3D Printing Designs: Octopus Pencil Holder

This document is an excerpt from “3D Printing Designs: Octopus Pencil Holder” by Joe Larson, published by Packt Publishing in February 2016. It serves as a practical guide for designing and 3D printing an octopus-shaped pencil holder using Blender, a free 3D modeling software. The text introduces fundamental 3D printing concepts, such as understanding overhangs, supports, and wall thickness, which are crucial for successful Fused Filament Fabrication (FFF) prints. Furthermore, it provides step-by-step instructions on utilizing Blender’s tools like Extrude, Subdivision Surface modifiers, Loop Cut, and Boolean modifiers to manipulate shapes and create functional, aesthetically pleasing designs. The overview also includes information about the author and reviewer, highlighting their expertise in 3D modeling and printing.

3D Printing Design: Techniques and Considerations

Designing for 3D printing involves understanding the capabilities and limitations of the technology, as well as utilizing appropriate software and design techniques. The sources primarily discuss design principles for Fused Filament Fabrication (FFF) 3D printers, which are known for being inexpensive and widely available.

Here’s a discussion on 3D printing design:

• What is 3D Printing Design?
• 3D printing allows for the creation of complex and detailed objects with relative ease, offering a new industrial age where objects are available at the touch of a button in schools, libraries, or homes.
• It’s a process of additive manufacturing, meaning it builds objects layer by layer, generating comparatively little waste. This method allows for rapid creation, testing, and modification of designs.
• Designing for 3D printing means creating 3D files using 3D modeling software, keeping in mind the strengths and weaknesses of the printing medium. The goal is to make designs that will successfully print.
• Software for 3D Printing Design
• Blender is recommended as a powerful and free 3D modeling software option, suitable for new 3D printing designers due to its comprehensiveness and versatility.
• To use Blender, it needs to be downloaded and installed on a PC or Mac. Users can adjust settings for a more intuitive experience, such as changing the select button or emulating a 3-button mouse and NumPad for laptops.
• Joe Larson, the author, has a background combining art, mathematics, teaching, and technology, having pursued 3D modeling in high school and college before returning to it with the advent of 3D printing. He won a Makerbot Replicator 3D printer in 2012 for a chess set that assembled into a robot, and his designs have been featured in various places.
• Key Design Techniques using Blender The “Octopus Pencil Holder” project serves as an excellent example of designing organic and functional shapes using Blender. This project demonstrates several powerful editing tools:
• Extrude Operator: This tool creates new geometry from a selected part of an existing model, allowing the original part to be moved away while remaining attached. It’s highly versatile for altering object shapes and creating new faces. For instance, it’s used to create the octopus’s tentacles and head shape.
• Loop Cut (or Loop Subdivide): This tool adds points in the middle of an edge and around a portion of the geometry, which can then be transformed. It’s used for detailing and bending the octopus’s tentacles.
• Subdivision Surface Modifier: This modifier increases the smoothness of a model while retaining simple geometry for easier editing. It effectively acts as a “cage” for the smoothed mesh, allowing for a smoother final look.
• Boolean Modifier: This powerful tool combines objects in various ways (Intersect, Union, Difference) or cuts one object out of another. It is essential for creating 3D printable objects, such as flattening the bottom of the octopus pencil holder by cutting it with a “Floor” cube. Boolean operations require a clean mesh free from holes or problems, and issues can sometimes be resolved by removing doubles or recalculating normals.
• Edge Creasing: This technique allows users to mark edges to indicate to the Subdivision Surface modifier that they should be sharpened, helping to control the smoothness of specific areas, such as making the cup bottom flat while the rest remains smooth.
• Object Renaming: It’s considered best practice to rename objects in a scene for clarity, especially when dealing with multiple objects.
• Exporting: Once the design is complete, it can be exported as an STL (.stl) file, which is a common format for 3D printing.
• Considerations for FFF 3D Printing To ensure successful 3D prints, designers must consider certain rules and limitations of FFF 3D printers.
• Overhangs and Supports: An overhang occurs when a part of the design has nothing between it and the build platform during printing. To compensate, 3D printers can build a lattice of support material under the overhanging part. However, removing this support material can be difficult, often leaving traces or creating a mess, making it desirable to design for support-less printing.
• Support-less 3D Printing (YHT Rules): Designing to avoid supports improves print quality and reduces post-processing. The “YHT” rules are a mnemonic to help remember key principles:
• Y – Gentle Overhangs: A gradual outward slope (typically 45 degrees or less) allows each new layer to be slightly larger than the previous one without drooping, ensuring successful printing.
• H – Bridging: If a part of the print has nothing directly below it but is supported on either side, the printer can “bridge” the gap. Simple bridges, where the outline has something to attach to on both sides, are more likely to succeed.
• T – Orientation: Sometimes, the solution to overhang problems is simply to change the orientation of the model on the build platform. Not every print needs to be printed in its final use orientation.
• Wall Thickness: There is a minimum size a 3D printer can reliably print. For robust and reliable prints, a 2 mm wall thickness is recommended, as it allows slicers to create solid prints with outlines and infill without conflict, while still permitting considerable detail. A 2D wall without thickness is not printable, as 3D prints must be part of a three-dimensional shape with thickness.
• Model Size: Designers should consider the build area of common 3D printers, which can be around 150 mm or 6 inches across, to ensure their designs fit.
• Finishing and Personalization After completing a functional design, designers are encouraged to use their imagination to add accessories, personality, or change the base shape, while still adhering to rules like those concerning overhangs.

