The document describes the redesign of a filament feeder for an additive manufacturing research system. The original filament feeder design had several issues including inconsistent extrusion and difficulty removing the heating nozzle. The goals of the redesign were to allow for more consistent extrusion, easy access to components, and instrumentation to measure extrusion force. Several design concepts were considered before settling on a design using a single stepper motor, lever arm, and spring to apply constant force to drive the filament through a new guide path and single load cell into the heating nozzle.

1. Filament Feeder for Additive
Manufacturing Research System
Micah Miller
12/12/16
Advisor:
Ralph Stirling

2. Abstract
Additive manufacturing of plastics, commonly known as 3D-Printing, is the process of
extruding thin strands of melted plastic filament through a nozzle onto a workspace in order to
create three dimensional structures and models. Currently Walla Walla University owns a large
scale 3D-Printer intended for research purposes. This was retrofitted from a 2D Filament Printer
by Kyle Bahnsen and Katie Storm in a previous project.
One of the key components of a 3D-Printer is the filament feeding device that actually
pulls the plastic filament of a spool and pushes the plastic through a heated nozzle in order to be
extruded onto the workspace. Previously the first iteration of the device used for this process did
not perform optimally during operation. Therefore, a new design for this apparatus is necessary
for future use of the printer.
A detailed outline of the design process, component list, and operation manual is
included. The operations and procedures for this device must be understood before use of the
device. This will allow more efficient use of this device in order to proceed with further research.

3. 3
Filament Feeder
Table of Contents
FILAMENT FEEDER FOR ADDITIVE MANUFACTURING RESEARCH SYSTEM....................1
ABSTRACT.....................................................................................................................................2
TABLE OF FIGURES......................................................................................................................6
LIST OF TABLES ........................................................................................................................... 7
ACKNOWLEDGEMENTS ..............................................................................................................8
1 INTRODUCTION AND OBJECTIVES ...................................................................................9
1.1 Introduction ...........................................................................................................................................................................9
1.2 Project Objectives and Requirements..............................................................................................................................9
2 RESEARCH AND DESIGN ...................................................................................................11
2.1 Physical Requirements ......................................................................................................................................................11
2.1.1 Groove Mount...........................................................................................................................................................11
2.1.2 Load Cells ...................................................................................................................................................................12
2.1.3 Guide Path .................................................................................................................................................................12
2.1.4 Drive System..............................................................................................................................................................12
2.1.5 Spool Mount..............................................................................................................................................................13
2.2 Original Design ....................................................................................................................................................................13
2.2.1 Overview....................................................................................................................................................................13
2.2.2 Issues ..........................................................................................................................................................................14
2.3 Research ...............................................................................................................................................................................17
2.3.1 Filament Material Properties .................................................................................................................................17
2.3.2 Drive Mechanisms....................................................................................................................................................17
2.3.3 Load Cells ...................................................................................................................................................................18
2.3.4 Stepper Motor...........................................................................................................................................................18

4. 4
Filament Feeder
2.4 Initial Design Concepts ......................................................................................................................................................18
2.4.1 First Concept..............................................................................................................................................................18
2.4.2 Second Concept ........................................................................................................................................................19
2.4.3 Third Concept............................................................................................................................................................19
2.5 New Design ..........................................................................................................................................................................20
2.5.1 Initial Concept...........................................................................................................................................................20
2.5.2 Intermediate Design.................................................................................................................................................20
2.5.3 Final Design................................................................................................................................................................21
2.6 Analysis.................................................................................................................................................................................22
2.6.1 Free Body ...................................................................................................................................................................22
2.6.2 Component Comparison.........................................................................................................................................22
3 MANUFACTURING AND ASSEMBLY................................................................................24
3.1 Components to Manufacture...........................................................................................................................................24
3.2 Manufacturing Process......................................................................................................................................................24
3.3 Fasteners and Bearings .....................................................................................................................................................24
3.4 Instrumentation..................................................................................................................................................................25
3.5 Assembly ..............................................................................................................................................................................25
4 OPERATIONS MANUEL .....................................................................................................26
4.1 Mounting Device ................................................................................................................................................................26
4.2 Inserting Filament ..............................................................................................................................................................26
4.3 Replacing Components......................................................................................................................................................27
5 CONCLUSION.......................................................................................................................28
5.1 Future Work.........................................................................................................................................................................28
5.1.1 Complete Assembly..................................................................................................................................................28
5.1.2 Spool Mount..............................................................................................................................................................28
5.1.3 Extensive Testing......................................................................................................................................................28

