In discussions with professors in the Department of Molecular and Cellular Biology at the University of Guelph, we've discovered that research labs and start-up biotechnology companies often spend thousands on outsourcing pill packaging. Our goal is to provide a cost-effective, in-house solution, allowing labs to save money and streamline their research processes.

 

The purpose of our design was to create a compact and automated pill-filling and packaging machine for use within a research lab/industrial setting. Based on its intended uses, the machine itself needed to have low manufacturing costs, be semi-automated, and be compact enough to be able to fit into a sterile chamber. With the overall cost, size, and automation stipulated; factors such as pill sizing (and whether we could design the machine to be applicable to a variety of standard pill sizes), powder viscosity/ fluidity to anticipate clumping and powder blockage issues, and the reasonable degree of automation needed to be accounted for.

 

With these crucial questions in mind, we quickly realized that rather than creating one machine to fill, compact, and seal the pills, in order to achieve a simple design with the desired degree of automation; four different subsystems would be ideal. These subsystems included the capsule tray, capsule orienter, the filler, and the presser, all of which would be compatible with an interchangeable pill plate that can be used for a variety of pill sizes.

 

Each system underwent multiple design iterations using the design, build, test, and learn method. The designs were adjusted to meet fixed project constraints/ criteria, stable product definition, and most crucially; constraints that made multiple tests and design interactions unfeasible. The following sections outline the design, build, test, and learn cycle that was carried out while making the pill packer.

The design phase of the engineering process involved brainstorming ideas for each subsystem of the pill packer. Various ideas for each sub-system were contemplated and the pros and cons of different designs were considered. After the selection of the design, they began to be modeled in Solidworks 3D modeling software.

  Capsule Tray  

The brainstorming of the capsule tray resulted in two different conceptual designs: the square stationary plate and the circular rotating plate. The square stationary plate involved holding the capsules in straight parallel rows. Having a stationary plate would require that the capsule orientation, pressing, and filling subsystems act on all capsules at once. The rotating plate design involved having rows of 5 capsules arranged in a circular pattern. The plate would be rotated from one row to the next, and the plate orientation, pressing, and filling would act on a single row of 5 capsules at a time, which would allow for pressing and filling to be done simultaneously and for a higher degree of automation. The pros and cons of each design are considered in Table 1.

 

Table 1: Pros and Cons of Capsule Tray Designs

	Circular Rotating Plate	Square Stationary Plate
Pros	Allows for a higher degree of automation Allows for more precision with filling and pressing of capsules by working with a single row of capsules at a time	Simpler Design Requirements
Cons	More costly due to the requirement for a stepper or servo motor	Will lead to more manual filling and pressing process

   

We decided to build a circular rotating plate. The primary reason for this was the ability to incorporate the rotating plate into an automated system. The square stationary plate would lead a manual process which did not align with the design specifications.

    Filler  

The filling system is used for filling the capsules with the appropriate amount of powder. The brainstorming of the filler involved three different design considerations including a volumetric filler, a time-based filler, and a weight-based filler. The volumetric filler works based on a physical compartment that stores a certain volume of powder which is transferred to the capsules. The time-based filler works by releasing powder into the capsules for a predetermined amount of time. The weight-based filler works by dispensing powder until the appropriate weight of the powder is met, then transferring that powder to the capsules. A list of the pros and cons of each system is considered in the following table.

 

Table 2: Pros and Cons of FIller Design.

	Volumetric Filler	Time Based Filler	Weight Based
Pros	Very Accurate for filling Low cost to implement Intermediate difficulty for design	Cheapest option Most simple option to design and implement	Very Accurate with the correct measuring device
Cons	Most difficult to adjust for different capsule sizes or weight and volume requirements	Least accurate filling type Lot's of variation in filling with an inconsistent powder	Most difficult option to implement Most costly solution Accuracy may be reduced to the small weight of powder in the capsule

 

We decided to use the volumetric filler. The time based filler was ruled out as it is much less accurate than the other two. The weight based filler was very accurate but the cost and difficulty to implement ruled it out as well. The volumetric filler offered an economically feasible solution to fill the capsules with an accurate and precise amount of powder.