Blender Essentials for 3D Printing Design

Blender is a powerful and free 3D modeling software specifically recommended for new 3D printing designers due to its comprehensiveness and versatility. It is a robust tool that allows users to create 3D files essential for the additive manufacturing process of 3D printing. Joe Larson, the author, has a background combining art, mathematics, teaching, and technology, returning to 3D modeling with the advent of 3D printing and winning a Makerbot Replicator 3D printer in 2012 for a chess set design.

Here’s a discussion on Blender software usage based on the sources:

• Downloading and Installation
• To use Blender, you must first download and install it on your PC or Mac computer by visiting http://www.blender.org. You’ll locate the download button for the latest version and choose the appropriate installer for your system (e.g., MSI package for Windows if unsure). After downloading, run the installer and follow the prompts. Once installed, open the program and close the splash screen to begin.
• Setting Up Blender for User Friendliness
• Blender’s default settings can be unintuitive, but they are easily adjustable to make the software much easier to use.
• To access settings, navigate to File | User Preferences and select the Input tab.
• For users with a keyboard and a scroll wheel mouse: The primary recommendation is to change the “Select With” option from its default (right mouse button) to Left. The scroll wheel can then be used as a middle mouse button, which Blender uses to manipulate the view.
• For laptops with a touchpad and no number pad: It is recommended to check both the “Emulate 3 Button Mouse” and “Emulate Numpad” checkboxes. With these settings, the right mouse button is used to select objects, Ctrl + right mouse button acts as a middle mouse button for view changes, and the number keys across the top of the keyboard perform number pad functions. After adjusting settings, always click “Save User Settings”.
• Key Design Techniques and Tools in Blender Blender offers several powerful editing tools and modifiers crucial for 3D printing design, demonstrated through the “Octopus Pencil Holder” project.
• Extrude Operator: This tool creates new geometry from a selected part of an existing model, allowing the original part to be moved away while remaining attached. It’s highly versatile for altering object shapes and creating new faces. It’s used to define the shape of the octopus’s tentacles and head. You can extrude by pressing E or navigating to Mesh | Extrude | Region.
• Loop Cut (or Loop Subdivide): This tool adds points in the middle of an edge and around a portion of the geometry, which can then be transformed. It’s essential for adding detail and bending the octopus’s tentacles. It can be performed by pressing Ctrl + R or navigating to Mesh | Edges | Loop Subdivide.
• Subdivision Surface Modifier: This modifier increases the smoothness of a model while retaining simple geometry for easier editing. It effectively acts as a “cage” for the smoothed mesh. You add it via the Modifiers tab (wrench icon). Adjusting the “View” setting increases smoothness but can slow down the computer.
• Boolean Modifier: A powerful tool for combining objects in various ways: Intersect, Union, or Difference. It’s crucial for creating 3D printable objects, such as flattening the bottom of the octopus by cutting it with a “Floor” cube using the Difference operation. This modifier demands a clean mesh free from holes or problems; issues can sometimes be resolved by removing doubles (Remove Doubles button in Tool Shelf) or recalculating normals (Recalculate button in Shading/UV tab).
