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# CNC Machining Overview
The CNC (Computer Numerical Control) machine used in this lab is a large-format router capable of cutting full-sized wooden sheets using a 6mm cutting tool. It operates through instructions received from a computer, translating CAD designs into toolpaths that direct the cutting head’s movement, speed, and depth. These toolpaths ensure precision and repeatability by controlling the spindle’s rotation (RPM), feed rate (inches per minute), and cut depth.
**Functionality Summary:**
- Receives commands from a computer.
- Follows toolpaths derived from CAD designs.
- Cuts materials with controlled speed and depth.
- Used for manufacturing wooden structures, furniture, and fit-based assemblies.
![Insert image of CNC machine here](insert_image_path_here)
---
#### Video - Full Explanation
The video below showcases how the system works with explanation.
<div style="text-align: center;">
</div>
<div style="text-align: center;">
<iframe src="https://drive.google.com/file/d/1VN3HspvUYQrikhdPZ01qQcaQPyVWSw2N/preview" width="640" height="480" allow="autoplay"></iframe>
</div>
<br>
---
#### Safety Requirements
Strict safety protocols must be followed when operating the CNC machine:
- **Eye Protection:** Safety glasses must be worn to shield eyes from debris.
- **Face Mask:** Use a face mask to prevent inhalation of fine dust particles.
- **Clothing:** Avoid loose garments, jewelry, or accessories that may get caught.
- **Work Area Inspection:** Check the machine and all tools before starting.
- **Clean Environment:** Keep the machine and surroundings clear of clutter before and after use.
- **Hearing Protection:** Wear ear protection to prevent hearing damage.
- **Emergency Stop:** Be aware of the emergency stop button location.
- **Operational Distance:** Stay a safe distance from the machine while in use.
- **Handling Materials:** Never attempt to remove or adjust material while the machine is active.
- **Supervision:** Machine operation must always be monitored during cutting.
![Insert image of safety gear or workspace here](insert_image_path_here)
---
#### Design Requirements
When designing for CNC cutting:
- Maintain at least **20 mm gap** between each design part.
- Keep designs at least **30 mm away** from each sheet corner.
- Ensure holes in your design are **larger than the drill bit’s diameter (6mm)** so they can be cut cleanly.
- Select drill bits **longer than your material’s thickness** for full cuts.
- Export files in **DXF format** for compatibility.
- Double-check that the design size suits the tool (e.g., drill bit not larger than the smallest detail).
---
#### Debris Management
The CNC machine includes a built-in vacuum system that removes debris generated during cutting. This ensures:
<p align="center">
<img src="cnc-images/debris.jpg" style="border: 2px solid black;" />
</p>
<iframe src="https://giphy.com/embed/3apHw0wrSauGTP7yLf" width="480" height="269" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/3apHw0wrSauGTP7yLf"></a></p>
- Cleaner work environment.
- Improved visibility and safety.
- Better cut accuracy and finish.
---
#### Importance of Dogbones
<p align="center">
<img src="cnc-images/dogbone.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cnc-images/dogbone2.png" style="border: 2px solid black;" />
</p>
<iframe src="https://giphy.com/embed/Or8eV6iyuXgA9vTCIR" width="270" height="480" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/Or8eV6iyuXgA9vTCIR"></a></p>
<iframe src="https://giphy.com/embed/5jqEdWh3tQpRXeuB7w" width="480" height="269" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/5jqEdWh3tQpRXeuB7w"></a></p>
Due to the round shape of the cutting tool, internal corners in wooden joints are not naturally square. Adding **dogbone fillets** to these corners allows parts to fit tightly and accurately in press-fit constructions.
---
#### Material Alignment and Sacrificial Sheet
Proper material positioning is crucial to cut accuracy. A **sacrificial sheet** is placed under the cutting material to:
- Prevent damage to the CNC bed.
- Allow cuts to go slightly deeper than the material thickness.
