough edges. If that's your problem, then cutting the thing out roughly at first, leaving some margin for a continuous climb-only finishing cut at the end, might be your best solution.

Andrew,
Yes, I am cutting a SLOT....(one side is of the cut is climb...one side is conventionals...both show the chatter)
The problems is only in one of the 4 sides of the rectangle....:(
The other 3 are perfectly smooth and shiny.
What can be/is different in only one direction ?

Its weird but i sometimes face the same problem on my 6040. Sometimes theres just a spot on your toolpath that makes it resonant although nothing as severe as you describe. I do have som tips.

First of you are using a 4 flute cutter, which is way to much for these machines. If you calculate your feed and rpm you will see that you would have to have crazy fast feeds og horrible low rpm. Low rpm means that we fall out of the torque curve for our spindle and high feeds mean that the precision suffers... we may even find that our steppers overshoot. You need to use some of these:

5x 6mm Carbide CNC Router Bits Single Flute Tools 25mm

They are cheap but efficient. my record is 8 hours on aluminum without getting dull... then i slammed it into a fixture, so theoretichally way longer lifespan. 800 m/s @ 24k and 0.8-1mm DOC.

Checkout my reply last in this thread:

http://www.cnczone.com/forums/chines...inium-job.html

Btw i also mostly do climb-milling, but it dosent matter that much, since you will have material on both sides of the bit. And finish passes are required if you want a nice surface and precision in the 0.1mm ballpark.

Posted this in the linked thread in accident, I'll try to delete it:

800 mm/s? Wow that's fast lol. I've been testing out different speeds, feeds I do mostly profiles and at 1mm doc 12k @400mm/min the 2 flute 4mm endmill I was using started making crazy noise towards the end. I'm cutting shapes out of 6-7mm aluminum btw. I think a smaller doc would've yielded better results. I'm using vcarve for cam. What are you guys using for aluminum projects? Also any links to that homemade a mister setup you have there? I really need one

Here are one similar to mine:
Free Plans: Zero Fog Mister | MachinistBlog.com

For speeds and feeds calculation check this:
FSWizard - Free Advanced CNC Speed and Feed Calculator

It calculates the ideal speed and feeds, but dosen't take machine rigidity into the equation. Still it shows in what ballpark your setting should be. I only use 1 flute endmills usually 4 or 6mm. The 6mm really improves the deflection of the tool by many factors, so if possible i always go with a 6mm. If i take cuts from a really heavy plate (the weight kills the reasonans), then i have been able to go 1000 mm/s and 1mm DOC @ 24k rpm. But then i am really pushing if for aluminum. If it plastic i use the same speeds but go 2-3mm DOC. Just remember to leave 0.5mm for at finish pass.

I use Creo 2.0 for CAD and then export as IGES to MasterCam X5. I would love to go all Creo, but i can't get the post processor to work for Mach3 :s