Manufacturing Engineering Assignment -

Task 1: Calculation

1.1- Machining parameters

The machining parameters for an end-mill milling operation are listed in Table 1.

Assume K is the last digital number of your student ID. In stance, if your ID number is 1234567, the K=7, the machining parameters for you are: Chip load=0.06; cutting depth=3; spindle speed=6500; cutter size (diameter) = 20; number of teeth/flutes = 2

Based the Table 1 and K (the last digital number of your student ID, K=0), calculate the following:

(1) The feed rate (mm/min)

(2) The surface speed of the end mill (m/min)

(3) The material removal rate (mm³/min)

(4) Assume the specific power of the part is 15mJ/kg, assume the density of the part to be machined is 2,700 kg/m³, calculate the power needed for the machining.

1.2- Acceptance sampling plan K=0

A sampling plan has been agreed between a producer and his customer as below.

• Lot Size = N = 2000,
• Sample size = n = 20+2xK (K is the last digital number of your student ID. For instance, if your ID number is 1234567, the sample size is 20+2x7=34);
• Reject if the number of defectives > 2.

(1) What is the probability for accepting a batch containing 3% non-conforming?

(2) What is the probability for accepting a batch containing 10% non-conforming?

(3) Without further calculation, sketch on the operation characteristic curve for the sampling plan?

 (4) The producer wants to have <5% producer's risk, what should be the lot quality (percentage of defects) with this sample plan?

(5) If the customer is willing to accept lot whose defects percentage is less than 15%, what is the customer's risk for accepting non-conforming lots?

1.3- Statistical Process Control

(1) If the tolerance of a cylinder' length is 50±1. Determine which of the machines in Table 2 is able to achieve product specifications assuming Cp ≥ 1?

(2) A manufacturer is asked to suggest the tolerance x for a dimension 20±x based on the initial trials the manufacturer has conducted: mean=19.5, standard deviation σ=0.1. What should be the minimum tolerance x the manufacturer should recommend if the customer has demanded that Cp≥1.3 and Cpk>1.

(3) A production manager at a manufacturing plant has inspected the number of defective motors in 25 random subgroups with 300 observations each. Assume the average number of the defectives is 30 and the standard deviation is 3. For a subgroup, 45 out 300 are found defective, do you believe that "There are assignable causes for that subgroup"?

Task 2 - Analyses and Discussion

2.1- Quality control

Company Delta Plastics is a market leader in the design and manufacture of plastic container, primarily for kitchen and household use. Delta's R&D group has recently developed a new plastic material which the market team believed could revolutionize the industry. So they pushed for rapid production in spite objection from Joe De Costa, head of Manufacturing, stating that the new material is susceptible to cracking.

Exactly one month after production, the latest production quality report shown in Table 3 was produced showing weekly defects for products made with the new materials (dubbed by marketing as "super plastic") versus the standard material. Joe De Costa was nervous. Even if there were difference in quality, he was not sure what action to take.

Use one or more of the quality tools you have learned in the lectures and tutorials to analyze the defects in the case, and help Joe to decide.

(1) If the distributions of defect types differ between the two materials?

(2) Are there more defects associated with the super plastic versus the standard material?

(3) Is the new materials susceptible to cracking?

2.2- Manufacturing processes

For the manufacture of the parts whose engineering drawing is shown in Figure1 (attached), answer the following questions:

(1) Can a traditional 3 axis CNC machining centre for turning, milling and drilling be used for the machining of the parts? Why?

(2) If not possible to use a traditional 3 axis CNC machining centre for turning, milling and drilling, what are the possible conventional machining processes that could be used for the manufacture of the parts? Why?

(3) Can the parts be machined using non-conventional machining processes, if so, what are the possible processes?

(4) If the parts made of titanium are to be 3D printed, what are the possible 3D printing processes what could be employed?

Task 3 - Design for Manufacture

Machining Vices are widely used for holding parts for machining operations. As shown in Figure 2 (attached), a vice normally has two jaws. The surface on jaws that contacts parts is often flat and hardened. These make the vice incapable of holding complicated parts for machining and may mark on the finished part surfaces. In order to hold a specific shape of parts, soft jaws using softer materials such as Aluminium are machined to a specific shape and mounted on the original jaws.

Assume that you are a machinist and are given a job to machine a series of precision cylindrical bars with sizes ranging from 30mm to 50mm in diameter. Your task is to design soft jaws to replace the existing soft jaws shown in Figure 1. The requirements of your design are as below:

i) The cylindrical parts are held vertically;

ii) The cylindrical parts should have loading repeatability, in other words, the CNC machine knows the part position after the part is clamped in the vice.

iii) You can assume the cylindrical parts are sufficiently long to be held in the vice.

iv) since the parts are precision component, reasonable accuracy and surface finish is required for critical surfaces of your soft jaws (e.g IT grade 7 or 8, surface finish Ra3.2 or 6.3 for the critical surfaces)

v) You will need produce an Engineering drawing for the soft jaw based on which a block of Aluminium will be machined to the final shape by a 3 axis CNC machine at workshop. The CAD models of the vice and the existing soft jaw have been uploaded

Your soft jaw must fit on the fixed and movable jaws of the vice.

Attachment:- Assignment Files.rar