Doc #: 3500-AD Revision: Rev. WIYN Secondary Lead Screw Cleaning. Author(s): Tammie Lavoie, Robert Stupak

Transcription

1 Doc #: 3500-AD Revision: Rev WIYN Secondary Lead Screw Cleaning Author(s): Tammie Lavoie, Robert Stupak

2 Contents Revision History Purpose Applicable To Scope Definitions Training Safety Personnel, Equipment and Material Required Procedure References AD Docx Page 2 of 17

3 Revision History REV Date Approved Sections Affected -- mm-dd-yy Initiated Reason for Change Remarks and/or Change Details Name Approved by: SigEng Name, ME Title SigEM Name, EL Maint SigSci Name, SciOps Signature 28 August 2018 Tammie Lavoie, Safety Manager Date 3500-AD Docx Page 3 of 17

4 1.0 Purpose The following is a procedure for removing the WIYN 3.5M secondary lead screws Applicable To The WIYN 3.5M Telescope Secondary 3.0 Scope This procedure will describe how to remove, dis-assemble, clean, re-assemble, and test the lead screws. It is based on the summer shutdown of 2018 at the WIYN telescope. This procedure is executed with the secondary mirror cell in place on the telescope. With this being stated, the secondary/tertiary lifting fixture and the crane is required in order to support the mirror during the process. If the secondary mirror is removed from the telescope, this procedure would not require the lifting fixture. 4.0 Definitions 4.1 CLI: Command Line Interface, on the WIYN 4.2 OCS: Optical Control System, on the WIYN-page GUI window 4.3 OSS: Optical Support Structure 5.0 Training Electronics maintenance and engineering support. 6.0 Safety SOP 1000-AD Cranes SOP 1000-AD Personal Protective Equipment SOP 1000-AD Ergonomics SOP 1000-AD Safe use of acid solutions 7.0 Personnel, Equipment and Material Required Process #/Personnel Notes At least 2 people are required in order to secure and stabilize the flexure arms AD Docx Page 4 of 17

5 Equipment/Part/Tool List Location Notes Small dome crane Secondary/Tertiary Lifting fixture Ladders to reach the secondary at horizon Parts washer or cleaning tub One set of Allen wrenches and a set of Hex ball drivers Acid brushes for cleaning Rubber gloves, Kim-wipes Electrical tape A clean mat or wipes to lay the lead screw on while working on it. Gray Mills Agitene cleaning solvent, or Dow Silicone Moly-Kote 1292 Long Life Bearing Grease, _1292.pdf -Locktite Low Strength 222 low strength threadlocking adhesive htm?nodeid= Procedure 8.1 Telescope, Crane/Dome, and lifting fixture set-up preparations: Do a source startup and key start from the CLI Turn the DOME key to maintenance mode on the B floor in back of the electronics racks Connect the dome control hand paddle Turn OFF the OCS box located on the north side of the telescope's center section Using the hand paddle brake release box, move the telescope manually to the south horizon, and re-engage the brakes AD Docx Page 5 of 17

6 8.1.6 Rotate the dome/jib crane to align center to the secondary Place the lifting fixture inside the telescope struts. See Fig Set the lifting fixture to the widest setting (for the secondary mirror cell) Secure secondary making certain that there is only enough force to support the weight of the secondary cell and not to lift the telescope. Fig Secondary actuator removal (this is to be done one actuator at a time, so repeat steps 2-9 actuator): Disconnect the cable and wires for the motor (the MS connector) and the "hard" and "pre-limit" switches. See Fig.2 Fig Remove the connecting clamp set screw which fastens the secondary mirror cell to the flexure arm with a 1/4" Allen key. This is a captive screw. See Fig AD Docx Page 6 of 17

7 Fig Remove the 4x3/8x16-1" (5/16" Allen) screws that secure the assembly to the upper secondary cage struts. NOTE: The motor mount plate, the motor, the transmission, and flexure arm are now free. It is necessary to use caution while removing the flexure arm shaft by holding both the motor and supporting the shaft as it is being removed. Damage could be done to the flexure couplings at both ends of the shaft arm if not careful. 8.3 Secondary actuator Dis-assembly: Using a vice (the one on the blue cart works nicely), secure the assembly by the anti-rotation plate with the flexure arm hanging vertically down. See Fig. 4 NOTE: Use caution as to not put any strain or torsion on the flexure arm. Fig AD Docx Page 7 of 17

8 8.3.2 Remove the cover for the anti-rotation plate by unscrewing the 6x10-32x1/4" button head screws with a 5/32" Allen Unscrew the 2x6-32x1" SHC screws (7/64" Allen) which mount the home switch to the drive assembly Place the home switch into the Al crystal protector fixture and secure this with tape. This ensures that the switch is protected and safe. See Fig. 5 Fig Remove the "hard" and "pre-limit" switch plates by unscrewing the 2x10-32x1" SS SHC shoulder screws (for each plate) with a 5/32" Allen Tape the three switches (the home, hard, and pre-limit) to the motor casing in order to keep these safe and out of the way Removal of the flexure shaft from motor drive assembly: NOTE: Make note of the spacing between the flexure arms and the body of the flexible coupling, this should be labeled on the flexible coupler. Feeler gauges are more accurate than a dial caliper due to location. See Fig. 6 Fig Remove the 4x1/4-20x1" (3/16" Allen) that hold the motor drive transmission assembly to the actuator housing AD Docx Page 8 of 17

