What we did this week:
Since we are practically finished with the assembly of the project, we decided to take time to discuss the differences in our design compared to what was given to us.
• Transfer electricity via slip ring if you could manufacture/procure
one cheaply enough (Basically Hamel's recommendation)
• Wireless inductive heating like how they do for stovetops.
• Paint the bottom black with something heat resistant and blast it with
IR from a heat gun or heat lamp.
• Just use a wire and have the software prevent winding too many times
in one direction.
• Have stationary heater underneath, and plate spins on top of it.
• Have another plate underneath that it rubs against. Spin really fast.
Electronics placement :
In our senior design, we came across many different obstacles in improving our
customer’s design while maintaining functionality. Our first problem was placement of
the electronics that support our 3D printer. We had different options of either extending
our frame or building a separate compartment to house the decapede controller and the
rest of the electronics. Through our design process, we came to the conclusion that
building a separate compartment that can be bolted on the side would be better for our
group in terms of cost. The compartment will be either of wood or aluminum; a final
decision hasn’t been made yet. Tension belt:
The second challenge our group encountered was the rubber belt was sliding up
and down on the cogs. This problem didn’t allow the platter to move up and down
efficiently. First we replaced the 3D printed cogs with brand new plastic cogs that our
group found online. Our group still ran into the same problem, but the movement of the
belt was vastly improved. Finally we came up with the idea of adding tensioners. The
tensioners were made by stacking a bolt with washers along the frame and running the
belt through them to add tension. This idea solved the belt tension problem, and did so
without spending too much money on it.
For safety purpose, each frame will be covered by a panel. The panels will be designed to have holes for the heat to escape; also to be easy to mount or dismount whenever machine maintenance needed or printed object needs to be removed.
Original design has the top of the machine open. We decided to add and design a lid which function as a ventilation system, so that the heat and toxic fume will be removed from the inside. There will be holes on that top panel for air to blow through; underneath, 120-mm computer case fan will be attached to the top panel to suck the heat and fume out.
The initial design consisted of a table made out of wood. It is a good material since it has a low density, but other characteristics of wood did not meet our requirements. With alternating heat temperatures, wood tends to deform; therefore, the flatness of our table would vary over time. In addition, it is necessary to maintain a constant temperature on the table during operation in order to reduce the rate of heat transfer of the object being printed. This helps print the object with better precision. To meet these requirements, we decided to use an Aluminum alloy. Aluminum has a high thermal conductivity; therefore, it will heat up faster and help maintain the heat generated by a heating element. In addition, it will retain a tighter flatness tolerance than wood. With a density of 2.70 g/cm^3 and a Volume of 305.80 cm^3, the total mass of the table will be about 835.65 g or 1.82 lbm. Light enough for the motor to run efficiently.
Having limiting space for the 4-extruder arms to swing about a fixed axis, we minimized the size of the motors. This helps give enough clearance between extruders to avoid collision. When one extruder is at its maximum angle ( 90 deg or at center of table) , clearance is needed between the operating motor and the stationary extruder motor to the left.
The initial design of the cogs were made from 3D printed parts. On paper it seemed like it would work fine, but after assembly, we noticed the belt was slipping on the bottom. We decided to order new cogs that would hold the belt better and have better teeth. They also had parts on the top and bottom that would prevent the belt from slipping off. This keeps t inline to ensure it wont slip off.
What we need to do next week:
We need to figure out what to do about our decapede situation. After that, it's simply just electronics and coding.