Utveckling av processparametrar inom en hårdmetallindustri

Detta är en Uppsats för yrkesexamina på avancerad nivå från Uppsala universitet/Oorganisk kemi

Författare: Maria Sundman; [2012]

Nyckelord: Sintring; PEG; avdrivning; laststyrning; processdata;


This report analyzes and examines a hypothesis for finding a method to optimize thelength of the delubrication process time based on a total charge weight. The work hasfocused on the holding time for delubrication and the total charge weight.An important step in the manufacturing chain of cutting tools is when the greenbodies undergo the sintering process. Today, the delubrication step has the sameprocess time independent of the total charge weight. An implementation of a methodto adjust the delubrication process time would give more consistent quality of thecutting tool´s internal characteristics but also reduce the time course of the sinteringprocess. In the present project two methods for this goal were tested, thedevelopment of an algorithm and a weight interval subdivision with associateddelubrication process times.During delubrication a pressure increase is observed due to the decomposition of thePEG in the powder mixture. Previously, a larger total charge weight both increasedthe magnitude of the pressure increase and prolonged the time this increase took toreturn to the background pressure level. Earlier analysis of historical process datashowed indications of the possibility of developing an algorithm between total chargeweight and the time period defined by the time remaining for the delubricating stageafter the pressure increase has returned to its base level. This algorithm could thenbe implemented in production and lead to a charge weight adjusted delubricationprocess time, i.e. larger charge weights will need a longer delubricating period.A second method, involving a weight interval subdivision with specific associateddelubrication process times, was developed and a test was performed to determinewhether these ranges affected the quality of the sintering process.The results from the tests and the analysis of historical process data led to theconclusion that the hypothesis of dependence between the delubrication process timeand the total charge weight was not justified for the process investigated. Throughregression analysis it was found that the delubrication process did not dependsignificantly on the charge weight.The work resulted in a modification so that the delubrication process time couldtheoretically be shortened by approximately 60 minutes for the investigated processindependent of the total charge weight. Further analysis and tests are needed to findthe most optimal time reduction of the delubrication process without negativelyaffecting the internal properties of the inserts.

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