| Abstract [eng] |
The master thesis conducted is the investigation of the root cause of the high scrap rate of product FOT in laser engraving department. Product FOT splits into two versions after chrome-plating operation where one of the versions continue to laser engraving department, where the other is sold directly to the customer. High scrap rate occur at laser engraving department where the laser marking quality varies on parts from the same batch when laser parameters remain constant. An analysis done focusing on chrome-plating process variation throughout positioning of parts on the processing bar: the position on the rack as well as the orientation. One processing bar – 140pcs of parts were numbered and measured before and after the chrome-plating operation to find out how does this affect the product specifications. Furthermore, the positioning on the processing bar was noted, as well as two sub-groups were done. One sub-group was hanged orientating the marking surface outside the processing bar, while the second sub-group vice versa. Chroming process instability was noticed due to unstable current spread throughout the processing bar: part specification change amplitude was equal to the change of nine to ten times. Meaning that the difference of change of part weight or high from its nominal after the injection moulding operation to secondary after chrome-plating operation may vary nine to ten times on parts from the same batch. Additional analysis of coating thickness for the laser engraving area was done for five parts from first sub-group and five parts from second sub-group. Parts were selected including several parts that changed the most and several that changed the little. This resulted a conclusion that coating thickness of parts from the same batch varies from nine to ten times. These ten samples were laser engraved to see how does it affect the marking quality – parts with thicker coating layer were better in quality, while parts with thinner layer were scraped. Since the tendency of parts with thicker and thinner coating layer is visualised and noticed and the Company XXX wants to reduce the scrap rate without investments – the handling operation were introduced and tested. Parts are split into thin and thick layered straight after the chroming cycle is over. Parts with thicker layer continues to laser engraving operation, while the parts with thin coating layer are send directly to the customer. This change does not require an investment, but only administrational internal work. The part cost price does only increase by 0,1 €/pcs, while the scrap rate is reduced by 33%. However, this suggestion is considered as short-term solution, which does not solve the main root cause of the high scrap rate. Therefore, final recommendation for the Company XXX would be to invest into new racking system, which would require the designing of the racking system, as well as test runs, adjustments and similar analysis of the product change. |
