Introduction:
Consider a front-loading household washing-machine, as shown in Fig. 1. You are tasked to design the drive train, the suspension of the basket/drum, and the basket of this washing machine. The washing machine has several operational mode options (i.e. spinning the basket at different speeds), which will need to be accounted for when designing the system. It is anticipated to provide for the customer a five (5) year warranty, during which time as few as possible defects should occur. After 5 years of use, the machine should have an elevated failure rate. The machine contains a shaft that is responsible for powering the main drum to turn.
The shaft is driven by an electric motor.
Fig. 1: Front loading washing machine.
The following information about the machine is known:
• Load capacity: 4.5 kg (dry clothing)
• RPM for washing: 50 rev/min
• RPM for pre-spinning (drying): 800 rev/min
• RPM for spinning (drying): 1000 rev/min
• Drum diameter: 480 mm
• Drum mass (empty): 5.5 kg
• The washing machine is of regular size (27 in x 36 in x 27 in)
Electric motor specs:
• Weight 15 lb, dimensions 15in x12in x8 in
• 195 V, 5A, 300 Hz
• Rated power 820 W, 16,500 rpm
• Insulation class F
In order to design the different parts with the given requirements, you will need to do some research on the usage of the machine and its implication to its durability. You also have different drive options to transfer the electric motor torque to the drum (considering the different speed options as well). In addition to this, you also need to incorporate in your design waterproofing. As in all commercial designs, cost plays an integral role, hence your design choices and dimensioning, as well as manufacturing methods should reflect the aspect of cost. You can assume that the parts and this machine are mass produced (i.e. more than 2,000 units per year).
In your design report, address the following topics explicitly:
• Assumption on loading and usage
• Material selection and its reasoning
• Complete computation for the design of the shaft
• Power train options and reasoning for your selection
• Complete computation for power train design
• Complete computation of selected bearings
• Vibration considerations and affect to fatigue/warrantee etc.
• Detail drawings of all parts including dimensioning, tolerancing and assembly drawings with bill of materials (BOM)
• Information on manufacturing processes for all parts and implied costs
• (EXTRA CREDIT) Proof-of-product prototype (3D printed).
Report/Technical memorandum:
Your design report (technical memorandum) should include all topics listed above, with detailed calculations and assumptions/references.