Reducing Human Error at Mack Trucks Lehigh Valley

Overview

Mack Trucks is a global manufacturer of  Class 8  trucks, engines, and transmissions.  All  the trucks manufactured in  North America are built at Mack’s Lehigh Valley operations facility  located  in Macungie,  PA. Of late,  Mack Trucks has been experiencing  many  human errors at their Lehigh Valley operations facility. In 2019, Mack Trucks recorded 55,300 human errors from April through September within the conventional assembly area (VEH1-Finish) of the plant.  Mack Trucks administered a Human Error Root Cause Analysis (HERCA) and determined many errors are accredited to both operators’ lack of attention and forgetfulness.  These errors can lead to defects on truck assemblies,  routing  and clipping defects, and  missing parts in installations.

To tackle these errors, Mack Trucks recorded the  Urea  operators performing the  Urea Tank Assembly during both  day and night  shifts. Mack Trucks sent these recordings to the Penn State Mack Truck Capstone Project Student Team soliciting a hierarchical task analysis (HTA), transcriptions of the video recordings, a codebook to encode said transcriptions, and an analysis of the codebook. The Student Team reviewed 40 recordings of the assembly process throughout the course of one day. The team received recordings from both shift one and shift two, so the team was able to compare the actions of the urea tank assembly operators across both shifts. With these deliverables performed, The Penn State Mack Truck Capstone Project Student Team addressed the causes of lack of attention and forgetfulness.

The primary cause that the Penn State Mack Truck Capstone Project Student Team found was operators tend to perform the tasks in their own sequence instead of the sequence outlined in the standard operating procedure (SOP). This leads to unacceptable deviations, such as screws tightened improperly, improper part installations, or tasks listed in the HTA being skipped over. 20% of the deviations noted by the Penn State Mack Truck Capstone Project Student Team were screws tightened improperly, 9% of the deviations were attributed to improper installations, and 1% to missing steps in the HTA/SOP. While 70% of the deviations noted by the Penn State Mack Truck Capstone Project were operators simply performing the SOP tasks out of order. Although these deviations were deemed acceptable, the team concluded that these acceptable deviations led operators to perform unacceptable deviations through their development of a personal standard operating procedure.

The team recommends that Mack Trucks creates a checklist version of its current Urea Tank Assembly SOP to standardize the assembly process across both shifts. This checklist can be in the form of paper or tablet given to each operator, so he or she always has it on hand to manually check off each task as it’s performed. Nevertheless, a checklist via tablet is more convenient because it’s durable and harder to misplace. Yet, the Penn State Mack Truck Capstone Project Student Team has left that for Mack Trucks to decide. By giving the operators a physical checklist that requires parts to be assembled in a specific order, Mack Trucks will be able to yield more consistent Urea Tank assemblies and cut back on a considerable number of human errors the facility faces currently.

Objectives

– Develop Hierarchical Task Analysis​ based on current Urea Tank Assembly SOP

– Transcribe recordings of Urea Tank Operators in MAXQDA 2020 Plus​

– Code acceptable and non-acceptable deviations from Urea Tank Assembly SOP in MAXQDA transcriptions​

– Identify operator trends that may be leading to human error​

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Approach

– First, the group developed a hierarchical task analysis (HTA) based on the current Urea Tank Assembly SOP. Mack Trucks provided the team with video recordings from the Lehigh Valley facility in order to transcribe the actions of the operators during both shift 1 and shift 2.

– The team then used the HTA and the MAXQDA 2020 Plus software to transcribe the recordings and identify common deviations from the SOP.

– Based on the  different types  of errors found in the transcriptions, the team developed several categories of errors for a codebook that will  facilitate  the interpretation of the errors for Mack Trucks.

– The completion of these objectives will enable Mack Trucks to reduce a large  number  of human errors and provide the facility with a more efficient and productive workforce.  

Outcomes

– KEY FINDINGS ​

– Shift 1 Operator​

​- Failed to hand tighten screws​, as specified in the SOP

– Inserted screws directly with torque gun​

– Completed steps out of order from SOP in a sporadic manner​

– Shift 2 Operator ​

​- Failed to tighten hand screws as specified in the SOP, utilized torque gun directly​

– Completed steps out of order from the SOP but in a more methodical way than operator 1​

– Recommendation

– The team recommends that Mack Trucks creates a checklist version of its current Urea Tank Assembly SOP to standardize the assembly process across both shifts. This checklist can be in the form of paper or tablet given to each operator, so he or she always has it on hand to manually check off each task as it’s performed.

– By giving the operators a physical checklist that requires parts to be assembled in a specific order, Mack Trucks will be able to yield more consistent Urea Tank assemblies and cut back on a considerable number of human errors the facility faces currently.