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 – Variation and Form Deviation
Helix Chart – Taper
Helix Chart – Variation and Form Deviation
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
Gear Element Category
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
Troubleshooting Gear Errors
Involute (profile)
Gear Element Category
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
Troubleshooting Gear Errors
Pitch (index)
Gear Element Category
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
Troubleshooting Gear Errors
Tooth thickness
Gear Element Category
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
Troubleshooting Gear Errors
Gear Analysis Standards
AGMA 2000-A88 (Q) AGMA 2015 (A) ISO 1328 DIN 3960
Gear Analysis Standards
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
Gear Analysis Standards
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
Description ISO DIN 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
Comparing Gear Analysis Standards DIN, ISO, AGMA 2015
Description ISO DIN AGMA 2015
Profile Deviation, Total Fα Fα Fα Profile Slope Deviation fHα fHα fHα (DIN calls it Profile Angle) Profile Form Deviation ffα ffα ffα
Comparing Gear Analysis Standards DIN, ISO, AGMA 2015
Thank You!
Dwight Smith Cole Mfg. Systems, Inc.
Office: 248-601-8145 Mobile: 734-516-1365
American Gear Manufacturers Association
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