5. 5
Filament Feeder
5.2 Final Observations and Assessments .............................................................................................................................28
REFERENCES...............................................................................................................................29
APPENDIX A – ABS MATERIAL DATA SHEET........................................................................30
APPENDIX B – LOAD CELL SPECIFICATIONS ........................................................................31
APPENDIX C - STEPPER MOTOR SPECIFICATIONS.............................................................32
APPENDIX D – COMPONENT DRAWINGS AND PARTS........................................................33
D-1 – Back Housing .......................................................................................................................................................................33
D-2 – Bottom Housing ..................................................................................................................................................................34
D-3 – Top Housing.........................................................................................................................................................................35
D-4 – Base .......................................................................................................................................................................................35
D-5 – Lever......................................................................................................................................................................................36
D-6 Filament Guide .......................................................................................................................................................................37
D-7 – Groove Mount Clamp ........................................................................................................................................................38
D-8 – Support Rod .........................................................................................................................................................................39

6. 6
Filament Feeder
Table of Figures
Figure 1. Filament Feeder Diagram, Ref. 1
Figure 2. Research Printer with Original Filament Feeder
Figure 3. Groove Mount Diagram, Ref. 2
Figure 4: Hot Shot Heating Nozzle
Figure 5. Sample Load Cell, Ref. 3
Figure 6. Wheatstone Bridge Diagram
Figure 7. Sample Stepper Motor, Ref. 4
Figure 8. Original Filament Feeder
Figure 9. Filament Guide/Groove Mount Holder
Figure 10. Load Cell Screws (Original)
Figure 11. Open Housing (Original)
Figure 12. Filament Guide/Groove Mount Holder (Original)
Figure 13: Groove Mount Holder without Nozzle (Original)
Figure 14: Groove Mount Holder with Nozzle (Original)
Figure 15. Lever Arm Mechanism
Figure 16. Initial Teeth Concept
Figure 17. Initial Spring Concept
Figure 18. Gear Rod Bearing Concept
Figure 19. Screw Bearing Concept
Figure 20. Intermediate Design
Figure 21. Intermediate Design (Exploded View)
Figure 22. Final Design
Figure 23. Mounting Rod

7. 7
Filament Feeder
List of Tables
Table 1. Component Comparison
Table 2. Manufacturing Processes

8. 8
Filament Feeder
Acknowledgements
Kyle Bahnsen and Katie Storm, for their previous work on the printer and contribution to
figuring out some of the issues with the old design.
Don Riley, for his feedback in helping me refine my design.
Ralph Stirling, for providing feedback and inputs when required as well as providing all the
materials and recourses required to design and create all the components in this project.

9. 9
Filament Feeder
1 Introduction and Objectives
1.1 Introduction
The purpose of this project is to improve and redesign the device used to extrude plastic onto the
workspace of Walla Walla University’s research 3D-Printrer.This project was introduced to
Micah Miller in the winter if 2016 by Ralph Sterling. This project is directly related to the work
that Kyle Bahnsen and Katie Storm did previously on this research printer for their senior project
in 2014. However, during the process of working on their project, they discovered that the
extruding mechanism, or filament feeder, did not perform very well. But redesigning this portion
of the overall printer assembly was outside the scope of their project. Therefore, this task was to
become this particular project. The main components of the filament feeder are the filament
itself, the drive mechanism, the extruder, and the guide that directs the filament into the heated
end of the extruder. Through this assembly melted filament is extruded from the end of the
nozzle in order to create an object.
Figure 1. Filament Feeder Diagram, Ref. 1
1.2 Project Objectives and Requirements
The objective of this project is to redesign the filament feeder in order to allow more
consistent extrusion from the nozzle, as well as allow for instrumentation to be implemented for
research and testing purposes. Another requirement was for every part in the assembly to be

