AGMA Webinar Series - millfam.orgmillfam.org/terry/Agma/Part2.pdf · AGMA Webinar Series Analytical Gear Chart Interpretation: Solving Manufacturing Problems . PART TWO . Dwight Smith

AGMA Webinar Series Analytical Gear Chart Interpretation:

Solving Manufacturing Problems PART TWO

Dwight Smith President, Cole Mfg. Systems, Inc.

June 7, 2012

Dwight Smith, President of Cole Mfg. Systems, Inc., has a wide range of experience in gear manufacturing, workholding, metrology, analysis, and project management. He has been developing and presenting the Gear Basic training sessions throughout North America since 1989. Smith serves as chairman of the AGMA Nomenclature Committee and is an instructor for the Basic Gear School for AGMA. His company, Cole Mfg. Systems, Inc., represents complementary gear-related equipment manufacturers.

American Gear Manufacturers Association

Dwight Smith

1. Some Things to Consider 2. Pitch Errors 3. Helix Errors 4. Profile Errors 5. Brief Overview of Several Gear

Standards

Chart Interpretation : Part 2

Errors occur outside of the analyzed area. Errors can occur between the measured teeth. Special Situations –

Burrs Improper Undercut Short Involute Broaching Tears

Things to Consider When Interpreting Gear Inspection Charts

A burr on the end of the tooth may be outside the analyzed zone.

This end of the tooth does not have a burr.

Special Situations: Burrs

Proper undercut will appear on the chart as minus material.

Plus material below the SAP indicates improper undercut, possibly a damaged or worn hob.

Special Situations: Improper Undercut

Proper involute length or minimum chamfer diameter falls off beyond end of analysis.

When the involute trace falls off prior to the end of analysis, it indicates a tooth that is shorter than specified.

Special Situations: Short Involute

Special Situations:

Broaching

Special Situations:

Broaching

Understanding Pitch Errors

Correcting Helix

Variation (wobble)

Relocate part on inspection arbor

Correcting Radial

Runout

Cumulative Pitch

vs.

Single Pitch

Cumulative Pitch (index) with Radial Runout

Data Calculated From Pitch Data

Three start hob cutting a 30 tooth gear.

Non-Hunting Tooth Pattern

Understanding Helix Errors

Helix Variation

Helix Variation

Helix Variation

It is impossible for the tool to cause helix variation. It is in all cases caused by axial wobble. If you use helix average values for tolerances, you need to consider variation as well.

Helix Angle Deviation and Form Deviation

Helix Form Deviation: Cause?

In Tolerance Helix Chart – Hobbed Part

Helix Chart – Variation and Form Deviation


Helix Chart – Taper


Understanding Profile Errors

Profile Chart Overview

OD Variation from Runout

Profile Form Deviation

Profile Chart

Profile Form Deviation – Cause?

Profile Form Deviation – Cause?

Involute Error Patterns

•Plus slope (balance) •Both flanks

•Very rough and irregular surface

•Form error •similar pattern RF and LF

Tears from broaching

Involute Form Waviness

Problem: Involute Waviness on right

flank

Potential Cause: Loose/worn outboard bearing assembly on hob

head

Fix: Tighten/replace outboard

bearing

Involute Form Waviness

Problem: Plus material near root

Cause:

Excessive wear on hob cutter teeth after only 50 pieces.

Cutter probably not completely sharpened.

Fix:

Resharpen or scrap hob cutter

Involute Form Deviation

Pitch, Helix and Profile Charts

Surface Finish Measurement

Factors Influencing Gear Quality

Common Variables that Influence all processes • Hob, shave, roll, broach, tool sharpening and measurement

– Workpiece spindle tooling • Axial runout or wobble • Radial runout or eccentricity • Repeatability of mounting accuracy

– Tool spindle and bearings • Radial and Axial Runout • Backlash

– Tool maintenance and tool mounting

• Hobbing machine – Number of teeth – Root diameter – Tooth size or thickness – Index – Pitch – Helix angle (lead)

• Wobble (lead variation) • Taper, crown

– Profile form – Pitch diameter runout – Scallop pattern

• depth and variation • Hobbing Tool

– Profile angle – Profile modifications – Tip chamfer – Undercut

Contribution to Errors: Machine vs. Tool

Gear Element Category

Runout

Total Composite

Tooth to Tooth

Nicks

Characteristics

Inspection chart appearance

Hobbed/checked off center Possible contamination Profile error Mesh interference

Possible root cause

Verify tooling (radial runout) Verify Master Check for involute error Check for plus tip

Corrective action

Troubleshooting Gear Errors

Helix


Slope (Angle) error

Variation (wobble)

