P19603: Rod Feeding Mechanism
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Systems Design

Table of Contents

System Design Review Agenda

Team Vision for System-Level Design Phase

What did we hope to achieve?:

What did we actually achieve?:

What didn't we finish?:

Updated Engineering Requirements

After phase 1 we updated the engineering requirements. The live document is here.

Functional Decomposition

DecompTree FunctionalDecomp

Benchmarking

Because this is a clean-sheet design project, benchmarking was primarily used to assist with concept generation later in the phase by finding industrial precedent.
Benchmarking of wire feeding mechanisms

Benchmarking of wire feeding mechanisms

Benchmarking of rod hoppers

Benchmarking of rod hoppers

Benchmarking of rod magazines

Benchmarking of rod magazines

Benchmarking of power supplies

Benchmarking of power supplies

Morphological Chart and Concept Development

Morphological Chart

Morphological Chart

System Concepts

System Concepts

Concept Selection

Detailed System Concepts

Detailed System Concepts

Pugh Chart Iteration #1

Pugh Chart Iteration #1

Pugh Chart Iteration #2

Pugh Chart Iteration #2

Feasibility: Prototyping, Analysis, Simulation

Listed here are some questions that we answered to help solidify the feasible of our concept:

To answer this, calipers were used to measure the opening at the top of the micro-crucible. The smallest limiting dimension was measured because of the oddly shaped opening. Below is a diagram showing where the measurement was taken. The opening was measure to be 0.2750 inches wide. This will allow us to satisfy our engineering requirements of feeding 1/8" and 1/16" rods into the crucible.

Phase 1:

To test whether the vertical hopper concept was sound and wouldn't jam, we created a prototype using a 3D printed funnel, a 1" PVC pipe as the hopper, and a cell phone as the agitator. The mockup was mounted to a counter and 6" steel rods were placed inside and the agitator activated. A dremel was used to smooth the inside of the funnel and some lubrication was applied.

The first prototype failed, rods were jamming in the bottom of the funnel.

A video of the initial test can be seen here

public/Systems Level Design Documents/prototypefunneljam.jpg

To determine whether this failed because of the particular design of the prototype or because the hopper concept was unsound, we decided to test again with different funnel angles.

Phase 2:

To improve on our first prototype, we decided to test many different angles instead of just one. The funnels were 3D printed with 60, 50, 40, and 20 degree slopes. The dremel left the inside surface of our first prototype very rough, so we decided to leave the surface untouched. We also created a custom agitator which vibrated more violently than the phone used in our first prototype.

Setup Funnels Agitator

public/Systems Level Design Documents/HopperPrototype.jpg

This setup proved to be very successful. The more shallow angles also worked much better than the 60 and 50 degree funnels. The rods were able to drop out of the funnel consecutively without gaps between them.

We also tested rods of two different finish qualities. One had rough cut ends with sharp points and burrs, the other had smoother ends with all burrs removed. The smooth rods flowed out of the funnel very quickly. The rough rods flowed out considerably slower than the smooth rods, however it still functioned adequately. The funnel jammed if the ends of the rod were bent or severely misshapen. The results of time trials are shown below.

public/Systems Level Design Documents/FunnelAngleTest.png

20 Degree Rough Trial Video

20 Degree Smooth Trial Video

The power/voltage requirements for our design can be accomplished by two ways; either using the power supply from the Vader systems itself or using an external DC voltage supply. Below is a diagram of what the circuit would be if the power was taken straight from the Vader using two DC/DC converters to step down the voltage from 200V to 3.3V to power the MSP430 and the sensors required for the design. This solution is not financially practical due to the prices for both the VI-263-CV and the NDY2403C. The price for the VI-263-CV 200V/24V DC/DC converter is $240.64 and the price for the 24V/3.3V DC/DC converter is $15.91. This solution is impractical due to the financial constraints when compared to an external DC power supply that can be obtained by the RIT Electrical Engineering Department for free.

Power Supply

Originally the 1x1x3' size constraint was meant as a place rough estimate place holder. This feasibility analysis is meant to solidify a size constraint. The volume inside of the Vader machine and above the print head was measured. It was determined that a rod feeder should fit comfortably inside a volume 2' wide, 1.5' deep, and 3' tall.

With parameters for rod types specified for the design (12” long and 1/8” and 1/16” in diameter), research into industrial uses for magazines with metal rods was conducted to determine if this was feasible. The Ranger 112, FMB Micromag, and Tryton 112 (shown in order from left to right) are magazine designs used for storing and feeding metal rods. All three magazines hold rods with diameters less than 1/16” and hold bars that are longer than 12” (up to 2 meters). The Ranger 112 is a scroll-fed magazine while the Tryton 112 is a barrel loading magazine. With precedent in industry, it is feasible for our design of a magazine to hold the rod types we intend to use.

Magazines

As several of our designs use a motor to hold the rods in a hopper, we wanted to know about how much torque a motor would need to output to hold the rods in a resting position. For this worst case scenario all the force from the weight of steel rods was placed at a 90 degree angle of the arm. A factor 3.0 factor of safety was used to ensure the speced motor will not be over loaded. With the number of rods shown in the table below, and a 1" arm .29 Nm of torque would be needed. This is reasonably achievable, for example many common drills can output well over ~40 Nm of torque.

Expenses Cost
Rod stock for testing $150
Microcontroller & Electronics $350
Housing & Attachments $700
Prototyping & Disposable parts $200
Imagine RIT & Display $100
Risk & Breakage $375 (25% of above)
Total $1875

Systems Architecture

The proposed design is that of a vertical hopper with an agitator supplying rods into a set of feed rollers similar to a welding wire feeder. The system is controlled by a microcontroller (MSP 430). A proximity sensor checks the level of the hopper, a photogate determines when the agitator should be active, and a logic loop detects jams. A vibration isolator prevents the agitator from impacting the Vader and a drop catch at the bottom of the feed tube maintains constant control of the rods.
CAD mockup of design

CAD mockup of design

Vertical Hopper Block Diagram

Vertical Hopper Block Diagram

Risk Assessment

The risk assessment was reviewed and edited; a mitigation plan for each risk was drafted and is shown in the image below. The live document for Risk Assessment can be found here:Risk Assessment

The team is concurrently designing a magazine based storage alternative as part of a risk mitigation plan, in case the hopper fails further testing.

Risk Mitigation Plan

Risk Mitigation Plan

Alternate Magazine Concept Alternate Magazine Concept

Vader Printhead

Preliminary Test Plan

Below shows our first cut at creating plans to test each of our engineering requirements. This is a draft, to make sure we that we can envision how each can be tested, and detail will be added as we get closer to MSD 2. The live document can be found here: Test Plan

Preliminary Test Plan

Preliminary Test Plan

Plans for next phase

Team Vision for Phase 3:

At the end of phase 3 the team hopes to have fully designed the highest risk subsystem of the device, with first cut designs of all other subsystems, and draft design output created. We want to have performed further feasibility study and prototyping to confirm that our proposed design will definitely be able to fulfill the requirements, or, failing that, to have successfully pivoted to our back up plan. We want to have spoken with an expert in vibrations engineering and from that meeting have a solution for vibration isolation in place. We will have a detailed project schedule for the rest of the MSD 1 course and a partial draft schedule in place for MSD 2.

Updated Phase 3 Plan:

Phase 3 project schedule

Phase 3 project schedule

Three Week Plans:

James Boyers: Here.

Mark Brown: Here.

Connor Connaughton: Here.

Mathias Mereles: Here.

Josh Hilton: Here.

Ryan Hollender: Here.


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