10. 10
Filament Feeder
easily accessible both during assembly and operation. The instrumentation must measure force
required to extrude filament through nozzle with resolution of 0.1 N or better, with a man of 25
N. There is also a filament nominal diameter of 1.75 mm, which the device must be able to
account for.
The main goals of this project consists of creating consistent performance as well as simple
operation and easy access of necessary components.
Figure 2. Research Printer with Original Filament Feeder

11. 11
Filament Feeder
2 Research and Design
2.1 Physical Requirements
2.1.1 Groove Mount
The groove mount is the section of the heating nozzle that allows for the nozzle to be mounted to
the filament feeder assembly, Figure 3. This mount has standardized dimensions, regardless of
the model of the heating nozzle. Therefor the clamp used to hold the nozzle must have a close
tolerance to this specific size. A sample heating nozzle groove mount is shown below, Figure 4.
Figure 3. Groove Mount Diagram, Ref. 2
Figure 4: Hot Shot Heating Nozzle

12. 12
Filament Feeder
2.1.2 Load Cells
In order for a force to be measured on the filament, we need a specific type of instrumentation. In
this specific application, load cells were chosen in order to perform this task. A load cell is a
device that utilizes strain gauges on a long piece of metal with a specific section cut from the
center of the piece, Figure 5. In order to determine the force acting on the device, deflection
must occur on one end of the load cell.
Figure 5. Sample Load Cell, Ref. 3 Figure 6. Wheatstone Bridge Diagram, Ref 4
2.1.3 Guide Path
The guide path is the section between the drive mechanism and the heating nozzle that allows the
filament to be forced into the heating nozzle without buckling and bending off in a random
direction. This must also must take into consideration the mounting of the load cells as well.
2.1.4 Drive System
The drive system is the method by which the filament will be forced into the heating nozzle. This
is typically done with some type of stepper motor of sorts that has a wheel or gear that pushes the
filament along a specific path. A stepper motor is a brushless, synchronous electric motor that
converts digital pulses into mechanical shaft rotations, Figure 7. Steppers motors can come in a
variety of sizes and torques, making them ideal for this application.

13. 13
Filament Feeder
Figure 7. Sample Stepper Motor, Ref. 5
2.1.5 SpoolMount
The method by which the spool of filament is also important as well. This is due to the fact that
if the filament is not easily accessible by the filament feeder assembly then the drive mechanism
might not be able to drive the filament very well into the heating nozzle. Therefore, it is
important that the spool is mounted properly inside the research printer assembly.
2.2 Original Design
2.2.1 Overview
The original design for the filament feeder, Figure 8, consisted of two stepper motors with drive
wheels which were mounted to rotating arms inside a main housing. These two arms were
pressed together via a screw on either side of a central load cell system in order to determine how
hard the filament was being pinched between the two drive wheels. Below the two drive wheels
was the guide system, Figure 9, which was mounted on a pin to the far side of the housing, this
guide rested on a linear force gauge. The guide piece also had a slot to allow the groove mount to
slide in from the side. The idea behind this was to have there be only one component in order to
guide the filament down to the heating nozzle, as well as allow the force to be measured on the
force gauge from this guide piece.

