Typical Tolerances of Manufacturing Processes（制造过程的典型公差）.pdf

EML 2322L – MAE Design and Manufacturing Laboratory Typical Tolerances of Manufacturing Processes In the past, one of the traditional weaknesses with graduating mechanical design engineers is their inability to select tolerances. Most students were reasonably proficient using one or more CAD packages and could produce drawings which were pretty good (given their limited experience levels). However, despite knowing how to put a tolerance on a drawing, most students generally had no idea what the actual numbers should be, or any sense of what the process for selecting reasonable tolerances might consist of. Since Geometric Dimensioning and Tolerancing (GDT) is in widespread use in industry, the MAE curriculum has changed to include it in EML2023. Nevertheless, knowing how to properly express a tolerance for cylindricity or parallelism between two surfaces on a part drawing is not the same thing as knowing what a reasonable number for that tolerance should be. After taking EML2322L, the students should be much more proficient in these areas. To facilitate the students’ understanding of this important area of mechanical design, we have put together a few slides on some common manufacturing processes, and what their tolerance producing capability is. After taking EML2322L, the students should have a tangible understanding of the tolerances associated with basic manufacturing processes used in this course (i.e. milling, turning, drilling, reaming, bandsaw cutting, etc.) Process Tolerances Process Tolerance vs. Feature Size Surface Finish vs. Production Time FIGURE 15.10. Surface finish produced by various processes. (Source: Wikipedia) Figure 15.5 presents a collection of the most common manufacturing processes and the tolerances commonly associated with each of them. As explained in the legend, the shaded portions of the bars represent the average application of these processes and mean virtually any manufact