| | | Plastic injection molding design guideline | Purpose | Guideline followed? | Explanation
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| 1 | | Used for high production rates | Molds expensive | Yes | Mass production of components
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| 2 | | Integrate as many components as possible | Reduce material and number of molds needed | Yes | Battery holder is part of Bottom cover (023); gear train supported by bosses versus additional component
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| 3 | | Use draft features vs. sharp edges or angles corners | Facilitate removal from mold; eliminate extra finishing processes | Yes | Angled surfaces in corners and around all projections
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| | 3.1 | Draft angle = 1 to 2 deg | For surfaces <5 in | Yes | Smaller angles for larger parts (as low as 0.5 deg)
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| 4 | | Even wall thickness | Lower cost of mold, simplify manufacturing | Yes | All component features have even wall thickness and cross sections
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| 5 | | Use thinner walls (1/32 in to 1/10 in) vs. thicker | Decrease weight and material needed; aids proper cooling | Yes | Components are cored out, leaving ribs and bosses instead
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| | 5.1 | Wall thickness > wall length/50 | Assure proper cooling | Yes | Measured ratios all > wall length/50
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| | 5.2 | 90 deg walls < 0.25 in high | Avoid defects such as warping and sinking | Yes | Measured < 0.2 in, except for 90 deg walls supported by gussets
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| 6 | | Rounded corners have even wall thickness | ID and OD have same center point | Yes | OD = ID + wall thickness consistent
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| | 6.1 | Larger radius in areas with significant stress | Distribute stress more uniformly | Yes | Corners of outer covers have large radii
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| | 6.2 | At 90 deg walls, ID = OD > 0.1 in | Decrease tooling cost and failure | Yes | Measured > 0.16
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| | 6.3 | Min radii > ¼ min wall thickness | | Yes | Min radii > ½ min wall thickness for all components
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| | 6.4 | Radii = ½ to ¾ nominal wall thickness | | Yes | Measured to be never less than 1/2
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| 7 | | Tapered sides and projections ~ 1 to 2 deg | Facilitate removal from mold | Sometimes | Some ribs exhibit no tapering
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| | 7.1 | Rib thickness = ½ to ¾ nominal wall thickness | | Yes | Measured
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| | 7.2 | Rib height < 3x wall thickness | Avoid thin sections requiring extra mold fill time | Yes | Measured
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| 8 | | Bosses | Act as screw holes, instead of using solid mass | Yes | Used in all casing components
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| | 8.1 | Diameter | OD/ID = 2 to 3 | Yes |
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| | 8.2 | Thickness | = 1/2 to 2/3 nominal wall thickness | Yes |
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| | 8.3 | Gusset Height | = 2/3 height | Yes |
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| | 8.4 | Height | = fastener minimum requirements | Yes |
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| | 8.5 | Taper | = 1 deg (uniform) | Yes |
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| | 8.6 | Diameter Ratio > 2 | Reduce risk of failure | Yes |
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| 9 | | Consideration of weld line location (where flow fronts meet during injection) | Plastic susceptible to cracks and stress here | Yes | Can be seen in dark color of plastic
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| 10 | | Surface finish > 64 µin | Molding into final appearance with no additional processes | Yes | Approximate measuring
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| 11 | | Raised vs. recessed text | Avoid shrinking deformation | Yes | All component numbers are recessed
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