- Help hold the material in place with screws.
**Tips for Alignment:**
- Max sheet size: 2440 x 1220 x 12 mm (L x W x T).
- If the sheet is curved, place the concave side down.
- Secure with screws placed within 20 mm of the corners and across the center.
---
#### Materials Used
Two materials are commonly available:
| Material | Characteristics |
|-----------------------------|-------------------------------------------------|
| MDF (Medium-Density Fiberboard) | - Smooth surface<br>- Easy to machine<br>- Less durable |
| Plywood | - Layered structure<br>- Stronger and more resilient<br>- Harder to cut cleanly |
<body>
<div class="row">
<div class="column">
<img src="cnc-images/mdf.jpeg" alt="Image 1">
<p class="caption">MDF Wood</p>
</div>
<div class="column">
<img src="cnc-images/plywood.jpeg" alt="Image 2">
<p class="caption">Plywood Wood</p>
</div>
</div>
</body>
Cutting tests were conducted using MDF, optimizing speed and feed rate for best results.
---
#### Machine Alignment
Machine calibration is required before each cutting job. For this CNC machine:
- **Z-axis calibration** is automated.
- A metal plate and wire clip are used. Once the drill touches the plate, an electrical signal finalizes the zero position.
- Regular checks are needed for worn parts and tool integrity.
<body>
<div class="row">
<div class="column">
<img src="cnc-images/metal.png" alt="Image 1">
<p class="caption">MDF Wood</p>
</div>
<div class="column">
<img src="cnc-images/clip.png" alt="Image 2">
<p class="caption">Plywood Wood</p>
</div>
</div>
</body>
---
#### Drill Bit Selection Guidance
Choosing the right drill bit (end mill) is essential for clean, efficient cuts and depends on your material and the operation:
- **Bit Diameter:**
- 6mm (default) is versatile for general cutting.
- Use smaller bits (e.g., 3mm) for detailed work.
- Larger bits (e.g., 12mm) for faster rough cuts on thicker materials.
- **Upcut Bit:**
- Best for fast chip removal.
- Leaves a rough top surface but clean bottom.
- Good for deeper cuts.
- **Downcut Bit:**
- Pushes fibers down.
- Leaves a smooth top surface.
- Good for thinner materials or laminated surfaces.
- **Compression Bit:**
- Combines upcut and downcut features.
- Smooth on both sides.
- Ideal for plywood or double-sided finish materials.
<body>
<div class="row">
<div class="column">
<img src="cnc-images/drill.png" alt="Image 1">
<p class="caption">MDF Wood</p>
</div>
<div class="column">
<img src="cnc-images/drill2.png" alt="Image 2">
<p class="caption">Plywood Wood</p>
</div>
</div>
</body>
---
#### Speed & Feed
Proper speed and feed rate settings are critical for effective cuts:
<p align="center">
<img src="cnc-images/feed.jpg" style="border: 2px solid black;" />
</p>
- **Speed (RPM):** Determines how fast the tool rotates.
- **Feed Rate (in/min):** Determines how fast the tool moves across the material.
For MDF using a 6mm tool:
- Optimal Speed: 8000 RPM
- Feed Rate: 80 in/min (can vary based on tool condition and material)
Monitor chip formation and surface quality during tests to fine-tune settings.
---
#### Tips to Reduce Material Waste
<p align="center">
<img src="cnc-images/material.png" style="border: 2px solid black;" />
</p>
- **Group Parts Efficiently:** Nest your parts close together in CAD to use the least amount of space. [20mm space]
- **Use Off-Cuts:** Save and reuse unused areas of the sheet for future small projects or test cuts.
- **Add Labels:** Include engraved labels to organize parts and reduce re-cuts.
- **Test on Scrap:** Run test cuts on scrap wood or corners before running the full job.
- **Minimize Tabs:** Use just enough tabs to hold parts in place without excess material.
