Kelly Alexander Rolling Ball Kinetic Sculpture Summary This design was prompted by a request to create a model exhibiting the capabilities of the selective laser sintering process. It was completed as an independent project during my last year of study in the Department of Mechanical Engineering at the University of Texas at Austin. The goal of this project was to design and fabricate a part that exhibits the unusual capabilities of the selective laser sintering fabrication process and advertises the process to interested parties. I wanted to demonstrate the unique geometry and assemblies that can be created when the designer is not limited by the constraints of conventional machining. A significant ability of SLS is to create moving parts that are manufactured in assembly, so I wanted to create a model with interacting components. I designed an interactive rolling ball sculpture. A rolling ball sculpture is a kinetic sculpture in which one or many balls are moved around a closed system, usually involving a mechanism which lifts the balls and releases them to roll down a track. The Archimedes screw is a common device used to lift objects by employing a rotating screw to push them up a fixed track. I used a double helix track to illustrate the ability to create intertwined parts and paths in a single SLS assembly. The balls are ½ inch steel bearing balls. The SLS model (without the balls) has a volume of 19.581 cubic inches. Most rolling ball sculptures have welded metal parts and tracks to direct the balls. These sculptures usually require a significant amount of time and careful construction. They also require many different parts assembled by hand. Each sculpture is a unique piece of art which is rarely duplicated. With SLS, the piece could be constructed overnight instead of over weeks or months. It could be constructed entirely assembled, whereas the traditional method of building requires skilled assembly by hand. It would also be possible to produce multiple identical models, which would be challenging with traditionally building techniques. SLS also allows duplicates with minor variations. For example, in this design there is a band around the center displaying the letters UT and ME, for the University of Texas Mechanical Engineering Department. The final build also included the date and designer s initials embossed on the inside surface of the base. SLS offers an almost infinite ability to customize a part without any additional investment in manufacturing and tooling.
Kelly Alexander Rolling Ball Kinetic Sculpture Justification Report Since this design was created in response to a request for a model using selective laser sintering, SLS was the obvious choice for the process. The goal of this project was to design and fabricate a part that exhibits the unusual capabilities of the selective laser sintering fabrication process. The resulting product is a kinetic sculpture inspired by rolling ball sculptures. A pair of rails forms a double helix pattern around an Archimedes screw. When the handle at the base is turned, a pair of gears translates the motion into vertical rotation of the Archimedes screw. The screw raises the steel bearing balls up along the center posts and releases them at the top. The balls then roll down the rails and accumulate at the bottom, ready to be picked up again. The double helix pattern results in two separate closed systems; the balls from each side of the screw travel around the center screw while rolling down, but always return to the same side of the screw to be lifted. The 3D model and a photograph of the final part are shown below:
A view from the bottom reveals the gears that transfer the rotation of the handle. The embossed initials of the designer and the year the sculpture was designed are also visible: The SLS process is appropriate for this model for several reasons. SLS can create complex geometries with good surface resolution, such as the unusual curves of the narrow rails. The SLS process has a.004 inch layer thickness, which makes it possible to create small details and narrow interfaces between moving parts. Because the parts are created floating in a chamber of powder, interlocking parts with relative motion can be manufactured in assembly. This allowed for components such as the rotating Archimedes screw, gear assembly, and handle. Each of these interacting components has very small clearances. Like most rapid prototyping processes, personalization is also very easy. This particular build exhibits a ring around the center bearing the letters UT ME and the initials of the designer and the date are embossed inside the base. The material choice for this project is Nylon 12. Nylon 12 is a good basic plastic powder used in SLS. It has good surface resolution and feature detail, and it is a relatively inexpensive SLS powder. It was also important that the material have a small amount of give in it, requiring a plastic instead of a metal or other stiff material. The steel balls have to be inserted into the system between the rails at the top. This piece was designed as an interactive sculpture and an advertisement for SLS, so did not require a material with extreme temperature properties. The SLS machine operates in an 80-120 C range (or 176 248 F). The final part is designed for use in a temperature range around 20-27 C (approximately 68-81 F), although any temperature in which a person would be comfortable should not adversely affect the part. The original design
called for the balls to be made of Nylon 12 as well and manufactured in assembly. However, preliminary builds revealed that the balls were too lightweight and the surface was too rough for the balls to roll well. The balls used in this model are ½ inch E52100 alloy steel bearing balls, although any ½ inch bearing balls would be appropriate. For aesthetic purposes, materials like glass or wood could also be used. This model was designed to be built on an as-needed basis, which is perfect for SLS. For the purpose of advertising SLS technology at UT, only one is needed. The model is on display in the engineering building with a brief explanation of the process. Additional builds could be created as needed. At the UT facility, SLS parts cost $25 per inch of build height, so to build this part would cost approximately $140. Since the original part was created for the school, the cost would be limited to the actual cost of production. Nylon 12 PA costs approximately $50 60 per pound and has a density of 0.033 pounds/in 3. The part is 19.58 cubic inches. The actual cost of a build is estimated at approximately $35 in powder. Electricity and manpower will also contribute to the cost of a build. Four models can be built in a single build chamber, or just two can be manufactured horizontally, minimizing the depth of powder needed, thus minimizing time and cost per model. The potential cost benefit for the SLS lab is significant. The sculpture serves as an example of many of the abilities of SLS and can advertise the process to artists or manufacturers. A build requiring the full chamber can cost up to $300, so the return on investment could be as little as a single build. Additional models could also be personalized and sold for a small fee to offset the cost of production.