    Capsule Orienter  

The capsule orienter is used to orient the capsules in the capsule tray with the capsule bodies underneath the capsule caps. There were two designs that were considered for the capsule orienter being a mechanical ramp and color based orienter. The color based orienter would use a color sensor to detect the orientation of the capsules which have different colored bodies and caps and then adjust the orientation accordingly. The mechanical ramp leverages the difference in diameter between the body and cap of the capsule. The capsules drop onto a fork whose gap size is in between the diameter of the body and cap. If the larger cap is below the body it will flip the capsule and slide down the ramp, otherwise it will simply slide down the ramp with the body of the capsule below the cap.

 

Table 3: Pros and Cons of Orienter Designs.

	Mechanical Ramp Orienter	Colour Based Orienter
Pros	Works for any colour of capsules Simple and cost-effective design	Smaller room for error in orienting the capsule	Very Accurate with the correct measuring device
Cons	Requires a precise tolerance for the gap in between the forks	More costly solution requiring electrical components Only functions with a capsules that have bodies and caps which differ in colour

 

The mechanical ramp was selected over the color based orienter. The primary reason was due to the large drawback of the color based orienter only working with capsules with different colored caps and bodies. The lower cost of the mechanical ramp also contributed to its selection.

    Presser  

The goal of the presser subsystem is to compact powder into the capsules. For powders with a high compressibility this is an important step. While brainstorming the presser system it became clear that what was required for the system was a linear actuator that pressed down into the capsules. The three primary types of linear actuators used in automated systems are hydraulic, pneumatic, and electro-mechanical. All three types of actuator would work with the presser system in theory, so pros and cons of each were considered.

 

Table 4: Pros and Cons of Presser Designs

	Hydraulic	Pneumatic	Electro-Mechanical
Pros	Highest force generation for pressing	Highest speed allowing for a quicker overall process	Most precise control over speed and distance allowing for greater control
Cons	Slowest system Requires water reservoir	Most difficult to control the precise depth of pressing	Most costly solution

 

The hydraulic system was ruled out due to the need for a water reservoir and the slow speed. We decided to use the pneumatic due to its low cost and higher speed compared to the electro-mechanical. Even though the pneumatic had the least precise control, we could find adjustments to improve its accuracy.

 

 

The build & test phase of the design process involved creating detailed designs in Solidworks 3D modeling software to assess the viability of the selected designs. Physical models and prototypes were created to test features of the designs.

 

Capsule Tray  

The initial design of the pill plate consisted of a 3D-printed circular plate with concentric rows of 40 pill slots intended solely to hold the pills as they were transferred between subsystems. Through careful consideration of the plate multiple problems were identified.

 

Figure 1: Initial Prototype of Capsule Tray

   

1. The thinness of the plate left it vulnerable to cracking and breaking 2. The cost of 3D-printing such a large part was too much for the budget 3. The plate offered no means of separating the capsule bodies and caps 4. The number of holes on the plate greatly increased the difficulty of implementing other subsystems

 

Filler  

The initial filler mechanism consisted of a stationary part and a moving part. The moving part (shown in white) collects the powder from the stationary part (shown in gray) that is connected to the bottom of a container. The moving part would slide from one end of the stationary part to the other carrying a specific volume of powder with it and releasing it into the capsules. 4 of these mechanisms would be connected side by side to fill one row of capsules at a time.

 

Figure 2: Initial Filler Design.

 

1. Powder would come out of cracks in the sides of the mechanism
2. Controlling the movement of the slider would require precise linear motion control
3. If one mechanism fails the entire filling process would fail

 

Capsule Orienter  

The initial ramp mechanism for the capsule orienter was designed in solidworks and 3D printed to test the viability of the design. The following two videos demonstrate the device orienting the capsules with the cap above the body whether the capsule is initially dropped in the correct or incorrect orientation.

   

The first complete design in solidworks of the separator consisted of a capsule container which sat overtop of the orienter mechanism, with tubes directing the oriented capsules to the capsule tray.

 

Figure 3: Initial Prototype of Capsule Orienter.

 

A prototype for this design was 3D printed placed on top of a makeshift cardboard base to test the functionality of the design. The initial prototype revealed issues with the original design that needed to be accounted for which are as follows.

 

Figure 4: Prototype for the capsule orientation design.

 

1. The angle of the ramps on orientation mechanism was too small preventing the capsules from sliding down the ramp 2. The shape of the capsule container prevented capsules from being directed to the orientation mechanism 3. The overall system was too large and blocky to fit inside a sterile chamber 4. This mechanism lacked the ability to release four capsules into the plate at a time to load the capsule tray

 

Presser  

The initial design for the presseer consisted of a pneumatic linear actuator involving a small air compressor that would expand a syringe. The syringe was connected to a spring loaded mechanism similar to a ball point pen. The end of this mechanism contained a presser head, with 5 circular extrusion that would align concentrically with capsules in the capsule tray.

