P16601: Glass Cutting Machine:Guide Rollers
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Systems Design

Table of Contents

Phase 2: Systems Design is considered the first major step to "engineering" a final design. This is the bridge between design concepts and detailed engineering designs. It details the functions of your system, concept generation, feasibility analysis, and more, all of which is detailed below:

Team Vision for System-Level Design Phase

Key Questions for This Phase

1. Modeling off of the DS264 or unique design? - still open

2. How many rollers are going to be used? - still open

3. Where in the cutting process is the most power being used? - still open

4. How powerful do we need the motors to be? - still open

5. What material will the guide rollers be made of? - still open

There are still many questions that need to be answered after our team gets the opportunity to visit our customer to answer additional questions and conduct feasibility testing.

Functional Decomposition

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Engineering Requirements Mapping

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The live document can be found here

Morphological Chart

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The live document can be found here

Selection Criteria

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Pugh Chart

Iteration One

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Iteration Two

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The live document can be found here

System Design

Top Design

 Outside View

Outside View

 Cutaway View

Cutaway View

Selected Design

Selected Design

Alternative Designs

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Function Considerations

Select Pitch

Jumpable pitches are ideal but if this is not possible the next best case would be to use different rollers for each

Align Rollers

Pins are the easiest and used industry wide. Possibly combine with “V”-slot and bearing to make changing rollers easy for operator. We believe that precise machining will be necessary to ensure alignment. We want to see how it is currently placed on the machine before making a final decision

Cool Wire

Keep rollers hollow for future implementation of a cooling system. We do not feel it is necessary to worry about this right now (future project). We would like to see how the DS264 currently cools the system before making a final decision.

Protective Shielding

Plexiglass will allow us to see inside the system while it is running and provides an adequate amount of safety for this standalone fixture.

Mount Rollers

Bolts are simple and used widely in industry. They go hand-in-hand with the pin alignment. We want to see how it is currently placed on the machine before making a final decision

Attach/Interface Rollers and Motors

Direct drive is the simple, cheap, and reliable option. This option provides all of the necessary torque and control that is required while preventing slippage.

Control Speed of Motor

VFD because they are simple to use and are used widely in industry.

Synchronize Rollers

One motor is the front-runner because it prevents any chance of motors getting out of sync and is a cheaper option. We want to continue more research before making a final decision to optimize the solution.

The live document can be found here

Research and Benchmarking

A live document detailing the references we have used throughout this phase can be found here

A detailed benchmarking document which shows tables of specifications, links to additional information, and more can be found here

Feasibility Analysis

Vibration Stability

How sensitive are the rollers to unbalance instabilities and vibrations?

The maximum frequency ratio for the DS264 is much less than 1. Therefore, assuming a rotating, unbalanced system model, for essentially all operating conditions the output excitation will be reduced from input excitation due to unbalanced mass.

To gain more quantitative information about output excitation and force transmissibility, information about the damping parameter of the system must be measured or estimated.

We also need to measure and gain more data about how the roller is mounted and the dimensions of the mounting structures to get a better idea of how accurate this model is.

Assuming the spring constant can be estimated as a simply supported circular cross section beam, the expression for natural frequency of the roller is calculated and shown below.

Natural Frequency Equation

Natural Frequency Equation

L is the length of the mounting rod, R is the radius of the mounting rod, M is the mass of the roller and mounting rod, E is the modulus of elasticity of the mounting rod

This allows us to see the relationship between parameters that we could potentially change and its impact on the natural frequency. We want the natural frequency to remain high relative to the operating frequencies to maintain reduction of response.

The key final results are as follows:

Final Results

Final Results

The hand calculations completed in log books can be found here: Part 1 and Part 2

The detailed document can be found here

Roller Torque Derivations

How much torque is necessary to turn the guide rollers? What variables/forces need to be accounted for and which ones can be ignored?
Forces Diagram

Forces Diagram

Torque Applied Derivation

Torque Applied Derivation

Calculations using Torque Derivation

Calculations using Torque Derivation

The first calculation is an approximation of the machines maximum torque needed. Each guide roller motor is rated at 500 Nm so surprisingly the equation makes some sense. Calculation 1 is essentially a test of the equations validity and it seems to hold up. However, 8000 loops is impossible when we take into account the thickness of the wire; 4000 loops is more reasonable. Calculation 1 would then be about 266 Nm, which may mean that some of the coefficients of friction are slightly greater in reality. Calculation 2 removes wire loops by a factor of 10 and the rolling friction drops significantly along with the other terms by a factor of 10. Doing 30 cuts with the DS 264 only requires about 36 Nm out of the 500 Nm available according to this derivation, so clearly this is the reason we are designing a smaller machine (calculation 3). Also, bearing friction, rolling resistance, and cutting friction are now negligible in comparison to the inertia of the rollers.

Calculation 4 takes a roller that would fit 9” ingot diameters (same design as DS 264 but scaled down with same length) with 30 cuts and the same maximum wire cutting speed. The result is very small and will be smaller considering the new rollers will not be the same length as the current design. 9" is about 230 mm. However, to maintain the maximum wire speed of 15 m/s, the roller RPM must increase to about 1245. Three-phase motors usually have a standard RPM values such as 3600, 2400, and 1200. Therefore, to take advantage of those motor standards, a 240 mm (for example) guide roller could be built in a two-roller system.

Based just on the torque analysis, 10 Nm would probably be enough for each roller. Then, the horsepower required for a torque of 10 Nm at 1200 RPM can be approximated as T*N/5250, or about 2-3 Hp.

The detailed document can be found here

Inertia, Power, and Gear Ratio

Is it feasible to directly drive the rollers or should we incorporate a gear ratio? How does switching to a three roller system affect this?

