P16603: Glass Cutting Machine: Work Piece Movement
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Customer Handoff & Final Project Documentation

Table of Contents

Team Vision for Phase V

Pugh Matrix: Comparison of Two Concepts

Current Design Proposal

Isometric Views

Front View

Side View

Exploded View

Locking Mechanism

Cylinder Extension and Clevis Connection

Front View
Side View

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To view the Clevis Connection in finer detail, click here.

Linear Bearings and Guide Rail

Proposed Shielding

Up Position
Down Position

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To view the Translating Plate Shielding, short side,in finer detail, click here.

To view the Top Plate Shielding, long side,in finer detail, click here.

To view the Top Plate Shielding, short side,in finer detail, click here.

Overview and System Level Description

Fixture Control Scheme

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To view the System Control Scheme in finer detail, click here.

Word Form Description Workpiece Movement

The workpiece movement fixture has 5 distinct control stages that it goes through in the process of cutting glass. Prior to any cutting the glass ingot will be epoxied to a sacrificial glass piece and the dovetail mount. The first stage of the machine is Setup Mode which includes mounting the workpiece and inputting some specific parameters to the human machine interface (HMI). Then the second stage, Cycle Up, makes sure that all necessary input conditions are met prior to the machine beginning cutting. The third stage, In Cycle Operation, is where all the cutting takes place. Beginning in the In Cycle Operation stage the machine will begin polling the system for a number of different emergency stop conditions. Depending on the type of emergency stop that is triggered the fourth stage, Emergency Stop, will be triggered in one of two ways. The fifth and final stage is the Cycle Down stage and this occurs once cutting has been completed.

Like in the current Glass Fab. system the workpiece that is to be cut first needs to be prepared. This procedure includes using epoxy to affix all the glass ingot pieces together and then to a sacrificial glass piece. The sacrificial glass piece also needs to attached to the dovetail mount. Unlike current Glass Fab. procedures the workpiece will need to be weighed and the sacrificial glass piece measured for thickness. The weight will be an input to the HMI that will allow the pneumatic counterbalance cylinders to calibrate to a proper offsetting force. The sacrificial glass thickness will also be input to the HMI so that the machine will know exactly how far down it needs to travel in order to do a full cut.

The first main stage of cutting is Setup Mode. During this stage the HMI will be looking for multiple inputs including the workpiece weight, the sacrificial glass thickness, and whether the operator wants to set a specific feed rate or time for the cut. During this stage the workpiece locking mechanism will be disengaged. This will allow the workpiece to be mounted to the fixture. Once mounted the HMI will be used to engage the workpiece locking mechanism. The last part of this stage will see the pneumatic counterbalance cylinders brought up to pressure to offset the weight of the workpiece.

The second stage of cutting is Cycle Up Mode. During this stage the system will look at readings from different sensors to determine if the system is indeed ready for cutting. These readings include if the machine is powered on, if the workpiece is locked into place, if the safety interlocks are engaged, and if the pressure on the cylinders is correct. If any of these conditions are not met then the machine will indicate what is wrong and go back to Setup Mode. In Setup Mode changes to the machine can be made to ensure that Cycle Up Mode is completed properly.

The third stage of cutting is In Cycle Operation. This is the stage where all the cutting actually takes place. The workpiece will be fed down towards the wires at a user selected rate. Once the wires contact the wires an indication will be given on the HMI. The feed rate will still be able to be adjusted by user input to ensure the proper bow in the cutting wires. The workpiece will be fed through the wires at a user selected rate until the wires start cutting into the sacrificial glass piece. The machine will determine if the sacrificial glass piece has been contacted by knowing the sacrificial glass thickness (user input) and the length that the actuator has moved throughout the cutting process. Once cutting has finished an indication will be given on the HMI. The workpiece will then be retracted either at a manual or automatically selected rate until reaching home position.

The fourth stage of cutting is the Emergency Stop. This stage initially begins during In Cycle Operation. The fixture will begin polling for a number of different conditions that would trigger an emergency stop. Pneumatics losing pressure, compromising safety interlocks, triggering overtravel switches, the motor taking on too much current, and wires breaking would cause the machine to engage an immediate emergency stop. During an immediate stop all power to the motors is immediately cut, breaks are engaged, and the machine will go into emergency fault mode and require a reset. An immediate stop is not ideal as cutting all power immediately could potentially break motors, but this is necessary to keep operators safe when certain things occur. Alternatively a controlled emergency stop would occur if there are AC drive failures, power loss, incorrect feedback about workpiece movement, or incorrect weight parameters. This controlled stop would slowly bring the system to a halt without potentially breaking any parts of the system. In these cases the system does not need to immediately halt because there is no danger being posed to the operator.

