Production scrap ration reduction

Results

At the company one of the machines in a group was producing significantly higher scrap results than other similar machines. This type of machine created finished goods from raw materials through a multiple step process. Between the steps a servo drive powered belt moved the semi finished goods with a chain drive.
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Goals

Reduce scrap
Increase availability of the machine

Participants:

  • 1 manager
  • 1 production support engineer
  • 2 operators
  • 1 quality engineer

scrap_rcaCourse of the Kaizen week:

Defining goals and measurements
Training of participants for Root Cause Analysis
Analysis of the results of scrap collection
Detailed analysis of product movement
Using Ishikawa (fishbone) diagram to explore possible causes
Different measurements to prove these causes
Processing measurement results, selecting root cause
Creating To Do List with responsibilities

 

Measurements:

  Before the Kaizen eventAfter the Kaizen eventChange(%)
Scrap ratio 10,18% 4,1% - 60%


Experiences, observations, difficulties:

  • At the first analysis of scrap collection data it was visible that most of the quality issues could be traced back to product movement in the process. During root cause analysis several possible reasons were collected that can result such an issue. Adequate measurement methods were needed to prove the real root cause.
  • Measurements finally proved thet the system responsible to forward the products creates several millimeter differences between different steps. This means that products will not step into correct position for further shaping at later stations. Processing enough measurement points also showed that there is recurrence in the data.
  • Analyzing the drive system in details revealed that in the trio of servo drive - auxiliary chain - main chain the length of the auxiliary chain matched the above recurrence. Replacing a relatively cheap (compared to all the other parts) part in the machine solved the problem and reduced scrap significantly.
  • The biggest difficulty during a root cause analysis is to achieve that the participants are ready to examine the problems from a different perspective and to forget all existing habits and prejudice for a short period of time.
  • It can also be difficult to find adequate measurement methods to prove the assumptions. If the results are not enough to proceed, narrowing the examined area or selecting a different approach can be the solution.

 


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