Spike Trochoidal Milling

america Trochoidal
Milling Study

axial force torque bending moment temperature

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Goal: Determine how CAM system programming can improve variable force loading on
tools, cutter engagement and disengagement, machine optimization and process security.

Method: Applied Engineering of Yankton, SD programmed a demo cut using their current
CAM system, GibbsCAM with a plug-in from Volumill. This would be considered „current
state“ for our comparison test. Autodesk, INC. provided a CAM system post to match part
production. This would be considered „future state“ All variables remained constant in our
comparisons of tool paths. All cuts were made in 6061 aluminum on a Makino A51
horizontal machining center.

Current State Definitions:

The above image is a completed component after machining with GibbsCAM and Volumill.

Looking closely, you can easily see evidence of tool path during trochoidial milling, as well as

the perimeter clean up passes and other aspects of the roughing operation.

measurement file: Current State

Path: C:\Users\JBoring\Desktop\SPIKE_Measuring\Gibbs with Volumill ,50 step 1DOC
Date: 1/18/2016
Time: 4:15 PM
Operator: JB

documentation:

Tool: Guring 3 flute

Material: 6061

vc (SFM): 1571 f (in/r): .01666 ap (ap/in): 1.000
vf (in/min): 200 ae (in): .250
n (rpm): 12000

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d (in): .500 flutes: 3 X° (Grad): -

Testing time: 04:02.02
Used filter:
Notes: Average 100

GibbsCAM + Volumill roughing operation 6061 aluminum on Makino A51 Horizontal Machining
Center

data: from 12.26 to 03:56.29

Bounds:

tension / pressure (N) mean max. value min. value slope
torsion (Nm)
bending moment (Nm) -308.1 29.1 -702.8 -0.4
temperature (°C) 3.2 8.6 -0.3 -0.0
41.4 119.0 -0.8 -0.1
29.1 29.6 28.2 0.0

Observations on Current State using Bending Moment as a critical factor:

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Let us delve into certain characteristics of force at work on the current state cycles. In the above
graphic, I have labeled major operations within the rough machining cycle.
Outside Roughing – Here, we are quite literaly cleaning up the outside of our features, and I have
zoomed in to the outside operations.

Some things to note:
1) On the first rough passes, there are a lot of times where we are cutting air. Any time the
bending moment drops down to 0Nm, the cutter is no longer engaged.
2) On the second rough passes, the tool is engaging, but the forces vary (just like the stock) and
we get force variation of about 20Nm across the pass.
3) The third rough pass is nearly optimized.
4) The keyway trochoidial cuts and last rough pass all seem to be pretty much in line with what I
have come to expect for a milling operation.

Inside Roughing – Here, we are observing force characteristics of the interior features. Again, zoom
has been used.

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Something to note:
1) The variance in forces over the interior trochoidial and linear machining section indicates
uneven cutter paths. Ultimately, this can equate to uneven (or accelerated) cutter wear and
an increase in time required to run the program.

Let us now look at „Future State“.

fmeasurement file: Future State

Path: C:\Users\JBoring\Desktop\SPIKE_Measuring\Autodesk 2 1.000 DOC

Date: 1/18/2016

Time: 4:27 PM

Operator: JB

documentation:

Tool: Guring 3 flute

Material: 6061

vc (SFM): 1571 f (in/r): .01666 ap (ap/in): 1.000
vf (in/min): 200 ae (in): .250
n (rpm): 12000 flutes: 3 X° (Grad): -

d (in): .500

Testing time: 02:44.25
Used filter: Average 100
Notes: Autodesk roughing operation 6061 aluminum on Makino A51 Horizontal Machining Center

data: from 06.16 to 02:35.20

Bounds:

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tension / pressure (N) mean max. value min. value slope
torsion (Nm)
bending moment (Nm) -283.4 349.8 -644.4 0.2
temperature (°C) 4.1 8.6 -0.4 -0.0
60.4 -0.8 -0.2
29.1 123.7 28.2 0.0
29.5

Observations on „Future State“ using Bending moment as a critical factor.
Outside Roughing: Again, let us look in-depth at the outside roughing passes.

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Some things to note:
1) There is some variability in cutter engagement on the first rough pass (material
inconsistency).
2) The second and third rough passes are quite level in force, which indicates consistent cutter
engagement.
3) Very little time is spent at a 0Nm force reading, which indicates more cubic inches per
minute of material are being removed.
4) Cycle time is significantly shorter since there is one fewer roughing pass.

Inside Roughing – Here we are again looking at the force variance for interior features. Again
zooming in for clarity.

Something to note:
1) Very little time is spent without the cutter engaged, and engagements are stable and linear.

Comparitive Analysis:
Let us look a bit deeper into the comparison between these two CAM programs. First, let us explore
the differences between outside roughing operations. The following graphic is an overlay of

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Autodesk and Gibbs + Volumill comparing the outside roughing forces at work with each program.
Time is used on the X axis of the graph and bending moment is used on the Y axis.

Immediately apparent is the difference in time to complete the operation, which is not a large
amount, around 4 seconds. Also easily seen is the difference in cutter engagement over the first two
roughing passes. If we look at the difference in cutter engagements with the Polar Plot feature for
the first roughing pass section, it is very evident the change in utilization of the cutter.

The left diagram is the Autodesk cut, the right is Gibbs+Volumill. What we are seeing is the
intersection of the forces at work on the X and Y axis of the tool holder over about 2/3 of 1 second in
the cut. When the points on the graphs come to center, that shows the cutter is not engaged. We
can also clearly see the three cutting edges, and their engagment, which is a bit off center, indicating
a bit of runout on the tool. It is easy to determine based on these graphs that one mode of running is
preferable to the other.
Now, let’s look at the internal trochoidial operations in the same fashion.

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Again, immediately apparent are a few things:
1) The helical boring cycle is considerably shorter with the Autodesk tool path.
2) The forces are higher overall, and more consistent with the Autodesk tool path.
3) There is less time spent in positioning moves with the Autodesk tool path.
4) The Autodesk tool path finishes the internal machining about 1 minute faster.

During my analysis, there were a few other things I noticed that were curious regarding comparison
of forces. To show this, we need to look at 1 trochoidial cut, comparing between each tool path, as
seen below to see the characteristics of the cuts.

It is interesting to me to note how much more quickly the Autodesk data set reaches its peak force,
and holds the force nearer to the peak for longer than the Gibbs+Volumill data set. This, to me, is a
good indication of maximizing metal removal for the time the cutter is engaged. There is also an
interesting comparison in how the cutter comes out of the material. Instead of tapering off down to
zero load, the Autodesk path seems to get out of the cut a bit more quickly than the Gibbs+Volumill.

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Conclusions: It is my opinion, based on looking at and comparing forces at work during these
operations, that there is a significant benefit to utilizing Autodesk’s product over simply Gibbs +
Volumill in roughing trochoidial milling operations.

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