High Speed Machining
Reference using UGX and NX CAM by Siemens PLM Software
(formerly known as UGS PLM Software http://www.plm.automation.siemens.com )
Contents
Introduction and Background
HSM / Hard Milling
Components of HSM
HSM aspects outside your CAM system
HSM aspects inside your CAM system
Case Study
Q&A
2
High Speed Machining
What is it?
Very high tool rpm, small
depths of cut and high feed
rates
Mostly used in milling hard
mold and die steels (hence
term “hard milling”)
Also appears in airframe
work for different reasons
Different materials
(aluminum)
Used to reduce heat and
material stress during
machining
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High Speed Machining
Value
Maximizes overall productivity – fewer
process steps, faster machining
Machining Mold and Dies made of very
hard materials (P20, H13, D2, etc.), deep
cavities and fine details typically require
time consuming EDM processes.
HSM produces high quality finish on
milling machine – reduces need for EDM
electrodes, burning and hand finishing
Challenges
How to drive HSM machines to capacity
without breaking tools
Tool makers cutting data ranges from very
safe to highly optimistic - “what data do we
use and why doesn’t this data always work
for me?”
4
Hard Milling
Machining Mold and Dies made of very hard materials (P20,
H13, D2, etc.), deep cavities and fine details typically require
time consuming EDM processes. HSM helps users bypass
EDM with out-of-the-box “hard-milling” solutions.
HSM Capable HSM capable Programming
Machine Tool Cutting Tool Controller CAM System Know-how
HSM - High Efficiency Hard Milling
“It is only as good as the weakest link.”
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Hard Milling
Do you have all the components you need?
Increasing spindle speed and feed while decreasing
chip load is just the beginning step of successful high
speed programming.
Further understanding of the cutting action is
essential. (chatter, vertical engagement angle,
material removal rate, effect of surface speed on the
finish, etc.)
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Hard Milling - Machine
HSM Capable
Machine Tool
A stable machine capable of running at high speeds
and feeds without the machine dynamics coming into
the machining equation.
The cutting forces and vibration caused by the actual
contact between the tool and the material becomes
the primary action.
High Speed Spindle retrofits are not High Speed
Machines.
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Hard Milling – Cutting Tools
Cutting Tool
Tools capable of handling very high surface temperature.
Available High Length to Diameter ratios for reaching into
intricate cavities
Gold coating
TiN High surface hardness
Lubricity
Blue-gray coating
TiCN
Moderate temperatures
High Temperature applications
TiAlN Forms Al Oxide coating -low thermal conductivity
Longer tool life
10
Hard Milling – Cutting Tools
Ball End Mills rough closer to the part than End Mills
with small corner radius.
Original Part and 30mm End Mill with 30mm Ball End Mill
Blank 1mm Corner Radius
Ball End Mills produce consistent finish along the
entire slope spectrum.
11
Hard Milling – Cutting Tools
End mills always get stressed at the same point.
Effective engagement of ball end mills is distributed
Contrary to popular beliefs, ball mills cut more effectively at
the tip than end mills. While it is correct that ball end mills do
not have surface speed at the center, it is true for flat end
mills as well. Unless you are cutting flat horizontal faces,
there is no need to use flat end mills for finishing.
12
Hard Milling - Tool Holder
Holders capable of very low run-out at high
spindle speeds and acceleration.
HSK
Shrink fit
„Tribos‟
Dynamic vs. static run-out.
Example holder standards. 3Gs
13
Hard Milling - Machine Controller
Controller
Support for various high speed interpolation types
Look-ahead
Corner acceleration and deceleration curves.
Distinction criteria for Linear Vs Spline interpolation.
NURBS (Non-Uniformal Rational B-Spline)
Non-Uniform Rational B-Spline: This is a mathematical representation for smooth curves and
surfaces. A type of curve or surface for which the delta (difference) between successive
knots need not be expressed in uniform increments of 1. This non-uniformity distinguishes
NURBS from other curve types.
B-Spline: A particularly smooth class of approximating curves. B-Splines are fully
approximating: such a curve generally passes through its control points if several of them
are in the same location. B-Spline curves are converted to NURBS curves when imported
into Industrial Design softwares for example 3D Studio MAX.
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Hard Milling – Machine Controller NURBS
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Hard Milling - Machine Controller
Smooth Interpolation
Exact positioning
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Hard Milling - Machine Controller
Discrepancy between actual and requested high feed
rate.