• Edge Creasing: This technique allows users to mark edges to be sharpened for the Subdivision Surface modifier. It helps control the smoothness of specific areas, such as making the cup bottom flat while the rest remains smooth. It can be applied via Mesh | Edges | Edge Crease (Ctrl + E) or by setting the Mean Crease value in Properties (N panel).
• Object Renaming: It is considered best practice to rename objects in a scene (e.g., from “Cylinder” to “Octopus Body” or “Cube” to “Floor”) for clarity, especially with multiple objects. Renaming is done in the Object tab of the Properties panel. Objects can also be hidden (H) to avoid accidental transformations.
• Exporting: Once the design is complete and ready for 3D printing, it can be exported as an STL (.stl) file by navigating to File | Export | Stl (.stl).
• General Editing Actions Blender also utilizes numerous hotkeys and view options for efficient modeling:
• A to select/deselect all.
• X to clear a scene.
• Shift + A to add new objects (e.g., Mesh | Cylinder, Mesh | Cube, Mesh | Circle, Mesh | Plane).
• Tab to switch between Object Mode and Edit Mode.
• Ctrl + Tab to switch to Face Select, Vertex Edit, or Edge Select mode.
• E for Extrude.
• S for Scale.
• G for Move.
• R for Rotate.
• Z to switch between Solid and Wireframe view.
• NumPad / for Local View (isolates selected object).
• NumPad 1, 3, 7 for Front Orthographic, Side Orthographic, and Top view, respectively.
• Ctrl + Z to undo actions.
• Shift + C to ensure the 3D cursor is at the origin.
• H to hide objects and Alt + H to unhide all.

By mastering these Blender tools and techniques, designers can create complex, detailed, and functional objects, ensuring they are suitable for Fused Filament Fabrication (FFF) 3D printers and adhere to principles like minimizing overhangs and ensuring adequate wall thickness.

The Octopus Pencil Holder: A Blender 3D Print Project

The Octopus Pencil Holder is a featured project in the “3D Printing Designs: Octopus Pencil Holder” book, serving as an excellent starting point for learning 3D modeling in Blender for 3D printing. It demonstrates a simple yet versatile modeling technique involving editing a basic mesh and smoothing it to add detail.

The project aims to create a functional pencil holder that also has an aesthetic and cute design resembling an octopus. The specific design goals for the pencil holder include:

• A roughly cylindrical hole for pencils, about 40-50 mm wide at the base.
• A total height of at least 80 mm.
• A cute and friendly face.
• The octopus’s tentacles are planned to provide a sturdy base to prevent the cup from tipping over.

The creation of the Octopus Pencil Holder involves several key Blender techniques and tools:

1. Initial Setup and Basic Shape:

• The project begins by opening Blender, clearing the default scene, and adding a cylinder.
• Immediately after adding, the cylinder’s parameters are adjusted in the Tool Shelf: Vertices are changed from 32 to 8, Radius to 25, and Depth to 15. This creates an octagonal base for the octopus.

1. Editing the Basic Shape using Extrude:

• The primary tool for shaping the octopus is the Extrude operator. This tool creates new geometry from a selected part of an existing model, allowing the original part to be moved while remaining attached.
• In Edit Mode and Face Select Mode, the eight vertical sides of the cylinder are extruded about 40 mm each.
• Each extruded face is then scaled down to about 20% (0.2) to form the tentacles. This process is repeated for all eight tentacles.
• The top face of the cylinder is then extruded about 30 mm and scaled up slightly to create a bulbous head. Another extrusion of about 20 mm and scaling helps give the top a more rounded shape.