Form or

waviness

Characteristics

Inspection chart

appearance

Input correction needed on machine Chips on fixture or workholding misaligned (axial runout) Chips on cutter edge Cutting force to high

Possible root cause

Input correction Verify axial runout of fixture wear Inspect cutter Verify workholding rigidity

Corrective action


Involute (profile)


Angle (slope) error

Variation (runout)

Form or

waviness

Characteristics

Inspection chart

appearance

Hob rake angle error Radial runout of gear Cutter mounting error Excessive finish stock Worn tool

Possible root cause

Check hob sharpening Check workpiece and fixture runout Check hob mounting and quality Check stock removal amount

Corrective action


Pitch (index)


Pitch (symbol fp)

Index (total

accumulated pitch error-symbol Fp)

Characteristics

Inspection chart

appearance

Runout of production fixture or inspection arbor Thread error on hob Wear or chips on broach bar

Possible root cause

Verify workholding Inspect hob for thread error Clean chips off broach

Corrective action


Tooth thickness


Size over pins or balls

Relative tooth thickness

Characteristics

Inspection chart

appearance

Tapered hob Heat causing machine growth Hob swivel angle error

Possible root cause

Check hob for proper quality Monitor cutting oil temperature Adjust hob swivel angle for correct size over pins (DOB or DOP)

Corrective action


Gear Analysis Standards

AGMA 2000-A88 (Q) AGMA 2015 (A) ISO 1328 DIN 3960


JIS JGMA France, Australia, Italy, UK CAT GM, Ford, Eaton, Honda, etc.

AGMA 2000-A88 AGMA 2015 DIN ISO

Allows use of "Design Profile" X X Allows use of "Design Helix" X X

Total Deviation X X X Angle Deviation X X X Form Deviation X X X

Smooth Tolerance Curve X X Optional Band Fit Analysis X

Bands Straight or Curved X Steppped Tolerance Curves X X

Requires Band Fit Analysis X


AGMA 2000-A88

Gear Analysis Standards - AGMA 2000-A88

Gear Analysis Standards – DIN, ISO, AGMA 2015

AGMA 2015-1-A01

Gear Analysis Standards - AGMA 2015

Description ISO DIN AGMA 2015

Cumulative Pitch Deviation Fp Fp Fp Difference Between Adjacent Pitch Measurements fu Single Pitch Deviation fpt fp fpt

Comparing Gear Analysis Standards DIN, ISO, AGMA 2015


Helix Deviation, Total Fβ Fβ Fβ Helix Slope Deviation fHβ fHβ fHβ Helix Form Deviation ffβ fβf ffβ (DIN calls it Tooth Trace) Helix Crown Cb



Profile Deviation, Total Fα Fα Fα Profile Slope Deviation fHα fHα fHα (DIN calls it Profile Angle) Profile Form Deviation ffα ffα ffα


Thank You!

Dwight Smith Cole Mfg. Systems, Inc.

[email protected]

Office: 248-601-8145 Mobile: 734-516-1365

mailto:[email protected]


If You Missed an AGMA Webinar Visit AGMA Webinar Series Archive at www.agma.org

These are just a few of the archived programs available – Charting the Course Through Profound Demographic Change Kenneth W. Gronbach Design and Development Procedure for High-Precision Molded Plastic Gear Transmissions Dave Sheridan Introduction to Gear Rating Suite 3.0 John Rinaldo Analytical Gear Chart Interpretation: Reading Between the Lines Dwight Smith

http://www.agma.org/


AGMA 2012 - Education Calendar

January 24-26 Gearbox CSI: Forensic Analysis of Gear & Bearing Failures, Concordville, PA April 16-20 Basic Training for Gear Manufacturing, Chicago, IL May 15-17 Gear Materials - Selection, Metallurgy, Heat Treatment, and Quality Control, Milwaukee, WI June 11-13 Gear Failure Analysis, Big Sky, MT June 19-21 Gearbox System Design: The Rest of The Story…Everything But The Gears and Bearings, Clearwater Beach, FL Sept 17-19 Gear Failure Analysis, Big Sky, MT Oct 1-5 Basic Training for Gear Manufacturing, Chicago, IL Nov 13-15 Gear Manufacturing & Inspection ― Methods, Practices, Application & Interpretation for the Design Engineer, Las Vegas, NV - MM Dec 4-6 Detailed Gear Design – Beyond Simple Service Factors (Not for the Faint-Hearted! Alexandria, VA

Visit www.agma.org for full details and registration.

Documents

AGMA Webinar Series - millfam.orgmillfam.org/terry/Agma/Part2.pdf · AGMA Webinar Series Analytical Gear Chart Interpretation: Solving Manufacturing Problems . PART TWO . Dwight Smith