 

Figure 5: Initial Prototype of Presser.

 

This prototype was 3D printed and tested. After testing multiple issues were encountered with the design.

 

1. The linear motion was not smooth and would get stuck due to the roughness of the 3D printed parts sliding over each other 2. The presser head would rotate rather than staying fixed in place 3. The air compressor filled the syringe but there was no method of removing the compressed air to retract the syringe

 

The learning phase of the design process involved fixing the issues associated with each subsystem highlighted through the build & test portion of the design process. Learning through mistakes identified by testing new and improved designs for each subsystem were built.

 

Capsule Tray

Table 5: Design Improvements on the Capsule Tray

Design Flaw	Solution
The thinness of the plate left it vulnerable to cracking and breakings	A new plate was designed with increased thickness and using particle board which won't crack
The cost of 3D-printing such a large part was too much for the budget	A much cheaper sheet of particle board was used instead of 3D printing. Additionally, the capsule tray was changed to a square plate rather than circular plate while maintaining the circular pattern of holes in the center to reduce complexity
The plate offered no means of separating the capsule bodies and caps	The plate was reproduced, along with the addition of a thin “squeeze” plate. This created a system to separate the capsules by squeezing the caps and bodies at the same time and pulling them apart
The number of holes on the plate greatly increased the difficulty of implementing other subsystems	The plate was reproduced, along with the addition of a thin “squeeze” plate. This created a system to separate the capsules by squeezing the caps and bodies at the same time and pulling them apart
The number of holes on the plate greatly increased the difficulty of implementing other subsystems	The number of holes on the capsule tray was drastically reduced to facilitate prototyping. The new capsule tray had 8 rows of 4, for a total of 32 holes

 

Figure 6: 3D model of Capsule Tray Final Design.

 

Figure 7: Physical Capsule Tray Final Design.

 

Filler

Table 6: Design Improvements on the Filler

Design Flaw	Solution
Powder would come out of cracks in the sides of the mechanism	The same general volumetric filling mechanism was used but instead using a block with four holes that had less cracks that could allow powder to escape
Controlling the movement of the slider would require precise linear motion control	The same pneumatic actuator that was used with the presser was designed to be compatible with the filler. This also allows for further interchangeability of parts

 

Figure 8: 3D Model of Final Filler Subsystem.

 

Figure 9: Physical Final Filler Subsystem.

 

Capsule Orienter

Table 7: Design Improvements on the Capsule Orienter

Design Flaw	Solution
The angle of the ramps on orientation mechanism was too small preventing the capsules from sliding down the ramp	The angle of the ramp was increased from 25° to 35°
The shape of the capsule container prevented capsules from being directed to the orientation mechanism	The container for the capsules was adjusted to be a funnel shape so the pills were directed straight to the mechanism
This mechanism lacked the ability to release four capsules into the capsule tray at a time	The redesigned filler mechanism described was designed to act as a capsule loader that could load capsules into the capsule tray. This further allowed for the interchangeability of parts, reducing cost and complexity
The overall system was too large and blocky to fit inside a sterile chamber	Using the redesigned filler mechanism allowed for the powder container to be used as a capsule container while loading capsules onto the plate, which reduced the size of the capsule orienter subsystem

 

Figure 10: 3D Model of Capsule Orienter Subsystem.

 

Figure 11: Physical Capsule Orienter Subsystem.

 

Presser

Table 8: Design Improvements on the Presser

Design Flaw	Solution
The linear motion was not smooth and would get stuck due to the roughness of the 3D printed parts sliding over each other	The presser was redesigned to use linear ball bearings and linear shafts which allowed for extremely smooth linear motion of the presser
The presser head would rotate rather than staying fixed in place	TTwo linear motion rods were held by shaft coupling that were screwed to the frame of the system preventing any unwanted rotationhe container for the capsules was adjusted to be a funnel shape so the pills were directed straight to the mechanism
The air compressor filled the syringe but there was no method of removing the compressed air to retract the syringe	A three way solenoid valve was added which opens an exhaust port between the air compressor and the syringe. This allows for springs to push the syringe pack in position and expel excess air

 

   

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Materials and Cost