Overview Presented By: Manufacturing Laboratories, Inc. Frequency Response Function (FRF) Stability Map

OverviewOverview

Presented By:

Manufacturing Laboratories, Inc.

Frequency Response Function (FRF) Stability Map

MetalMAX Training Manufacturing Laboratories, Inc. MMOVER-2

Purpose of SoftwarePurpose of Software

To predict, measure, avoid and control machining Vibrations.Uses common vibration measuring

techniques.Applies them specifically to the

machining process.


Problems With Today’s Problems With Today’s Machining (Dynamics)Machining (Dynamics) All machines and tool stack-ups exhibit dynamic characteristics that will impact the

cutting process. Machining by definition is a dynamic process. Dynamic Characteristics Limit Machining Performance (Ti vs AL). These characteristics can vary significantly and can be difficult to predict reliably.

Measurement is required. Primary contributor for cutter failure, spindle failure, limits machining capabilities, etc. Theory and understanding well known by many MR&D Depts. and Universities but only

recentlygaining awareness andacceptance on shop floors.


What Is High-Performance (HP) What Is High-Performance (HP) Machining?Machining?

There are many definitions: Cutting speed

s(m/min)=pd(m/rot)n(rot/min) Spindle speed or DN

DN = bearing bore diameter x spindle speed Torque and Power others

All of the definitions of high-performance machining are correct in some context.

High-Power is a natural artifact of high-speed. Power = Torque x speed


Added considerations for High-Added considerations for High-Performance (HP) MachiningPerformance (HP) Machining

We have the additional influence of machining feed rates.

What is the “average” feed rate.Chip-thinningSurface area


What Limits HP-HS Machining What Limits HP-HS Machining Productivity?Productivity?

Different types of machining operations have different limitations.

HP-HS machining may be limited by: The onset of chatter Tool-work piece materials Available power Tool geometry Work piece geometry Controller or servo performance (acc-dec) Inadequate knowledge about machine capabilities


Chatter LimitationsChatter Limitations

Particularly in high speed operations where the objective is to have the metal removal rate as high as possible, the onset of chatter will be a limiting factor.

Chatter arises due to insufficient dynamic stiffness Long slender tools Small diameter spindles

(DN limitation) Flexible work pieces

(although the selection of a tool path can avoid this in most cases)


Tool-Work piece Material Tool-Work piece Material LimitationsLimitations

With work piece materials such as aluminum, the availability of a tool material is not a limitation. Tools are available which can tolerate the melting temperature of aluminum.

With hard steels, and even more so with titanium, maintaining acceptable tool life is a major problem. There has been some success with light cuts.


Power LimitationsPower Limitations

In some cases where the machine-tool-work piece combination is dynamically stiff enough, the cutting operation may be limited by the available power.

Even for the stiffest machines, there are usually some tools which are not power limited.


Tool Geometry LimitationsTool Geometry Limitations

In cases where the dynamic stiffness and power are sufficient, the cutting operation may be limited by the tool configuration (the length of the cutting edge or tool diameter, for example).

Cutting edge geometry may be dictated by material property characteristics, thermal behavior, shearing, etc.


Work piece GeometryWork piece Geometry

In some instances (many die and mold applications), the geometry of the cut is dictated by the desired work piece geometry. For example, the step-over dimension may be limited. In such cases, most of the machining can happen well below the available power.


Controller or Servo Performance Controller or Servo Performance LimitationsLimitations

Especially for complex geometries, the block throughput rate of the controller can be a limiting factor. Some easy tests exist

As the speed of the axis motions increase, the dynamic performance of the servos become more significant High accelerations/decelerations (acc/dec) Lightweight yet stiff moving elements Look-ahead or feed forward control


Knowledge LimitationsKnowledge Limitations

A lack of understanding of high speed machine capabilities frequently leads to under-utilization of such machines.

A large, traditional experience base does not exist for high speed machine tool use.

Many high speed phenomena are counter-intuitive for users accustomed to conventional speed machines.

