Table of Contents
P11008 Test PlansSubsystems Requiring Test
- Blade Choices
Once our machine is able to be mocked up in a semi-complete fashion which will allow for the blade mount to be actuated a cutting test will need to be performed to determine if the cut which is produced will be acceptable for ArcWorks. Procedure:
A specified number of cuts (Approx. 10) will be performed using the razor blade option under different pressure values. The first pressure which will be tested is 80psi. The pressure values will be gradually stepped down by 10 psi to give us a range of values which our system will be able to operate at. The quality of the through cuts will be observed. These values can be determined from the pressure gauge which will be setup on our regulator. An optimum cutting setup can then be determined from this rough DOE. The resulting cut quality will be observed and the ease in which the machine cuts through the straws will determine which option is chosen. The way the scrap material is extracted will also be monitored. Ideally we do not want the scrap shooting in uncontrollable directions once the straws are cut. So this will need to be observed as well. Deformation of the Straws will be unacceptable. If this occurs during any of the setups, those setup options will not be chosen since they are obviously not ideal.
This cutting blade test was performed at 80 psi and the cuts which were produced had some burrs and pitting. The blades also did not have a completely straight cut due to the deflection of the straws within the base plate. When the psi was reduced the quality of the cut got continually worse. The flow control for the cutting blade cylinder was adjusted to allow for the maximum amount of air in the system. Due to the intermittency with the air supply on the 4th floor it was difficult to for extended amounts of time at a pressure greater than 80 psi. The cuts which were produced at this pressure did not show any improvement with quality. Next Steps:
1. To improve the quality of the cuts a support block was placed underneath the straw insertion plate to decrease deflection. It was also noticed that the force generated by the cylinder was forcing the entire machine to move. A base plate will need to be implemented to reduce this movement. Once a base plate was added the quality of the cuts were seen to improve minimally.
2. To test if the quality of the cut straws was improved with a decrease in the speed of the cut, but not a decrease in the pressure the Two Hand Anti Tie Down system was compromised to allow for a reduction in the speed of the cylinder. This allowed for the flow controls to be adjusted. The quality of the cut was seen to improve slightly.
The ease in which the blades can be loaded into the plate will be observed. Ideally our spec will be less than 5 minutes. Result: This was tested and it was determined that the blade could be changed within our target spec of 5 min. The cross support piece in the middle of the machine makes it difficult to unscrew the back screw because it interferes with the Allen wrench which is required. A longer Allen wrench should be used to make changing of the blade easier.
Production RateThis test will be executed prior to the delivery of the system to Arc Works. All of the associated systems must be working flawlessly in order for this test to be valid. The production rate will be determined by running the machine for a 5 minute period and extrapolating this figure out to determine the hourly rate. The current automated machine in use can produce 700 straws/ hr. Ideally we would like to be able to produce 1000 straws/ hr. With this level of production in addition to the rate of the machine already in place, a substantial efficiency improvement will be seen. The production rate which is possible with the machine is shown below. The new device is capable of producing 1200/ hr. if it is run continuously.
- The pneumatic system will be tested out for functionality before it is ever hooked up to actuate the components of our machine. These components will include the two handed switch, the cylinder driving the cutting force and the cylinder operating the trap door. Once all of the valves and cylinders are able to be assembled outside of our mechanical system we can determine if the logic is correct before actually hooking up the pneumatics into the machine. Of course once the machine is assembled the pneumatics will be tested to verify that they can work within our system.
Result: All of the components and logic were tested prior to being hooked up to the cylinders and frame of the machine. Some tweaks needed to be made to allow for the system to work up to its desired capability. It was seen that a large amount of exhaust was being lost from the logic board so a fitting was inserted to allow this air back into the system. After this fix the pneumatic logic was verified and hooked up onto the cylinders which controlled the motion of the machine. The pneumatics were again checked to make sure all of the cylinders were operating correctly. The flow controls were adjusted to produce our desired motion.
Length Adjustment SystemDue to the length adjustment system not being fully operational we were not able to test the height adjustment system completely. Ideally the height adjustment system would have been fully functional to allow for testing. Since the system was not the backup block system was used to hold up the straws to the 9 different specified lengths.
A test was completed using all of the different size blocks and all cuts were made within the desired tolerance. However the quality of these cuts was not acceptable.
Future Process Capability Test-Similarly to how the Process Capability of the current machine was determined we will perform a capability analysis on our machine once it is operational. This will include cutting 200 straws at the 4.33’’ length and verifying that we have the capability to stay within the specifications of +/- .2’’. Even though this tight of a tolerance is not necessary for the function of the final assembly it is important that our machine does not decrease the capability of the system at Arc Works. Currently the Process has a Cpk of around 5. Originally this was thought to be much lower because the specs were so unnecessarily tight. After clarification from Arc Works the specs were altered. It was determined that the original specs were too tight the tolerances are this is not unacceptable, but are machine should allow for an improvement in this area. Smaller amounts of samples can be collected from different length adjustments to confirm that our capability does not depend on the straw length which is cut. If it is determined that length adjustment is affecting the capability a more extensive test will be utilized to confirm before any alterations are made.
Safety SystemThe major safety concern associated with our project is the hazard associated with the blade which we are utilizing to cut the straws. To eliminate this risk the pneumatics will not be activated until the safety interlock switch which is installed on the side support of the device is depressed from the Plexiglas door hatch system. Another backup system to this will be the utilization of a two handed anti tie down switch which will only actuate the system if both buttons are pushed at the same time. This will guarantee that the operator’s hands are not within the travel of the blade. Result: The interlock system was tested. No air will be allowed into the pneumatic logic loop if this switch is not depressed. The Two hand anti tie down switch was also tested by pressing both at separate time and watching to see if the device actuated. This is important because the operator will need to press the buttons at exactly the same time. The machine will not actuate if one button is compromised (depressed by an item being set on it) and then hitting the other button. To satisfy the Minimal Physical Exertion Engineering specification a small number of buttons/switches are required to activate our device.
Removal SystemA preliminary test will be conducted to determine if the scrap straw material can be eliminated from our current design using a vacuum attachment. This test should be conducted as soon as the pneumatic cylinder is able to be actuated and the straws are able to be placed within their designated locations on the loading plate.
Result: Once the straw ends were cut the scrap pieces are pushed in the direction of the vacuum attachment even without a vacuum present to provide the suction. A follow up test with the vacuum on was completed and the debris from the straws was readily removed from the cutting area.