Master's Thesis - Dylan_Greene

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  • i

    Development of a CNC

    Cold Spray Laboratory

    Facility by

    Dylan Greene

    A Thesis submitted to the University of Dublin in partial fulfilment of

    the requirements for the degree of

    Masters in Mechanical & Manufacturing


    Trinity College Dublin, April 2014


    Dr. Rocco Lupoi

  • ii

  • i


    I declare that I am the sole author of this dissertation and that the work present in it,

    unless otherwise referenced, is entirely my own. I also declare that the work has not been

    submitted, in whole or in part, to any other university as an exercise for a degree or any

    other qualification.

    I agree that the library of Trinity College Dublin may lend or copy this dissertation

    upon request.

    Signed: _______________________________

    Date: _______________________________

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    The general objective of this project was to develop a CNC Cold Spray Facility

    capable of coating flat and pipe substrates. The specific purpose of the machine build was

    to provide control of the substrate feed rates accurately and safely into the path of the static

    Cold Spray nozzle and to pave way for novel surface coating research to follow. A three

    axis CNC machine was built, calibrated and used to conduct two basic Cold Spray tests.

    All motion parameters of both the XY table and spindle axis are set, controlled and

    monitored by the CNC controller software (Mach3) in open loop control mode. The XY

    table positional accuracy is within 0.01 and the spindle accuracy is within 1 RPM. All

    three CNC axes have a high degree of precision combined with excellent operational

    repeatability. Both Cold Spray tests were conducted with (15-38) copper powder &

    aluminium substrates; a Static Pipe Substrate Test & a Dynamic (Rotational) Pipe

    Substrate Test. An approximate coating width at the set process parameters was taken from

    the successfully Cold Sprayed Static Pipe Substrate and used to set the axial pitch for the

    Dynamic (Rotational) Pipe Substrate Test. The Dynamic (Rotational) Pipe Substrate was

    also successfully Cold Sprayed. These successful coatings tests verified the CNC machine

    functionality and competency to conduct flat and pipe substrate Cold Spray experiments.

    This Cold Spray facility will make TCD the National leader in Cold Spray technology and

    applications and on this basis the impact of this work is extremely high. PIV analysis must

    be conducted to measure the coatings particle velocity under set process parameters, a

    camera must be installed to record Cold Spray tests for post analysis and way cover

    bellows must be mounted to protect the platform ball screw mechanisms.

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    There are people that deserve sincere acknowledgement for their help and advice.

    Mr. Sen Doonan, Mr. Alex Kearns, Mr. Jj Ryan, Mr. Gabriel Nocholson, Mr.

    Michael OReilly & Mr. Danny Boardman were immensely helpful in the TCD workshop

    throughout the year and regularly went out of their way to sort me out with any problems I

    was having. I learned a lot from them and I cant thank them enough for the continuous

    support and genuine interest they showed in my project; they are truly class acts.

    My supervisor Dr. Rocco Lupoi made time to discuss the project and answer any

    queries I had at the drop of a hat and often worked with me after hours to ensure project

    completion and success. He was a good motivator and a model supervisor from beginning

    to end.

    Mr. Rory Stoney put up with a lot from me as I bombarded him with hundreds of e-

    mails about motor specs and electronics related questions all hours of the day. He never

    failed to reply to a single question and frequently kept tabs on me to see how I was getting

    on. He did so on his own free time, 24 hours a day, and for that I am extremely grateful.

    I would like to thank Mr. Paul Normoyle for sanity checking my wired control bay

    and for his general circuitry advice.

    Thanks a lot Ms. Claudia Robbe for the help with the experiment set-up and I wish

    you all the best in your own Masters.

    I would to acknowledge Mr. Gordon OBrien for the 3D model of the CNC XY

    Stage he gave to me to adapt and add to. The finished product looked great with the spindle

    included looked great.

    Finally I would like to thank my parents, Emer & David. They provided me with

    the nutritional & emotional support I needed to pull through and keep going when things

    werent going so great in the project.