An acceptable part program is usually not the optimal part program.

The programmer needs the machine performance information at the time that the program is written.


3 Knowledge Possibilities Exist3 Knowledge Possibilities Exist

You understand the performance capabilities of your machine very well and write part programs respecting the limitations.Or

You fight chatter problems every day.Or

You are under-utilizing your machine.


Which Qualities Of High-Performance Which Qualities Of High-Performance High-Speed Machines Are Most High-Speed Machines Are Most Important?Important?

Spindle Speed alone is not enough. High power alone is not enough. Fast motions or tool changes alone are not

enough. High performance controllers alone are not

enough. Advanced tool materials alone are not enough.

Certainly, these things are important, but…..


“High-speed (HS-HP) machining occurs when the tooth passing frequency approaches the dominant natural frequency of the system”.

-Scott Smith, UNCC

For reasons which will become For reasons which will become apparent, the definition we will apparent, the definition we will use is:use is:


What Is Different About HP-HS What Is Different About HP-HS Machining?Machining?

HP-HS machining is different from conventional machining, particularly in the strong influence of the dynamic characteristics of the machine-tool-work piece system on cutting performance.

In HP-HS machining, the metal removal rate (MRR) is usually limited by the onset of “chatter”.

Success in HP-HS machining depends heavily on the ability to recognize and deal with dynamic problems.

Selection of an appropriate spindle speed and depth-of-cut is extremely important and not obvious.


What Kinds of Parts Can Benefit What Kinds of Parts Can Benefit From High Speed Machining?From High Speed Machining?

Parts which have a large volume of material to be removed.

Aluminum and cast iron parts especially, but also hard materials such as dies and molds.

Parts with thin structures. Parts which conventionally spend a long time

on the machine either due to large metal removal or large surface areas to be machined.

Short runs, or frequently changed designs. Many others.


Pocketed and Thin Section PartsPocketed and Thin Section Parts


Monolithic StructuresMonolithic Structures(formerly stack-ups)(formerly stack-ups)


Shop Floor Friendly Approach Shop Floor Friendly Approach

Supply a complete solution to the problems with dynamics and machining. Model and predict dynamic behavior and its affect on the cutting process. Effectively measure and adjust to unexpected changes. Maximize Cutting performance (MMR)

Simplify analysis of machine tools and cutters. Distill technology down to its most essential parts

(measurement and prediction).

Machine a part right the first time!


Exactly what are we talking Exactly what are we talking about?about? Methods for obtaining information about the cutting

process dynamics and quickly utilizing this information to maximize cutting performance. Currently available by various means. Applied in a way for maximum usability.

Our goal is to maximize metal removal rate and reduce or eliminate detrimental vibrations.

We want to utilize basic frequency analysis at the machine or on the shop floor (machinists, NC programmers, process planners, manufacturing engineers) to improve process setup, correct problems when they occur, and objectively evaluate performance.


What are we evaluating?What are we evaluating? Design Parameters Frequency (fn), Stiffness (k) and

damping (damping ratio ). They do not change over time or with load.

Dynamic stiffness (~2k) at Frequency (fn).

Sometimes we are concerned with the magnitude response, for cutting performance the negative real part of the FRF

Negative Real Peak

(chatter)

Static Compliance

Dynamic flexibility=~1/2k

Magnitude Response Real part of FRF

Frequency =fn


Why bother?Why bother?

In a dynamic system component behaviors are highly interelated (e.g. everything affects everything).

Change one parameter and it is likely that the dynamic response will change, sometimes substantially.

Counter-intuitive behavior is inevitable. Dynamic parameters, particularly damping can change.All this will affect how much can be cut

and how much the operation will vibrate (normally, resonate or chatter).