---
#### CNC Cutting Process
This section outlines the full workflow for using the CNC machine, from preparation to final cutting.
---
#### 1. Preparation
<iframe src="https://giphy.com/embed/3apHw0wrSauGTP7yLf" width="480" height="269" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/3apHw0wrSauGTP7yLf"></a></p>
- Remove debris and previous sheets using a vacuum.
- Unscrew and clear the CNC bed.
- Place the new sheet (MDF or Plywood).
- Adjust the sheet if bent; curve should face up with the middle touching the base.
- Fasten using screws placed within 20 mm from the edges.
- Use a minimum of 8 screws for secure attachment.
<p align="center">
<img src="cnc-images/screw.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cnc-images/screw2.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cnc-images/sheet2.png" style="border: 2px solid black;" />
</p>
---
#### 2. VCarve PRO Setup
- Export the design as a **DXF** file.
- Send the file to: `fablabbh.share@gmail.com`
- Open the file in **VCarve PRO**.
- Add a **30 mm offset** around the perimeter to avoid bolts.
<p align="center">
<img src="cnc-images/vcarve.png" style="border: 2px solid black;" />
</p>
---
#### Assigning Cut/Pocket
Select the lines or shapes to define what will be cut or pocketed, then apply the relevant toolpath operation (profile/pocket).
---
#### 3. Toolpaths: Cut
- Cuts along the outer or inner edge of a part.
- Defines the final shape by following the contour
- Choose **Profile Toolpath**.
<p align="center">
<img src="cnc-images/cut.png" style="border: 2px solid black;" />
</p>
- Set:
- **Start Depth:** 0 mm
- **Cut Depth:** 13 mm (12 mm material + 1 mm into sacrificial sheet)
- Specify Machine Vectors:
- Select **Outside/Right** for vector machining to preserve size.
- Select **Inside/Left** for cutting internal shapes or holes.
- Select **On** for trimming directly along the vector line.
<p align="center">
<img src="cnc-images/cut2.png" style="border: 2px solid black;" />
</p>
- Tool Settings (6 mm bit):
- Spindle Speed: 8000 RPM
- Feed Rate: 80 in/min
- Plunge Rate: 15 in/min
<p align="center">
<img src="cnc-images/cut3.png" style="border: 2px solid black;" />
</p>
- Specify the Number of Passes:
- Press "Edit Passes"
- Number of Passes: 2
- First Pass Depth: 6.5mm
- Second Pass Depth: 13mm
<p align="center">
<img src="cnc-images/pass.png" style="border: 2px solid black;" />
</p>
- Click **Calculate**, then read the warnings, if it is within your expectations click **OK** to confirm.
<p align="center">
<img src="cnc-images/calculate.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cnc-images/warning.png" style="border: 2px solid black;" />
</p>
---
#### 4. Toolpaths: Pocket
- Used to hollow out an internal region.
- Useful for engravings or fitting one piece into another.
- Choose **Pocket Toolpath**.
<p align="center">
<img src="cnc-images/pocket.png" style="border: 2px solid black;" />
</p>
- Set:
<p align="center">
<img src="cnc-images/pocket2.png" style="border: 2px solid black;" />
</p>
- **Start Depth:** 0.0 mm
- **Cut Depth:** 2.0 mm
- You can specify this value for engraving operations to achieve precise and consistent depth.
- Recheck "Tool" Parameters:
<p align="center">
<img src="cnc-images/pocket3.png" style="border: 2px solid black;" />
</p>
- Press "Edit":
- Geometry:
- Diameter: 6mm
- Cutting Parameters:
- Pass Depth: 6mm
- Stepover: 4.002mm || 66.7%
- Feeds and Speeds:
- Spindle Speed: 8000 RPM
- Feed Rate: 80 in/min
- Plunge Rate: 15 in/min
- Tool Number: 1
- Press "OK"
#### Dogbone Fillet
<iframe src="https://giphy.com/embed/Or8eV6iyuXgA9vTCIR" width="270" height="480" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/Or8eV6iyuXgA9vTCIR"></a></p>
- Apply Dogbone Fillet to all internal corners used as joints
- Match radius to tool size (e.g., 3 mm radius for 6 mm bit)
- Allows square parts to fit snugly despite round tool paths
- Ensures clean, accurate assembly in CNC-milled joints
#### 5. Tabs
- Small, uncut sections to keep parts attached to the sheet.
