American Made - Case Studies
Sheet Metal Stamping in the Automotive Industry
An automotive plant today produces some 40~50 critical panels per model of car in-house, that require some 100~150 automotive metal stamping dies.
Criteria for taking decision about the panels to be manufactured in-house vary from company to company. Very lately, the stamping plant of the automobile manufacturers includes the types of panels as given below in-house:
1. External (skin) panels, such as fenders, bonnet, decklid, roof, side panels, doors, etc. Some of these are two panels in a set as left hand and right hand
2. Internal mating panels, such as bonnet inner, decklid inner or door inner deciding subassembly quality
3. Dimensionally critical inner panels that are complicated either because of their complex shape or severe draw condition, such as, floor pans, dash panel, etc. Automanufacturers prefer to procure the medium and small size panels from vendors depending on the availability (nearer facilities are preferred) and their capability to meet demanded specifications. Some are even farming out the major subassemblies such as doors to specialised vendors. Trends are for farming out as much as possible. The 2 3 automobile plants are trying to concentrate on assembly operations, leaving specific technology related manufacturing, such as machining and pressing as separate facilities.
Automotive Metal Stamping Processes
Stamping processes to be used for a panel depend on its design. However, normally the processes used extensively are blanking, drawing, piercing, forming, notching, trimming, hemming, etc. Blanking prepares the initial approximate form of the part in flat sheet. Drawing is generally the first operation to attain depth related form. Piercing, notching, hemming, are product design related operations. Trimming generally removes the extra material on the periphery of the panel provided for blankholding during draw operation. Decision on trim line is very important and becomes deciding factor to obtain good draw.
SHEET METAL PRESS TOOLS - Progreessive Dies for Auto Industry
Approximately, the cost of a set of press dies to stamp all the sheet metal panels for a model of car may be as much as Rs. 2500~ 3000 crores or so. Everything possible is being explored to reduce this cost with certain amount of trade off such as tool life. Developments in conventional soft materials of low-cost press tools such as zinc alloys, resins, etc. that used to be for few hundred panels, have led to considerably increased tool life. Some new zinc alloys are claimed to provide a life approaching 1 million pressings. Low cost tool materials can now selected for low/medium volume production, that are particularly suitable for countries like India, and other countries in South-East Asia. Besides, with the use of these low cost dies, these companies may rem