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5 6 Long parts A/B ≤ 3, A/C > 4 Flat (see note 6) parts 4 3 L/D > 1.5 (see note 5) Flat parts L/D < 0.8 (see note 5) 2 Cubic parts Long cylinders L/D > 1.5 (see note 5) 1 0 0.8 ≤ L/D ≤ 1.5 (see note 5) Short cylinders Discs 0.8 ≤ L/D ≤ 1.5 (see note 5) 7 8 9 A/B ≤ 3, A/C ≤ 4 Cubic (see note 6) parts Parts are difficult to feed using conventional hopper feeders (see note 1) Rectangular A/B > 3 parts (see note 6) (see note 4) Triangular or square prismatic parts (see note 3) Rotational parts (see note 2) L/D < 0.8 (see note 5) Long parts Parts can easily be fed (but not necessarily oriented) using conventional hopper feeders (see note 1) Small Parts for Automatic Handling (Choice of the first digit) 396 Assembly Automation and Product Design Appendix D 397 Small Parts for Automatic Handling (Choice of the first digit) 1. A first digit of 0-8 is for parts that can be fed easily (but not necessarily oriented) using conventional vibratory or nonvibratory hopper feeders. Parts having characteristics making them difficult to feed, irrespective of basic shape, are assigned a first digit of 9. Difficult-to-feed parts include those that are flexible, delicate, sticky, light, overlap, large, very small, nest, severly nest, tanlge, severly tangle or are abrasive. 2. A part whose basic shape is a cylinder or regular prism whose cross section is a regular polygon of five or more sides is called a rotational part. 3. A part whose basic shape is a regular prism whose cross section is a regular polygon of three or four sides is called a triangular or square part. 4. A part whose basic shape is a regular prism is called a rectangular part. 5. L is the length and D is the diameter of the smallest cylinder that can completely enclose the part. 6. A is the length of the longest side, C is the length of the shortest side, and B is the length of the intermediate side of the smallest rectangular prism that can completely enclose the part. SECOND DIGIT Part is ALPHA symmetric (see note 2) End surface Side view Principal axis 6 7 8 9 BETA symmetric step, chamfer or taper too small for orientation purposes Other features, slight asymmetry, features too small or non-geometric features [such as paint, lettering, etc.] (see note 8) 5 On end surfaces only BETA asymmetric features or BETA symmetric parts with features other than steps, chamfers or tapers but too small for orientation purposes (see note 9) 4 On side surface only 3 2 1 0 BETA symmetric hidden features with no corresponding exposed features (see note 7) BETA symmetric grooves, holes or recesses (see note 6) On both side and end surfaces BETA symmetric steps or chamfers on external surfaces (see note 5) Part can be fed in a slot supported by large end or protruding flange with center of mass below supporting surfaces (see note 4) End view Transverse axis Side surface Centroid Rotational Parts (Parts with a first digit of 0, 1, or 2) Part is not ALPHA symmetric [code the main feature or features, causing ALPHA asymmetry] (see note 3) 0 To be fed end-to-end (see note 11) 1 2 3 4 5 Through grooves can be seen in end view 6 On end surfaces 7 On side surface Through grooves cab be seen in a side view 8 9 Other features, slight asymmetry, features Holes or rece- too small or, sses [cannot non-geometric be seen in out-features [such er shape of sil- as paint, letthouette in ering, etc.] end views] BETA asymmetric grooves, holes, recessess on external surfaces Part is not BETA symmetric [code the main feature or features causing BETA asymmetry] (see note 10) THIRD DIGIT BETA asymmetric projections [can be seen in silhouette] To be fed side-by-side On both side (see note 11) On side On end and end surface only surfaces only surfaces Part is BETA symmetric (see note 9) 398 Assembly Automation and Product Design Appendix D 399 Rotational Parts (Parts with a first digit of 0, 1, or 2) 1. A rotational part is one whose basic shape is a cylinder or regular prism having five or more sides. The part is not difficult to feed. 2. The part does not require orientation end to end. 3. A main feature causing ALPHA asymmetry is one defining the endto-end orientation of the part. 4. These are parts that will orient themselves with their principal axis vertical when placed in a parallel-sided horizontal slot. 5. A BETA-symmetric step or chamfer is a concentric reduction in diameter. The cross section can be circular or any regular polygon of four or more sides. Discrete projections, recesses or irrelevant features should be ignored in choosing this digit. 6. The reductions and increases in diameter forming the groove must be concentric. The cross sections can be circular or any regular polygon of four or more sides. Discrete projections, recesses or irrelevant features should be ignored in choosing this digit. 7. These parts have an ALPHA-symmetric external shape but their center of mass is not at the geometric center of the part. 8. If exposed features are prominent but the symmetry caused by these features is too small to be employed for orienting purposes, then the symmetry is said to be slight asymmetry. 9. A BETA-symmetric part does not require orientation about its principal axis. 10. A main feature causing BETA asymmetry is one that completely defines the orientation of the part about its principal axis. 11. Some parts can only be fed one way. However, when a choice exists, the technique employed and hence the code can be affected by the delivery orientation. 