- Prevents shifting or flying parts.
- Size: Usually 3 mm wide and 2 mm high.
- Automatically added in the Toolpath menu.
- Best used manually to avoid tabs at the edges.
---
#### 6. Preview Toolpaths
- Click on **Preview Toolpaths**.
<p align="center">
<img src="cnc-images/preview.png" style="border: 2px solid black;" />
</p>
- In the drop-down, select **Preview Visible Toolpaths**.
<p align="center">
<img src="cnc-images/preview2.png" style="border: 2px solid black;" />
</p>
- Go to the **3D View** tab.
- Click on **Toolpaths** in the top-right corner.
<p align="center">
<img src="cnc-images/preview3.png" style="border: 2px solid black;" />
</p>
- Then do the following:
<p align="center">
<img src="cnc-images/preview4.png" style="border: 2px solid black;" />
</p>
- Manually lower the **Speed** setting.
- Select **Reset Preview**.
- In the **Toolpath List**, select the part to inspect.
- Select **Preview Visible Toolpaths**.
- If the toolpath preview appears erratic, the design may be *too small for the selected drill bit*.
<p align="center">
<img src="cnc-images/example.png" style="border: 2px solid black;" />
</p>
<p align="center"><em>Example</em></p>
- To fix this:
<p align="center">
<img src="cnc-images/preview5.png" style="border: 2px solid black;" />
</p>
- Return to the **Project** tab.
- Resize the design by dragging from its edge.
- Or adjust the design in your original software and re-export it.
- Back in the **Toolpath List**:
<p align="center">
<img src="cnc-images/preview6.png" style="border: 2px solid black;" />
</p>
- Double-click the part to re-inspect.
- Scroll down and click **Calculate**.
- If the toolpath still appears irregular, repeat the adjustment steps above.
#### 7. Changing the Drill Bit
- For a better understanding, watch the first video on this page starting at 14:40.
- Turn off the CNC machine using the key (located at the bottom right) and remove it.
<p align="center">
<img src="cnc-images/preview7.png" style="border: 2px solid black;" />
</p>
- Use two wrenches to loosen the collet assembly.
<p align="center">
<img src="cnc-images/preview8.png" style="border: 2px solid black;" />
</p>
- Hold both wrenches in one hand to stabilize, and twist the lower wrench to loosen the collet nut.
- Remove the collet and clean both the collet and nut for a secure fit.
<p align="center">
<img src="cnc-images/preview9.png" style="border: 2px solid black;" />
</p>
- Reinsert the collet into its housing.
- Insert the new drill bit, leaving ~20 mm (or two fingers) exposed for cutting clearance.
- Tighten the collet assembly firmly using both wrenches.
- Reinsert the key, power on the machine, and re-calibrate the Z-axis.
#### 8. ShopBot 3 Setup
- After checking that every toolpath is using Tool 1, Click **Save**.
<p align="center">
<img src="cnc-images/save.png" style="border: 2px solid black;" />
</p>
- Click **Save Toolpath(s) to File** -> save it as **all**
<p align="center">
<img src="cnc-images/save2.png" style="border: 2px solid black;" />
</p>
- Open **ShopBot 3** software.
<p align="center">
<img src="cnc-images/1.png" style="border: 2px solid black;" />
</p>
- Clip the wire to the collet nut or the spindle body of the CNC machine.
- Place the **metal calibration plate** on the surface of the sheet.
