Assignments

Mechanical Design, Machine Design

Part 1: Mechanical Design

Part 2: Machine Design

IT'S MACHINE WEEK!!!

For this week's group assignment, we decided that we will work together on building an automated radio telescope mount.

Design plan and idea

To get started, we sketched our design plan and divided our individual tasks within the three of us. You can find out more about our individual contribution by visiting our personal documentation page.

The idea for our project stemed from a project that was already being done in our school - a radio telescopope, which had to be manually positioned in the sky in order to recieve the radio signals. In order to complete this assignment and also contribute to this project, we decided to make an automated one. We will design and develop a mount consisting of 2 main motion - the base rotation and the elevation.

3D Design

To design the mount structure we make use of the Fusion360 to design the mount

Given below is the process of designing the mount

This horn was design based on the

Gear Ratio

A gear ratio is the ratio between the number of teeth on two meshing gears or the ratio of their rotational speeds. It indicates how many times the driving gear must rotate to make the driven gear complete one full rotation.
In our design, the gear on the side originally had a gear ratio of 1:12.5 in a full circle, but we had to divide the circle in half to meet the design requirements. The base gears had a gear ratio of 1:14.

Formula

Gear Ratio = Number of teeth on driven gear / Number of teeth on driving gear

Example

If the driving gear has 10 teeth and the driven gear has 20 teeth:

Gear Ratio = 20 / 10 = 2:1

This means the driving gear must rotate 2 times for the driven gear to rotate once.

Module in Gears

The module is the fundamental unit of tooth size in the metric system. Gears with the same module will have teeth of compatible sizes and shapes, ensuring proper meshing. If you were to use gears with different modules, their teeth wouldn't align correctly, leading to jamming, excessive wear, and ultimately, failure of the system.
Module (m) = Pitch Circle Diameter (D) / Number of Teeth (T)

Pressure Angle (20°)

It's the angle at which gear teeth push on each other.

20° is the standard angle.

Why it matters:

Clearance (0.05 mm)

It's the tiny gap between the top of one gear tooth and the bottom of the other.

Why it matters:

As mentioned before, I used an online gear generator and inserted these requirements which gave us an image of how those gears will look which can be downloaded with either in dxf or svg format.

    
Parameter	Value for the Base gears that has a big gear of 40 cm diamter and 8 cm diamter small gear.
Gear 1 Tooth Count (n1):	100 (external gear)
Gear 2 Tooth Count (n2):	8
Module (mm):	4
Pressure Angle (degrees):	20
Clearance (mm):	0.05
Gear 1 Center Hole Diameter (mm):	4
Gear 2 Center Hole Diameter (mm):	4
Gear Center Distance (mm):	225.000
Gear 1 Pitch Circle Diameter (mm):	400
Gear 1 Outer Circle Diameter (mm):	32
Gear 2 Pitch Circle Diameter (mm);	408
Gear 2 Outer Circle Diameter (mm):	40.000
Show Crosshairs:	No
Show Reference Geometry:	No
Show Gears;	Yes



                    
Parameter	Value for the side gear that has a radius of 21 cm(which will be a semi circle) and then the small gear will have a diameter of 3 cm.
Gear 1 Tooth Count (n1):	84 (external gear)
Gear 2 Tooth Count (n2):	6
Module (mm):	5
Pressure Angle (degrees):	20
Clearance (mm):	0.05
Gear 1 Center Hole Diameter (mm):	4
Gear 2 Center Hole Diameter (mm):	4
Gear Center Distance (mm):	225.000
Gear 1 Pitch Circle Diameter (mm):	420.000
Gear 1 Outer Circle Diameter (mm):	430.000
Gear 2 Pitch Circle Diameter (mm);	30.000
Gear 2 Outer Circle Diameter (mm):	40.000
Show Crosshairs:	No
Show Reference Geometry:	No
Show Gears;	Yes

3D prinitng

Measured in millimeters (mm).

3D Printing the small gears for the Base and Side Gears

Once the small gear was finalized, I sliced the STL file using PrusaSlicer and printed it using PLA filament on the Prusa i3 MK3S 3D printer. The infill was set to 15%. After printing, I cleaned the support structures and tested its fit on the motor shaft. The results were accurate, and the teeth meshed well with the larger gear during testing.

Then I CNCed and used laser cutting for the big gears. This is how they turned out!

Design and Fabrication

...stand and base (sir anith).....

Base support

This is the design we made for the base support.

How it turned out attached to the base gear:

Electronics

Components

We will be using stepper motors in order to be able to move the telescope. Let's undertsand the components needed first.

Nema 17 stepper motor

A stepper motor is basically an electric motor whose shaft spins by executing steps, or by moving by a predetermined number of degrees, unlike a brushless DC motor which rotates continously. This function, which is made possible by the internal design of the motor, eliminates the need for a sensor by enabling one to determine the precise angular position of the shaft by counting the number of steps taken. It is also suitable for a variety of applications because of this property. I went through this website to better understand how it works.

LRS-350-24 transformer

The Mean Well LRS-350-24 is an AC to DC switching power supply that delivers 350.4W of power at 24V DC with a current rating of 14.6A.

The LRS-350-24 receives AC from a wall outlet which is converted into DC through a process called rectification. Capacitors are used to smooth out the DC voltage to reduce fluctuations. To control the amount of output delivered, a very high speed switch is turned on and off continuously. A feedback loop monitors the output voltage and adjusts the switching to maintain a stable 24V DC output. There is also a built-in fan to prevent overheating.

TinyG v8

The TinyG project is a high performance, USB based CNC 6-axis controller that supports XYZ linear and ABC rotary axes with 4 motor outputs. It is designed for small CNC applications and other applications that require highly controllable motion control. TinyG is meant to be a complete embedded solution for small or medium motor control. -Website

We will basically be using the TinyG to control multiple stepper motors using G-code.

Power source Switch IEC-320 C-14 AC Power Entry Module

UGS

This is the application we will be using to send G-code to TinyG.

Click on this link to download UGS.

This will take you to a page with various download options. Click on the one with your operating system.

Programming

Now, lets connect the components.

This is the connection we made between the Nema 17 stepper motor and the TinyG.

Image source

This is the pinout of LRS-350-24.

Connect V+ and V- to the ground and VCC of the Tiny G.

Connect the wires labled GND, L, and N to the gound, line, and neutral wire of the power entry module which will then be connected to the wall socket for the AC supply.

For reference, this is how the components should be connected. I got it from Ngawang Pemo's documentation. Thank You ashim!

Yay! I connected it!

Now, we can start using UGS to control the two stepper motors. Here is how it turned out.