Table of Contents
Team Vision for Detailed Design Phase
The team used the Detailed Design Phase to refine the plan and design proposed in our Preliminary Detailed Design Review. The work and data obtained during these weeks helped the team establish priorities, which will give us a clear direction to follow during the coming phase of MSD II. The main goals to accomplish during this Detailed Design Phase were the following:
- Design preliminary 3-D models
- CAD Modelling
What does the team plan to accomplish by the Detailed Design Review? The team has set out to work in four main components of the project prior to the Detailed Design Review Testing Testing involving the heating components CAD Modelling A complete CAD model detailing the different subsystems working congruently Technical Requirements Research More research regarding technical aspects of the heating elements and their interactions with the lead screw and barrel is required. Some values we would like to determine are:
- The amount of heating expansion undergone by the lead screw that must be accounted for
- The expected flow rate of the material
- The optimal dimensions for the Hopper Design
Procurement The team will start investigating what items we want to start acquiring in order to move forward in the project. Key items to consider are the stepper motors, microcontrollers and their relevant drivers.
What tasks have been accomplished so far? A preliminary model of the subsystem comprised of a stepper motor, the lead screw and the barrel has been designed.
Programming Stepper: The Arduino library has been explored and we have successfully programmed both a stepper and servo motor. Continued research into Anaheim motor controllers is needed in the future.
Theoretical Study of Lead Screw: The lead screw has been modeled so that known parameters can be used to study flow rate based on stepper motor RPM. Continued troubleshooting and friction drag studies need to be done to complete model.
Die Design: Plastic extrusion and die design techniques have been explored. A rough prototype has been 3-D printed. Roller Wheel Testing: Wheels have been printed and the proof of concept test shows positive results. An updated design and styles of manufacturing the wheels need to be studied in the future.
CAD Model: Sizing hardware to mount the lead screw to the stepper is being explored. Bearings and flange mounts will be needed to mount the motor and barrel to the frame. While the parts do not need to be bought from McMaster, the CAD model uses the 3-D part files from McMaster for sizing purposes.
What tasks remain, and who is the owner of each? The table below shows the tasks that must be complete by the time of the Detailed Design Review. Each member of the team has been assigned a task for which they are responsible.
Notes: Testing of the heating components is scheduled to be completed by Tuesday, November 21. Tim has been working on this task and Adam will support him to make sure it’s complete on time.
What decisions have been made so far? Regarding our options for microcontrollers, the original idea was to explore the methods used to build homemade 3-D printing machines and translate it so that it meets our system’s requirements. However, it is possible that the firmware available (Repetier) will not be able to meet our requirements. The new plan is to explore the system used in coffee roasters. Once we have a good understanding of the methods they use in their heating systems, we will attempt to convert the equipment we have available at the Construct to replicate their methods.
What questions does the team have for the customer and/or guide in order to continue moving forward? Questions for Mike:
- Do we have the necessary equipment at The Construct in order to adapt the mechanism coffee roasters use to our system, or will he have to purchase it?
- What alternatives to the heating cable could we explore in order to address our heating requirements?
- How do we use the PID controller to determine the temperature of the heating cable?
- Where/How do we acquire 3-D printing firmware and is there a possibility of a brief team overview from Mike on the programming of a 3-D printer?
- Does Mike have smaller 8020 to use for the frame? What does he like about our current frame and would he mind if we used smaller pieces to mount our system?
Engineering AnalysisUpdated Requirements For testing purposes, it was decided that motor controllers would be simplified from the original into the following systems:
- Potentiometer: Lead Screw Speed
- PID Controller: Used to set heating temperature
- Arduino Run Stepper Motor: Used to drive roller speed (adjustable)
An upgrade to these features will be further developed once the system achieves basic functionality. The main focus for team is to get the system to extrude a consistent line of filament. Once this goal is achieved, higher level control systems will be implemented in the system.
