P17676: Vacuum Former

Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

This phase our team planned to begin buying parts and materials for our build. We also planned to test our vacuum system, have our heating system complete designed, and verify the quality of our frame motion.

Progress Report

Accomplished so far:

Need to know:

Prototyping, Engineering Analysis, Simulation

Slider Binding Test

In order to verify validity of the motion of the frame, a test was designed to calculate the binding moment.
  1. A 6"L-bracket slider was built according to the predetermined design
  2. A 36" rigid rod of 1/2" tube stock was secured to the slider perpendicular to the direction of intended motion
  3. A long piece of 1.5" 8020 rack was clamped vertically
  4. The slider with the rigid rod attachment was assembled to the vertical 8020 track
  5. Held at the top of the track, 2 lb weights were strung at the far-end of the rod
  6. The slider was releases, and motion was studied for binding
  7. If binding was not observed, the slider was returned to the top of the track, and the mass was moved slightly inward
  8. The test was repeated until binding was found
  9. Distance along the rod and weight were recorded at the point of binding
  10. Binding moment was calculated

Vacuum Pressure Test

To both ensure the vacuum pump can evacuate the system down to the desired vacuum pressure in a reasonable amount of time and to ensure the tank can withstand this desired vacuum pressure.
  1. The vacuum pump was connected to the tank with vacuum-rated tubes and equipped with a vacuum pressure sensor and an outlet ball valve (initially closed)
  2. The pressure sensor was connected to a LabQuest data logger where vacuum pressure data could be collected
  3. The pump was plugged in and turned on, allowing the pump to draw air out of the sealed system
  4. Observing the system, the vacuum pressure increased in "inHg" to an asymptotic value where it stabilized. The system was allowed to remain stable for several seconds to confirm the vacuum pressure could be maintained
  5. The ball valve was opened quickly and completely, allowing atmospheric air to rush into the system and attempt to return to a stable pressure. As the pump was still running, the system appeared to stabilize at a slightly positive vacuum pressure
  6. Vacuum pressure data was recorded and analyzed

Bill of Material (BOM)

BoM and Budget

Test Plans

Oven Heating Test

Test to observe the effects of different temperatures and time exposures of plastic samples utilizing an oven heating element
  1. Secure the 12"x12" plastic sample to a wooden clamping frame, with support legs such that there is at least 8" of open depth below the surface of the plastic, so that it may soften and sag unobscured
  2. Set the oven to 250 degrees Fahrenheit, on the "Broil" setting, to simulate the top-side heating that would be seen in the final vacuum former machine
  3. Once the oven is brought up to temperature, insert the clamped plastic into the oven (with the light on so that the plastic can be observed)
  4. Begin a timer and record observations over time, noting how the plastic appears to soften, deform, or sag at the given temperature and duration. The material may sag and "rebound", becoming flat again
  5. Once the plastic has appeared to sag sufficiently and rebound, remove the plastic sample from the oven
  6. Allowing the sample to cool and become rigid once more, remove it from the wooden clamping frame and secure a new sample of plastic
  7. Repeat the previous steps, increasing the temperature in the oven in 50F increments until a temperature of 400F is reached
  8. Repeat this set of trials with various plastic materials and record results and observations to develop a preliminary plastic heating procedure

Vacuum Table Test

Test various vacuum table properties to seek the optimal table design. Design and create various 12"x12" vacuum tables out of Medium-Density Fiberboard (MDF) containing variations of vacuum-port hole diameters and on-center grid spacings. The default that has been selected is 1/16" diameter holes in a 1"-on-center grid. This test will either validate that assumption or find a more optimal table design.
  1. Secure the test vacuum table to a vacuum box, maintaining a 1/2" interior depth of the vacuum box
  2. Position the test part to be molded onto the vacuum table surface
  3. Connect the vacuum pressure hoses to the bottom of the vacuum box
  4. Perform the Oven Heating Test on a plastic material that performed well in the metrics of duration and softening
  5. During heating, evacuate the vacuum tank by turning on the vacuum pump with the ball valve connected to the vacuum box completely closed
  6. Once the plastic is heated sufficiently and softened, and the vacuum tank is evacuated, remove the clamped plastic from the oven and carefully place it over the test part on the vacuum table, ensuring the clamping frame remains level and is secured sub-flush to the vacuum table surface
  7. Once secured, quickly open the ball valve under the vacuum table completely, drawing a vacuum underneath the vacuum table
  8. Observe and record the effects of the vacuum forming operation
  9. Allowing the new mold to cool and harden, separate the plastic mold from the test part and make and record observations on the quality of the mold
  10. Make any necessary adjustments and repeat trials until the best quality mold can be produced, recording any procedure changes
  11. Repeat this set of trials with each vacuum table design and compare the quality of the produced plastic molds. Reach a consensus on the optimal table design

Design and Flowcharts

Vacuum Process
  1. To start you will have to determine the proper plastic to use for your application along with which table size will be the most efficient. If the desired table size needs a clamp insert put the insert in while the clamp is in its initial position. Place the desired table size onto the table platform making sure to center it and connect the vacuum line to the table. With the frame in the initial locked position you will secure the plastic into the clamp, begin to preheat the oven, start charging the air tank, and set your mold piece or pieces on the table.
  2. Once the setup is complete you will raise and lock the clamp into the oven position and wait for the plastic to be at the desired droop for forming.
  3. Once the plastic is ready you will turn off the oven and then lower the plastic into position over the mold and table. Immediately release the vacuum to allow the forming process to occur. Then wait for the plastic to cool and harden.
  4. Once the forming process is complete you will return the clamp to its initial position to remove the plastic and the mold.

Risk Assessment

Risk Assessment

Plans for next phase

Gantt Chart

3 Week Plan

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