400 Assembly Automation and Product Design Triangular and Square Parts (Parts with a first digit of 3, 4, or 5) 1. A part whose basic shape is a regular prism whose cross section is an equilateral triangle or square is called a triangular or square part. The part is not difficult to feed. 2. Part does not require orientation about its principal axis. 3. A part has rotational symmetry about a specified axis if the part’s orientation is repeated by rotating it through a certain angle (less than 360 deg) about that axis. 4. When the envelope of a part is a perfect cube, the principal axis should be selected according to the following priorities: a. Any axis about which the part is 90 deg rotationally symmetric. b. An axis about which the part has 180 deg rotational symmetry and clearly not 90 deg rotational symmetry. c. An axis about which the part has 180 deg rotational symmetry and almost 90 deg rotational symmetry. d. When a part has no rotational symmetry and there is more than one main feature, the principal axis should be the axis of symmetry of one of the main features. When utilizing the above rules and multiple choices still exist, then the axis that will provide a code with the smallest third digit should be selected as the principle axis. 5. Part does not require orientation end to end (it has 180 deg rotational symmetry about at least one transverse axis). 6. A main feature causing ALPHA asymmetry defines the end-to-end orientation of the part and distinguishes the end and side surfaces. 7. The various aspects of a part resting on a plane are called natural resting aspects. 8. If exposed features are prominent but the symmetry caused by these features is too small to be employed for orienting purposes, then the asymmetry is said to be slight asymmetry. When the part is 180 rotationally symmetric about a certain axis, slight asymmetry implies that the part is almost 90 deg rotationally symmetric about the same axis. 9. Steps, chamfers or through grooves are features which result in a deviation of the silhouette of the part from the silhouette of its envelope. 10. These are parts that will orient themselves with their principal axis vertical when placed in a parallel-sided horizontal slot. Side surfaces Side view Principal axis Part has 90 or 120 rotational symmetry about the principal axis (see notes 2, 3 and 4) End view End surfaces Transverse axis Centroid 0 0 Part has only one natural resting aspect or end and side surfaces can be readily distinguished by their shapes or dimensions (see note 7) 1 End and side surfaces can be distinguished because of steps, chamfers, holes or recesses 2 End and side surfaces can only be distinguished because of other features, features too small or slight asymmetry (see notes 8 and 12) Part is ALPHA symmetric (see note 5) Triangular and Square Parts (Parts with a first digit of 3, 4, or 5) 3 4 5 6 7 8 Part is not ALPHA symmetric [code the main feature or features causing ALPHA asymmetry] (see note 6) Steps or chamfers Through grooves (see note 9) (see note 9) Part can be fed in Part cannot be Holes or receslot and support- fed in slot and sses (cannot Other ed by large end or supported by protruding flang- large end or pr- Can be seen in Can be seen in be seen in outer geometric es with center of otruding flanges end view side view shape of features mass below supp- with center of mass below sup- (see note 11) (see note 11) silhouette) orting surfaces and the part is not porting surfaces or part is triangular triangular (see note 10) THIRD DIGIT 9 Slight asymmetry, features too small or non-geometric features [such as paint, lettering, etc.] (see notes 8 and 12) Appendix D 401 Part does not have 180⬚ rotational symmetry about the principal axis [code the main feature or features causing rotational asymmetry] (see notes 4 and 14) Part has 180⬚ rotational symmetry about the principal axis [code the main feature or features causing 180⬚ rather than 90⬚ rotational symmetry about the principal axis] (see notes 4 and 13) End view End surface Side view Principal axis Non-external External to the envelope Other features, features too small or slight asymmetry (see notes 8 and 12) Holes or recesses [cannot be seen in outer shape of silhouette] Through grooves can be seen in side or end views (see note 9) Steps or chamfers can be seen in side or end views (see note 9) Other features, features too small or slight asymmetry (see notes 8 and 12) Holes or recesses [cannot be seen in outer shape of silhouette] Through grooves can be seen in side or end views (see note 9) Steps or chamfers can be seen in side or end views (see note 9) Transverse axis Side surface Centroid 9 8 7 6 5 4 3 2 1 0 1 Code the same feature or features coded in the second digit Steps, chamfers Steps, chamfers or grooves can or grooves can be seen in side be seen in end view or other view or other features on features on side surfaces end surfaces (see note 9) (see note 9) 2 End and side surfaces can only be distinguished because of features too small or slight asymmetry (see notes 8 and 12) Part is ALPHA symmetric (see note 5) 3 Features on side surfaces (see note 15) 4 Features on end surfaces (see note 15) 5 Features on side surfaces (see note 15) 6 Features on end surfaces (see note 15) Steps or chamfers provided by non-external features (see note 9) 7 On side surfaces (see note 15) 8 On end surfaces (see note 15) Holes or recesses [cannot be seen in outer shape of silhouette] Part is not ALPHA symmetric [code the main feature or features causing ALPHA asymmetry] (see note 6) Steps or chamfers provided by external features (see note 9) Triangular and Square Parts (Parts with a first digit of 3, 4, or 5) (continued) SECOND DIGIT 9 Other features, slight asymmetry or features too small (see notes 8 and 12) 402 Assembly Automation and Product Design Appendix D 403 Rectangular Parts (Parts with a first digit of 6, 7, or 8) 1. A part whose basic shape is a rectangular prism is called a rectangular part. The part is not difficult to feed. 2. 