<p align="center">
<img src="cnc-images/2.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cnc-images/3.png" style="border: 2px solid black;" />
</p>
- Run the **Z-zeroing command** (machine lowers bit to touch the plate).
<p align="center">
<img src="cnc-images/4.png" style="border: 2px solid black;" />
</p>
- A warning will pop-up, and press **OK**.
<p align="center">
<img src="cnc-images/ok.png" style="border: 2px solid black;" />
</p>
- System detects contact and sets Z = 0.
<iframe src="https://giphy.com/embed/hiA4oUAEYvE0RDByUW" width="480" height="269" style="" frameBorder="0" class="giphy-embed" allowFullScreen></iframe><p><a href="https://giphy.com/gifs/hiA4oUAEYvE0RDByUW"></a></p>
- After calibration, remove the clip and plate, then return them to their original location with the clip still attached to the plate. This ensures smooth CNC operation.
- Then, move the drill head to desired origin (corner of the sheet).
- Set:
- **X = 0**
- **Y = 0**
---
#### 9. Z-Axis Calibration
- Clip the wire to the collet nut or the spindle body of the CNC machine.
- Place the **metal calibration plate** on the surface of the sheet.
- Run the **Z-zeroing command** (machine lowers bit to touch the plate).
- System detects contact and sets Z = 0.
- After calibration, remove the clip and plate, then return them to their original location with the clip still attached to the plate. This ensures smooth CNC operation.
---
#### 10. Start Machining
- Click **Start** to begin the operation.
- Monitor the machine continuously.
- Do not touch or adjust material until the machine is fully stopped.
- After cutting completes, remove remaining debris.
![Insert cutting process image here](insert_image_path_here)
---

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# Two-Disc Cycloidal Gearbox Design
#### 1. Project Description
The two-disc cycloidal gearbox is designed to convert high-speed, low-torque input from a stepper motor into low-speed, high-torque output. It utilizes two synchronized cycloidal discs that rotate in opposite phases, interacting with drive pins to transmit motion to an output shaft.
This configuration minimizes backlash and distributes load across multiple contact points, offering smooth and powerful transmission. The system is fully enclosed and features multiple mounting options for external attachments.
#### 2. Application & Use Cases
##### Applications
- Robotics joints and arms
- CNC rotary tables
- Precision camera mounts
- Automated actuators
- Small-scale industrial machines
##### How to Use
- Mount the gearbox base to your motor using the provided holes.
- Connect the NEMA-17 motor shaft to the input via the motor shaft connector.
- Attach your load or mechanism to the output shaft area.
- Power the motor through a driver board and microcontroller (e.g., Arduino).
- Control the motion using programmed step sequences.
- Ensure lubrication (grease) between the discs and drive pins for smoother performance and longer lifespan.
#### 3. Engineering Drawings
##### Description
The design is a compact, scalable two-disc cycloidal gearbox intended for high-torque, low-speed applications. Its parametric structure makes it easy to adapt in size and material. The current prototype has a 90 mm diameter and 54 mm height.