14. 14
Filament Feeder
Figure 8. Original Filament Feeder
Figure 9. Filament Guide/Groove Mount Holder
2.2.2 Issues
There were a number of issues regarding the original design of the filament feeder. Hence why a
new design was recommended.
 The first was that in order to pinch the filament between the two drive wheels, manual
adjustments were required each time that the filament had to be changed or adjusted. The
two screws that pressed against the top load cell didn’t always give consistent results. See
Figure 10 and Figure 11.
 Having two drive wheels seemed to add unnecessary complexity. The same function
could be performed with a single motor pressed against a bearing or something similar.

15. 15
Filament Feeder
 A major issue was the guide for the filament that was right underneath the drive wheels,
Figure 12. The original design needed to be greatly modified due to a couple critical
flaws. The first being that the groove that was initially meant to guide the filament down
its hole did not have enough clearance and would grind against the drive wheels. So a
section needed to be gouged out in order to create room for the drive wheels. Also the
drill to create the hole wasn’t long enough, so the other side was drilled with a larger bit
and piece of Teflon with a hole the same size as the smaller hole in order to have a
consistent diameter all the way through the part.
 The force gauge that was used to measure the force that the filament was placing on the
heating nozzle was not as accurate as would be preferred.
 The final issue was the fact the heating nozzle became very difficult to remove from the
groove mount slot once the filament was melted inside the heating nozzle, Figure 13 and
Figure 14. Because the nozzle mount need to be slide to the side, the filament needed to
be sheared in order to remove the nozzle. This proved to be very difficult without any
clearance between the groove mount and the groove mount holder.
Figure 10. Load Cell Screws (Original)
Figure 11. Open Housing (Original)

16. 16
Filament Feeder
Figure 12. Filament Guide/Groove Mount Holder (Original)
Figure 13: Groove Mount Holder without Nozzle (Original)
Figure 14: Groove Mount Holder with Nozzle (Original)

17. 17
Filament Feeder
2.3 Research
2.3.1 FilamentMaterialProperties
An important aspect of this project is determining the material properties of the plastic we are
using for the filament. In this application we will typically be using ABS (acrylonitrile-
butadiene-styrene) or PLA (poly lactic acid) plastic. It is a low cost/ easy to machine and
fabricate. The reason this is so important is because in a filament feeder, the coefficient of
friction and the modulus of elasticity are required in order to determined how to optimize the
drive mechanism for the filament. Refer to Appendix A for material data sheet.
2.3.2 Drive Mechanisms
There are a lot of different methods that people have found for driving their filament into a
heating nozzle. The most common method however uses a single stepper motor with either a
drive wheel or a gear in order to drive the filament. The motor is typically mounted rigidly to a
housing while a bearing of sorts is pressed against the motor wheal via a lever arm and spring,
Figure 15. With this method, the bearing will be constantly applying force to the filament until
the user manually presses on the lever to counteract the spring force and release the bearing. This
allows the user to replace filament with easy without having to worry about manually adjusting
the bearing against the filament each time the filament needs to be changed.
Figure 15. Lever Arm Mechanism

18. 18
Filament Feeder
2.3.3 Load Cells
One of the main objectives of this project is to measure the force of the filament on the nozzle.
To accomplish this, the chosen method was to use load cells which utilize a series of strain
gauges in order to accurately measure force via deflection of the load beam. Dr. Stirling already
possessed a large variety of strain gauges and after analyzing the specs of a few of these load
cell, a cells that meets the 25 N requirement was found, Appendix B.
2.3.4 Stepper Motor
To save time and resources, the same stepper motor used in the old design will be used along
with initially machined drive wheel attached to the shaft of the motor. This particular motor
provides a maximum torque of 1.75 N·m.
2.4 Initial Design Concepts
2.4.1 First Concept
The initial designs involved modifying the original designs in order to allow for more consistent
results. One such idea involved keeping both motors and using two linear gear rods and a
circular gear in order to push both motors together at the same time, Figure 16. The other
involved using springs instead to push the two motors together, Figure 17.
Figure 16. Initial Teeth Concept

