Report 3 Update 2

Bubble

1. Justification and discussion of the process optimization and possible mold redesign. Include what problems occurred if any and give reasoning behind the parameter adjustments or mold modifications that were made that improved the condition.

The thermoform component in our yoyo is the clear bubble. We had no major mold redesigns. In fact, we kept the dimensions fixed and redesigned the inner diameter of the inner ring to fit closer to the outside of the bubble. However during the first runs, we ran into issues with the plastic not being fully flush around the pegs due. This posed a problem in the long run because the not flush plastic would cause a weaker seal  between the housing and the flat of the bubble thermoformed part, increasing the likelihood of water seeping out. The problem was primarily because there were not enough air holes around the die-cut pegs to allow the hot plastic to nicely conform around the pegs. We started with stainless steel pegs and then tried coiled pegs in hopes of making use of the interface for air to pass through and suck the plastic. The coiled pegs did not provide enough of a gap and we resorted to filing a flat in brass pegs and filing into in the peg holes in the mold. These corrections significantly improved the thermoformed part. We also changed the thermoform parameters to make the plastic conform to the pegs further. Below is table of our tested parameters for various runs.

	Run 1	Run 2	Run 3	Run 4
#02 Heat Time	150	225	225	225
#03 Form Time	100	100	200	175
#05 1st Platen Open Delay	150	150	200	200
#06 Cooling Fan Delay	25	25	25	25
#07 Cooling Fan Time	100	100	100	150
#08 Air Eject/Platen Hold Time	5	5	5	5
#12 Main Vacuum Delay	3/0	3/0	3/0	3/0
#13 Main Vacuum Time	100/0	100/0	100/0	100/0
Top Oven Temp	650	675	650	650
Bottom Oven Temp	650	675	650	650

Figure 1

Figure 1 shows the results from the 4 runs. At first, we increased the heat time and oven temperature so that the plastic would be more amorphous and conform to the pegs. Run 2, however, was too hot and did not hold its shape during demolding. To correct for this, we brought the temperature back to 650 and maintained the heat time while adding longer form time to allow the part to cool longer. We also increased the open delay a bit. Run 3 was pretty successful but we wanted to corrected one more time to get the plastic to conform to the pegs even better. The plastic was still pretty hot so we increased the fan cooling time. We decreased the form time slightly to activate air eject, which would break the vacuum and assist the formed part off the mold. Run 4 was successful. Each run is about 40 seconds.

However, after 20 runs, we realized the thermoformed parts were decreasing in quality. Figure 2 shows the results after 20 runs. Some parts were coming out not holding shape due to the machine overheating and some parts were not fully conformed to the pegs. We supposed this issue has to do with the faulty air compressor. For this lab we made 30 successful parts using the 2.999 diameter circular die-cutter. 

Figure 2

2. A fully dimensioned drawing of the part. In the event of a redesign, a fully dimensioned revised

drawing showing the new design specification as well as a fully dimensioned revised drawing of the

mold including matching revision levels.

4. Update the posted Gantt chart. (Your team’s component(s) only).

Due to the faulty air compressor, we will need to wait and hear back from the 2.008 staff to complete another production run. Alternatively we can produce 20-25 parts in a batch and wait 10 minutes before starting another batch. The thermoformed bubble part will be completed and die cute by the end of next week.

5. Post your component’s set-up sheet showing all the optimized parameter settings that will be used to run production for the component.

#02 Heat Time: 225

#03 Form Time: 175

#05 1^st Platen Open Delay: 200

#06 Cooling Fan Delay: 25

#07 Cooling Fan Time: 150

#08 Air Eject/Platen Hold Time: 5

#12 Main Vacuum Delay: 3/0

#13 Main Vacuum Time: 100/0

Top Oven Temp: 650

Bottom Oven Temp: 650