Key Assumptions

Knowns:

Key Results:

The hand calculations completed in log books can be found here: Part 1, Part 2, Part 3, Part 4

The detailed document can be found here

Roller Inertia Reduction

How much can the team reduce inertia by altering the dimensions of the rollers?

Key Assumptions:

Roller Geometry

Roller Geometry

Starting with the equation of inertia of a rotating shaft, the equation of inertia on the rollers was calculated using simple derivations found in the document attached below. The final equation mathematically modeling the inertia in the rollers is shown below:

Moment of Inertia Equation

Moment of Inertia Equation

The equation was used to populate a spreadsheet that changed the outer diameter and thickness of the rollers. The results are shown in the plot below.

Inertia Calculation Results

Inertia Calculation Results

Overall, if we can reduce the diameter and/or thickness at all, it will drastically reduce the inertia of the rollers. This makes sense given that the diameter is raised to the fourth power in the inertia equation. Decreasing the roller inertia would decrease the torque required to turn the rollers, which would in turn decrease the load the motor experiences as well as the power consumption to accelerate and decelerate the motors. This is desirable as it would decrease a major source of power consumption and the overall cost of running the machine. If smaller rollers are feasible, this could change the number of rollers in our system because we may need more rollers (3 or 4) to accommodate the ingot diameter size. The downside to decreasing the size of the rollers is that there will be an increase in stress that the rollers have to resist. The rollers may also be more difficult to control with less inertia, therefore requiring more precise motors. All of this will be quantified moving forward.

Moving forward, we need to model the stress on the rollers due to wrapped wire. This will allow us to compare the competing designs to minimize roller inertia while ensuring the rollers will hold up to the compressive force of wire tension. We will also analyze the effects of inertia on the ability of the rollers to move together. We will verify the roller thickness during the team visit to our customer

The detailed document can be found here

Roller Configuration

What is the optimal roller configuration relative to cost?

Four Rollers

Four Rollers

Two Rollers

Two Rollers

Three Rollers

Three Rollers

THREE ROLLERS VERSUS FOUR ROLLERS

The minimum diameter of the rollers is limited, so the cost of four rollers at that minimum diameter is greater than the cost of three rollers. Four rollers also involve more parts to buy and potentially repair. In current designs, four roller machines are used to increase production. This is unnecessary for our machine because we do not need to increase production.

TWO ROLLERS VERSUS THREE ROLLERS

Three rollers will mean that each roller can have a smaller diameter and ultimately a lower inertia value, making them easier to turn. This will draw less power from the motors. Additionally, power is used to fight friction during cutting which will be minimized based on surface area. The cost per roller for the two 320 millimeter diameter roller configuration will be multiplied by two rollers. The cost per roller for the three roller configuration is to be determined based on the minimized diameter multiplied by three total rollers. This analysis will be completed after sourcing and parts become available.

Moving forward, the equation below will be used to optimize the cost per roller

Configuration Cost Equation

Configuration Cost Equation

Cinitial is the inital roller cost, Xrollers is equal to the number of rollers, freplacement is equal to the frequency of roller replacement, Pconsumption is the power consumed during startup and the cutting process, and Ckw is equal to the cost of power per kilowatt.

Before the configuration of rollers can be determined by minimizing cost, a few questions need to be answered.

To answer these questions we will try to measure the amperage of the motor on the DS264 to determine where the most power is used.

The detailed document can be found here

Heat Generation

How much heat is generated in the system and is it harmful?
Motor Efficiency Standards

Motor Efficiency Standards

Based on the NEMA standards, the original 37 kW motor puts approximate 32.7 kW of energy in to the system. We are assuming that this energy is turned into heat that needs to be dissipated through the system at some point during the cutting process.

We are assuming that most of the cooling needed for the wire specifically is managed by the slurry. We feel comfortable making this assumption because no additional cooling system is currently in place to manage the heat in the brass coated wire.

The remainder of the heat is dissipated through the roller. There is currently a cooling system going through the center of the roller that is unfamiliar to the team. Assuming the heat generated by friction is negligible relative to the heat generated by the motor, we can attempt to calculate the amount of heat in the system.

To complete this analysis, the following information is still needed:

The detailed document can be found here

Motor Power

How much power can be reduced on the motors?

The current Meyer Burger DS264 uses two motors rated at 47 kW. The nameplate is shown below:

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From the face plate we gather that the motor is 47 kW.

From previous calculations for power we found that at 900 RPM there is a required power of 2.9 kW (3.9 Hp). This yields a torque 30.725 N.

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A 3 phase, 3 Hp motor at 1800 RPM yields a torque of 1.175 N at 1800 which equals 2116 W. With two motors the total is 4 kW which is 4.25% power of the original design.

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The 4.25% power of the original system does not include the other units that use power. Form the nameplate the Meyer Burger is listed for 135 kW instead of the 94 kW. This means that there are 40 kW unaccounted for. The efficiency of the machine may be even better than the 4.25% listed above.

Calculations for the amount of time it takes to cut the volume of ingots for the job versus the energy still needs to be computed.

The detailed document can be found here

Risk Assessment

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The live document can be found here

Plans for next phase

Deliverable Completion Plan

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The live document can be found here

Project Plan

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The live document can be found here

Key Questions For Next Phase

1. Modeling off of DS264 or using a unique design?

2. How many rollers are going to be used and their approximate size?

3. Where in the cutting process is the most power being used?

4. How powerful do the motors need to be?

5. What material will the guide rollers be made of?

Questions For Our Customer

Want to Ask

Want to See

Want to Measure and How

Things to Think About

The live document can be found here

Engineering Roles For Next Phase

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The live document can be found here

Individual Contributions

This document was removed due to proprietary information. If you would like to request a copy, please email a team member. Contact information can be found on the home page.


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