Fundamental Tool:Fundamental Tool:

Frequency Response Function (FRF)Frequency Response Function (FRF) (20 mm 3-fluted Tool in 30 kW 24 krpm Spindle)(20 mm 3-fluted Tool in 30 kW 24 krpm Spindle)

Flexibility


Basis for Analysis:Basis for Analysis:The Stability Lobe DiagramThe Stability Lobe Diagram

Process Damping


5 areas of machining5 areas of machining

Con

vention

al Region

Blim1

High-Performance Region

PoorMan Region

Blim2 – High-Speed Machining


5 Regions of Machining5 Regions of Machining Conventional

Typically Slow RPM with high Feed and DOC Blim1

Light DOC where all RPM are chatter-free, but not necessarily most robust

Blim2 – High-Speed Region “industry accepted” low DOC high feed rate finishing All RPM are chatter –free, but not necessarily most

robust PoorMan Region

Minimal or NO Sweet Spots, almost all RPM chatter High-Performance Region

Largest Metal Removal Rates Must select matching RPM and DOC


Desired BenefitsDesired Benefits

Promote UnderstandingExplain Non-intuitive behavior, e.g. lobing

diagram and the dynamics that produce it.Guide user to Optimal SolutionNot necessarily looking for “precise” predictions

but good guidance.Fast Improvements

90% results with 10% of the effort.

Clearly identify limitations, eliminate………..

“finger pointing”


What’s Needed?What’s Needed?

Not as much as you may think.Frequency Analyzer.Widely available

SensorsBasic Cutting TheoryCommercial applications

are becoming widely available that do not require the expertise of a “vibration expert”. MLI’s MetalMAX™ kit with computer.


PCScope MilSimTM

Packages for Dynamic/Chatter Prediction and ControlPackages for Dynamic/Chatter Prediction and Control

Harmonizer®

TXF™

Measurement and Analysis Computation and Prediction

SPATM

Cutting Performance Analyzer for Machine Tools

Data Acquisition and Machining Analysis

CHiPSTM

Milling simulation

Finite Element Spindle Analysis and Cutting Performance Analyzer

Audio Monitoringof Cutting Process

Track Data withparticular setup,tool, machine, etc.

Page 5

Verification and Tracking


How is it typically appliedHow is it typically applied Front Line Solutions

“TXF” Chatter free speeds and power or depth of cut levels.

“Harmonizer®”

Audio monitoring and chatter detection and correction Existing NC Program correction.

PCScope Generic data collection Track balance levels and spindle vibrations, temperatures.

Off-Line Solutions MilSim and SPA

Off-line in-depth analysis. Good NC-Programmer tool

CHiPS Organize and track data.


Two Basic Approaches: Two Basic Approaches: “Trial and Error” and Predictive“Trial and Error” and Predictive

Trial and Error Similar to how we do it now in that we take test parts or

run test work pieces and change things based on experience.

Additionally, we can integrate cutting theory and signal analysis to direct the changes more efficiently.

Predictive Measure dynamics of tooling before cutting then

compute behavior. Simulate cutting and establish maximum parameters. Verify results when implemented and have the ability to

correct for subtle changes that may occur.


Predictive Approach. Predictive Approach. How do we do this? How do we do this?

Easiest way is called “impact” testing or modal analysis.

Use a hammer to excite the tool over a wide frequency range and and an accelerometer to measure the response and create an FRF (Frequency Response Function).

With proper software and setup measurement takes less than 5-minutes per tool.


Advantages and Disadvantages of Advantages and Disadvantages of Predictive ApproachPredictive Approach

Advantages: Fast with minimal machine downtime. No requirement to run machine. Flexibility to determine performance for all operation conditions. Quick check for changes after “events”.

Disadvantages: Limited accuracy depending on inputs. Some technique and equipment needed


What is our concern.What is our concern.

Obviously the tool-work piece interface.The flexibility and frequency behavior on the tool and

on the part at the location of the cutting interface.

The entire machine and all its components contribute to this behavior but we are only concerned with how it is affecting just “ONE” location: Where cutting occurs (the cut interface).

We are only concerned with displacement for a given force, or the flexibility.