Kelly Alexander Rolling Ball Kinetic Sculpture Justification Report Since this design was created in response to a request for a model using selective laser sintering, SLS was the obvious choice for the process. The goal of this project was to design and fabricate a part that exhibits the unusual capabilities of the selective laser sintering fabrication process. The resulting product is a kinetic sculpture inspired by rolling ball sculptures. A pair of rails forms a double helix pattern around an Archimedes screw. When the handle at the base is turned, a pair of gears translates the motion into vertical rotation of the Archimedes screw. The screw raises the steel bearing balls up along the center posts and releases them at the top. The balls then roll down the rails and accumulate at the bottom, ready to be picked up again. The double helix pattern results in two separate closed systems; the balls from each side of the screw travel around the center screw while rolling down, but always return to the same side of the screw to be lifted. The 3D model and a photograph of the final part are shown below:
A view from the bottom reveals the gears that transfer the rotation of the handle. The embossed initials of the designer and the year the sculpture was designed are also visible: The SLS process is appropriate for this model for several reasons. SLS can create complex geometries with good surface resolution, such as the unusual curves of the narrow rails. The SLS process has a.004 inch layer thickness, which makes it possible to create small details and narrow interfaces between moving parts. Because the parts are created floating in a chamber of powder, interlocking parts with relative motion can be manufactured in assembly. This allowed for components such as the rotating Archimedes screw, gear assembly, and handle. Each of these interacting components has very small clearances. Like most rapid prototyping processes, personalization is also very easy. This particular build exhibits a ring around the center bearing the letters UT ME and the initials of the designer and the date are embossed inside the base. The material choice for this project is Nylon 12. Nylon 12 is a good basic plastic powder used in SLS. It has good surface resolution and feature detail, and it is a relatively inexpensive SLS powder. It was also important that the material have a small amount of give in it, requiring a plastic instead of a metal or other stiff material. The steel balls have to be inserted into the system between the rails at the top. This piece was designed as an interactive sculpture and an advertisement for SLS, so did not require a material with extreme temperature properties. The SLS machine operates in an 80-120 C range (or 176 248 F). The final part is designed for use in a temperature range around 20-27 C (approximately 68-81 F), although any temperature in which a person would be comfortable should not adversely affect the part. The original design
called for the balls to be made of Nylon 12 as well and manufactured in assembly. However, preliminary builds revealed that the balls were too lightweight and the surface was too rough for the balls to roll well. The balls used in this model are ½ inch E52100 alloy steel bearing balls, although any ½ inch bearing balls would be appropriate. For aesthetic purposes, materials like glass or wood could also be used. This model was designed to be built on an as-needed basis, which is perfect for SLS. For the purpose of advertising SLS technology at UT, only one is needed. The model is on display in the engineering building with a brief explanation of the process. Additional builds could be created as needed. At the UT facility, SLS parts cost $25 per inch of build height, so to build this part would cost approximately $140. Since the original part was created for the school, the cost would be limited to the actual cost of production. Nylon 12 PA costs approximately $50 60 per pound and has a density of 0.033 pounds/in 3. The part is 19.58 cubic inches. The actual cost of a build is estimated at approximately $35 in powder. Electricity and manpower will also contribute to the cost of a build. Four models can be built in a single build chamber, or just two can be manufactured horizontally, minimizing the depth of powder needed, thus minimizing time and cost per model. The potential cost benefit for the SLS lab is significant. The sculpture serves as an example of many of the abilities of SLS and can advertise the process to artists or manufacturers. A build requiring the full chamber can cost up to $300, so the return on investment could be as little as a single build. Additional models could also be personalized and sold for a small fee to offset the cost of production.