A New Box Idea March 15

It has been a few days since we began working on our boxes. The goal for today's class is completing our first box designs. This does not necessarily mean making our final box. I am feeling a bit under pressure since I am still undecided in how to attach my sides.

This is how I was planing to make the box.

Oscar noticed that my box design was going to take me a while to produce so he suggested that I make something similar to Kelsey's idea of making the sides function with hinges. This idea would be faster to draw on inkscape which would give me more time in the class room to test out my designs.

The sides will act like a spring by making lines close together. When the laser cutter makes the incisions they will bend.

To make the sides bendable I will use plastic because wood is more difficult to bend. The sides will be attached with a screw on the end. I tested out a few designs with incisions at different distances. When I tried bending the first design, the plastic sides broke because the cuts were too far from each other. The following design had the sides closer at a distance of .024 instead of .03 however my one inch model broke when I tried to bend the sides. I realized that my design needed to have at least three cuts in the center and six parallel cuts on the sides.

Box design that will use screws. The holes for the screws have not been made.

 I still have to test out this design to see if it will work. Once I have the correct number of cuts that will make the box close I will work on the movable joint.

Box in Progress March 12

Shortly after class began, we learned how to use the laser cutter on our own so Oscar will not have to constantly cut designs for us. A few laser cutter safety tips that we were given included not jamming or touching the laser, use the buttons on the side to raise or lower the stage and move the laser, and use the plastic maker to properly adjust the height on the stage. Before printing we must preview the area we will cut and check the velocity and power. Different thicknesses and materials require different velocities and powers. Learning how to use the laser cutter is beneficial because now I can utilize the machine in the future outside of class.

Unfortunately, my first wooden prototype had to be cut five times before the shape came out. The initial velocity at 2 was too slow for the quarter inch piece of wood and the initial power at 75% was not enough. With Oscar's help I was able to cut my shape and find the proper velocity and power.

1/4 in wood requires a power of 100% and a velocity of .7.

As you can see from the image of the fixed sides, the dimensions are incorrect. The sides are too short to be connected. In addition to having short sides, I still have to find a solution to connect the fixed sides. I am currently thinking about using screws to attach the sides.

A BOXy Problem March 8

Now that we have gone over the design process, each one of us must design a box that meets the following requirements:
1. each side must be 2'' long
2. 2 fixed sides
3. 2 movable joints

     - free

     - friction

  *bonus if you do both*

4. consider potential materials, manufacturing, performance, and appearance of the box

In addition we must document the process (ideas, testing results, changes in design). Although a box is a simple object, designing one that meets all the requirements is not as easy as. My initial idea for making the box was to have the fixed sides cross like a puzzle. I sketched the sides on Inkscape but left out the bottom (image below).

My idea for how the box will open. (Credited to Hype Beast Gallery)

The more I thought about building the box, the more I thought about what type of materials I would use. Even though I personally like wood, plastic would be more durable. If I do make my box plastic my next question would be how thick do I want the plastic to be? I would then ask myself how will the sides stay together? Would I use glue, tape, or screws? I know for a fact that I must test out my first design in order to see if it will work. If not, I must make changes to the design. Once I decide how to put the sides together, I will figure out a way to make it open. Oscar said that it is okay if the box opens side ways instead of up and down so I would like to try making a box that opens like the image above.

Design Process March 5

My finished carabiner.

Once everyone used the laser cutter to make their carabiner, we discussed the engineering design process. In reality there is no correct way or defined process in engineering. The design process is simply an agreed upon scientific way of caring out a design step by step. An important factor to know about all design processes is that the design will always undergo changes.

The three processes we focused on were  product, iteration, and user. The product process, which is the old way of designing products without much user involvement, begins with research followed by a concept. From a concept one thinks about the feasibility or requirements of the design. This is followed by the system design, detail design (the design must have a precise plan), manufacturing design (diagrams), and finally gets manufactured.

The iteration process begins with identifying a problem (there must be a purpose). Afterwards the design must fulfill the requirements in order to move on to the ideation which is multiple ways of carrying out the design. You narrow down your ideas by selecting a concept to prototype. After testing the model you identify any problems, fix the design, and test it again.

In the user process, the general public is observed to identify what sort of product is needed or will be used by many. A person's age, preferences, etc. are taken into account. After observing and analyzing, an idea is developed for a future product. The product design must be representative of the people therefore the consumer co-designs the product. Consumer feedback can alter the initial goal of the product. The user process is the modern version of the design process.

When designing a product, you must consider the ways people can upgrade and maintain the item in case it breaks (an engineer must be certain that the structure of product will not fail such as a bridge). You must consider the business venture (How will you sell it? How affordable, quick, and effective will it be?) and the social and environmental impacts it will have. Good engineering involves agreeing on a concept, testing it, and improving the design.