FRF Measurement with FRF Measurement with MetalMAX™ EquipmentMetalMAX™ Equipment

Schematic of Measurement Setupfor TXF “Tap” or “Ping” test.

Actual MetalMAX™ Equipment

4

3

2

1EXCITATION

(HAMMER)

RESPONSE

(ACCEL)

Sensor Interface Module

PC

Accelerometer

STRIKE

Hammer

Power Cable

Sensor Cable


Frequency Response Function to Cutting Frequency Response Function to Cutting Performance (Analytical Solution, TXF)Performance (Analytical Solution, TXF)

Measured Frequency Response Function (FRF)

Lobing Diagrams

Provide MRR (Depth of Cut) and

Spindle Speed values

Chatter in red areasMRR Axis

Chatter freqs. (in red) and resonant speeds


General FRF ProcedureGeneral FRF Procedure

A FRF quantifies a tool’s “flexibility” frequency by frequency. Excite systemMeasure forceMeasure responseTransform into frequency domain (Fourier

Transform)divide frequency by frequencySee video demonstration. (PLUCKING A TUNING FORK)


Cutting Performance (TXF)Cutting Performance (TXF)

Stability Lobes Power Lobes

Max Torque

Max Power


Advantages and Disadvantages of Advantages and Disadvantages of Trial and Error ApproachTrial and Error Approach

Advantages: Most Accurate Easy Low skill level required Software/hardware aids are

commercially available, vibration meters, audio detectors, etc.

Disadvantages: Time consuming Consumes work piece material and tools

and machine time.


Maximizing MRR with Width Maximizing MRR with Width of Cut Increasesof Cut Increases

Harmonized

Spindle Speed: 20,000 RPM

Axial Depth of Cut 25 mm

Radial width of cut 0.25 mm

Cut Power 0.3 kW

BAD SURFACE

> 475% increase in Power

and MRR

Spindle Speed: 16,580 RPM

Axial Depth of Cut 25 mm

Radial width of cut 1.8 mm

Cut Power 1.75 kW

GREAT SURFACE!!!


Knowledge of the spindle speed is essential. Spindle speed components

generally dominate the audio spectrum unless chatter is very severe.

Other audio sources are related to spindle speed, bearing passing frequencies, air-oil hiss, etc.

Correct setting of threshold maximizes sensitivity.

Unfiltered

Filtered


Trial and Error ExampleTrial and Error Example

10,000 RPM 8393 RPM

Corner Cut, 10 mm deep, 12 mm wide


Trial and Error ExampleTrial and Error Example

8393 RPM

Frequency content no filters.

10,000 RPM

Frequency Content with no filters.


Milling SimulationMilling Simulation

Simulation package needs measured dynamics as input. Rapid more accurate solutions to speeds, depths of cut,

feeds, cutting forces, tool deflection and surface error. Include tooth run-out, imbalance, non-uniform pitch. Excellent front-line, solution for process engineers and

NC programmers.


Most Important: Cutting Tool Tracking and ControlMost Important: Cutting Tool Tracking and ControlThe CHiPSThe CHiPS(TM)(TM) Database Database

To get the maximum payback each cutting tool assembly must be uniquely identified.

Machine, spindle, holder, cutter, manufacturer’s, stick out length’s, etc. must be tracked by either the customer tool management system or our customized Microsoft Access database for tool setup tracking with dynamics (CHiPS).

Record optimum speeds, feeds and depths of cut. Based on measurement and calculation (TXF, MilSim™,

etc.) and verified by cutting tests (Harmonizer). Emphasize slotting information (the least stable case). Data will not change unless a different tool, machine tool,

or spindle is used. In fact results for identical model machines and spindles can be used on all machines of that model and spindle type.

Control of tool set up is required to insure database speeds, feeds, and DOC’s are valid (Dynamic repeatability and consistency).


CHiPS: Tracking all Tooling informationCHiPS: Tracking all Tooling information


Is this Technology new?Is this Technology new? No!, only in the way it is being applied.