To clearly illustrate the internal mechanics, structural design, and assembly steps, the following visuals are provided:
- Included Media
- **Assembly Video** – starts with an exploded view and step-by-step buildup
<iframe width="560" height="315" src="https://www.youtube.com/embed/ylcnBYmR19A?si=1Pg3t_qRczJDjIow" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>
<iframe src="https://1drv.ms/v/c/62d760a9f409a919/IQSXz1cAg1KlSb5fDzi06m4CAZDB0oQq2RIVgFQe7C54sDk" width="640" height="480" frameborder="0" scrolling="no" allow="autoplay" allowfullscreen></iframe>
- **Disassembly Video** – shows teardown process in reverse order
<iframe src="https://1drv.ms/v/c/62d760a9f409a919/IQQ4qZmvm7WjQYJxuO3emguuAbylCQiWgdHhauW3no3YGVE" width="640" height="480" frameborder="0" scrolling="no" allow="autoplay" allowfullscreen></iframe>
- **Transparent Body Image** – reveals internal components without hiding the casing
<p align="center">
<img src="cycloidal-images/Transparent.png" style="border: 2px solid black;" />
</p>
- **Visual Assets & Drawings**
- Engineering Drawing Sheet
<p align="center">
<img src="cycloidal-images/2.png" style="border: 2px solid black;" />
</p>
- Cross-Sectional Analysis (x2)
<p align="center">
<img src="cycloidal-images/SubSectionAnalysis.png" style="border: 2px solid black;" />
</p>
<p align="center">
<img src="cycloidal-images/sectionanalysis2.png" style="border: 2px solid black;" />
</p>
- Isometric View
<p align="center">
<img src="cycloidal-images/1.png" style="border: 2px solid black;" />
</p>
#### 4. List of Materials & Components
- ##### Standard Components
| Part | Quantity | Approx. Size |
| ------------- | -------- | -------------------------------------------------- |
| Bearing | 2 | Ø65 mm (outer) × Ø50 mm (inner) × 7 mm (thickness) |
| Bearing | 4 | Ø32 mm (outer) × Ø20 mm (inner) × 7 mm (thickness) |
| Stepper Motor | 1 | NEMA-17 |
- ##### Bolts & Nuts (*with available size approximations*)
Note: If a bolt is slightly longer than needed, it can be trimmed using a saw. Nut sizes should fit snugly but not too tight.
1. (A) Connecting Base to Base Cover
- 7 × Flat Head Machine Screws (Type B)
- Size: M4 × 50 mm
- Head Diameter: ~7.5 mm
- 7 × M4 Hex Nuts
- Edge-to-Edge: ~6.9 mm
- Thickness: ~3.2 mm
2. (B) Drive Pins Area (Replaces 5 mm Pins)
- 4 × M3 × 50 mm Bolts (hex or socket head)
- Head Diameter: ~5.5 mm
- 4 × M3 Hex Nuts
- Edge-to-Edge: ~5.5 mm
- Thickness: ~2.4 mm
3. (C) Mounting Points on Top of the Gearbox
- 7 × M4 Hex Nuts
- Edge-to-Edge: ~6.9 mm
- Thickness: ~3.2 mm
4. (D) Shaft Connector
- 2 × M3 × 40 mm Bolts
- Head Diameter: ~5.5 mm
- 2 × M3 Hex Nuts
- Edge-to-Edge: ~5.5 mm
- Thickness: ~2.4 mm
5. (E) NEMA-17 Shaft Connector
- 1 × M3 × 6 mm Bolt (may require sanding)
- Head Diameter: ~5.5 mm
- 1 × M3 Hex Nut
- Edge-to-Edge: ~5.5 mm
- Thickness: ~2.4 mm
6. (F) NEMA-17 Connector
- 4 × M3 × 15 mm Bolts
- Head Diameter: ~5 mm
- ##### 3D-Printed Components
- Material: PLA (tested), PETG (recommended for durability)
- Parts: Housing, base cover, discs, shaft connectors, output caps, circlips
- Infill: Suggested 40% or more for torque applications
#### 5. Cycloidal Drive Strength Analysis
---
##### **1. Motor Output Torque**
* **Motor Stall Torque**: 0.45 Nm
* **Gear Ratio**: 21:1
* **Estimated Efficiency**: 85%
$$
\text{Output Torque} = 0.45 \times 21 \times 0.85 = \boxed{8.03 \, \text{Nm}}
$$
---
