10. Machine and Mechanical Design¶

Presentation¶

Youtube link to the same video

I will embed the mp4 to my website soon!

Team members¶

Himanshi, Siddharth and Tejas, it is a team of 3! Below are the links of our pages:

Designing and making a machine felt both scary and exciting. It was a new frontier for us, and we’ve never tackled anything this significant before. However, the charm of Fab academy comes from applying our thinking to create something that may not be as good. And then learning along the way till it we get it right.

A Brief Overview:¶

The following explanation of Aluminum Extrusions and Stepper Motor is generated by chatGPT for our better understanding.

Types of Aluminium Extrusions¶

T-Slot Extrusions:
T-slot extrusions feature a T-shaped slot running along the length of the profile, allowing for easy attachment of accessories, fasteners, and other components. These extrusions are versatile and widely used in framing systems for machine guards, enclosures, workstations, and other modular structures where flexibility and adaptability are required.
Angle Extrusions:
Angle extrusions have a right-angle shape, making them suitable for constructing frames, supports, and corners. They are often used in architectural applications, such as framing windows, doors, and partitions, as well as in machinery and equipment where structural support is needed.
Round Extrusions:
Round extrusions have a circular cross-section and are commonly used for applications requiring a smooth and sleek appearance, such as handrails, furniture, lighting fixtures, and decorative elements.
Square Extrusions:
Square extrusions feature a square cross-section and are well-suited for applications requiring rigidity and stability, such as frames, racks, shelving, and structural components in machinery and equipment.
Rectangular Extrusions:
Rectangular extrusions have a rectangular cross-section and are used in applications where a higher load-bearing capacity or increased surface area for mounting is needed, such as frames for heavy-duty machinery, automotive components, and structural frameworks.
Custom Extrusions:
In addition to standard shapes, custom aluminium extrusions can be designed and manufactured to meet specific requirements for unique applications. These extrusions are tailored to fit the precise dimensions, profiles, and features needed for specialized projects in industries ranging from aerospace and automotive to construction and electronics.

Stepper Motor¶

A stepper motor is a type of brushless DC motor that divides a full rotation into several equal steps. It moves in precise increments, making it suitable for applications requiring accurate position control, such as robotics, CNC machines, and 3D printers. A typical stepper motor consists of several key parts: a rotor (shaft), stator (housing), coils, and a permanent magnet. The rotor is connected to the output shaft and moves in response to changes in magnetic fields created by the stator coils. The stator contains multiple coils arranged around the rotor, which generate magnetic fields when energized by electrical currents. The interaction between the magnetic fields of the rotor and stator causes the rotor to rotate in discrete steps. Additionally, some stepper motors may include a gearbox or gearing mechanism to increase torque or reduce speed.

We started by understanding what is stepper motor and the parts of the stepper motor, then we looked at the basic circuit diagram of the stepper motor to understand the connections required and the overall working of the motor.

The above image is taken from https://forum.arduino.cc/t/5v-stepper-motor-not-working-with-uln2004a/430621

Planning and Ideation¶

We started with ideation first where we along with our mentors sat and discussed the ideas which we initially had.

Clay 3d printer
A pen plotter on wheels
A conveyor belt robot

After this, we realized that this was all very new to us. Hence we finalized on the idea that we would be making a linear actuator.

Final Idea:
A Single-Axis Paper cutter!

Why did we select this idea?

Well, as design aspirants, we work a lot with paper for making prototypes. Paper is our starting point for any protypes. But sometimes, the old-fashioned way of cutting can be slow and tricky. So, we are building this machine to make our lives easier- so that our design process is made smoother and quicker.

This is how our classroom looks! Papers everywhere!

Inspiration¶

To create this product, we delved into the documentation of Quentin’s Beehive along with the Tea Dipping machine from last year which our instructors told us about. By studying the making and funcitoning of these existing machines, we understood better the requirements and for our own machine.

List of Materials:¶

After that we looked at different materials available, what materials we have, what we do not have. And we made a list of things we will be needing. This list eventually translated into our checklist when we went shopping. A lot of this was based on Quentin’s Beehive documentation as our primary goal was to replicate the basic Beehive to learn machine-building, and change the carriage to serve our purpose of cutting. Based on recommendation from Jesal sir, our machine also swapped out the Kevlar String and Capstan of the Beehive with Pulleys and a Timing belt.

