Week 15 : Assignment

For mechanical design Week we want to make mechanism for the Marble maze puzzle.

Purpose

As I mentioned above we wanted to have made something fun game in machine design we are going to make fun of the marble maze and wanted to control the maze Rotation with servos below, for now, we started working on the mechanical part. Visit the Group website for more detail.

Inspiration

Our inspiration for the project was the [amazing] Maze made by Katie Levine and our regional instructor Ohad Meyuhas.

Input

Our main objective is to control the Marble maze with Hand movement. So our input is Hand gesture which will control the Maze. we are using an accelerometer sensor for giving inputs. the accelerometer will give the relative value of x and y position and according to the value, Servos will rotate for a specific degree..

output

Our Mechanical output is Rotation of servo limited to a specific degree. we are planning to rotate the servo 20 degrees. It will rotate the maze around 40 degrees.

My Role

In Mechanical Design Me and Dhruv Thakkar took responsibility for making the mechanism of Marble Maze. Many marble maze has already been made, we wanted to try different mechanism for our maze.

As a team, we did all work together and help each other when needed, but My special task was to make sure the mechanism shall able to handle the Load of maze after Finalizing the design phase with Dhruv Thakkarr I took responsibility for making upper part of mechanism and he will see the Base part.

Design phase

in the initial designing process, we started with reverse engineering Katie Levine. instead of using four servos We though we may able to use Two Servos with long arms which will rotate the Maze as we want!

We came to the conclusion that we will place this servo in the center of the maze. But the challenge was how can we place the servo which will be able to move the maze and X and Y axis which center point will lie only on the One Z-axis. If we don’t design the base correctly it will tilt on the side by the time and create a moment on the servo which will Tear off the servo and the mechanism will fail.

initial Base design

In the initial design, Dhruv came off with the below idea. The idea was good and our Objective of the same Z-axis was fulfilling. But there was little concern about load it was not advisable to put Load directly on the servo Shaft. We are going to use MG995 servos - tower pro for our mechanism. This base idea is forgetting the initial idea, later he designed a stronger servo mounting base.

Reasons why not :

1.5 or 2 kg load directly will be on shaft in static condition

When mechanism will move it will create extra moment on servo shaft adding load

solution

so We found this problem very necessary to be solved, one way it could solve it to make one Gear Drive Designed for the taking the load and Applying the Torque given by Servo to Maze.

I started making Gear drive according to requirements. I estimated a total load of around 3800 gram.

Gear Specifications :

Module : 2  : Lower module for High torque Conversion

Pressure angle : 25 Degree Higher pressure angle for better torque handle capacity

Gear(Reduction) ratio : 2:1 : for Double the Torque

I designed gears on fusion 360 with the help of FM gear script. check week 8 for more details.

Possible Gear SERVO Assembly

mechanism

In mechanism I started working on the cad model, as we finalized the base I designed the base according to that, my scale was 0.5. our objective for making cad is to test the mechanical joints and to know which type of joint assembly will fulfill our purpose.

We used two type of Joints

Ball Socket Joints on top

Pivot joints bottom

Ball socket Joint

I started designing the ball sockets then, we wanted 40 degrees of inclination in Maze. For that, I started designing joints which will have 40 degrees of movement. below is the first design I tried!

Fusion 360

Visit week 3 for modeling in fusion 360.

Clearance

I gave clearance Of 1 mm.

Cura softwere

visit week 6 for know parameters in Cura.

Layer height : 2  :

wall line count : 5

Infill density : 15 %

Print speed : 80 mm/s

parametric file of Arms

Parameters I have given, check week 4 and week 8 for more parametric work!


Arm length : ball socket vertical arm length

Ball socket outer diameter

Distance : Distance between centers of two gears which will be subtracted in vertical arm

Length-Horizontal : Horizontal length of Arm

Length-vertical : vertical length of Arm

Width : Width of Arms

thickness : Thickness of the material

Self Locking mechanism

I wanted to try a Self-locking mechanism on the mechanism, it will eliminate the use of mechanical fasteners there. I have to do some iterations to get perfect dimensions so it can give require compressive force on joints.

For clamping or Fitting the Arms in the ball socket I was thinking to make One self-fitting mechanism, so I 3d print some rectangle slots in which inner dimensions are lesser then outer of socket arms when it spreads, it will create compressive force and the assembly will stick in.

Coupler

We also made one 3d printed Coupler which will hold the Pinion gears to the servo with the help of friction. we just wanted to make it for demonstration purposes so we can know Everything will be good in a bigger scale, for bigger scale we intended to use a Coupler comes with a servo and mount it with a center screw which will sufficient to transfer a large amount of torque.

The dimensions Of Box are perfect and the Gear profile is great.

Assembley of prototype

In assembly, we just started joining our Top and Bottom assembly. Dhruv made a great base for Servo and gear assembly we just fix them and check as it can work or not.

In the prototype, the mechanism is working perfectly Fine now the only thing we have to deal with is the load capacity of the mechanism.

Final version

For the final mechanism Dhruv started designing a bigger base and did some improvement we found on a smaller scale, I also start working to make bigger ball sockets and arms. for the final design, our maze will be approx. 20 inch wide so I decided to make it 16 inches wide: 400 mm

AutoCAD

check out Week 4 to know laser-cut in detail.

Ball sockets

For the bigger model, I had to designs ball sockets that can be capable to handle large shear. I increased Arm length with thickness, if I kept the sphere dimensions the same I will not able to get a degree of freedom I wanted in design, so I had to increase sphere size, it will increase printing time, but it was the only way to maintain strength.

First version

Second Version

I made a second version in which I increase fillet on a slot so it can be safer in Action

Self locking mechanism