Is SuperGI (Geometric Intelligence) or similar
algorithm turned on ?
Is SuperGI disabled due to programming/post errors?
Subroutines within a Super GIMakino block
Cutter Compensation
Using multiple Super GI modes for finishing,
roughing and non-cutting moves (M250, M251,
M252Makino)
Bi-directional copy-mill example
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Hard Milling - CAM
HSM capable Programming
CAM System Know-how
Consistent use of chatter free machining parameters.
Do not exceed the intended Metal Removal Rate.
Leave uniform amount of stock after every tool.
Consistent finish in both steep and non-steep areas.
Smooth, continuous cutting.
Fine tuned HSM data for CNC controllers
Divide and conquer. Do not apply templates to the entire
part.
19
Hard Milling - Chatter
Chatter is the #2 cause of tool failure in hard milling
applications. (It is also the most overlooked)
Process for avoiding chatter
Chatter Zone
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Proven Integrated Machining Data
Integrated, customizable
machining database enables
storing, retrieving and
associatively using the data in tool
path operations.
NX-CAM for example includes
proven machining data for
commonly used raw materials.
P20 in NX3
More materials coming up in NX4.
21
NX Milling – what can you do?
Avoid over-loading the tool while maintaining high feed
rates
Controlling tool step-over, managing tool embedding
Z-level plus path
Enhanced trochoidal paths
Efficiently locate the optimum machining areas
Use the in-process workpiece
The key issue is achieving a constant rate of material removal
22
Trochoidal Toolpath
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Material Removal Rate - Roughing
Typical roughing path exceeds requested metal
removal rate at corners and fully embedded first cuts.
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Metal Removal Rate - Roughing
Without trochoidal, if you are not breaking the tool,
you are not cutting efficiently.
25
MRR & Vertical Engagement Angle
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MRR & Vertical Engagement Angle
27
Metal Removal Rate
Order your flowcuts
28
Metal Removal Rate - Uniform Blank
Cut between your Z-Levels
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MRR & Z Level Operations
Easy control of vertical and horizontal engagement
angles.
Z-lock provides much better Super-GI performance
at the controller.
Watch out for Z level passes near horizontal corners.
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Metal Removal Rate & Finish
On part stepover option enables constant metal
removal rate and uniform surface finish
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Cleaner Toolpath
Too many engages and retracts are unsafe and
should be avoided.
Level based Rest Milling is faster too.
32
Constant Surface Speed ??
Varying RPM as the effective cutting diameter
changes.
This is important for good surface finish.
Chatter characteristics could be ignored since the
depth of cut is really small.
34
Tool Length
Keep the tool length as short as possible.
Increased tool length causes increased deflection.
Even in big tools this makes a difference.
Even if there is insignificant un-measurable deflection, you need
only a small disturbance to start vibration. (which is very bad for
the coating.)
35
Divide and Conquer
Different machining regions require different strategies.
Mass machining of the entire part does not produce efficient
HSM tool path.
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Case Study - HSM on Connecting Rod Die
Measurement NX2 NX3
Operations required 11 7
Rest mill path 4:30 1:30
generation time
Overall Programming 6 hr 2 hr
Time
Improved In-process work-piece performance
Automatic cut levels in cavity milling
How did we New Z-level Plus path to contour floors while
do it? roughing
Trochoidal cutting to avoid over-embedding tool
Holder checking for multiple tools
37
Case Study - HSM on Connecting Rod Die
Measurement NX2 NX3
Operations required 11 7
Rest mill path 4:30 1:30
generation time
Overall Programming 6 hr 2 hr
Time
Improved In-process work-piece performance
Automatic cut levels in cavity milling
How did we New Z-level Plus path to contour floors while
do it? roughing
Trochoidal cutting to avoid over-embedding tool
Holder checking for multiple tools
38
Articles, papers, presentations
“Faster and Finer”
“Is Your HSM Investment Paying You Dividends” - by Edwin Gasparraj
“Constant Material Removal – The Key to Hard Milling” - by Edwin Gasparraj
“Critical Machining Data for HSM Process Specification” - by Edwin Gasparraj
Customer facing presentation – “Die/Mold and HSM”
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Website reference
• UGS PLM Software
http://www.plm.automation.siemens.com
• Vibrafree.com
http://www.vibrafree.com/UHSHM/UHSHM.htm
•For more case studies please visit Vibrafree.com. There
a lot of case studies about HSM in pdf format.