Vibration measurement is very well developed. Basic machining dynamic theory well-known for decades by academics

and large corporate MR&D departments. The process or practice is the focus rather than its affects. Detect what is happening in the cut, not at the bearings, the motor,

under the work piece, etc. “Modal” Analysis or Frequency Analysis has been utilized

extensively with the advent of the digital computer and algorithms. Mostly in the design and product test areas. To determine and measure resonance's (aircraft, autos, disk drives,

etc.). Even in the design of machine tools and components.

Spindle Rotor Analysis Damping of fixtures


Is this all worth it? Is this all worth it? The Good News: The Good News: YES!YES!

PREDICTABLE and CONSISTENT: Well controlled setups will behave consistently. Identical model machines even of different age will show

minimal variation in frequency. Stiffness will not change significantly over time. Damping may change somewhat but its affects can be avoided.

PERFORMANCE IMPROVEMENTS: Stable cutting horsepower can generally be increased 50-200% or more compared to practically applied techniques.

COST AVOIDANCE: Tool life, time between spindle rebuilds, longevity of the machine, rotary table life, any machine component wear can generally see substantial (> 50%) improvements.


Other Benefits of Easy Other Benefits of Easy Dynamic MeasurementDynamic Measurement

Rapid dynamic measurement can quickly identify many conditions.Non-intuitive behavior.Most flexible mode may not be the most likely

to chatter.Quickly identify which component is producing

the most flexible mode. Identify when stiffness or damping is loss.

Quickly detect changes or compare performance.


Automotive Part Example: Automotive Part Example: Mild Steel TubingMild Steel Tubing

1. Starting Point: Company, Tooling Company, and 1. Starting Point: Company, Tooling Company, and Machine Tool company spent 15 months designing Machine Tool company spent 15 months designing process – POOR TOOL LIFEprocess – POOR TOOL LIFE

2

2. Ending Point: DATA driven Stability Diagram 2. Ending Point: DATA driven Stability Diagram provided MAP to change RPMprovided MAP to change RPM

1


Shop chose: 24,000 rpm 3mm ADOC 10,000 mm/min

0.208 mm/tooth Tool Life 20 pcs Endmill Cost: $200 45 second cycle time

Changed Parameters 15,500rpm

6,000 mm/min 0.193 mm/tooth

Tool Life 80 pcs Endmill Cost: $65 53 second cycle time

Not constraint machine

Improved Cost: ($10/part – $0.81/part) = $9.19/partYearly Savings: $9.19/part * 700 parts/day * 250 days/year = $1.6 million

Automotive Part Example: Automotive Part Example: Mild Steel TubingMild Steel Tubing


Story 2: OutsourcingStory 2: Outsourcing 8000 rpm 0.375” ADOC Same Tool, Same Toolholder, Same Stickout Different machines have Different Stability

Diagram

1


Die Shop Example: Cast IronDie Shop Example: Cast Iron

1. Starting Point: Machinist chose DOC based on CAM 1. Starting Point: Machinist chose DOC based on CAM software and past practice – HEAVY CHATTERsoftware and past practice – HEAVY CHATTER

2

2. Ending Point: DATA driven Stability Diagram 2. Ending Point: DATA driven Stability Diagram provided MAP to change RPMprovided MAP to change RPM

1


Die Shop Example: Cast IronDie Shop Example: Cast Iron

Die shop chose:1146 rpm0.125” ADOC23 ipm (0.005 ipt)Chatter

Changed Parameters2120 rpm0.040” ADOC84 ipm(0.010 ipt)No chatter

Improved Performance: (5.04-4.31)/4.31 = 17%

MRR = 1.5* 0.125 * 23 = 4.31 in3/min MRR = 1.5 * 0.04 * 84 = 5.04 in3/min

Cost Savings: $175/week ($100 inserts + 1 hour/week time * $75/hour)$8750 savings/year + Reduced spindle wear and tear + improved quality


Cutting Parameter SelectionCutting Parameter SelectionComparison of how are speeds, feeds and depths of cut chosen?Comparison of how are speeds, feeds and depths of cut chosen?

