DMAIC Project: Reducing Waste in Painted Products
Baseline (Define)
At the start of the project, there were errors in the surface treatment process of the wood material, which were monitored after the pieces were finished. Since quality defects could only be addressed once the products were finished, the aim was to prevent them from occurring at the very beginning of the painting process.
Based on the data collected in the company, the largest category of defects was debris on the paint surface. The aim of the project was to reduce the amount of debris on the painted pieces. In order to do this, the root causes of litter had to be identified. In order to control litter, the project had to identify which factors in the process should be monitored and adjusted to avoid quality defects caused by litter.
Process performance at the beginning (Measure)
At the start of the project, 3.66% of the doors painted were defective due to debris. Although the process was stable, there was a lot of variation (3.0) and 62.5% of the process did not meet the customer's needs. Based on the data, the aim was to both reduce the average (the amount of debris) and reduce the variation.
The project set a target of less than 2% of rejected pieces due to debris per painting cycle.
Improvement measures (Analyze & Improve)
Three main reasons were identified for the generation of litter:
- Dust left on the workpiece during grinding
- Dust in the paint on the track
- Dust from line structures and/or the surrounding space
The probability of access was examined through monitoring and observation. A multivariate test was also conducted. Based on the measures taken, it was found that:
- Dust on the surface of the piece during grinding: hypothesis tests showed the influence of the substrate on dust adhesion (static electricity)
- Dust in the paint on the track: no causal relationships between spray process variables and debris were found in hypothesis tests and multivariate tests
- Dust from line structures and/or surrounding space: process observation showed dust coming off the line structures after spraying
Based on the measures taken, it was decided to improve dust management by standardising working practices and providing cleaning/maintenance guidelines.
Results (Control)
Following the introduction of the new guidelines, a new monitoring exercise was carried out. The monitoring data showed that the number of rejects due to litter after the changes was 0.4% per coating cycle (variation 0.75).
The project was successful in reducing the amount of litter on painted parts through maintenance methods, but in terms of litter management, the project was not able to determine the correlation between spray process adjustments and litter.
During the project, several process changes occurred. For continuous improvement, the whole process, including the environmental factors, needs to be standardised in order to investigate the correlation of process adjustments with defects.
This project was a Black Belt training project, which the participant did as part of the training and received a Black Belt certificate at the end of the project.
If you are interested in learning how to improve your processes using Lean and Six Sigma, and earn your Belt Belt certification at the same time, check out the training at the link: Black Belt training.