180 deg rotational symmetry about an axis means that the same orientation of the part will be repeated only once by rotating the part through 180 deg about that axis. 3. Part can be oriented without utilizing features other than the dimensions of the envelope. 4. Steps, chamfers or through grooves are features which result in a deviation of the silhouette of a part from the silhouette of its envelope. 5. If exposed features are prominent but the symmetry caused by these features is too small to be employed for orientation purposes, then the symmetry is said to be slight asymmetry. For a part with 180 deg rotational symmetry about a certain axis, slight asymmetry implies that the part is almost 90 deg rotationally symmetric about the same axis. 6. A feature is too small, if it is too small to be employed for orientation purposes. 7. A part having no rotational symmetry means that the same orientation of the part will not be repeated by rotating the part through any angle less than 360 deg about any one of the three axis X, Y, and Z. The Xaxis is parallel to the longest side of the envelope, the Y-axis is parallel to the intermediate side and the Z-axis is parallel to the shortest side. 8. A main feature is a feature that is chosen to define the orientation of the part. All the features that are chosen to completely define the orientation of the part should be necessary and sufficient for the purpose. Often, features arise in pairs or groups and the pair or group of features is symmetric about one of the three axis X, Y, and Z. In this case, the pair or group of features should be regarded as one feature. Using this convention, two main features at most are needed to completely define thed orientation of a part. 9. Sometimes, when a part has no rotational symmetry, its orientation can either be defined by one or by two main features. Under these circumstances the part code is determined by the following in decreasing order of preference: a. Choose one main feature, if it results in a third digit less than 5. b. Choose two main features if they result in a third digit less than 5. c. Choose one main feature, if it results in a third digit greater than 5. d. Choose two main features if they result in a third digit greater than 5. 10. The symmetric plane is the plane that divides the part into halves that are mirror images of each other. Y axis C Rectangular envelope B Part has 180⬚ rotational symmetry about all three axes (see note 2) X axis A Z axis 0 0 Three adjacent surfaces of the envelope have significant differences in dimensions (see note 3) 1 Parallel to X axis Rectangular Parts (Parts with a first digit of 6, 7, or 8) THIRD DIGIT 2 Parallel to Y axis 3 Parallel to Z axis 4 Parallel to X axis 5 Parallel to Y axis 6 Parallel to Z axis 7 Holes or recesses (cannot be seen in outer shape of silhouette) 8 Slight asymmetry or features too small (see notes 5 and 6) Two or more adjacent surfaces of the envelope have similar dimensions [code the main feature or features which distinguish the adjacent surfaces having similar dimensions] Steps or chamfers Through grooves (see note 4) (see note 4) 9 Other geometric features or non-geometric features (such as paint, lettering, etc.) 404 Assembly Automation and Product Design SECOND DIGIT C Part’s orientation is defined by one main feature only (see note 90 9 8 7 6 5 4 3 About Z axis Part has a symmetric plane (see note 10) 2 1 About Y axis About X axis Rectangular envelope Y axis B Part has no symmetric plane (see note 10) One feature is syPart’s orientation mmetric about X is defined axis and the othby two main er one is symmetric about Y axis features and at least one One feature is syof them is a mmetric about Y axis and the othstep, er one is symmechamfer or tric about Z axis through One feature is sygroove or a mmetric about Z group of su- axis and the othch features er one is symme(see note 9) tric about X axis Part has slight asymmetry about at least one of its axes or the orientation of the part can only be defined by two main features neither of which are steps, chamfers or through grooves (see notes 5 and 8) Part has no slight asymmetry and its orientation can be defined by one main feature only or by two Part has no main features at rotational least one of symmetry which is a step, [code the main chamfer or feature or through groove features that or group of such can completely features define the (see note 5) orientation] (see notes 7 and 8) Part has 180⬚ rotational symmetry about one axis only (see note 2) X axis A Z axis 0 Parallel to X axis 1 Parallel to Y axis Steps or chamfers (see note 4) 2 Parallel to Z axis 3 Parallel to X axis 4 Parallel to Y axis Through grooves (see note 4) 5 Parallel to Z axis 6 Holes or recesses [cannot be seen in outer shape of silhouette] Code the main feature [code the feature that gives largest third digit, if more than one feature is utilized to define the orientation of the part] (see note 8) 7 Other geometric features 8 9 Non- geometric Features too features [such small as paint, (see note 6) lettering, etc.] Appendix D 405