1. Smoothing the Mesh with Subdivision Surface Modifier:

• To make the blocky octopus much smoother for the final result, a Subdivision Surface modifier is added via the Modifiers tab.
• This modifier increases the smoothness of the model while retaining the simpler underlying geometry, which acts as a “cage”.
• The “View” setting in the modifier can be adjusted (e.g., set to 2 for this project) to control smoothness, though higher values can slow down the computer. The modifier can be temporarily turned off (by pressing the eyeball icon) for easier editing.

1. Bending the Tentacles using Loop Cut:

• The Loop Cut (or Loop Subdivide) tool is used to add detail and bend the tentacles. It adds points in the middle of an edge around a portion of the geometry, which can then be transformed.
• A loop cut is added to each tentacle, typically at the default middle location, and the “Number of Cuts” is changed to 2 in the operator settings.
• In Vertex Edit Mode, points at the end of each tentacle are selected and then rotated (R) around the z-axis (Z) and moved (G) along the x and y axes (Shift + Z) to bend the tentacle.
• The selection is expanded (Ctrl + NumPad +) and the process of rotating and moving is repeated to create a more pronounced bend.
• Constraining movement and checking views (e.g., Top view (NumPad 7) or Wireframe view (Z)) is crucial to avoid twisting tentacles incorrectly or causing overlaps that would prevent proper printing. The final tentacles should not overlap to ensure proper 3D printing.
• Consideration is also given to the total width of the model (e.g., under 150 mm or 6 inches) based on common 3D printer build areas.

1. Flattening the Bottom with Boolean Modifier and Renaming Objects:

• A solid, flat base is essential for a 3D print. For this project, a Boolean modifier is used to cut the bottom of the octopus.
• A cube is created at the 3D cursor’s origin (Shift + C).
• In Edit Mode, the cube’s points are moved 1 unit down along the z-axis (-1) so that when scaled, its top remains on the XY plane.
• The cube is scaled to cover the bottom of the octopus body.
• A Boolean modifier is added to the octopus body, with the Operation set to Difference and the Object chosen as the “Cube”. This effectively cuts the cube out of the octopus, creating a flat bottom.
• The Boolean modifier requires a clean mesh; potential issues like duplicate points or flipped faces can be resolved by using “Remove Doubles” and “Recalculate Normals” in Edit Mode.
• Objects are renamed for clarity (e.g., “Cylinder” to “Octopus Body” and “Cube” to “Floor”). The “Floor” object is then hidden (H) to prevent accidental transformations.

1. Adding a Pencil Cup with Edge Creasing:

• The Subdivision Surface modifier is temporarily turned off to simplify editing.
• In Face Select Mode, the topmost face of the octopus is selected and extruded (E) into the body, stopping just above the red x-axis line. It may be scaled to fit.
• After turning the Subdivision Surface modifier back on, edge creasing is applied to make the cup’s bottom flat and its lip sharper. This is done by selecting edge loops (Alt + click) and adjusting the “Mean Crease” value (e.g., to 1.0 for maximum crease). This technique is a powerful way to control the Subsurf modifier.

1. Adding a Face:

• A circle is created (Shift + A) at the origin, named “Face”, and then switched to Edit Mode.
• The circle’s points are selected, and the “Make Edge/Face (F)” command is used to create a face from the ring of points.
• The points are moved to the left side, and then duplicated (Shift + D) and placed on the opposite side to create two eyes.
• A plane is added to the “Face” object while in Edit Mode. Two points at the top of the plane are scaled up to form a smiling mouth.
• All points of the face are then extruded (E) about 4 or 5 units to give it thickness.
• The completed face object is rotated (R) 90 degrees around the x-axis (X) and positioned relative to the octopus body using move (G) and scale (S) commands. It is moved slightly into the body without cutting through the cup space, relying on some bridging during printing for the mouth’s top.
• Finally, another Boolean modifier is added to the octopus body (Difference operation with the “Face” object) to cut the face into the model. The “Face” object is then hidden (H).

