ME 355 Manufacturing Processes

Transcription

1 ME 355 Manufacturing Processes Injection Molding Lab Report Due next lab. 1. Purpose: a. Gain some hands-on experience with polymers, particularly injection molding. b. Apply Design of Experiments (DOE) methodology to an actual process. 2. Experimental Plan: You will actually run two experiments in this lab. You will run a simple 2 3 factorial design to allow you to visualize what is happening in a DOE more clearly. Additionally, the entire class will be conducting a large designed experiment with the intent of optimizing the process of injection molding this part. a. The large design is what is called a Central Composite Design or CCD. This design will calculate all the linear and interaction effects, as well as the quadratic effects. For those of you who may be well versed in DOE, you will note that the run order is not the best, as I have opened this design up to biasing the temperatures by grouping them the way that I have. That is intentional because this is for a class, and I want to save some of your time. I would NOT do this if it were a real experiment. 3. Procedure: a. With the instruction of the TA, use the injection molding machine to produce parts in accordance with the DOE data-sheet provided. i. Be sure to number all parts with the Run number on the DOE data sheet for later analysis. b. Collect data as follows: i. Set up the machine for the temperatures that you will first be running in the larger experiment. 1. Once temperatures have stabilized, record those temperatures. ii. Run the following 2 3 factorial and record just the flash ratings on these parts. 1. Analyze for a flash rating. This is a rating from 1 to 10, with ten being the best. (Always have 10 be the best, 1 be the worst.) Group the samples in rating groups from 1 to 10. Once all samples have been evaluated, then check the ratings to be sure they are consistent with one another. Make the worst flash group (or individual) a 1, the best flash group or individual a ten, etc. Mold Temp: Melt Temp: Clamp Time: 20 seconds Run A:Clamp Force B:Injection Pressure C:Injection Time Tons psi sec

2 iii. Time the production cycle. Be sure to time more than one cycle, but make sure that you don t need to change mold temperatures during that time, as that is not a desired part of the cycle time calculation. Your time should be from a definite point in the cycle, until the time that definite point happens again. For example, cavity open, to cavity open. iv. As a class, complete the following table, which will then be analyzed by me. The TA should divide the experiments up into appropriate blocks for each section. v. Upon completion of the table, (the last section of the week), have someone an excel spreadsheet with the response columns filled in, with the associated run order. Run A:Clamp Force B:Injection Pressure C:Injection Time D:Clamp Time (after stopping injection) E:Temp Melt F:Temp Mold Gloss Full Cavity Fill Sink Marks Tons psi sec sec deg F deg F

3 Report: a. This is NOT a full report. Just answer the questions. b. Create a Cube Graph with the following as an example. A hand-drawn cube plot is acceptable if it is neat and straight edges are used to create the plot. The numbers on the plot are the responses for flash as you measured them. DESIGN-EXPERT Plot X = A: Clamp Force Y = B: Injection Pressure Z = C: Injection Time Cube Graph 2 6 B: Injection Pressure B C+ C: Injection Time B C- A- A+ A: Clamp Force c. The main effects in a DOE are calculated in this way: i. For Clamp Force, take the right face of the cube and average all the response values. ii. Take the left face of the cube and average those values. iii. Take the difference in the averages. That is the effect that you would expect to see if you changed only the clamp force from a low value to a high.

4 iv. Note that this is only an average change. That is why the whole model will also include the interaction terms to express how the response will be affected from a change in clamp force, based on different levels of the other variables as well. v. Calculate the main effects of the three factors of clamp force, injection pressure and injection time. vi. Don t worry about calculating the interaction effects as that gets a little more confusing, but suffice it to say that it is done in a similar fashion. d. Explain the process of injection molding with respect to the following: i. What factors affected all the measurements (individually ie. )? 1. How did they affect it? 2. Why did they affect it this way? e. What factors control the throughput (production rate) of the process? f. What was the cycle time of the process, as measured? i. How much product, in dollars, can this machine produce in a year? 1. Assume 3 shifts per day about 20 hours of production per day. 2. Five days per week weeks per year. 4. Assume that the parts are each worth $1.00 each to the company. ii. What is the profit? 1. Assume that the labor cost is $25/hour (after benefits, taxes, etc). 2. Overhead burden is 100% (this machine is inexpensive). 3. 5% off quality. 4. Material cost is $0.10 per piece. g. What did you learn about Design of Experiments? 4. In addition to the report for this week, you have an additional item that is required to be turned in at the next lab. Please fill in the following form. The intention of this form is two-fold: 1) To force you to go through a critical self-analysis to determine what your performance was, in hopes of improving for the future, and 2) To provide you with solid details upon which your lab grade will be evaluated.

5 ME 355 Manufacturing Processes Lab Evaluation Form Please take the time to think about these questions before answering them. Your evaluation will be based upon your answers as well as the observations and interactions of the instructional team in the lab. Note that there are several items on this evaluation that some might misconstrue as behavior evaluation. However, it is important that you understand, (as has been previously discussed in class), your attitude is part of your performance. In fact, YOUR ATTITUDE WILL DICTATE THE SUCCESS OR FAILURE OF YOUR CAREER FAR MORE THAN YOUR ABILITY. 1. Fan Parts: a. Assigned Parts: i. List the parts you were assigned. ii. Were the parts completed in a timely manner with the rest of the parts so that the fan can be assembled without a crisis? If not, explain. iii. Did you receive significant assistance from anyone, and if so, what, who and why? iv. Explain any difficulties that you may have experienced. Note that it is expected that you would have had some problems, so don t be afraid to list and discuss them. In your discussion, please be clear on the number of parts that you needed to make to get a good one. v. What is the quality of your parts, in terms of: 1. Dimensions (I am not worried about to the drawings, but rather, are they correct to what is needed to assemble and run the fan.) 2. Cosmetic

6 3. Functionality 4. Innovation b. Additional Parts: i. What was your level of involvement in completing the additional parts? ii. Why were you involved with making them? iii. What is the quality of your parts, in terms of: 1. Dimensions (I am not worried about to the drawings, but rather, are they correct to what is needed to assemble and run the fan.) 2. Cosmetic 3. Functionality 4. Innovation 2. Lab Performance: a. How was your attendance? Were you always present, or did you miss a lab or two? b. Were you always on time for labs? If you were late, how often? c. What was your attitude towards the labs? Was it an attitude that you wanted to learn, or that you had to get this out of the way so that you could get to other things?

7 d. Were you an active participant in the lab, or just there? 3. Evaluate yourself numerically from 0 to 100%. As a guideline, use an 80% as a score for someone who did their job, nothing more, nothing less: a. Fan project: b. Lab performance: 4. The instructional team will assign your grade by filling out the following for your feedback: a. Fan project (individual note that group grades will be assigned verbally at the fan presentations): i. Justification: b. Lab performance: i. Justification: