Die Design Fundamentals. Vukota Boljanovic

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impractical and another method of operation must be substituted.

      Before beginning the sketch, gather before you the part print, operation sheet, and design order. The three must be studied together so that a complete and exact understanding of the problem will be realized. This study will form the basis for creating a mental picture of a tool suitable for performing the operations—one which will meet every requirement. The sketch you make may be a very simple one, for simple operations, or it may be more elaborate. In fact, a number of sketches may be required for more complex operations and intricate designs. In any event, the sketch will clarify your ideas before you attempt a formal layout. In addition, it will form the basis for a realistic estimate of the size of the finished die so that you may select the proper sheet size for the layout.

      Layout. Laying out the die consists of drawing all views necessary for showing every component in its actual position. In the layout stage, no dimensions are applied and neither is the bill of material nor the record strip filled out. After the die has been laid out, the steps necessary for completing the set of working drawings are more or less routine.

      Assembly drawing. A properly prepared assembly drawing contains six general features:

      1.All views required for showing the contour of every component including the workpiece.

      2.All assembly dimensions. These are dimensions that will be required for assembling the parts, as well as for machining operations to be performed after assembly.

      3.All explanatory notes.

      4.Finish marks and grind marks to indicate those surfaces to be machined after assembly.

      5.A bill of material listing sizes, purchased components, materials, and number (quantity) required for all parts.

      6.A title block and record strip with identifying information noted properly.

      Detail drawing. After the assembly drawing of the die has been completed, detail drawings are prepared, unless all dimensions were previously placed on the assembly drawing (as is done for simple dies). Detail drawings are drawings of individual components. They contain all dimensions, notes, and supplementary information so that each part can be made without reference to the assembly drawing or to other detail drawings. Such information usually includes 10 distinct elements:

      1.All views required for identifying every detail of the part must be drawn.

      2.Every dimension needed for making the part must be given.

      3.Suitable notes for furnishing the supplementary information that dimensions do not cover must be applied.

      4.Finished surfaces must be identified.

      5.The name of the part and its number must be given.

      6.The material from which the part is to be made must be specified.

      7.The number of each material required per assembly must be stated.

      8.The scale to which the drawing has been laid out must be listed.

      9.The draftsman’s name or initials must be signed.

      10.The date must be specified.

      Dimension and notes. With the die design completed, all dimensions and notes are applied to the drawing. Figure 1.24 shows the die set note, which tells the die maker exactly what die set to order and gives required information about punch shank diameter, type of guide bushings, and diameter and length of guide posts.

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      b) Checking the Die Drawings

      After a set of drawings has been completed and the designer has reviewed them for possible omissions or errors, the set is turned over to the group leader, who will bring it to the checkers for further review. The design order, part print, and any notes or sketches that may have accompanied the drawings when the designer first received the job will now travel with the drawings. Checkers require all of these in order to do their work properly.

      Checkers first study the operation of the die to make sure that it will function properly and that its cost will not be excessive for the work it is to perform. After they are satisfied that it has been designed properly, they will check every dimension, note, and specification for accuracy. They usually work from a check print. This is a blue and white print having blue lines and a white background. With a yellow crayon, they will cover every dimension they find to be accurate, and with a red crayon they will cover every dimension they find to be wrong. Above or to the side they will write the correct dimension in red.

      The tracings, along with the check prints, are then returned to the designer for correction. Incorrect dimensions are carefully erased to remove all graphite from the paper. An erasing shield is ordinarily used to prevent smudging of other dimensions or lines. Correct dimensions are then lettered in place.

      After the tracings have been corrected, they are returned to the checkers, who review the job again to make sure that no correction was overlooked. They then sign the drawing in the space provided and enter the date the drawing was checked.

      After drawings have been completed and checked, they must be approved by the chief designer, chief tool engineer, and possibly the plant superintendent and others who are held responsible by the management for the cost and quality of dies used in the plant. Usually, these approvals are routine after drawings have been approved by the checker. However, it may sometimes happen that these personnel will refuse to sign because they believe that the die will not work as well as expected, will not deliver the number of parts required per day, will be too expensive to build, or for some other reason. If they convince others that their objections are valid, the drawings will have to be altered or a new design begun, depending upon the extent of the changes to be made.

      c) Prints and Distribution

      After drawings have been approved, blueprints are made from the tracings, or originals. A small print is taken of the bill of material only. This is sent to the stock cutting department where steel is stored and cut as required. The stock cutter goes over the list, selects bars of proper thickness and width, or diameter, and saws the bars to the lengths specified for each item listed. These cut blocks and plates are placed in a pan, along with screws, dowels, and other parts, which are kept in stock. When purchased components are delivered to the plant, they are also placed in the pan. Finally, the pan contains a set of die prints and a part print and it is delivered to the tool room, where the tool room foreman turns it over to the die maker, who will build the die.

      One of the prints is sent to the purchasing department. There, orders are written to authorize purchase of all components needed to build the die. If the entire die is to be built by an outside tool shop, a purchase order is sent to it. If it is to be built within the plant, an order authorizing construction is sent to the tool room. In addition, requisitions are made out for the following:

      •Standard parts or assemblies that are not kept in stock and which must be purchased.

      •Castings, forgings, or weldments required for construction of the die.

      •Steels of special analysis not carried in stock.

      •Special sizes of steels or other materials not stocked.

      The

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