P20652: 3D Concrete Printer
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Systems Design

Table of Contents

Team Vision for System-Level Design Phase

We plan to formulate a system architecture while putting forth the best effort to complete tasks correctly the first time. Efficient use of people, resources and time will allow the team to improve performance.

A functional decomposition was created in order to determine the functions that the 3D concrete printer will need to achieve. Other currently available 3D concrete printers were benchmarked. Next, concepts were generated to complete the functions generated from the functional decomposition. We selected concepts that will be implemented in the final solution. Block diagrams were created to detail how the 3D concrete printer will work.

Systems Design Review Materials

Based upon feedback from our Problem Definition Design Review, we will be presenting directly from the EDGE website. By doing this, full documents can be reviewed by the Guide, Customer, and audience as opposed to excerpts of documents or links out of a presentation as found in PowerPoints. The presentation agenda and pre-read can be found here. In addition, the Customer and Guide were also linked to the systems design page prior to the presentation.

Functional Decomposition

The first step in a system level design is to determine what the resulting product or service needs to be able to do, and how it will achieve that. For team P20652, this includes the functions of a 3D concrete printer.
Functional Decomposition.

Functional Decomposition.

Systems Architecture

To represent the system architecture of the 3D printer, block diagrams were used. Three separate block diagrams were created with three different levels of detail.
Simple Block Diagram of Design.

Simple Block Diagram of Design.

More Detailed Block Diagram of Design.

More Detailed Block Diagram of Design.

More Detailed Block Diagram of Design.

More Detailed Block Diagram of Design.

Benchmarking

In order to understand and create a realistic scope for our 3D printer, research was done into other 3D concrete printing solutions. Since the mixture of the printed material as well as the machine are within the scope of our project, separate benchmarking documents were generated for each category.

Machine benchmarking was done based on many commercially available and research phase 3D printers. The excel document containing the complete machine benchmarking document can be found here.

Latest Benchmarking of Machine.

Latest Benchmarking of Machine.

Mixture benchmarking was done based upon previous 3D concrete printing projects with publicly available mixture information. Additionally, there are some detailed research papers done on the optimal concrete for 3D printing. The excel document containing the complete mixture benchmarking documents can be found here.

Latest Benchmarking of Mixture.

Latest Benchmarking of Mixture.

Concept Development and Morphological Chart

Concept development was done through brainstorming and research. Several concepts were generated for a variety of machine subsystems. Potential concepts for 8 categories were collected into a Morphological Chart. The Morphological Chart is shown below.

Latest Morphological Chart

Latest Morphological Chart

General Feasibility: Prototyping, Analysis, Simulation

These documents pertain to feasibility analyses performed prior to the concept selection tasks began:
Controller board
the analysis is provided here.
Edge detection system
the analysis is provided here.
Concrete mixing systems
the analysis is provided here.

Focused Feasibility: Prototyping, Analysis, Simulation

After determining the categories of components to be used by our design, a feasibility analysis was performed for each category.

Interface

We will be using a computer software such as RepRap Firmware as our interface. Most RIT engineering students have knowledge of how to use 3D CAD software. From the software, CAD files are converted to an STL file format. After selecting a layer depth, the printing path for each layer is generated to create a G Code file for printing. Proof can be found in Mix Design and Fresh Properties for High-Performance Printing Concrete or in Lund University 3D concrete Mobile Print.
 Model of how user will interface with printer.

Model of how user will interface with printer.

Mixer

The printer will not have an integrated mixer; the material fed to the printer will be pre-mixed, according to a procedure to be developed later in the project timeline.

Controller

Feasibility for the controller was fairly simple. We needed a controller board that would be able to handle many stepper motors and that can easily interface with 3D printing software. Arduinos have a library for translating g-code files to physical movement which can be found here. However, the Arduino lacks a lot of the stepper motor driver features that are required for stepper motor functionality.

The company Duet3D provides reasonably priced microcontrollers that include stepper drivers as well as an open source software package. For these reasons, it was determined that a Duet3D microcontroller solution would be feasible for our 3D printer.

Extruder Force Generation

The chosen concept for the extruder force generation was the auger. The purpose of the auger is to create enough force for the mixture to go through the nozzle. This concept is relatively cheap, and has been proved to work. For proof, visit the Lund University 3D concrete Mobile Print.

Material Delivery System to Extruder

The concept selection for the material delivery system to extruder was the auger, the same component selected in the extruder force generation. These two concepts relate to each other as one makes use of the other to generate the delivery of the mix (concrete).

Nozzle Design

The selected nozzle will be a square nozzle shape. It has been proved to be the most stable shape for Concrete printing, as it has been documented with fewer accidents than circular shapes. Documentation for this study is found in, Development of 3D Concrete Printing, which is a thesis for the degree of Master of Science in Building Technology.

