CHAPTER 3 | PART DESIGN GUIDELINES Wall Thickness (mm) C o o li n g T im e ( S e c ) 40 35 30 25 20 15 10 5 0 0 1 2 3 4 ABS PC Nylon 6/6 Figure 2 - Designing for Wall Thickness Changes Bad Better Recommended Recommended Poor High Stress Ideal Figure 3 - Internal and External Radius Guidelines .5W Min Inside Rad + W Poor High Volume FIGURE 1 - Wall thickness vs. cooling time of various plastics FIGURE 2 - Designing for wall thickness changes FIGURE 3 - Internal and external radius guidelines Design Guide 9 RIB DESIGN GUIDELINES The minimum distance ribs should be spaced is three times the nominal wall thickness (3W). Hoop stress can be determined using the following equations (figures 15–18).1 • V = Length of Boss (figure 14) = .400 • I = Interference Fit (figure 15) • W = Geometry Factor (figure 16) • H = Hoop Stress (figure 17) • E = Material Modulus • μ = Frictional force between materials • lEngage = length of engagement between the shaft and the hub Press Fit Example Problem Figure 14 is an example of a press fit problem. N” is the total number of branches.

Richardson N/A - - - V. Garratt N/A - - - M. Nikrant N/A - - - S.D.

MAX FRESH PROCESS BLUE C MAX FRESH PROCESS BLUE C MAX FRESH PROCESS BLUE C

13920GNS BETA WARM GRAY C PE WARM RED C 186CAB SP PANTONE(R) 186 C SIMULATION

DGB0091 C/M RUGGED CANYON ST DGG0079 C/M QUITE WILLOW ST DGA0149 C/M SILVER GRAY ST

Geon(TM) Second Coat Version "C" 7427GNSPL PANTONE(R) 7427 C SIMULATION 1585GNSPL PANTONE(R) 1585 C SIMULATION

281CGNS PANTONE(R) 281 C SIMULATION 259CGNS PANTONE(R) 259 C SIMULATION 3295CGNS PANTONE(R) 3295 C SIMULATION

1807CGNS PANTONE(R) 1807 C SIMULATION 1255CGNS PANTONE(R) 1255 C SIMULATION 1805CPFX EPIC PANTONE(R) 1805 C SIM.

TPE PURPLE C PURPLE C TPE TRANS BLUE PMS 281 C

193CPFXAB EPIC PANTONE(R) 193 C SIM 227CPFXAB EPIC PANTONE(R) 227 C SIM 41294PFX EPIC SPL WF RED 485 C