##### **2. Load Handling Capability (Based on PLA Disc)**
###### PLA Parameters:
* **Yield Strength of PLA**: 50 MPa
* **Safety Factor**: 3 → Allowable stress = 16.7 MPa
* **Contact Area (per lobe)**: 5 mm²
* **Lobes in contact**: 4
* **Radius from center to lobe force point**: 33.5 mm = 0.0335 m
* **Infill Density**: 25%
###### Calculations:
* **Force per lobe**:
$$
F_{\text{lobe}} = 16.7 \times 10^6 \times 5 \times 10^{-6} = 83.5 \, \text{N}
$$
* **Total force from 4 lobes**:
$$
F_{\text{total}} = 4 \times 83.5 = 334 \, \text{N}
$$
* **Torque handling at 33.5 mm radius**:
$$
\tau = 334 \times 0.0335 = 11.2 \, \text{Nm}
$$
* **Account for 25% infill**:
$$
\tau_{\text{safe}} = 11.2 \times 0.25 = \boxed{2.8 \, \text{Nm}}
$$
---
##### **3. Drive Pin Strength (Bolts with PLA Sleeves)**
###### Assumption:
* Bolts used instead of precision 5 mm mild steel pins
* Outer diameter maintained at **5 mm** using **PLA sleeves**
* Inner bolt shaft assumed 4 mm (typical M4 bolt shank)
* Steel Yield Strength: 260 MPa
- **Cross-sectional Area (4 mm bolt)**:
$$
A = \frac{\pi D^2}{4} = \frac{\pi \cdot 4^2}{4} = 12.57 \, \text{mm}^2
$$
- **Force per bolt**:
$$
F_{\text{bolt}} = 260 \times 12.57 = 3,268.2 \, \text{N}
$$
- **Total force (4 bolts)**:
$$
F_{\text{total}} = 4 \times 3,268.2 = 13,072.8 \, \text{N}
$$
- **Torque capacity**:
$$
\tau = 13,072.8 \times 0.0335 = \boxed{437.9 \, \text{Nm}} \quad \text{(Safe✅)}
$$
> Note: **PLA sleeves** do not contribute significantly to strength — they act as spacers or guides. Only **steel bolts** are load-bearing.
---
##### **4. Max Load at 50 mm Arm**
$$
F = \frac{\tau_{\text{safe}}}{r} = \frac{2.8}{0.05} = 56 \, \text{N}
$$
$$
\text{Mass} = \frac{56}{9.81} = \boxed{5.7 \, \text{kg}}
$$
---
##### Final Summary Table
| Category | Value | Safe? |
| --------------------------- | -------- | ------------------------ |
| Motor Stall Torque | 0.45 Nm | ✅ |
| Output Torque | 8.03 Nm | ❌ Exceeds PLA safe limit |
| PLA Torque Limit | 2.8 Nm | ✅ |
| Bolt + PLA Pin Torque Limit | 437.9 Nm | ✅ (way overbuilt) |
| Max Load (at 50 mm arm) | 5.7 kg | ✅ |
---
##### Final Conclusion
The **cycloidal drive system is likely to fail at the PLA disc lobes under full output torque**, especially if printed with only **25% infill**. Although the **bolts (with PLA sleeves)** acting as drive pins are structurally sufficient, the **PLA disc is the mechanical weak point**.
##### If tested:
* The drive **will function under light loads (below \~5.7 kg at 50 mm arm)**.
* Under full load or high-torque demand, **plastic deformation or cracking is expected at the lobes**.
* The bolts will hold without issue, but **localized PLA wear or failure around the lobes and sleeves is likely.**
##### Recommendations:
* Increase **infill to at least 75%** or use a stronger material like **PETG**.
* Consider **fillet reinforcement** around lobes to distribute stress.
* Reduce gear ratio or torque output if high load isn't needed.

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# 🔲 How to Use the Laser Cutting Machine
*(This page provides step-by-step instructions for students on how to prepare and operate the laser cutter. Insert images where noted to enhance clarity and guidance.)*
---
#### 1️⃣ Preparing the File
**Software: SolidWorks / Illustrator / CorelDraw / etc.**
- Export the design as a **DXF (.dxf)** file.
- Send the file to the designated **email account** `fablabbh.share@gmail.com`.
