Dynamic Mill Vs Traditional Toolpaths  
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Mazatrol M2
Experiment - Zig Zag Experiment - Dynamic Conclusion



Introduction (Spanish Translation)

In Mastercam X3, 2D high speed toolpaths where introduced. In X4, they were augmented with an awesome pocketing procedure called dynamic pocket. We will compare the results of this new toolpath as opposed to the age old Zig Zag toolpath.

Contrary to popular belief, 2D High Speed toolpaths are not just designed to run on "high speed" expensive equipment. This experiment was done on an older 1995 vintage low end vertical machining center. Its acceleration and speed is no were near the performance of today's mid range or even low end machinery.

The Victims: High Speed Steel 3/8" Two Flute End Mills.

Test End Mills

The Machine:
Mitsubishi M50
An old Leadwell VMC-25 with a slow Mitsubishi Meldas M50 Control.

The Pocket:

An open pocket was selected for this project to highlight how the 2D high speed toolpaths can handle open pockets with islands. They will also handle multiple entry points!
Dimensions - 5" x 3" x .75"
Pocket Depth - .5"
Material - AL 6061-T651

Mastercam File

How?:

We used the same methods any good mechanic would use to properly torque a bolt. - Turn it up till it feels really funny, then back it up a notch!
A Zig Zag toolpath was first used to see how fast this pocket could be milled out.

Experiment - Zig Zag

It was noted that at 30 inches per minute at a full depth of cut the tool would fail as soon as the cutter made a full material cut on both sides for any extended amount of time.

Classic Failure
4000 RPM, 30 IPM .5", Depth of Cut, Zig Zag Pocket - Failure Point
Failure of the 30 IPM zig zag - VIDEO

At 15 IPM, this pocket would cut successfully with a zig zag approach, albeit close to the failure point of the too

.Successfull Zig Zag Pocket
4000 RPM, 15 IPM .5", Depth of Cut, Zig Zag Pocket - Successful Pocket
Total Time - 4:10 - VIDEO

This full depth of cut method cannot be used for more than a few parts. In our case, the third part failed at these settings due to excessive chip loading.

Chip Load Failure
4000 RPM, 15 IPM .5", Depth of Cut, Zig Zag Pocket (Third Part)
Note how close to failure the tool is on the second part. - VIDEO
On the third part, the tool broke due to excessive chip loading.

Experiment - Dynamic

A dynamic toolpath with core roughing passes turned on was used to rough out the next series of parts.

Backplot
Note how the tool never cuts on both sides. It always maintains a climb cut by pecking away at the material as to maintain a constant 45% engagement when cutting and never more.

Failure @ 45 IPM
To find out how fast the tool could go without loading up, we just increased the speed until the chip load was simply too much. The failure point in this pocket was at the narrowest section as seen under the F
Adjusting the feed rate to 40 IPM yielded a reliable pocket operation in well under 3 minutes!

Dynamic 40IPM
The chips cleared consistently and reliably, making for an awesome material removal rate of .005" per tooth on a 3/8"diameter tool.

Thick Chips
.005" Thick, .5" Long chips!

Dynamic Videos:
Full Length Movie
Short Movie

Conclusion

The Dynamic pocketing toolpath offers an incredible speed advantage over the zig zag or any other traditional toolpath because it removes full tool burial. I could not belive it myself, untill I tried it on a practical example. Even in aluminum, it proved to substantialy reduce machining time and increase the life of the tool. This happens because more of the tool is actualy used to cut the part, and it is constantly taking small skim cuts and never fully engaged. It's as if you were taking a cut on the side of a block, all the time! This translates into huge feedrates and material removal rates in pockets.

Here is a comparison of actual feedrates and stepovers that can be used to reliably machine this pocket with a HHS tool in 6061 Aluminum.

Pocket Type IPM RPM step_over step_down cycle time
Dynamic Pocket 40 4000 45% FULL 00:02:26 (Calculated Time - Actual time is 2:45)
Zig Zag Pocket 25 4000 75% 0.25 00:06:12


An incredible time difference is seen. Even if we were to double the speed to an impossible 50 IPM, the pocket would never be under 3 minutes as is the dynamic pocket. The ability to clear out the chips makes the dynamic pocket incredibly fast.
One should note that since there is a large amount of acceleration and deceleration in the toolpath, mastercam estimates will be off depending on the speed of your machine. In this case it ran on an old Leadwell with a slow Mitsubishi Meldas M50 Controller, thus the times are slightly off. Nevertheless, a huge 55% reduction in time was observed with this toolpath! The tool will theoretically last at least twice as long since a full .5" length is cutting as opposed to just .25" in the zig zag pocket.
Using a carbide tool would effectively make this pocket in under 2 minutes if we were to run the spindle at a fairly tame 8,000 RPM.

NOTE: Always use the filter when posting to an older machine. This will make the toolpath run at full speed since the amount of code posted is relatively short and easy for the controller to execute.

Links

Cimquest
Mastercam
Spanish Translation of This Page
by 3dcadportal