19. 19
Filament Feeder
Figure 17. Initial Spring Concept
2.4.2 Second Concept
The second concept involved using a linear gear rod again. But this time the purpose was to press
a bearing against a single motor to drive the filament, Figure 18.
Figure 18. Gear Rod Bearing Concept
2.4.3 Third Concept
The third concept was similar to that of the second. But instead of using a gear rod, a lead screw
is used in order to push the bearing against the drive wheel in order to pinch the filament, Figure
19.
Figure 19. Screw Bearing Concept

20. 20
Filament Feeder
2.5 New Design
2.5.1 Initial Concept
After analyzing initial design concepts and researching a variety of methodologies for the main
drive mechanism, the lever arm/spring mechanism was chosen, Figure 17. Part of this was
influenced by the fact that many of the smaller 3D Printers used by The School of Engineering
utilized this method. Therefore, it was thought best to utilize this method for this project as well.
The rest of the filament feeder assembly is based around this mechanism and has been designed
to work in direct correlation with the described mechanism above.
2.5.2 Intermediate Design
The intermediate stage of the design process, a design was created in Creo of the drive
mechanism, Figure 20. This part of the design used a cover within the lever arm in order to keep
the bearing in place. The base that the lever arm is attached to provides a space for motor to be
mounted to, as well as an initial guide section for the filament and a boss for the spring that is
between the base and the lever arm. This provided the force that presses the bearing against the
drive wheel. At this stage of the design process, the analysis for the lever arm and forces on the
filament had not yet been completed.
Figure 20. Intermediate Design

21. 21
Filament Feeder
Figure 21. Intermediate Design (Exploded View)
2.5.3 Final Design
For the final design, there were a large number of changes that needed to be made. This was due
to the fact that the manufacturability of the individual parts was quite low. It is best to reduce the
number of parts that require tight tolerances to a minimum. So the lever arm was redesign to
utilize just a shoulder screw to keep the bearing in place. Also, after completing the analysis of
both the sum of forces and moments, it was determined that the distance between the point of
rotation and the bearing should be shortened as much as possible to allow more force through the
bearing with less for via the spring. This was done in order to allow the lever arm to release the
filament from between the bearing and drive wheel with ease. Beneath the initial guide of the
base was an extra guide for the filament, which was meant not only to act as an extension of the
initial filament guide, but to allow the heating nozzle to be mounted to the assembly via two
clamps. The purpose of this is to allow the heating nozzle to be screwed into the assembly
directly into the assembly instead of having to be slid into place and sheared off like the original
design. The guide part was also designed to be mounted to two load cells which are to be
mounted to the overall housing of the filament feeder. This housing was designed around the
internal components and is designed to be open and easy to access all component of the assembly
during operation, Figure 22. All STEP files for the assembly are located on the CD included in
this report. Reference Appendix D.

22. 22
Filament Feeder
Figure 22. Final Design
2.6 Analysis
2.6.1 Free Body
All the analysis for the forces acting upon the filament and the sum of the moments for the lever
arm are given in Appendix C. The sum of the forces on the filament is important because it will
help determine the force that the spring needs to be in order to force the bearing against the
filament to prevent slipping as the filament is being driven down into the heating nozzle. There
are a number of forces acting on the filament at the point between the two wheels. This includes
tension and compression as the filament is being pulled off the spool and the compressive force
acting at this point from the heating nozzle. There are also frictional forces acting from the
bearing and the torque applied at that point creating a net force downward toward the heating
nozzle. Also, a sum of the moments was required in order to optimize the members of the lever
arm to allow the most amount of force on the bearing, with the least amount of spring for to
allow for easy release by the user.
2.6.2 ComponentComparison
There is a total of 63 components in the old design assembly and the new design has 42
components used in its assembly. There is a larger variation of components within the new
design but it only requires about 2/3 of the parts to create the final design for the filament feeder.

