Improvement of Punch and Die Life and Part Quality in Blanking of Miniature Parts

Blanking or piercing is one of the most commonly used sheet metal manufacturing processes in the industry. Having a good understanding of the fundamentals and science behind this high deformation shearing process can help to improve the tool life and blanked edge quality in various ways. Finite Element Modeling of the blanking process along with experimental testing is used in this study to study the influence of various process parameters on punch and die life and blanked edge quality. In high volume blanking and blanking of high strength materials, improving the tool life can save not only tool material but also change over time which can take up to a few hours for every change over.The interaction between punch, stripper plate and sheet material is first studied experimentally since a fundamental understanding of the behavior of these components at different blanking speeds is very essential to design robust tooling for high speeds. A methodology is developed using the experimentally obtained blanking load and FEM of blanking to obtain flow stress data of the sheet material at high strains and strain rates. This flow stress data is used to investigate the effects of various process parameters on tool stress and blanked edge quality. The influence of all these parameters on tool stress, blanking load and blanked edge quality are studied. Some factors are found to influence the tool stress and blanked edge quality more than others. Parameters like punch-die clearance, punch corner radius, application of stripper pressure and blanking velocity affect the blanked edge quality. As punches and dies wear, the punch-die clearance and punch corner radius increase, causing the blanked edge quality to deteriorate by increasing the rollover and burr. Punch-die clearance along with other factors like lubrication conditions, sheet material, tool material and coating also affects the rate of tool wear. The punch tip geometry significantly affects the blanking load. For a given sheet material, tool material and punch geometry, can selecting the right punch-die clearance minimize punch wear? Since small radii in the punch geometry wear or chip earlier and more often than the straight edges, there is also non-uniform wear pattern observed in the punch due to the non-uniform stress on the punch. The effect of punch geometry on punch wear is studied by conducting FE simulations of blanking and correlating the punch stress obtained from FEM and punch wear obtained via experiments. The effect of sheet material and thickness on punch stress is also studied. In addition, the effect of punch-die clearance for different geometries is investigated. After having a good understanding of the relation between punch geometry and punch wear for different sheet materials, a guideline for selecting the most suitable punch-die clearance for a given punch geometry to have more uniform wear on the punch is suggested.The performance of geometry dependent variable punch-die clearance and commonly used uniform punch-die clearance is compared by conducting blanking experiments and comparing the wear patterns for both cases. It was observed that the tooling with variable punch-die clearance could punch almost three times more parts (350,000 parts) with significantly less but more uniform wear on them than the tooling with uniform clearance (126,000 parts).Methods to improve part edge quality by using the optimum stripper pressure and to improve tool life using geometry-dependent variable punch-die clearance are suggested in this study.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

doctoral

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Subramonian, Soumya

Contributors dc:contributor

• Altan, Taylan
• Lilly, Blaine

• Mechanical Engineering
• High Speed Blanking
• Punch
• Die Life

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1365523543

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1365523543