Nozzle Material

The chosen material for the nozzle will be metal. The nozzle must be able to resist pressure build-up and at the same time, be lightweight. Also, as we benchmarked, most products used this material as a source for nozzle design. Proof of this can be found in Lund University 3D Concrete mobile Print , or the article A study into the effect of different nozzle shapes and Fiber-Reinforcement in 3D Printed Mortar.

Structure Material

A feasibility analysis was performed on the structure material to be used. The calculations assume a design solution (8020 material), but it is a good starting point for estimating the load the machine will need to support.

Concept Selection

Criteria Description Engineering Requirements Addressed
Easy to Integrate The ease with which the component can be incorporated into the printer design. ER1, 4
Repairability The ease with which a component can be repaired after it has been integrated into the system. Implicit to Design
Manufacturability The ease with which a component can be fabricated by our team. Implicit to Design
Budget Will this component cost a disproportionate amount of money? ER 21, 22
Lightweight Components Low weight components will reduce wear and tear on motors. ER15, 16, 17, 18
Flexibility The versatility of components and ability for components to interface together. ER13, 14
Rapid R&D Product allows for fast setup and use. ER3
Durability How long will the component last? ER2, 3, 7, 8, 12
Prevalence How supported is this solution? Will the development team be able to find support using forums or manuals? ER19
Safe Does this component cause risk to other components or the user? ER19, 20, 24, 25, 26, 27
Easy to Program How easy is this component to integrate in software? ER13, 14
User Accessibility How easy is this component for the end user to use? ER5, 10
Simplicity Is the component more simple or more complicated? Implicit to Design

Pugh Charts

For each category from the Morphological Chart, a Pugh chart was created. Pugh charts were used to decide which concepts to pursue in each category. Below, the chosen concept for each category is held as a datum while the remaining concepts are compared. A PDF version of the entire Pugh chart is also included in a link.

Interface

The interface is how the user will interact with the 3D printer. Primary decision factors for the interface were price, ease of executing a print file, and interfaces of 3D printers. Entire Interface Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Mixer

From the Pugh chart results, a mixer was decided to be an unnecessary component of the printer. However, the way in which the concrete is mixed was still considered. The mixing process comes down to what is available to the user. Rotating concrete drums are the construction industry standard way that concrete is mixed, but hand mixing is viable for smaller batches. Entire Mixer Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Controller

There are many potential micro-controller options for 3D printing applications. Essentially, the micro-controller has to move 3-6 stepper motors. An Arduino is suitable for this purpose, however there are controllers specific to large scale 3D printing such as the Duet 2. Entire Controller Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Extruder Force Generation

The way in which the concrete is extruded determines the uniformity of the extrusion. A system for generating constant pressure while also being easy to clean and mechanically simple was chosen. Entire Extruder Force Generation Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Material Delivery System to Extruder

The material needs to be delivered to the extrusion head. Other teams have relied upon simple gravity from a hopper to feed concrete to their print head, but the concrete mixture was too thick and did feed the mixture in a smooth constant manner. For this reason, a mechanical solution is being explored to augment the hopper system. Entire Material Delivery System to Extruder Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Nozzle Design

The nozzle shape determines the characteristics of the extruded material. A square shape has been proven to clog less and create a more uniform shape. Entire Nozzle Design Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Nozzle Material

The nozzle material determines the durability and robustness of the nozzle. Entire Nozzle Material Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Structure Material

The structure material impacts how modifiable the machine is and the rigidity of the structure. Entire Structure Material Pugh Chart
Latest Datum Pugh Chart for Component

Latest Datum Pugh Chart for Component

Final Concept Selection and Morphological Chart

The final concept selection is detailed in the updated morphological chart. A concept highlighted in green is the primary concept, yellow is the secondary concept, and red is the tertiary concept.
Morphological Chart with selected components.

Morphological Chart with selected components.

Risk Assessment

The Risk Management document for this phase can be found here. A preview png can be found below. For the final Risk Management and Progress document, see this link.
Risk Management Document for Systems Design Review.

Risk Management Document for Systems Design Review.

Preliminary Test Plan

A test plan was designed for several critical Engineering Requirements and prototypes. The latest documents are found below.

Test Plan Description

Test Plan System Design Review

Controller_Driver_Motor Circuit Test Plan

Nozzle Design Test Plan

Nozzle Material Test Plan

Printhead Structures_Auger Test Plan

Test Plan Example (Cement Mixer)

Plans for Next Phase

As a team, we would like to have selected exact components for the detailed design review. The Gantt chart below shows a plan of tasks that need to be completed during the next phase and the tentative schedule for each task. For the final Schedule Management document, see this link.
Gantt Chart of Preliminary Detailed Design Phase.

Gantt Chart of Preliminary Detailed Design Phase.

The three week plans for the system level design review are found below.

Alex K.

Alex P.

Amiee

Chad

Joe

Mary

Nick

Seth


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