HARDWARE:
- 5x 40mm M5 socket head
- 15x 10mm M5 socket head
- 8x 8mm M3 button head
- 5x M5 nuts
- 2x M3 nuts
- 4x Derlin V-wheel
- 1mt T-slot Aluminium extrusion 20x20mm
- Pulley 20 teeth
- 1.5 mt, 6mm wide timing belt
- Grub screws for the pulleys
- Mild Steel sheet

ELECTRONICS:
- 1x Stepper motor Nema 17 with D shaft link to buy
- 1x Arduino UNO CNC shield V3 for Engraving Machine 3D Printer A4988 DRV8825 driver expansion board link to buy
- 1x Stepper motor driver A4988 for Arduino UNO link to buy
- 1x Arduino UNO
- Jumper cables
- Tactile switch

Procuring Materials¶

We browsed through Robu.in to explore available components and their prices. This helped us choose the appropriate stepper motors, drivers, and other necessary parts for the project. We did not place any order on Robu as the delivery day was way ahead.

After that, we brought in electronic components from Lamington Road, Mumbai and for hardware, we went to Nagdevi street, Mumbai. There we learned a lot about different materials available, and their usage.

At Nagdevi street, we wanted 50 cm of aluminium extrusions but the entire extrusion was 3.6 meters and it was a new learning for us to see the cutting processof the Al-Ex.

Electronics¶

In the time we got all of our hardware, we used our mentor Jesal sir’s stepper motor and driver, along with CNC shield, to learn the connections of all three.

Connections:

In the above image, the pins marked GREEN are the enabler pins. You need to short them inorder to make the driver work. To add to this, make sure you fit the driver properly- connecting the corner pin marked Enabler/EN to the correct pin on the CNC shield.
The area marked BLUE is the where you will be attaching the 4 pins of your Stepper Motor.
Finally, the area marked YELLOW is the area with 5V, GND, and other Signal pins of the Arduino. There, we have connected the button and the servo motor.

Pinout Image Source

We referred a lot of youtube videos and guides online which are linked below:

LeMAster Tech: How to Control Stepper Motors with Arduino using a GRBL CNC Shield!

Controlling NEMA 17 Stepper Motor with Arduino and A4988 Stepper Driver Module

Using an Arduino CNC Shield V3

Make Your Own Automated Paper Cutting Machine with This Guide

DIY Arduino Based Paper Cutting Machine

Automatic Paper Cutting Machine

Next, we began learning about the coding of the motor as per our design. While Tejas and Himanshi went to the Nagdevi market, Siddharth stayed back and completed the remaining coding and electronics.

The coding of the electronics was done on the Arduino IDE.

We first made just the motor rotate:

Then we added the servo:

Finally, we added a button on a breadboard to trigger the motors.

We programmed it such that first the servo would go from 0 to 180 degrees to lower the Z-axis and the blade. Next, the stepper would run enabling the blade to slice through the paper. Finally, the servo would go from 180 to 0 degrees lifting the Z-axis and then the stepper would rotate in the opposite direction so that the blade returns to the starting point.

Eventually, we learnt how to crimp the wires using a crimper tool.

3d Modelling¶

There were three major parts that made the linear axis machine: - Endcap with Motor - Endcap with Pulley - The Carriage

We once again referred to Quentin’s Beehive machines’ 3D files to model our own parts.

Old design for carriage:¶

We first modelled the carriage to have 2 delrin wheels just that only the wheels on the top would rest on the Aluminium extrusion. We 3d printed the carriage but the printer ran out of filament and did not finish the print. However, it was good enough to test it out. On testing this part with 2 delrin wheels, we realised that the carriage is not stable on just 2 Delrin wheels and that we require 4 Delrin wheels to make it stable.

New design for carriage:¶

The new carriage was divided into two parts. The main skeleton which would have the delrin wheels and would attach to the aluminium gantry. And a shield/cover for the carriage which would have attachments for the paper-cutting blade.

We modelled and printed out the new carriage:

Shield:¶

The shield is meant to have holes so that it can be screwed to the main body of the carriage. And it has a slot for the cutting blade to fit inside.