23. 23
Filament Feeder
Table 1. Component Comparison
Old Design New Design
4 Washers 1 Washer
20 Small Hex Bolts 2 Clamps
8 Bearings 2 Bearings
1 Double Load Cell 1 Lever Arm
1 Top Housing Plate 1 Top Hosuing Plate
2 Side Plates 2 Support Rods
1 Bottom Plate 1 Bottom Housing Plate
1 Force Gauge 2 Load Cells
1 Grooved Mount 1 Base
2 Axis Rods 1 M6 Pin
9 Medium Hex Bots 7 M6 Button Bolt
2 Motors 1 Motor
2 Threaded Rod (Top) 1 Shoulder Screw
1 Threaded Rod (Housing) 1 Back Housing
4 Nuts (Top) 4 M4 Button Bolt
2 Nuts (Housing) 10 M3 Button Bolt
2 Motor Wheels 1 Motor Wheel
1 Filament Guide
1 Bearing Ring
1 Spring
Total 63 Total 42
Components List

24. 24
Filament Feeder
3 Manufacturing and Assembly
3.1 Components to Manufacture
There are a wide range of parts that are used in the entire assembly. Twelve of these parts must
be manufactured. A complete list of all the manufactured parts and their specifications can be
found in Appendix E.
3.2 Manufacturing Process
Virtually all of the parts required to be created were manufactured via CNC (Computer
Numerical Control) milling and turning machines. Two parts were created in a standard lathe due
to their simplicity. Table 2 shows a list of all the manufacturing processes for each part in the
assembly.
Table 2. Manufacturing Processes
3.3 Fasteners and Bearings
There are a wide variety of fasteners that were needed in order to assemble all the manufactured
parts. A complete list of all these fasteners can be found in Appendix F. There are also two
shielded bearings that were used in this assembly. One bearing being used to clamp down the
filament as it is being driven downward. The other bearing is used in order to allow the lever arm
to freely rotate around a pin connection to the base. These bearings can also be found in
Appendix F.
CNC Mill CNC Lathe Standard Lathe Drill Press Tapping
Base X
Lever X
Back Housing X X X
Top Housing X X X
Bottom Housing X X X
Support Rod X X
Bearing Ring X
Filament Guide X X X
Clamp X X X
Drive Wheel X

25. 25
Filament Feeder
3.4 Instrumentation
There are only two types of instrumentation that are used in the construction of the filament
feeder. The two load cell mentioned earlier that are referenced in Appendix B. These are used
also as a support for the guide system, clamps, and heating nozzle. The other instrumentation is
the stepper motor that is used to drive the filament.
3.5 Assembly
The finally assembly of all the parts, included drilling and tapping some of the components
manually. This is due to the fact that it would be too tedious to change the drills out in the CNC
mill for each operation. Instead, some of the simpler parts, such as the housing components, were
spot drilled in the CNC so they could either be drilled by either the end mill or a drill press. All
the necessary components were then tapped by hand. After this task was completed, the entire
assembly could be assembly with the necessary fasteners, bears, and instrumentation.

26. 26
Filament Feeder
4 Operations Manuel
4.1 Mounting Device
The filament feeder assembly is mounted to the hanging rod in the center of the research printer,
as shown in Figure 23. The rod has a base section with two screws that are designed to be
attached to the two open holes in the top of the filament assembly.
Figure 23. Mounting Rod
4.2 Inserting Filament
In order to insert the filament into the feeder, the filament must be fed through the guide tub until
it is directly above the feeder. With the heating nozzle detached, pull the filament down through
the large open hole at the top of the feeder housing. Then press down on the lever and feed the
filament through the hole in the lever and down through the hole below the bearing and the drive
wheel. Continue to feed the filament through the guide hole until it can be seen at the bottom of
the assembly. Put enough filament through to allow the filament to be inserted into the top
opening of the heating nozzle. Make sure that the two clamps meant for holding the nozzle are
placed into the groove mount. After the filament is firmly inserted into the nozzle, pull on the
lever again and press the nozzle up against the bottom of the feeder guide hole until the two
clamps line up with their screw holes. Insert screws into each clamp and tighten down until the
two clamps are firmly in place. Make sure when releasing the lever, that the filament is pinched
between the drive wheel and the bearing.