The main safety requirements we must take into account are those highlighted by the Occupational Safety and Health Administration (OSHA). For our particular project, the main concern is the health hazards posed by the burning of ABS plastic. According to OSHA, “Materials made from and/or containing AN for which objective data is reasonably relied upon to demonstrate that the material is not capable of releasing AN in airborne concentrations in excess of 1 ppm as an eight (8)-hour time-weighted average, under the expected conditions of processing, use, and handling which will cause the greatest possible release.” In addition, we are required to minimize exposure to heating and pinch points as much as possible. This will be dealt with by the use of insulation and safety guards.
The main goal of the Detailed Design Phase was to develop a comprehensive CAD Model of our proposed design.
The footprint of the frame will be 14 x 16 inches with a height of 40 inches. This will require us to cut the current frame we have to these dimensions.
The stepper motor will be attached to the lead screw using a belt and pulley system as seen on a previous design. The reason we are not using an "in-line" system is so that there is more room to access the lead screw, giving us several options for a hopper design.
- Hopper: The hopper will be made of 3-D printed plastic so that it can be both easily made and assembled. It will be sized so that enough recycled/raw material can be stored in the hopper to make an entire spool of filament.
- Steel Trough: An extension of the hopper, this trough is how the material will proceed to the lead screw. It will need to welded together from 3/16" steel as well as welded to the barrel itself. The trough will not be physically attached to the hopper, as the barrel is made to be removable.
- Flange: The flange will allow the barrel assembly to disconnect from the rest of the system. Allowing the barrel and trough to detach will be convenient if there are issues with the lead screw of the system clogging.
Die Design Features
- Thread & Shoulder: The die will thread onto the end of the barrel and have a shoulder so that the user knows when the die is in the proper position. The die will have flats on it so that a wrench can be used to assemble/disassemble.
- Streamlined Design: The 30 degree streamline will eliminate areas of stagnation and will ultimately benefit the quality of the filament being extruded. This should also make the filament less susceptible to burning during the extrusion process. Following standard design heuristics, the land length will be 10 times the diameter of the die.
- Shear & Flow Rate Control: Unlike other designs on the market, both the shear and flow rate of the system will be controlled by the angular velocity of the lead screw. This will be set by hand with a potentiometer and will require testing to observe what speeds work best with certain thermoplastics.
Bill of Material (BOM)
Once the CAD Model has been approved, the team will be able to build a Bill of Materials. Preliminary discussions of what we will need to build our machine have taken place. However, there are some technical items that are yet to be determined, such as the decision regarding our heating system. We will discuss as a team what our best options are for this, as well as other important technical requirements. Based on the feedback from the Detailed Design Review, we will select an option and then we will be on course to produce an accurate Bill of Materials.
Procedure We connected the heating cable to a Solid State Relay and ran a current through it to determine rise in temperature. Conclusions The main takeaways we got from this test are that this heating cable will not be sufficient for our project's needs. While the cable could most likely reach the temperatures that we require (which is about 400 degrees Celsius), it likely doesn't have enough thermal mass to keep the barrel and flowing material hot for continuous use. Going forward We will consider alternate heating solutions such as a cartridge heater or a band heater. These options have been tried and tested on benchmarked rigs. The next steps we need to take regarding our heating system are:
- Purchase and experiment with proposed heating systems.
- Perform tests on the lead screw and barrel to verify theoretical calculations.
- Buy insulation for heat escape tests.
Completing these steps will enable the team to move forward in terms of developing the rest of the system.
Design and FlowchartsThis section should continue to be updated from your systems level design documentation.
- Updated assessment from Preliminary Detailed Design.
- Our Risk Analysis Matrix was updated to consider several risks that were identified through our findings so far.
Design Review MaterialsInclude links to:
- Notes from review
- Action Items
Plans for next phase
Prior to the start of MSD II, the team has taken the time to analyze carefully several aspects of the project so far, regarding what we have done up to this point and what we will need to do moving forward.
What we've done
We sat down as a team and discussed were we stand at this particular point of the project and what we have done so far. Several items, such as team dynamics, team work ethic and the team's level of preparedness were discussed. The full results of this Team self-critique can be found in the document Self-critique