Case Studies: Dynamic Balancing

Case Study 1:
System Vehicle Stability

Case Study 2:
High Speed Cutting Head

Case Study 3:
Dynamic Balancing of a Large Hammer Mill

Case Study 4:
Quality Assurance/Quality Control – Balance Analyzer

Case Study 5:
Quality Assurance/Quality Control II – Balance Analyzer

System Vehicle Stability

Problem: Large heavy trucks are prone to loss of control and rollover, as these vehicles tend to have widely varying loads with high centers of gravity. Rollovers are the leading cause of death in heavy trucks and often result in passenger vehicle fatalities, significant property damage, and traffic disruption.

Investigation Present rollover minimization technology uses selective and automatic braking systems. Driver-initiated judgment based operational choices add or diminish vehicle stability.

Measurements: Lateral acceleration and trailer position oriented load is measured using accelerometers and differential air pressure sensors. Rollover propensity is then calculated for all driver judgment based vehicle control actions. Vehicle navigation data including location, speed, and direction are measured using satellite technology.

Solution: Developed, designed and built a computerized system to measure the dynamic loading of heavy truck trailer center of gravity in real time. Provide driver with display of results under normal conditions, as propensity, to rollover.

Note: Vehicle Stability System is presently being tested in cooperation with Federal Highways Administration, Kentucky Department of Transportation and the University of Kentucky Transportation Research Center.

Results: Drivers have visual representation of the effect their judgment-based vehicle control actions have on loss of control and rollover propensity, regardless of trailer load. Data is logged automatically for future analysis.

Serendipity: Roadway geometry variations are measured at driving speeds allowing for rapid data collection. Geometry variations leading to loss of control and rollover of all vehicle types are quantified and available to transportation officials for considerations of roadway corrective treatment options.

High Speed Cutting Head Dynamic Balancing

Problem: A large cabinet manufacturing facility purchased a multi-million dollar machine. This machine automated the trim cutting on their cabinet doors. Upon delivery it was observed that the cut was leaving a “chatter mark” that was not aesthetically pleasing. VESCO Incorporated was brought in to investigate the problem.

Investigation: VESCO Incorporated thoroughly measured the cutting head dimensions, design drawings and operational parameters.

Measurement: Cutting head dimensions were within specification therefore vibration data was collected on the machine. Using a digital filter, VESCO Incorporated determined that the cutting heads were severely out of balance. The rotational speed of the cutting head shaft was in excess of 6000 rpm therefore balancing would require fractional gram weights.

Solution: VESCO Incorporated used a computerized multi-plane balance technique that balanced the cutting heads in place. The company saved a tremendous amount of money in disassembly costs.

Results: Upon the completion of balancing, the cutting heads delivered excellent trim cuts. The machines factory representative has recommended that VESCO Incorporated be utilized on all their new installations.

High Speed Cutting Head Dynamic Balancing

Problem: A customer’s large hammer mill was vibrating severely due to a foreign object passing through. VESCO Incorporated was called in to investigate the problem and determine the best possible solution.

Investigation: VESCO Incorporated collected vibration and phase data on the mill at the customers facility. The mill was severely out of balance. Expedient balancing was necessary or permanent bearing wear would occur. It was determined that attaching a weight to the mill rotor was not possible due to the complexity of opening up the mill. Through data analysis, VESCO Incorporated concluded that a balancing weight could be attached on the external bull wheel with good results.

Measurement: Cutting head dimensions were within specification therefore vibration data was collected on the machine. Using a digital filter, VESCO Incorporated determined that the cutting heads were severely out of balance. The rotational speed of the cutting head shaft was in excess of 6000 rpm therefore balancing would require fractional gram weights.

Results: VESCO Incorporated successfully dynamically balanced the hammer mill. Excessive bearing wear was eliminated. The mill has been operating problem free for over 3 years now.

Note: Hammer mills can require frequent balancing due to hammer wear. When new hammers are bought, they are individually moment weighed and matched, however imbalance occurs before hammers are completely worn. One of the most difficult aspects of balancing a mill is where to attach the balance weight. It is difficult, time consuming and usually impossible to attach a weight on the mill rotor, therefore another location must be found. VESCO Incorporated has been very successful in dynamically balancing mill, fans, blowers, and cutting heads in place.

Quality Assurance/Quality Control – Balance Analyzer

Problem: The annular ring around a cylindrical perforated drums were loaded with a granular material to make up the basket component for residential and commercial laundry machines. Baskets with high imbalance caused excessive rework and customer complaints. Rapid assembly cycle time precluded dynamic balance testing and correction.

Investigation: It was determined by dynamic testing that a check of the basket’s static balance would suffice to confirm its dynamic balance, or annular ring fill quality.

Measurement: Balance was evaluated using an accelerometer and digital tracking filter which showed that when dynamic imbalance occurred it could be detected and corrected with a static balance test and procedure. Resonance and impact testing was done in order to determine isolation and damping requirements. Damping materials were incorporated and verified. Analog and digital filtering were added for rapid signal conditioning.

Solution: The design incorporated a method to protect sensitive elements by only exposing them briefly when actual measurements were made. Designed and built a high speed computerized static balance system using strain gauge-based load cells to:

  • Measure imbalance of various sized baskets and calculate corrections
  • Compare the results to QA/QC specifications
  • Display results to operator in less that 5 seconds with single button operation
  • Log results within hierarchical database format

Results: Performed 100% inspection of basket balance (bulk loading quality), eliminating the most pervasive customer complaint for over 40 years, saving $1M/year in warranty claims.

Quality Assurance/Quality Control II – Balance Analyzer

Problem: The items loaded in Balance Case Studies #1 & #4 are cylindrical perforated drums or baskets used as a component for residential and commercial laundry machines. Baskets with high imbalance caused excessive rework and customer complaints. Rapid assembly cycle time precluded dynamic balance testing and correction.

Investigation: It was determined by dynamic testing that a check of the basket’s static balance would suffice to confirm its dynamic balance, or annular ring fill quality.

Measurement: Balance was evaluated using an accelerometer and digital tracking filter which showed that when dynamic imbalance occurred it could be detected and corrected with a static balance test and procedure. Resonance and impact testing was done in order to determine isolation and damping requirements. Damping materials were incorporated and verified. Analog and digital filtering were added for rapid signal conditioning.

Solution: The design incorporated a method to protect sensitive elements by only exposing them briefly when actual measurements were made. Designed and built a high speed computerized static balance system using strain gauge-based load cells to:

  • Measure imbalance of various sized baskets and calculate corrections
  • Compare the results to QA/QC specifications
  • Display results to operator in less that 5 seconds with single button operation
  • Log results within hierarchical database format

Results: Performed 100% inspection of basket balance (bulk loading quality), eliminating the most pervasive customer complaint for over 40 years, saving $1M/year in warranty claims.