End caps design¶

For the end caps, we made the design and after taking the guidance of our Mentors, we understood that our endcaps will not take the weight of aluminium extrusion as it was not stable in the design, also we made a 5mm rod on one side of the end cap for the pulley to rotate but our mentors suggested that it will break.

We had to scrape these endcaps.

Instead, we decided to use a metal sheet at the motor end of the machine. This was suggested to us by our instructor Pranav Sir. We would attach a metal sheet to the stepper motor while the motor faced up. This way the motor itself would act as a base. Metal working was again totally new for us, so it was scary and exciting to learn. (Metalworking will be covered in a later section)

We redesigned the pulley end cap and finally had our 3D models ready for printing:

Endcap with pulley:
Carriage mainframe:
Carriage with the cutter shield:

Carriage design considering belt clamping¶

The timing belt was open and not a complete loop. To fix it, we looked at our Creality 3D printer’s timing belt and carriage.

Here, they simply crimped it to the carriage.

We inserted the two open ends into the carriage, as shown in the image, and secured it with nuts and bolts.

Our first carriage design had the belt bolted in the center:

Our new design, had the belt bolted in the sides:

This was actually for a very funny reason. After making the first carriage and assembling it on the extrusion with the motor and the belt, Siddharth found it wise to cut the belt to the exact length we would be needing. However, he did not account for the other (free pulley) endcap at all! This resulted in the cut belt being 5 cm shorter than actually needed. So, to tackle this, in the redesign for the carriage, we decided to change the positioning of the belt locking system from the center to the sides. This allowed us to gain that 5 cm back and the belt became of EXACT required length.

Metal working¶

We sketched out and printed a quick FLAT sheet metal design for the stepper motor. Next, we stuck the prinout on a sheet of Mild Steel and used an angle grinder with the metal cutting blade to cut the metal out. The sheet was clamped to the edge of the table with a good portion of the sheet sticking out over the edge.

Following the cutting process, we utilized a filer to remove burrs and rough edges.

Next, we used a drilling machine to create holes in the metal sheets as required for our design.

Assembly¶

After this, we attached the metal piece with aluminium extrusion with the help of fasteners (nuts and bolts), and then we attached a pulley to the shaft of the stepper motor and connected it to the timing belt. To make sure the pulley and the shaft of the stepper motor were tightly locked, we used a grub screw. This made sure that the rotation of the motor would make the pulley rotate along with it without slippage.

Next, we attached the other end cap with the free to rotate pulley:

We used an M5 bolt and nut to make the shift/axis for the pulley to rotate around.

Attaching the delrin wheels

For attaching the shield:

First attach the blade on the slot given in the shield and attach the entire shield with the carriage with the help of m5 nuts and bolts.

After assembling everything, we began testing the cutting process manually, without connecting the electronics. We moved the carriage by hand during these trials.

We took care to not keep our hand in the way of the blade. Since we were moving it manually, we could coordinate and take care of not cutting into each others fingers!

Problems we were facing:

We required something to hold and align the paper.
We had 2-3 different sizes of blades, so we chose one sharp blade and adjusted its height accordingly. We provided multiple holes to fix the blade at different heights, depending on our requirements.
We needed some downward force for the cutter to make clean cuts without pulling the paper along with it.

We got back to the drawing board to ideate on how the to-be-cut paper could be held in place.

We were initially trying to cut the paper from the tip of the blade but that was not helping as it would just drag the paper along due to no downward force. So, we made a base which had a GROOVE and then we lowered the blade height so now the tip is not cuttin but the center part of the blade is. We also added weight on the paper which held the paper in place.

This base with groove was laser cut:

Here you can see the groove.

We even gave the endcaps a depression so that the machine did not move around relative to the base.

After this we painted the base.

Final:¶

In the baove video we manually held the mdf strip to add weight. The plan was to use screws and tighten the mdf strip on the paper. This way the paper would not move.