The Conventional ApproachEmpirical/Experimental Guidelines

Highly Experienced Planner.Technological database from cutting tool supplier.Operational limits from machine tool supplier.Turn Key applications.Note: The guidelines are subjectively applied depending on the situation.

Program and Make PartsDetermine AcceptabilityAccept or Modify

Programwith empiricalguidelines

Make Part Determine acceptability

Modify

Yes

No

A Process Based Approach(Strategy 2)Measure the dynamics.Define Dynamic Condition at cutting

interface.Compute optimum cutting parameters

and compare to other operational

guidelines.Program and make part.Monitor results.

MonitorResults

MakePart

MeasureSetups

Computeparameters

OperationalGuidelines


Resource Investment:Resource Investment:Conventional vs Process based (MetalMAXConventional vs Process based (MetalMAX))

Activity Conventional MetalMAX More Resources

Tool/Machine Selection Arbitrary Based onmeasurements

MetalMAX

Selecting Machining Values(DOC, Speed, Feed)

Historical Scientificallydetermined

Neither

Optimizing Trial/Error orIterative

Deterministic Conventional

Producing Part Acceptable Optimized Conventional

Resources Expended:Conventional

MetalMAX


Implementation Strategy #1:Implementation Strategy #1:Eliminating ChatterEliminating Chatter

OFF-LINE (new cutter or new program): Use hammer kit and TXF software to develop “Stability Charts” for problematic cutters.

In-Process (current chatter condition with pre-existing NC program). Use microphone and Harmonizer software to monitor chatter signal and suggest new speeds and feeds.

Record results in tooling database or CHiPS database program for future reference.

Periodically monitor high volume jobs using Harmonizer to insure chatter is not present.

Unstable

Torque Limit

StableSpeeds

Chatter

TXF

Harmonizer


Implementation Strategy 2:Implementation Strategy 2:Maximizing Machine and Cutter PerformanceMaximizing Machine and Cutter Performance

Identify 20% of tooling that performs 80% of metal removal or consumes 80% of machining time.

Use MetalMAX hammer kit and TXF program to create stability charts (maps) for each cutter.

Perform cutting tests on a few selected cutters using microphone and Harmonizer to validate predictions and to calibrate results on all cutters.

Record data in CHIPS database. Make information accessible to NC

programmers. Have machinists monitor and provide

feedback periodically regarding performance. Use Harmonizer for periodic monitoring, fine tune when necessary, update database and re-measure as needed (generally not required).

Highest Power Stable Region with little chance to chatter.


Implementation Strategy 3:Implementation Strategy 3:Matching tooling to machineMatching tooling to machine(and tool tuning).(and tool tuning).

Identify possibly redundant tooling systems, e.g. multiple length cutter configurations, multiple flute, cutters used across machine platforms, etc.

Measure redundant tooling systems across machine tools using TXF.

Review “stability chart” results. Identify those cutters with superior

cutting performance in a given machine and machines-cutting tool combinations with superior cutting performance.

Will result in dramatic reduction in required setups and provide preferred machine-tooling configurations (e.g. better identify roughers, finishers, face millers, end millers, 2 flute machines, 3 flute machines, etc.)

Alternatively, multiple length cutters of a given size can be measured to identify which length provides the optimal cutting performance (e.g. shorter not always better, see right)

ShorterCutter

LongerCutter

Larger deeperStable pocket,(shorter cutternot needed).


Implementation Strategy 4:Implementation Strategy 4:New Equipment QualificationNew Equipment Qualification Similar to matching machine to

tooling strategy except current measurements will afford the analyst benchmark results for popular shop setups to be compared against “test” cutters or alternative OEM designs without having to run cutting tests.

These setups can be quickly compared with any new setups considered for the shop through a quick TXF hammer test.

