UW-Health Automated Pill Dispenser
Overview
While I was completing my master’s in mechanical engineering I assisted a biomedical engineering senior design capstone team develop an automated pill dispenser for researchers at UW-Madison’s Pharmacy School to improve patient medication adherence rates. Estimates have indicated that about 125,000 Americans die each year from medication non-adherance [1]. I helped the team by designing the mechanical/electrical systems, modeling components with solidworks, manufacturing components, and assembling the device. A business model was also developed for an entrepreneurship pitch competition to present the product. The final product utilized a NEMA stepper motor and motor controller to provide motion to the system. A pulley belt was used to drive the removable and refillable pill wheel. A IOT connected arduino was used to connect the system to an app. The pill wheel would be filled by the pharmacist and placed into the machine. The system would then dispense the pills based on prescription quantity and timing. The machine would register that the patient took the medication and provided live information to the pharmacist to track medication adherence. The system also allowed users to dispense over the counter medications at will.
The pill dispenser was designed to act as a complement to a home. Many products on the market today are sterile looking medical devices with limited design options. Organic geometries in combination with a soft maple wood were used to create a modern look. Inspiration was taken from espresso machines that complement modern kitchens. Welded sheet metal and plastic housings were used for the internal supporting structures. The primary rotating shaft was machined from 6061 aluminum.
[1] Benjamin RM. Medication adherence: helping patients take their medicines as directed. Public Health Rep. 2012 Jan-Feb;127(1):2-3. doi: 10.1177/003335491212700102. PMID: 22298918; PMCID: PMC3234383.
Processes Utilized
3D Modeling & Rendering (Solidworks)
Laser Cutting
Waterjet Cutting
Woodworking
Welding
CNC Machining
FDM & SLA 3D printing
Top Skills Utilized
CAD modeling
Mechanical Design
Sheet Metal Design
3D Printing
CNC Machining
Microelectronics
Biomedical Engineering
Concept Generation
Inspiration for the pill dispenser came from high-end espresso machines and organic structures typically used in high-performance vehicles to reduce weight. Sketches were used to develop concepts for the housing and brainstorm improvements for the mechanical systems.
Pill Dispenser Design
Housing
The housing was designed with multiple materials to achieve the modern/organic look. Maple was chosen for the housing and black plastic was chosen for the base. The base and lid were prototyped with black PLA. Sheet metal was used to create the structure to fasten the housing and rotating mechanism together. Heat set inserts were pressed into the plastic housing components to accept the mating fasteners.
Internal Wheel Mechanism
The key system of the pill dispenser is the dispensing mechanism for the refillable cartridge wheel (pink). The refillable cartridge wheel is placed into a round housing (grey) with a lid to allow the pharmacist to insert the cartridge into the device. The cartridge can rotate independently of the housing via a bearing in the cartridge housing and a splined shaft that is driven by a pully belt connected to a stepper motor. The cartridge housing is designed not to rotate allowing only the pill cartridge to rotate to dispense pills through an opening in the lid. A motor controller is used to control the position of the cartridge via a NEMA stepper motor. The mounting plate for the stepper is slotted to allow for quick tensioning of the pulley belt.
Manufacturing
Housing
The exterior maple housing of the pill dispenser was machined on a 4 ft x 8 ft Laguna CNC router using Vcarve to prep the Gcode. The components were then sanded and glued together with wood adhesive. The organic bottom structure was printed from PLA using a large Ultimaker printer. The sheet metal parts were cut using a waterjet and designed to be slotted for quick alignment for welding. I used a TIG welder to weld the aluminum components together. Welding was chosen because the sheet metal brakes on campus were not operational at the time to bend the components. Brass heat set inserts were pressed into the plastic and brass wood inserts were screwed into the maple housing to accept the fasteners to connect the sheet metal frame.
Internal Wheel Mechanism
The two bearings were pressed into their respective housings using a manual bearing press. The portion of the shaft connected to the pulley was machined from 6061 aluminum on the lathe at the machine shop. The spline half of the shaft was printed using tough resin on a FormLabs Form 3 printer to allow for quick fit checks. The stepper motor was connected to a motor controller, a microcontroller, a potentiometer, and a 12V power suppler to allow for quick testing of the system.
