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My First Custom Designed Robot Arm

Using my first 3D printer to create my first robot arm, putting knowledge acquired from college and university to the test, providing a practical means of revision. 

Project Contents

* The Application Autodesk Fusion 360 (Personal) Was Used to create the shown CAD

Robot Design

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The purpose of this project was to be an experimentative and educational method of testing out my first 3D printer and a practical way to apply what I learn on my course.

To start I wanted to come up with a general concept of how I might want the robot to look. This was done taking in consideration a rough idea of robot size but most importantly suited around the size of the robot.

I chose this method as I had very limited experience with a printer and wanted to start off exploring text, curved, chamfers, inserts and meeting surfaces, so creating a segment and playing around with design features seamed suitable.

This is in contrast to designing a robot on the use case, work envelope and payload etc... such as what I learned whilst in college, though that is not the intention of this project.

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The first segment of the robot was designed as a base (black) which will accommodate a motor and a stylish casing (gold) that will enclose the motor inside.

 

This was produced with the MG-90 hobby servo as the intended motor, a metal geared varient of the SG-90 servo used in the Chessbot demo robot project. These motors were glued in place as at this point I wanted a simple method of mounting without making holes, having no experience making screw holes. This became impracticle in some part, making harder to replace damaged mtors. This is what inspired the completely bolt modular robot Pegasus 2, a method that will be implemented in a later revision of this robot also.

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The base was designed with the features of spread out legs to cover a large platform surface area for stability and a circular, vented base that will allow the robot to easily rotate. It was also produced with the intentions to be removable, to allow for various base designs to be used, such as bench or ceiling mounted.

Initial Pillar Build

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The white material proved really simple to print and would make almost perfect prints on stock settings. This is very different from some of the custom settings that were used for other colours as mentioned in other projects.

As I only had the one colour to use as another reel of blue filament i had was too big to fit inside the printer, but the white quickly became my favourite with its stunning appearance in good lighting.

Below you can see the first printed parts along with a part for the ping pong ball rocket launcher project.

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Looking at the above picture you can see that the form of the prints turned out really well so the thickness of the components was appropriate. As well as this the text came out almost perfect art this size, something that seems difficult to produce clearly when using much smaller fonts, as shown in later parts of the project.

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As visible from the image above, the base was not designed to just to be thick for added rigidity but to allow for a close clearance between joining segments by having only a small portion of the servo protrude the base.

Top Mid Segment Build

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Creating the mid-section, the arm section above the shoulder pillars, it was designed to be comprised of two halves, each with a wrist motor for an end effector and a recess to accommodate the attachments to the pillars.

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During the printing of these components, it was evident there was an issue with the supporting material. I decided to have the pice be printed upwards where the exterior face will be on top. This was done so the exterior face and text will be produced without any marking from raft material, though it was shown that it will be more difficult to print.

When altering the support material settings, I chose to print the support structures thinner to make them easier to remove compared to how they were previously. This proved to be a bad idea as the supports were too thin and most would collapse before reaching the top layers, as seen in the above-left image. It can be visible in the above-right picture that the inside layers were affected by dropping, though the above layers were perfectly fine, as shown in the below images.

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It seemed that after a certain point, enough material was added onto the drooping surface that it was thick enough to produce enough rigidity to the remainder of the components. I slightly adjusted the settings for the next half with little no change apart form printing time.

The new parts took much longer to print, though  I kept it on the standard settings as printing the other side of the pillars using the faster mode proved week around curved and thin parts.

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Glue was used to stick the segments together as well as the attachments for the servo. This glue seemed mostly useless for these fixtured, not gripping at all. At this point i used the plastic/wood screws the servo came with and they seemed more than easy enough to fix the attachment without the need for drilling holes or cracking the plastic.

 
 
 

Project By Ryan Brown (CMOSS Founder)

January 22 2021