- On the laser cutting computer, **download** the file and **import it into RDWorks**.
---
#### 2️⃣ Setting Up in RDWorks
📌 *Insert screenshot of RDWorks interface here*
- **Arrange the parts** on the virtual sheet using directional arrow buttons.
- **Assign colors** to each part depending on whether it’s for cutting, engraving, or marking.
- **Double-click the selected color** from the left color bar to adjust settings:
- Input appropriate **Speed** and **Power** values based on material type and thickness.
- Alternatively, use **Parameter Library** to select preconfigured material profiles.
✅ After setting all values, click **“Download”** to transfer the file to the machine.
---
#### 3️⃣ Operating the Laser Cutter
📌 *Insert image of laser cutter with labeled parts here*
1. **Turn on** the machine and main power switch.
2. **Insert the material** (e.g., 3mm plywood, 6mm acrylic).
3. Flip the **light knob** to activate internal lighting.
4. On the machine panel:
- Press **“File”** and select the file
- Press **“Enter”** to load it into memory
5. Use **arrow keys** to move the laser head to the desired starting point.
6. Adjust the **Z-axis** (height) of the laser:
- Use a **spacer tool** (e.g., LEGO brick) for low thickness.
- For thicker materials, keep around **2mm distance** between the laser head and the material.
7. Press **“Origin”** to set the starting position.
8. Press **“Frame”** to preview the cutting boundary.
9. Once confirmed, press **“Start”** to begin cutting.
---
#### 🛡️ Safety & Efficiency Tips
📌 *Insert image of safety guidelines and PPE here*
- Always wear **safety goggles** during operation.
- Never leave the machine **unattended** while it's running.
- Use **tape or weights** to hold down curled or uneven sheets.
- Use **Frame preview** to avoid cutting beyond the material area.
- **Organize parts efficiently** on the sheet to reduce material waste.
---
#### ✍️ Engraving Notes
- Use **lower power and higher speed** for engraving.
- Perform a **small test area** first to avoid burning the material.
- Ensure the surface is flat and clean for consistent engraving quality.
---
#### 🧪 Cutting Efficiency Test Example
📌 *Insert photo of test squares with labels*
**Objective:**
Determine the optimal speed and power settings for clean cuts on 2.45mm plywood without manual force.
---
**Test Parameters:**
- **Speeds (mm/s):** 15, 20, 30, 40
- **Powers (%):** 15, 27, 40, 52, 65
⚠️ *Do not exceed 70% power. It may damage the machine.*
---
**Successful Cutting Combinations:**
| Speed (mm/s) | Power (%) |
|--------------|------------|
| 15 | 40 |
| 20 | 30 |
| 10 | 52 |
| 20 | 52 |
| 30 | 52 |
| 15 | 65 |
| 20 | 65 |
| 30 | 65 |
| 40 | 65 |
---
**Conclusion:**
Higher power settings (52–65%) combined with moderate to low speeds produced clean cuts. This combination allows the laser sufficient energy and time to fully penetrate the material without excessive scorching.
---
#### 🔍 Focal Point Experiment
📌 *Insert photo of inclined test setup with cuts*
**Objective:**
Understand how varying the laser's focal height (Z-axis) affects the quality of cuts.
---
**Setup:**
- A wooden plate was placed at an **inclined angle** on the cutting bed.
- The laser cut along the slope, testing multiple focal heights.
---
**Observations:**
- When **too far**, the beam was unfocused, producing wide and burnt edges.
- When **too close**, the beam was concentrated but often failed to cut through fully.
- The **ideal distance** created precise, clean lines without burn marks.
---
**Conclusion:**
The laser’s **focal point** plays a crucial role in cut quality. Proper Z-axis alignment ensures effective energy concentration, minimizing burns and maximizing precision.
---
#### 📎 Add Barcode Below
📌 *Insert a QR code here that links directly to this documentation page on your website*
---