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    Table of Contents:

    a) Declaration Page (i)

    b) Abstract Page (ii)

    c) Acknowledgements Page (iii)

    d) List of Tables Page (vi)

    e) List of Figures Pages (vi) (x)

    1. Introduction Pages (1-3)

    2. Literature Review - Pages (4-26)

    2.1 Cold Spray Process Overview (4)

    2.2 Cold Spray Testing Facility Set-up (7)

    2.3 DC Motors (8)

    2.3.1 Steppers Page (11)

    2.3.2 Servos Page (11)

    2.3.3 Servo Stepper Hybrids (13)

    2.4 Lead screw vs. ball screw & linear slide mechanisms (15)

    2.5 CNC Motion Control (19)

    2.6 Literature Review Conclusion (23)

    3. Proposed System Design Pages (24-26)

    4. Machine Build Pages (26-63)

    4.1 Planning & Organisation (26)

    4.2 Machine Housing (29)

    4.3 CNC XY Stage Assembly (33)

    4.4 Electronics Control Bay Installation (36)

    4.5 Motor Electronics Description (39)

    4.6 Safety Electronics Description (40)

    4.7 Spindle Design (Mechanical) (45)

    4.8 Hardware Software Calibration & System Settings Pages (49-55)

    4.8.1 Set the Native Units (49)

    4.8.2 Engine Configuration (50)

    4.8.3 Motor Tuning (52)

    4.8.4 Limit Switch & Homing Set-up (54)

    4.8.5 Soft Limits (55)

    4.8.6 Spindle Axis Set-up & Calibration (Closed-Loop & Open-

    Loop Control) (56-61) Open Loop Control (56)

  • v Closed Loop Control (59)

    4.8.7 System Functionality & Optimisation (61)

    5. Pressurised Gas & Powder Feeder System Pages (64-65)

    6. Spindle Speed Synchronisation Pages (66-68)

    7. Cold Spray Testing Pages (68-76)

    7.1 Mutual Test Process Parameters (68)

    7.2 Static Pipe Substrate Pages (69-71)

    7.2.1 Process Parameters & G-code (69)

    7.2.2 Results & Discussion Pages (71)

    7.3 Rotating Pipe Substrate Pages (72-76)

    7.3.1 Process Parameters & G-code (72)

    7.3.2 Results & Discussion (75)

    8. Problems & Delays Pages (76-79)

    9. Impact of Work Pages (79-80)

    10. Conclusion Pages (80-81)

    11. Future Work Page (82)

    12. References Pages (83-85)

    13. Appendix Pages (86-107)

    13.1 Supplemental Figures (86)

    13.2 Part Manuals & Specifications (108)

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    i) List of Tables:

    Table 6.1 Kinematic parameter table. Page (68)

    Table 7.1 Process parameters used in both Cold Spray Tests. Page (69)

    Table 7.2 Static Pipe Substrate Test specific process parameters & G-Code. Page (70)

    Table 7.3 - Static (Rotating) Pipe Substrate Test specific process parameters & G-code.

    Page (73)

    ii) List of Figures:

    Figure 2.1 - The evolutions of shapes of a 20 mm-diameter aluminium feed-powder

    particle and a copper substrate-crater for the incident particle velocity of 6(15-38) m/s at

    the times: (a) 5 ns; (b) 20 ns; (c) 35 ns; and (d) (15-38) ns (Grujicic et al., 2003). Page (4)

    Figure 2.1 - The evolutions of shapes of a 20 mm-diameter copper feed-powder particle

    and an aluminium substrate-crater for the incident particle velocity of 6(15-38) m/s at the

    times: (a) 5 ns; (b) 20 ns; (c) 35 ns; and (d) (15-38) ns (Grujicic et al., 2003). Page (5)

    Figure 2.2 Schematic of a typical Cold Spray system (Grujicic et al., 2003). Page (7)

    Figure 2.3 torque capability of stepper vs. servo motors over a range of speeds (green &

    red = servo motor, blue = stepper motor) (Carlberg, 2012). Page (10)

    Figure 2.4 (a) & (b) Experimental results displaying the removal of all stepper motor

    harmonic resonances using an open-loop damping algorithm (Tsui et al., 2009). Page


    Figure 2.5 Velocity Error Profiles with and without closed-loop damping algorithms at

    different velocities (Tsui et al., 2009). Page (14)

    Figure 2.6 Ball Screw Linear Stage/platform. Page (17)

    Figure 2.7 Friction velocity relationship as described by Stribeck friction (Armstrong-

    Hlouvry et al., 1994). Page (18)

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    Figure 3.1 (a) De Laval Nozzle to be used (b) Lead Screw CNC platform model, (c) T-

    slot XY table model, (d) Complete Spindle axis assembly model & (e) Complete CNC

    XY testing platform model assembly & (f) Complete CNC XY and spindle testing

    platform model assembly. Pages (24-26)

    Figure 4.1 Predicted Work Schedule (Gantt chart). Page (27)

    Figure 4.2 The exterior of the machine housing. Page (30)

    Figure 4.3 The inside of the process operating region (view room the retracted front

    window). Page (31)

    Figure 4.4 Passive Interlock switch on the right hand side housing window. Page (31