27. 27
Filament Feeder
4.3 Replacing Components
Since the filament feeder was designed to be open from the front and sides for easy accessibility,
replacing components is a simple matter. Simply loosen all fasteners that fold a particular
component to the housing and remove the desired component from the assembly. Replace the
necessary component and then make sure to re attach all necessary fasteners in order to make
sure the device operates properly.

28. 28
Filament Feeder
5 Conclusion
5.1 Future Work
5.1.1 Complete Assembly
There is still some work that needs to be done in the assembly process for feeder. A few more
specific screws need to be obtain in order to assemble the housing properly. Due to the fact that a
drill bit was broken into the guide hole of the filament drive base, a larger who was created in
order to remove the pieces. This hole will need to be inserted with Teflon and a hole created to
about 2 mm in diameter that lines up with both the drive wheel and the mounting component at
the bottom of the assembly.
5.1.2 SpoolMount
There also need to be an updated spoon mount for the research printer that reduces the amount of
force required to pull the filament off the spool. This will reduce the amount of tension is in the
filament and reduce the possibility of slipping between the drive wheel and filament during
operation.
5.1.3 ExtensiveTesting
The device needs to be thoroughly tested in order to make sure it always perform adequately
during operation. This also needs to be done in order to determine if the device works for the 15
N load requirement in the objectives for this project.
5.2 Final Observations and Assessments
Due to the fact that the assembly is not quite complete yet, it is hard to make an accurate
conclusion on the device. Most of the components were created without any issues and minimal
work was required in order to get most of the components to assemble together. Further
assembly and testing must be done in order to future out if any future improvements need to be
made or if an entirely new design is necessary. This new design seems more suited to the
required task than the previous design but this still requires validation.

29. 29
Filament Feeder
References
Ref 1: 3D Printing for Beginners. 2016. Illustration 1. Available at:
http://3dprintingforbeginners.com/3d-printing-technology/
Ref 2: 2016. Nozzle Holder. Available at: http://reprap.org/wiki/File:Jhn_nozzle_holder_v5.jpg
Ref 3: Al-Mtlaq, Sarah. 2016. One of many kinds of load cells. Available at:
https://learn.sparkfun.com/tutorials/getting-started-with-load-cells
Ref 4: All About Circuits. 2016. Quarter-Bridge Strain Gauge. Available at:
http://www.allaboutcircuits.com/textbook/direct-current/chpt-9/strain-gauges/
Ref 5: Amazon. 2016. Stepper Motor. Available at: https://www.amazon.com/Stepper-Motor-178-
5oz-1-26Nm-Stepping/dp/B00PNEPF5I
Ref 6: Tridimake. (2013, April 12). Rollerstruder: a filament feeder / driver / extruder. Retrieved
from http://www.tridimake.com/2013/04/rollerstruder-filament-feeder-driver.html
Ref 7: Heywood, Mark. (2013, May 30). Airtripper Extruder Filament Force Sensor -
Introduction. Retrieved from http://airtripper.com/1338/airtripper-extruder-filament-force-
sensor-introduction/

30. 30
Filament Feeder
Appendix A – ABS Material Data Sheet

31. 31
Filament Feeder
Appendix B – Load Cell Specifications

32. 32
Filament Feeder
Appendix C - Stepper Motor Specifications

33. 33
Filament Feeder
Appendix D – Component Drawings and Parts
D-1 – Back Housing

34. 34
Filament Feeder
D-2 – Bottom Housing

35. 35
Filament Feeder
D-3 – Top Housing
D-4 – Base

36. 36
Filament Feeder
D-5 – Lever

37. 37
Filament Feeder
D-6 Filament Guide

38. 38
Filament Feeder
D-7 – Groove Mount Clamp

39. 39
Filament Feeder
D-8 – Support Rod