Electrosurgical Life-test Fixture

Team E.L.F. Design Review

Mechanical Engineers

Mary Hamann

Brad Watson

Naomi Sanders

Electrical Engineers

Tony Giedl

Jim Michalk

Design Review Outline

•Background•Problem Definition•Project Needs•Flow Diagram•Components

FrameWand MountPressure ControlAngle AdjustmentTissue Holder

•Integrated Design

Background

ArthroCare manufactures a device used in surgery for the removal of tissue. This tool is more precise than previous methods of tissue removal and minimizes damage to healthy tissue. Currently, technicians have to hand-test a certain number of Arthro-Wands out of every new batch that is manufactured to ensure the life of each device. This is a very time and labor intensive task. ArthroCare would like an apparatus that is capable of mechanically testing their Arthro-Wands. This will cut down on labor costs of the technicians and allow more wands to be manufactured and tested.

Problem Definition

The purpose of this project is to develop a fixture that will automatically test Arthro-Wands. The device has to mimic the condition that the wand will observe during an actual surgery in order to ensure the reliability of the product.

Project Needs

•Downsize the footprint of the apparatus (roughly 1/4

original size)

•Easy reproducibility

•Short set-up time

•System completes one lifetime without traveling over used

tissue

•Capable of accommodating a variety of handle sizes

•Adjustable to a variety of angles and positions

Flow Diagram

Setup

Tissue Fixture Wand

Input

Time Speed

Run Fixture

Wand Oscillation Increment

Control Motion

Frame Designs

Concept #1 – X-Y Gantry Assembly

Concept #2 – Last Years Design

Concept #3 - “Toy Grabber”

Guide Rods

Lead Screws

Sliders

Wand Mount

Frame Concept #1X-Y Gantry Assembly

linear motion video

Advantages:

•Smaller Footprint than last years, due to the stationary tray

•Could Eliminate Scotch Yoke

•Stationary Tray and one moving assembly

Disadvantages:

•Vertical Lead Screw located to one side creates a torque on the top lead screw assembly

•Frequent direction change on the stepper motors

•Indexing of the wand is coupled with oscillatory motion

This Assembly has both the horizontal and vertical linear motion located on the top of the frame. The sinusoidal motion can be created by either an improved scotch yoke or the vertical linear motion lead screw.

Frame Concept #2Last Years Design

Advantages:

•Horizontal and vertical motion are de-coupled

•No moment created from off-centered lead screw

•Slides and Frame material all stock

•Could Eliminate the Scotch Yoke

Disadvantages:

•Larger Footprint due to moving tray

•Frequent direction change of the stepper motors

•Both the tray and the tissue mount observe movement

Concept #2 is similar to last years design, with the horizontal-motion on the top and the vertical motion on the bottom. The sinusoidal motion can be created by either an improved scotch yoke or the vertical motion of the tray.

Frame Concept #3 Toy Grabber

Advantages:

•Decreased moment on the horizontal lead screw assembly

•Smaller footprint in the vertical direction due to stationary tray

•Eliminates Scotch Yoke

Disadvantage:

•Less Space to adjust the position and angle of the wand

•Larger Footprint in the horizontal direction due to the vertical motion lead screw and guide rods

•Frequent direction change of the stepper motors

This design has the horizontal and vertical motion on top, with both lead screw assemblies having linear motion along the top rails of the frame. In this design the lead screws connect at the location of the wand mount platform.

Wand Mount Designs

Concept #3 – “Christmas Tree Mount”

Concept #2 – Vice Clamp

Concept #1 – Clamp

Wand Mount Concept #1Clamp

Advantages:

•Securely hold a variety of wand sizes and shapes

•Pre-manufactured options

•Clamp handle easily attaches to the wand mount platform

•Prevents motion of the wand during testing

•Quick set-up time

Disadvantages:

•May not accommodate all sizes of wand handles

This design is a spring loaded clamp that will hold the wand securely in place and will accommodate a variety of sizes

Wand Mount Concept #2Vice Clamp

Advantages:

•Securely holds a variety of wand sizes and shapes

•Accommodates all sizes of wand handles

•Quick set-up time

Disadvantages:

•Doesn’t easily attach to the wand platform

•May allow movement of the wand during testing

This design is a contoured vice clamp that can be adjusted with a screw to fit wand handles of various sizes

Wand Mount Concept #3Christmas Tree Mount

Advantages:

•Highly adjustable for a variety of wand shapes and sizes

•Easily Manufactured

Disadvantages:

•Difficult to align in the holder

•May allow motion of the wand during testing

•Increased set-up time due to the multiple screw adjustment

•Does not easily attach to the wand mount platform

This is a mounting device with three equidistant screws that can be adjusted to accommodate any size of wand.

Pressure Control Designs

Design Concept #1-

Spring Load Control

Design concept #2 – Gravitational Load Control

Pressure Control Concept #1Spring Load Control

Advantages:

•Works at all wand angles

•Design fully contained – no separate parts or weights

Disadvantages:

•Difficult to set desired pressure

•Contains more components

•Pressure not always constant

This design uses springs to create a constant pressure on the wand and allows vertical motion of the wand with the change in pressure of the test subject

Pressure Control Concept #2Gravitational Load Control

Advantages:

•Works at all wand angles

•Pressure always constant

•Easy set-up

Disadvantages:

•Requires additional parts -need separate weights to apply the constant load

This design simply uses gravity to maintain a constant force on the surface of the chicken. The assembly has a set weight applied and it can slide freely up and down with the contours of the chicken.

Angle Adjustment Designs

Concept #3 - Slotted Runner

Concept #1 – Screw adjustment

Concept #2 – Screw

Clamped Adjustor

Angle Adjustment Concept #1Screw Adjustment

Advantages:

•Quick set-up time

•Fine adjustment capabilities

•Easily connected to the wand platform

Disadvantages:

•Wand tip is only centered at a vertical angle

A threaded rod is used to attach to the wand holder to the pressure control device. The wand holder can be adjusted to any angle and bolted in place.

Angle Adjustment Concept #2

Advantages:

•Fine adjustment capabilities

•Easily connected to the wand platform

Disadvantages:

•More complicated set-up

•Wand tip is only centered at a vertical angle

A rod extending from the wand holder is clamped into the pressure control device. The wand holder can be adjusted to any angle and clamped in place.

Angle Adjustment Concept #3

Advantages:

•Quick and easy adjustment

•Wand tip is always centered

Disadvantages:

•Height differential is limited

•Does not connect easily to the wand platform

This is a slotted semi-circular device to which the wand can be attached to in a variety of angles and heights

Tissue Holder Design

The design for the tissue holder is essentially the same design as last year’s. A frame is placed over the chicken and bolted down to hold it still during the testing period.

Integrated Design

Assembled Design Components

Slider to allow for large vertical adjustment

Tray sits on platform

and indexes as well as oscillates the chicken

Mass applies constant load on chicken

Wand angle set by the wand holder

Wand mount slides with the contour of the chicken