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Last month's discussion centered on geometric dimensioning and tolerancing and several symbols used to describe the machining specifications when manufacturing parts. These symbols should be used on drawings found in several industrial settings.
One general grouping of drawings are called detail drawings. The detail drawing will provide all of the necessary information to produce the part. In addition to the part production, the detail drawing can be used when bidding a job or as a master drawing, from which other drawings are produced. The information on a detail drawing is specific to the part to be produced, drawn one part per page or sheet. The information must include the pertinent shape, size, specifications and notes. The notes and/or title block information would include scale, tolerances, surface texture and the material used. Additional information included may reflect finish requirements, moisture contents, glue type, wood color, grain direction and other specifications needed for the customer. Other specifications may be the laminate manufacturer or color code, veneer grade and type required, etc.
The term "detail drawing" is the general name that includes several types of specific drawings used in various industrial settings, all of which have ties to the wood industry. The term "casting drawing" details the size and location of separation lines called parting lines. When the mold separates, the parting line is left on the casting. The other information typically found on a casting detail drawing may be a pattern number, sand requirements, part numbers, customer name, draft, shrinkage, finish, ribs and other support webbing, and the material used in the casting/mold.
Wood patterns, made by patternmakers in the general male or female shape of the finished part, are configured into the sand mold and removed — leaving an impression to be filled with molten metal. When cooled, this metal casting is removed and the process is continued. These castings are then machined into items such as engine blocks, cast iron tools or other metal castings we use every day. Bearing blocks, machinery bases and parts, and many household items have castings produced in this manner.
MACHINING DETAIL DRAWING
A machining detail drawing is then used to machine the casting into a finished part. Also used when machining a rough part into a finished part, a machining detail drawing will specify the surfaces to be machined, bolt holes and locations, reference points, GD & T, and other machined areas. A machining drawing contains critical information to the traditional or CNC machinist, such as angles, reference points, surface finish, etc. Once complete, this machined part should match and fit other machined parts as defined in an assembly detail drawing.
ASSEMBLY DETAIL DRAWING
When all parts are produced using their respective machining detail drawings, an assembly drawing provides the information the print reader requires to assemble the components. Included on an assembly drawing is a bill of materials or list of component parts required for the assembly, necessary dimensions and component labeling. A three-dimensional picture of a complete assembled unit would aid the reader to understand the final shape of the assembly. A front, side and top view may be critical to communicate dimensions or shapes to the reader. If this assembly drawing is actually one of several subassemblies, the print should indicate this in the title block or bill of materials. Movements of components in an assembly detail drawing should be indicated with the use of phantom lines, described in an earlier article in Wood Digest.
Other versions of an assembly detail drawing may be for machinery components, also using section views clearly numbered showing interior and exterior parts.
Another version of an assembly detail drawing is the pictorial exploded assembly drawing, typically found in machinery catalogs designed for homeowners or parts suppliers to order parts. For further explanation of these drawing types, review your text or search online for additional guidance.
TO WOOD DIGEST READERS:
Several readers have commented on the effectiveness of these articles to them or their position in their company. If you have a comment, please let me know. Your comments are always read and if you leave contact information, you will be responded to.
TRY IT YOURSELF!!
To all readers and students: To explore the discussion topics above, you can follow along at home or at work. For enrolled students: As part of your homework, draw a simple pictorial assembly drawing. Dimension your drawing and send it to me. Provide a definition for the following terms from the glossary and the Internet:
- Assembly detail drawing
- Pictorial assembly drawing
- Machining detail drawing
- Bill of materials
- Subassembly
- Draft
- Casting
- Parting lines
- Full section
- Casting shrinkage
If you find technical information, please let the class know about them on Blackboards Discussion Board or e-mail to me.