Additionally, the shop’s current stackups may be taken and measured on potential new machines to see what stability performance improvement may be expected on the new machines.

Benchmarked cutter

Test Cutter

Performance atLeast 2X


Implementation Strategy 5:Implementation Strategy 5:Part-Try-Out (PTO) OptimizationPart-Try-Out (PTO) Optimization

Tooling should already have been qualified and measured with prior strategies.

Work piece and fixturing can now be added at selected machining states with TXF.

Milling Simulation MILSIM package can be used concurrently with programming to optimize feed rates based on bending moment limits, cutting force and dynamic cutting accuracy.

Harmonizer should be used to provide feed back for next


Implementation Strategy 6:Implementation Strategy 6:Predictive and Preventive Maintenance.Predictive and Preventive Maintenance.

Establish a measurement artifact for each spindle interface in the shop (e.g. HSK, ISO, etc.).

Dimensions of artifact should be approximately a 1 L/D with a diameter approximately equal to the gage length.

With machine in known “good” condition make TXF measurement, store, and during routine maintenance checks re-measure artifact and compare (reduction of damping or loss of stiffness will precede typical spindle wear or de-commissioning signals by at least 3 months).

After spindle or machine crashes or extraordinary events spindle dynamic condition can be check.

Dynamic performance and hence proper refurbishing or replacement of machine components, particularly spindle can be verified.

Dynamic consistency of machine can be established.

SpindleIn

GoodCondition

SpindleIn

BadCondition


Summary of Implementation Summary of Implementation IssuesIssues

Exploiting Dynamic Consistency By controlling our tool setups and measuring the dynamics the

optimal operating conditions can be repeatably targeted with corresponding benefits.

High production rates can be reached as well as high machine utilization.

Improve control of cutting processes Apparent random vibration behavior can be controlled by

implementing a means to define a previously unknown critical characteristic of the machine setup.

Better more consistent part quality is achieved. Maintenance improved

The control of vibrations dramatically reduces machine and tool wear thereby reducing maintenance and repair costs.

Quality control is improved as machines that are near design life of more easily identified.


SummarySummary

Dynamic analysis can be applied easily and in a “Shop Floor Friendly Fashion”. Both for trial and error approaches and predictive analytical

approaches. Cost and down time is minimal.

It can provide objective and clear understanding as to the dynamic affects driving cutting performance.

Benefits include both performance enhancement and “cost-avoidance”.

It is an excellent compliment to other machining systems for tool wear, cutting accuracy (machine metrology), etc.


Downstream BenefitsDownstream Benefits

Proper implementation of HP-HS techniques will lead to: Elimination of adverse vibrations Reduction of catastrophic wear on machine and

tools thereby lowering maintenance costs and consumables

Expanded flexibility in types of parts and manufacturing processes.

Improved quality and more predictable processes leading to better cost estimation.


Overall BenefitsOverall Benefits Deal with chatter problems effectively and quickly.

Minimal or elimination of down time due to chatter problems. Minimize part damage and scrap/rework.

Extend machine and tooling capabilities. Fewer tools needed to machine same features. Reduce tool fatigue failures and extend tool life. Add flexibility to part programming strategies.

Objectively deal with the natural limitations imposed due to machine and tool dynamics. Eliminate “Finger-Pointing” Accurately compare machines or tool stack-ups. Select the best machine and/or tool setup for a particular

application.


Limitations of ApproachLimitations of Approach

Critically dependent on cutting stiffness and process damping wavelength. Once established for a particular grind of tool and material then

will produce accurate predictability. Will change after tool wears (usually increase stable limits).

FRF measurement of 1/4” diameter tool is practical lower limit of effective measurement. Improvements currently being developed In worse case an indirect measurement approach can be applied.

Measurement of dynamics performed under static conditions. Measurements can be made at speed with non-contact sensor. A few advance and current spindle designs have poor dyna

repeatability and consistency.

Documents

Overview Presented By: Manufacturing Laboratories, Inc. Frequency Response Function (FRF) Stability Map