Inconel Tubing Pre-Pullout

The goal of the project is to provide the Boeing Company with a more ergonomic and consistent way to provide tubing material grinding prior to pullout. The purpose of the pullout is to join tubing in the most efficient and strongest way possible. This project aims to reduce the time and effort for the Boeing operators to obtain a successful pullout.

Problem Explanation
The Boeing Company's Tube, Duct, and Reservoir Center (TDRC) has asked the University of Idaho for assistance in creating a solution in their tubing pullout process. A tubing pullout is an alternate way to join two tubes in a duct system. This process is faster and stronger than other methods available. Currently, the cutting of the tubing is done by either a water jet or a laser cutter. Both of this methods create areas of weaker material around the hole that needs to be removed before the pullout can be done. This material is removed by grinding, using a soft stone, and is done by using a handheld grinder. The method requires the operator to hold both the tube and the tool. The completion of grinding is decided by the individual operator which creates inconsistency with time and pullout success. Not removing enough material will cause the pullout to tear and removing too much is a waste of time. The Inconel Tubing Pre-Pullout team aims to create a viable and easy to implement solution for Boeing's TDRC.



Engineering Requirements
1. Reduce the time of the grinding process to less than 20 minutes

2. Solution will be justified with a business case

3. Operator will have 1 point of contact or less with tool or part

4. Discover an accurate way to measure ground surface

5. Provide amount of material to be removed based on type of material (TBD using tests)

6. Solution must accommodate 15" duct section

Project Learning
Activities and information the team gained from the project learning phase of this project.

Initial Client Meeting
The team went to Boeing's TDRC in Auburn, Washington at the beginning of the project to have a face to face meeting with the client and witness the pullout grinding process first hand. Some of the things we learned from the meeting were:
 * Every operator likes to hold the part and grinder a different way
 * Whether the pulling die is hot or cold depends on the material
 * Inconel and Steel require a cold pull
 * Aluminum and Titanium require a hot pull
 * The water jet is preferred to the laser when cutting the pullout holes
 * There is use of both Inconel 718 and 625
 * Pullout takes less time to manufacture than a fish-mouth joint and has a higher strength after weld
 * Boeing is primarily concerned with operator's wrist position and use during grinding
 * Boeing would like to help avoid stress and overuse injuries
 * In addition to grinding, some larger pullouts also require polishing

The Design
We decided on two different ideas that would be complementary to each other. The first is a visual inspection of the ground surface and the second is an arm to fix the grinder to the table with a force feedback system with a digital display.

System Objectives
The next step for this subsystem will be to construct the microscope assembly and test it on both ground and not yet ground parts. Then we would like to create a system to etch or mark the lip, so that operators have a visual representation of the material they need to remove, approximately 5 thousandths of an inch. This will further accomplish the process being quicker and more consistent.

Initial Idea
The tube holds a magnification lens on one end and a light on the other, with a slot for the edge of the part in between the two. This design must be changed, as compound magnification will be required, and the tube must have a smaller diameter to fit into all the necessary slot sizes. A proof of concept was built using a toilet paper roll, flashlight, and 2X magnifying glass and we were able to see large cracks. Modification to this system is required, but the basic concept will remain the same.

Current Design
The current design for the visual feedback system will focus on the use of a 50X magnification pocket microscope. The grinding range that will need to be visible is approximately 5 thousandth of an inch, or .127 mm at 50X magnification; this range will appear as 6.35 mm when viewed through the microscope. The end of the microscope will have a fixture, with a slot for the part, and which holds the back light. The fixture to hold the system may be machined out of PVC or aluminum or 3D printed depending on the complexity of the finally design and the strength and durability required. These factors will be determined later in the design process.

System Objectives
This system will provide the support for the grinder and will house the force feedback system. Because it will be used in a manufacturing setting, there will be a large factor of safety to protect against impulse loads regularly found from accidental contact with the machine. The main goals of this machine are to increase consistency and durability, and insure ergonomic use to lower workplace repetition injury.

Initial Idea
The initial sketch for the grinder fixture has the grinder at an angle but it will be fixed vertically with the grinder tip pointing down. We have also removed the camera microscope in favor of the handheld visual inspection tool. The grinder for the system is the Bosch DG355LCE.

First Model Iteration
The grinder sub-assembly is essentially two pieces, an arm that telescopes up and down and the fixture that will hold the grinder in place. The arm will be made from heavy duty pipe with a flange on the bottom to fix the arm to the workbench. The upper part of the arm will be smaller so that it can fit inside the base. This will allow for the ability to telescope the arm. Telescoping the arm will allow the operator to move the grinder tip into the best position for the duct size being ground. The grinder fixture, the piece that will actually hold the grinder, will be made from aluminum. It will have a similar design to the V-blocks used to hold cylinders for machining. This will allow different kinds of grinders to be used in the same fixture. The fixture will be tightened into place using wingnuts. The sensors for the force feedback system will be placed somewhere on the arm to measure moment or torque, which can be calculated into force applied at the stone tip. The design for the telescoping arm will likely not change for the next iteration. The grinder fixture needs a redesign for the optimization of the force feedback system. For more information about the force feedback system, refer to that section.

System Objective
The objective of this system is to provide the operator instant feedback on the force being applied to the stone tip on the grinder. Through testing, an optimized force will be found to decrease the grinding time and increase the stone tip life. This system will make the grinding process more consistent and faster than it is currently.

Controller
The team plans to use an Arduino controller to convert an input signal to force. This force will be compared to the team’s test data. The applied force will be compared to the desired force and that information will be displayed on an LED screen for the operator to get instant feedback.

Initial Idea
The initial plan was to use strain gauges to measure the strain in the fixed grinder subsystem. Using the modulus of elasticity, a relationship between the force at the stone tip, and the measured strain was developed. This measurement technique had some difficulties. The fixed grinder system needs be quite stout. Since this will be used in a manufacturing environment, its longevity needs to be ensured. However, if we make the system stout so that there isn’t any deflection, then it will be difficult to accurately measure the needed strain. If the cross-sectional area is reduced to allow for strain, then there is the greater possibility of breaking the system to a force overload from the manufacturing environment.

Current Direction
Since there were several challenges with the initial force feedback system, the team decided to measure the force at the tooling rather than in the grinding fixture system. This method is still in its preliminary design state.

The Team
For any questions or errors on this page contact Matt Dieckmann at diec5358@vandals.uidaho.edu.