9 8.3.9 Carefully, unscrew the motor/lead screw assembly by turning it from the flexure arm nut. This will completely separate the motor/lead screw assembly from the flexure arm and actuator housing Set the motor/lead screw assembly aside on a clean surface. See Fig.7 NOTE: Lifting the flexure arm a bit will lift the lip of the motor drive assembly up allowing for the motor drive assembly to turn easier. NOTE: The lead screw is a very fine thread requiring many turns to dis-engage. Fig Remove the 6x10-32x1 3/4" cap head screws (5/32" Allen) fastening the flexure nut from the flexure arm, and safely set aside the flexure arm. See Fig. 8 NOTE: While one person holds the flexure shaft, the other person removes the screws so as to NOT drop the flexure shaft AD Docx Page 9 of 17

10 Fig Remove the nut and one of the sweeper spacers. 8.4 Preparation and disassembly for cleaning: Unthread one of white sweeper spacers to remove it from the lead screw Remove the 6x10-24x5/8" SS SHCS in order to detach the lead screw from the motor/transmission drive assembly. See Fig. 9 Fig Cleaning: Clean the lead screw, flexure nut, and white spacers in the Agitene bath. See Fig AD Docx Page 10 of 17

11 Fig Checking the drive transmission grease: Remove the four 10-32x5/8" SHCS (5/32" Allan) fastening the motor to the harmonic drive transmission. See Fig.11 Fig Inspect the grease in it and re-distribute it, if necessary Replace the motor by securing the four 10-32x5/8" SHCS (5/32" Allen). 8.7 Preparation for Reassembly: Lube the flexure nut and lead screw with Moly-Kote Long Life Bearing Grease. See Fig. 12 Fig.12 Note: Wear gloves and do this by hand AD Docx Page 11 of 17

12 8.7.2 Gently run the nut up and down the lead screw so as to evenly distribute the grease along the screw. 8.8 Reassembly: Secure the lead screw back onto the motor drive assembly with the 6x10-24x5/8" SS SHCS (5/32"Allen) Thread one of the white sweeper spacers onto the lead screw Carefully thread the nut onto the lead screw a few threads, so as to leave space to reattach the nut to the flexure shaft Thread the other white sweeper spacer onto the lead screw Reassembly of the flexure arm and motor/harmonic drive assembly: While one person holds the flexure shaft vertically, the other person installs the 6x10-32x1 3/4" cap head screws (5/32" Allen) securing the flexure nut to the flexure shaft assembly Carefully, screw the motor drive assembly by turning it onto the flexure arm nut. Note: The lead screw is a very fine thread requiring many turns Refasten the motor drive assembly with the 4x1/4-20x1" (3/16" Allen). Note: Measure the spacing between the flexure arms and the body of the flexible coupling, this should be labeled on the flexible coupler. Feeler gauges are more accurate than a dial caliper due to location. Adjust as necessary Actuator assembly: Remove the temporary tape holding the three switches to the motor housing Reinstall the "hard" and "pre-limit" switch plates using the 2x10-32x1" SS SHC shoulder screws (for each plate (5/32" Allan) Remove the home switch from the Al crystal protector fixture, and refasten it with the 2x6-32x1" SHC screws (7/64" Allan) using Loctite 222 on these screws Reinstall the cover for the anti-rotation plate by screwing the 6x10-32x1/4" button head screws with a 5/32" Allan. 8.9 Lead Screw Installation: Gently install the assembly into the secondary cage truss and secure it with the 4x3/8x16-1" screws (5/16" Allen). NOTE: It is necessary to use caution while installing the whole flexure arm/actuator assembly by holding both the motor and supporting the flexure shaft Secure the shaft to the secondary mirror cell with the connecting clamp and screw the captive screw tight with a 1/4" Allen key Reconnect the cable and wires for the motor (an MS connector) and the "hard" and "pre-limit" switches Clean up: 3500-AD Docx Page 12 of 17

13 Remove the secondary lifting fixture from the secondary mirror cell Stow the crane and the dome Testing: From the low-level software: Disconnect J24 on the OSSCS box and connect the laptop circular connector here. Note: This provides serial communications between the laptop and the OSSCS box Assure that a 'source startup.tcl' has be initiated and that an 'mdcs main power on' command has been issued from the CLI Turn on the computer. The laptop requires being plugged to AC power in order to be powered Select the OSSCS option Using the low level reference book. Power on the actuators Read the encoder positions for all three actuators From here the actuators can be moved and exercised Make sure to disable the power to the motors after testing From the CLI and sectilt programs: Assure that a 'source startup.tcl' has been executed and that the 'main power' is on Bring up the WIYN sectilt GUI. See Fig.13 Fig Hit the Initialize button Monitor the secondary from the OCS screen of the WIYN page. Here the command echos and the positions will be displayed. See Fig AD Docx Page 13 of 17

14 Push the start button in the WIYN sectilt GUI and check the OCS for the encoder count positions. Fig. 14 Note: 'start' from the sectilt program really means the 'home' position which is approximately counts. The 'initialize' positions for the three actuators are pre-defined in a set-up file and are currently defined to be around for 'A' and 'B' and ~48000 for 'C' actuators Deselect both 'start' and 'initialize' so that this process can be repeated as many times as necessary. 9.0 References DOCUMENT NUMBER 1000-AD Drawing E DOCUMENT TITLE KPNO Emergency Manual 3500-AD Docx Page 14 of 17

15 Drawing E Drawing E See Attachments 3500-AD Docx Page 15 of 17

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