Finishing Touches and Export: Once the design is complete, the model can be exported as an STL (.stl) file for 3D printing by navigating to File | Export | Stl (.stl). The project encourages users to use their imagination to customize the design, while remembering important 3D printing rules like considering overhangs (and the Y, H, T rules for support-less printing) and ensuring adequate wall thickness (e.g., 2 mm for details).

This project highlights how a combination of basic editing, modifiers, and Boolean operations in Blender can be used to create complex, detailed, and functional 3D printable designs.

Blender 3D Modeling: Octopus Pencil Holder Project

The Octopus Pencil Holder project, detailed in the sources, serves as an excellent starting point for learning 3D modeling in Blender, as it demonstrates a simple but versatile modeling technique. This project involves editing a basic mesh and then smoothing it to add detail, a method that, once mastered, can be used to create an unlimited number of cool things.

Here are the key modeling techniques discussed:

• Initial Setup and Basic Shape Definition The process begins by setting up Blender and adding a basic shape, typically a cylinder, to the scene. For the Octopus Pencil Holder, the cylinder’s parameters are immediately adjusted to have 8 vertices, a radius of 25 mm, and a depth of 15 mm, forming an octagonal base. This establishes the fundamental form before more complex modifications.
• Extrude Operator The Extrude operator is a primary and powerful tool for shaping objects. It takes a selected part of an existing model (like a face) and creates new geometry from its edge, allowing the original part to be moved away while remaining attached. This results in a new shape that can be further edited. In the Octopus Pencil Holder, extruding is used extensively:
• The eight vertical sides of the initial cylinder are extruded about 40 mm each and then scaled down to about 20% (0.2) to form the octopus’s tentacles.
• The top face of the cylinder is extruded twice to form the head: first about 30 mm and scaled up slightly to make it bulbous, then another 20 mm and scaled to give the top a more rounded shape.
• Subdivision Surface Modifier To transform the initial blocky shape into a much smoother final result, a Subdivision Surface modifier is added to the object. This modifier increases the smoothness of the model while preserving the simpler underlying geometry, which acts as a “cage” for editing. The “View” setting in the modifier controls the level of smoothness, with a setting of 2 recommended for the Octopus Pencil Holder. The modifier can be temporarily turned off during editing to simplify the view.
• Loop Cut (or Loop Subdivide) The Loop Cut tool is used to add detail and allows for bending parts of the mesh, such as the tentacles. It adds new points in the middle of an edge and around a portion of the geometry, which can then be transformed. For the tentacles, a loop cut is added to each, often with the “Number of Cuts” set to 2.
• Transformations (Moving, Rotating, Scaling) After adding loop cuts, specific points or selections of points are moved (G) and rotated (R) to bend and shape the tentacles. Movements can be constrained to specific axes (e.g., Shift + Z for x and y axes, or Z for z-axis rotation) to ensure proper shaping and prevent unintended twists. Careful attention is paid to ensure tentacles do not overlap, as this would prevent proper 3D printing.
• Boolean Modifier The Boolean modifier is a powerful tool for combining or cutting objects, crucial for creating a solid, flat base for 3D printing.
• To flatten the bottom of the octopus, a cube is created and positioned so its top aligns with the XY plane.
• A Boolean modifier is then applied to the octopus body with the “Difference” operation and the “Cube” as the target object, effectively cutting the cube out of the octopus and creating a flat bottom suitable for 3D printing.
• The Boolean modifier is also used to cut the face into the octopus model, again using the “Difference” operation with a “Face” object. Boolean operations demand a clean mesh; issues like duplicate points or flipped faces can cause problems, which can sometimes be resolved by using “Remove Doubles” and “Recalculate Normals”.
• Edge Creasing With the Subdivision Surface modifier active, edge creasing is applied to sharpen specific edges. By selecting edge loops (e.g., around the cup’s lip or base) and adjusting the “Mean Crease” value (e.g., to 1.0 for maximum crease), the Subdivision Surface modifier can be controlled to make the cup’s bottom flat and its lip sharper. This technique highlights the smart behavior of the Subsurf modifier in smoothing other edges while maintaining creased ones.
• Creating a Face (Making Edge/Face) To add details like eyes and a mouth, a circle is created, and its points are then used to form a face via the “Make Edge/Face” (F) command. Points are duplicated, moved, and scaled to form the eyes and a smiling mouth. These 2D shapes are then extruded to give them thickness before being positioned and Boolean-cut into the octopus body.

