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Previously, the team selected components and made a test PCB for the inside handle. Now it's time to wire it up; attach the motor, trigger, and hot end; and program it using AVR studio to control everything and see how it works. Once they put in the motor and hot end on top they'll have their first working prototype! |
Ben goes into Autodesk Fusion 360 to design a few features such as a spring to push back the trigger. He’s adjusted the design to have a quarter inch holes in the trigger. What he hopes to accomplish is to build up the extruder part of this so they can actually test the whole thing. They have all the controls to drive the gun. The extruder part might not be quite so refined. He creates some symmetrical mounting points for driving a size four screw on the inside. He starts printing one half of the trigger so he can get to work on designing the other half.
Ben is still working on the extruder design. It has a lot of mass to hold the silicon entry point of the nozzle. He hasn’t started on the nozzle holding yet but he shows where it is going to go. The bearing imported from McMaster Carr, a feature of Fusion 360. He adds a cap to go over the gear and shaft. The glue gun will go right down the middle.
Next, it’s time to figure out how to attach the part (using a foam mock up) to the main handle. What matters is the piece’s relation to the hot end as it shows us how far the nozzle’s actually going to be. If you put the motor too far the back the gun is not going to be too short. When he has an idea of how things are going to be put into place he 3D prints the parts.
Ben screws the new handle pieces together and then tests the spring. The main things that are going to go up are the motor control, the triac control for the hot end, and then the temperature control. There might be more things in the final product, such as a push button or an LED indicator, but what they have is enough for testing purposes. They test the ergonomics and it appears that the range of the magnetic field around the neodymium magnet is not linear, so as its being moved toward the hall effect sensor, the range of values is going to change in a non linear fashion making it more logarithmic. They’ll need to ramp up the speed quickly with a smaller trigger press. To do this they’ll have to take the range of the trigger and convert it to code while taking the by taking the range of the PWM and magnetic field.
Ben crams the hot end into the adapter and put some mounting holes. Meanwhile, Felix is still working on the float to char conversion. They’ll still be able to test even without the logarithmic to linear trigger control. This will give them an approximation of how big the final product will be. Ben rigs up the trigger so they can do some extrusion tests. Before making a real case, Ben wants to make sure all the angles are correct and everything works. They’ll need to rewire is the coil switch first.
Ben goes over his preliminary motor code. They get the speed from the hall effect sensor and look to see if its above a threshold. The threshold is the value you see on the ADC when the system first boots. If the trigger is past the threshold then you do a few simple calculations. You take the total ADC value minus the trigger value and divide it by two. You make sure the motor is going forward and then you inverse that to create the speed and then set a retract timer. Once they get the triac figured out they’ll pretty much have an early prototype. Finally, Felix goes over the AC control circuit.
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