The final stage of cutting is the Cycle Down stage. During this stage the locking mechanism on the workpiece is disengaged and the workpiece is unloaded. The HMI displays that the machine is no longer in cycle and the cutting process has been finished. The machine can then be shut down.

To view the word form description of the Workpiece Movement control scheme, click here.

Word Form Description Pneumatic Counterbalance

The original workpiece movement conceptual design utilized a single linear actuator. The special heavy-duty actuator that was selected would allow for the entire weight of the workpiece to be moved at the necessary speed. However, due to mechanical building constraints and budget concerns, the design was deemed to not be feasible.

The new design utilizes a pneumatic counterbalance system to offset most of the weight of the workpiece and other translating structural weight. The design still utilizes a single, smaller centrally mounted electric cylinder to obtain the slow feed rates. The system makes use of four pneumatic cylinders mounted on the top structural plate. When air-pressure is applied to the cylinders they apply a force opposite that of the gravitational force of all the hanging weight. The targeted net force between the upward force from the electric actuator and the downward force from the hanging weights is approximately 50 lbs. This would cause the electric cylinder rod to be in compression. The air pressure acting on the pneumatic cylinders would then be maintained through the entirety of the cutting process and thus the electric cylinder would always be in compression. Instead of using a large electric cylinder to hold up the workpiece, this method utilizes a smaller electric cylinder to push against the workpiece. This massively reduces the load requirements needed for the electric cylinder.

It was determined that the pneumatic cylinders would initially be in conjunction with only a single release valve and regulator (see Pugh Matrix). It was the most simple and cost effective approach. Not only would it be easier to construct, it would also be easiest option for controlling the system. The valve/regulator would allow for the pneumatic cylinders to be calibrated to always be applying a constant vertical force to offset the majority of the mass of the system as well as a preload on the electric actuator. More release valves could always be added at a later date if it was found that the weight distribution differed between pneumatic cylinders warranted it. One possible example in which more independent valves would be superior to a single valve would be the case in which the weight of the workpiece was concentrated on one side of the system - rather than being centered about the electric actuator - and the pneumatic cylinders would not need to all be at the same pressure.

The pneumatic cylinders could also be used to increase the speed of workpiece movement once cutting was finished. Since the weight is distributed evenly between four pneumatic cylinders they can move the fixture up and down as fast as an operator would want it to. In fact, the pneumatic cylinders were sized such that they could be used to help lift the guide rolls out if needed.

To view the word form description of the pneumatic counterbalance system, click here.

Structural Subsystem

Vertical Struts

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Top Plate

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Linear Rails and Carriages

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Translating Plate

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Fixture Mount

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Dovetail

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Mounting Plate

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L-Bracket

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Counterbalance Subsystem

Pneumatic Counterbalance Cylinders

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Pneumatic Regulator and Valve

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Other

Locking Subsystem

Pneumatic Locking Cylinder

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Locking Cylinder Brackets

Springs

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Bumper

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Other

Translation Subsystem

Electric Cylinder Assembly

Electric Cylinder

EXLKX90-0450-05NM-P10EMB Exlar Actuator (Parallel Mount)

Mounting Plate

AB Motor

A-BMPL-B310P-MJ74AA MP-Series MPL 480V AC

public/Photo Gallery/AB Motor 1.PNG

Gear Reducer

APXAB090A100S2P2/MPLB310

Overtravel Switch

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BOM

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Engineering Standards Utilized

Final Project Documentation

Technical Paper

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Team Poster

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Knowledge Transfer Documentation

Design Selection

Actuator Selection

Fixture Mount

Linear Bearings / Linear Rails

Locking Mechanism

Parts and Methods from Glass Fab

PLC Selection

Pneumatic Counterbalance

Top Plate

Translating Plate

Vertical Struts

Plans for Wrap-up

Recommendations for Future Work

Individual Contributions


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