Cross Sectional View
Design Background
Used for inserting cannulated screws for bone plate fixation, the attachment is intended to be multi-use and dishwasher/autoclave safe. The attachment was designed to interface with standard bits and powered devices currently on the market. The attachment’s offset design allows for use with these standard powered hand pieces without the need for a cannulated motor.
Design Concepts
This attachment was designed to utilize simple, interfaceable parts; sourcing off the shelf gears, o-rings, bearings, springs, and clips, custom parts were kept to a minimum to keep cost and lead time down. This design also has built in features for ease of assembly and disassembly, like a standard hex cut into the back of the drive shaft for easy installation and repair. The three drive shafts were designed to require minimal operation changes during the manufacturing process, allowing for tight runout tolerances to be held for the concentric surfaces. The offset design was selected to avoid the use of sourcing a cannulated motor for the whole powered hand piece. A 1 to 1 gear ratio was used, allowing for minimal loss in speed and torque output from the hand piece.
Exploded View
Functional Prototype
Design Analysis
Before machining prototype parts, design analysis was conducted including gear strength calculations, tolerance analysis, and biocompatibility. Gear strength calculations were performed based off of torque requirements known to seat selected cannulated screws. Tolerance analysis was performed to ensure that parts would assemble and function properly in a real-world application. Because of the nature of the device, materials were selected and processed specifically with biocompatibility in mind.