These techniques, when combined, allow for the creation of functional and aesthetically pleasing 3D printable designs, while also emphasizing important 3D printing considerations like overhangs and wall thickness (e.g., 2 mm for details).

FFF 3D Printing: Principles and Design Considerations

Fused Filament Fabrication (FFF) 3D printing is a widely discussed method for creating three-dimensional objects, and the sources provide a foundational understanding of its principles and design considerations.

Here are the basics of FFF printing:

• What is FFF 3D Printing? FFF 3D printing is one of the oldest, most mature, and cheapest forms of 3D printing. It involves melting a plastic filament and drawing the object layer by layer, with each layer sitting on top of the one below it. FFF 3D printers are popular because they are inexpensive and more readily available than other methods, and the parts they produce are suitable for a wide variety of functional uses. This series of books focuses on designing for FFF 3D printers.
• Designing for FFF Printing While 3D printing is often called “limitless technology,” it does have its own rules that must be followed for success. It’s best practice to always design according to the strengths and weaknesses of the medium you’ll be using. Many techniques for FFF design can also be transferred to other types of 3D printing.
• Overhangs and Supports A key consideration for FFF 3D printers is overhang. An overhang occurs when a part of the design, as it prints, does not have anything between it and the build platform. To address this, 3D printers can build a lattice of support material up to the overhanging part. This support material, typically made of the same material as the object for most FFF printers, must be removed after the print. Removing supports can be difficult to clean up completely and may leave a mess, especially in more complex prints. Because of these issues, it is generally a good idea to design for support-less 3D printing.
• Support-less 3D Printing (Y, H, T Rules) For successful support-less prints, each layer needs to have something to lay down on. If a part of the design dangles in the air without support underneath, the plastic extruded by the printer will drool and potentially ruin the print. The sources illustrate a few rules using the letters Y, H, and T to help design for success:
• Y – Gentle Overhangs: Like a capital letter Y standing up, changes in layers should be gradual. It’s possible for the current layer to be slightly larger than the previous one if the overhang is gentle. A 45-degree overhang is generally considered safe, though some users can achieve steeper angles, up to 80 degrees. However, if the overhang is too great or abrupt, the new layer may droop and fail.
• H – Bridging: Similar to a capital letter H standing up, if a part of the print has nothing above it but is supported on either side, the printer may be able to bridge the gap. The printer does not make special efforts for bridges; they are drawn like any other layer (outline first, then infill). Successful bridging requires the outline to attach to both sides and for the bridge to be simple and not too complex, avoiding parts that print in mid-air.
• T – Orientation: If trying to print a capital letter T standing up, problems with overhangs would arise. The solution is often simple: flip the object over or lay it down. It’s important to remember that not every print needs to be printed in the same way it will be used; sometimes reorienting the part is necessary for successful printing.
• Wall Thickness There is a minimum size that a 3D printer can print. While a 0.8 mm wall might be acceptable on most FFF 3D printers, a 2 mm wall is recommended. This thickness allows slicers to use one or two outlines with room for infill, regardless of the nozzle diameter, resulting in solid prints that will succeed in almost all cases. A 2 mm thickness is still considered fairly thin, allowing for considerable detail. It’s also crucial that a wall has an inside or outside (thickness), as a 2D wall has no thickness and is not printable.

In summary, successful FFF 3D printing depends on understanding how the material is laid down layer by layer, managing overhangs through gentle slopes, bridging, and careful orientation, and adhering to recommended wall thicknesses for robust prints.

By Amjad Izhar
Contact: amjad.izhar@gmail.com
https://amjadizhar.blog

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