Steps on using the machine:¶

Step 1- Loosen the nuts on either side of the paper holder¶

Step 2- Insert the paper in whichever direction you want to cut¶

Step 3- Tighten the nut that you loosened¶

Step 4- Press the button on the breadboard for cutting¶

Step 5- Removing the paper¶

Once the cutting is done again loose the nut and remove your paper

Challenges:¶

As the entire machine design was new for us, we all were totally lost at the start of the week and we were scared about how it would go and what we would do in the week.
Electronics and hardware used in making machines was also totally new for us (Al-Ex, stepper motor, CNC shields and motor drivers, even mild steel cutting! We didn’t even know what M5 and M3 screws were!) so we took time in doing the research and learning and failing at every step only to learn better.
As beginners, we took a lot of time to figure out how the machine can be made and what its design would be and which components or parts will be placed where.

Learnings as a group:¶

Make the entire list of materials first so that you have clarity on what all parts you need. Make detailed sketches showing which part will go where and how it will attach with one another so that you don’t miss any minor details and realize that things are wrong later on!
Never cut a belt or string too soon based on Siddharth’s experience.
Once we cut the metal sheet, we realized that not even an A4 sheet was fitting in the gap between the two endcaps (where the blade would run).So we measured how much the difference was (5 cm) and we trimmed the sheet metal down to match this new measurement. That way the blade would have enough of a range to cut atleast an entire A4 sheet.

From 4 holes,

We trimmed it down to 2 holes:

We did not consider the force and the angle of the blade, we took a lot of time to identify why the sheets were not cutting. Initially, we added a servo thinking that would give the required downward force and also act as a Z-axis. However, this made the designing of the carriage too complex and we were running out of time, so we decided not to go ahead with the servo (though it remained a part of the code). Adding the groove in the base and the holder to hold the paper worked well to solve this cutting problem.

Other Use cases of a linear cutter:¶

Cutting die-cuts of packaging designs
Making colorful buntings
Fabric Cutting: Adapt the machine to cut fabric patterns for sewing projects.
Vinyl Cutting: The machine can be made to cut vinyl sheets for creating stickers, signages, or custom heat transfer designs.
Cardboard cutting for model making and prototyping.
Foam Cutting.

My Contributions:¶

The initial sketches were made by me for better understanding of the machine we were going to build. This was when we were brainstorming.
Then, me and Tejas sat to figure out the Electronics. We understood the connections of the Motor, Cnc shield, Motor driver, and the Arduino UNO and started with the initial code of rotating the motor.
The next day, Tejas and Himanshi went to procure the materials while I stayed back and figured out how the Servo and the Button is attached and in what sequence each of them run.
Next, we split the CAD modelling. I chose to design the main Carriage body along with the Holder (Shield) with the blade while Tejas and Himanshi each took and designed the endcaps.
However, the endcaps designed in spiral 1 were discarded due to suggestions from our mentor about the endcaps having poor structure.
In spiral 2, I took up the task of designing the new Endcap with the Free-Pulley (With inputs on the design from the other two), while Tejas and Himanshi focused on metalworking to make the Endcap which attached to the Motor.
I also designed and printed the second iterations of the carriage main body and shield based on things that didn’t work out in iteration 1.
Me and Tejas, with our instructor Pranav sir, made the laser cutting files and laser cut the base. Himanshi spent time painting the base.
Finally, most of the documentation was done by Himanshi along with a second draft of the same by me. The video was made by Himanshi and Tejas, and the slide was made by Himanshi.

Overall, this week’s learnings were abdundant. I learnt how to design better CAD based on parts available- working with fixed measurements and most importantly, taking assembly into account. I also learnt a great deal about standard mechanical parts that go into a machine. The beauty of machine week was that we went from knowing nothing about making a machine and feeling really underconfident, to dealing with persisting chaos, confusion, and self-doubt, to finally bringing a machine to life. I know and understand that designwise the machine is very barebones and naked, and funcitoningwise it is very basic in the sense that it is only one-axis. However, it is a start!

Project Files¶

Combined STEP file
As the original file is larger than 10MB, I am uploading it on Google drive and providing the link here: F3Z file DRIVE LINK

Old carriage STL
New carriage STL
Old shield STL
New shielf STL
Free pulley End Cap

Stepper motor code
Stepper + Servo code

Laser cut base Illustrator file
Laser cut base DXF file

Metal Cut Part PNG
Metal Cut Part DXF