A Pendulum at Last Feb. 27

Today we finally got to make a platform out of Lego's and see a pendulum in action. Up to this point our circuit did three things: measure speed by making the voltage proportional to the speed, integrate for position (voltage is proportional to position), and exert a force (voltage is proportional to torque).

In a perfect pendulum, the position vs. speed graph would look like a spiral spinning toward the center (zero). This is because as the pendulum moves back and forth it starts slowing down until it comes to a complete stop at the resting position. Our circuit, however, is flawed. A force is applied as it swings back and forth which makes our pendulum continue to swing without slowing down (unless you adjust the speed on the potentiometer).

As you can see, the position vs. speed graph of the pendulum does not form a perfect spiral, spinning to the center. Our imperfect circuit exerts a force which creates a duck shaped graph that does not appear to slow down.

The abstraction for our pendulum would be voltage entering the current driver as proportional to position and coming out as voltage proportional to speed. The voltage then goes through the integrator and makes it voltage proportional to torque which is proportional to position. This is how the circuit comes to a full circle. Since there is a resistor within the motor the voltage proportional to speed can be voltage proportional to speed and torque.

Before activating our pendulum, we practiced circuit hygiene (circuits are messy objects); we shortened the wires and made our connections easier to be seen.  The only thing I wished I would have done at the beginning of circuit building is having a clean circuit. This would have reduced my confusion and frustration.  Observing and building the pendulum was the final topic we will cover on circuits.

Our circuit after we "cleaned" it up to increase circuit hygiene.

Picture of our pendulum. You are not able to see the pendulum because it is moving quickly back and forth.

Laser Cutter Madness March 1

Now that we have completed the formal learning about circuits for the semester, we began familiarizing ourselves with Solidworks and the laser cutter. Although I took a computer aided design class in high school doing the online tutorial in Solidworks was helpful. In high school I mostly did floor plans and simple 3D objects such as my bed room with a complete bed set and doors for closets and the entrance. Following the steps and selecting commands was comforting to me because I actually knew what certain commands did to the 3D object.

After an hour or more of doing the tutorial and listening to music which I truly enjoyed (thanks Cailey), we moved on the our next topic of the day, designing a carabiner on Inkscape. Downloading Inkscape took an incredibly long time so in the process of waiting for the program to download, we discussed the design of our carabiner which can be breakable and we were introduced to basic functions on Inkscape. We agreed that it had to be the maximum of 6cm long. 

My initial carabiner was not very pretty. It was not symmetrical or oval. A better mental image of my carabiner is picturing the letter D but not fully connected on the left side and rounder. I made a few designs for my carabiner and decided to make it the edges pointier instead of round.

This is my pointy carabiner design. I have not finished adjusting the dimensions on the actual one.

By the end of class we gathered around the laser cutter to retract the first carabiner design. The laser cutter had to trace the outline several times because the material was too thick. We were easily amazed by the glowing light of the laser cutting through the plastic. The wood samples of shapes made from the laser cutter were very detailed and smelled like a camp fire.

The only finished carabiner was functional (could hook onto another object and resist weight). I hope I finish my carabiner design and begin using the laser cutter for more complex designs.

Virtual Spring Feb. 23

Abstraction

We started off a new lesson with another abstraction. After the input voltage (RT/k, R=resistor T=torque and k=constant) enters the mystery box- the circuit - the output voltage results in -ΩKw. The actual circuit looks like the following diagram below.

In this diagram you can see the make up of the circuit. The virtual ground allows us to control the current on the motor.

To introduce virtual springs to the class, the equation for torque (T=-bw=iw,  i=current and w=speed) was compared to Newton's law F=ma (m=current and a=speed). Applying a torque proportional to the angular speed will create friction or damping so the object will ultimately slow down. For circuits when a motor is connected to a resistor the power is absorbed which slows it down. Similarly applying a torque proportional to the angular position will create a spring. Just like a pendulum, the energy in the spring switches from kinetic to potential energy.

To further explain the concept, the rate of change of position is angular speed and the rate of change of speed is acceleration. Here is the mathematical calculation to go from speed (w) to position. 

Note that a capacitor adds voltage to the circuit this is why you must add the input voltage (V+) to the voltage added by the capacitor (Vc) to obtain Vout. This is a rule of capacitors.

The abstraction for the calculation would show the input voltage (V+) going into the mystery box- circuit - and coming out as in output voltage (Vout in the calculation). When you put both abstractions together you end up creating a virtual spring.

 

Virtual Spring

We added two capacitors and a second potentiometer to our original motor circuit to create a virtual spring.

Circuit for virtual spring.

We were able to observe the spring in the circuit through the oscillator. When we held on to the motor the graph showed no change in the position and speed.

The position is represented by the blue line and the speed is represented by the yellow line.