Industrial Maintenance. Gear Drives 1. Job Sheets - Instructor F0

Transcription

1 Industrial Maintenance Gear Drives 1 Job Sheets - Instructor F0

2 Order no.: C First Edition Revision level: 11/2017 By the staff of Festo Didactic Festo Didactic Ltée/Ltd, Quebec, Canada 2017 Internet: Printed in Canada All rights reserved ISBN (Printed version) ISBN (CD-ROM) Legal Deposit Bibliothèque et Archives nationales du Québec, 2017 Legal Deposit Library and Archives Canada, 2017 The purchaser shall receive a single right of use which is non-exclusive, non-time-limited and limited geographically to use at the purchaser's site/location as follows. The purchaser shall be entitled to use the work to train his/her staff at the purchaser s site/location and shall also be entitled to use parts of the copyright material as the basis for the production of his/her own training documentation for the training of his/her staff at the purchaser s site/location with acknowledgement of source and to make copies for this purpose. In the case of schools/technical colleges, training centers, and universities, the right of use shall also include use by school and college students and trainees at the purchaser s site/location for teaching purposes. The right of use shall in all cases exclude the right to publish the copyright material or to make this available for use on intranet, Internet and LMS platforms and databases such as Moodle, which allow access by a wide variety of users, including those outside of the purchaser s site/location. Entitlement to other rights relating to reproductions, copies, adaptations, translations, microfilming and transfer to and storage and processing in electronic systems, no matter whether in whole or in part, shall require the prior consent of Festo Didactic. Information in this document is subject to change without notice and does not represent a commitment on the part of Festo Didactic. The Festo materials described in this document are furnished under a license agreement or a nondisclosure agreement. Festo Didactic recognizes product names as trademarks or registered trademarks of their respective holders. All other trademarks are the property of their respective owners. Other trademarks and trade names may be used in this document to refer to either the entity claiming the marks and names or their products. Festo Didactic disclaims any proprietary interest in trademarks and trade names other than its own.

3 Safety and Common Symbols The following safety and common symbols may be used in this manual and on the equipment: Symbol Description DANGER indicates a hazard with a high level of risk which, if not avoided, will result in death or serious injury. WARNING indicates a hazard with a medium level of risk which, if not avoided, could result in death or serious injury. CAUTION indicates a hazard with a low level of risk which, if not avoided, could result in minor or moderate injury. CAUTION used without the Caution, risk of danger sign, indicates a hazard with a potentially hazardous situation which, if not avoided, may result in property damage. Caution, risk of electric shock Caution, hot surface Caution, risk of danger. Consult the relevant user documentation. Caution, lifting hazard Caution, belt drive entanglement hazard Caution, chain drive entanglement hazard Caution, gear entanglement hazard Caution, hand crushing hazard Notice, non-ionizing radiation Consult the relevant user documentation. Direct current Alternating current Festo Didactic C III

4 Safety and Common Symbols Symbol Description Both direct and alternating current Three-phase alternating current Earth (ground) terminal Protective conductor terminal Frame or chassis terminal Equipotentiality On (supply) Off (supply) Equipment protected throughout by double insulation or reinforced insulation In position of a bi-stable push control Out position of a bi-stable push control IV Festo Didactic C

5 Table of Contents Preface...VII About This Manual... IX To the Instructor... XI Job Sheet 1 Introduction to Gear Drives... 1 Job Sheet 2 Spur Gear Installation and Alignment Job Sheet 3 Backlash Adjustment Job Sheet 4 Speed, Torque, and Teeth Ratio Job Sheet 5 Gear Trains Appendix A Equipment Utilization Chart Appendix B Lockout/Tagout Procedure Appendix C Post Test Festo Didactic C V

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7 Preface The Mechanical Drives Training System covers the installation, use, maintenance, and troubleshooting of mechanical drives. The curriculum is divided into levels and covers the following topics: Introduction to mechanical drive systems Belt drives Chain drives Gear drives Shaft alignment and couplings Bearings and seals Ball screws and linear bearings Clutches and brakes Vibration metering and analysis Notions of lubrication The figure below shows the available course material for the Mechanical Drives Training System. Festo Didactic C VII

8 Preface Mechanical Drives Training System course material. We invite readers of this manual to send us their tips, feedback, and suggestions for improving the book. Please send these to The authors and Festo Didactic look forward to your comments. VIII Festo Didactic C

9 About This Manual The Gear Drives 1 manual introduces the basics of gear drives. The topics covered in this manual are presented in the form of job sheets. The job sheets include a description of the objectives, a list of equipment required, safety procedures, and a list of steps required to attain the objectives. The topics are usually introduced in an information job sheet. However, to obtain detailed information about the covered topic, you should refer to your text book or ask your instructor to guide your learning process. The job sheets follow a logical sequence which allows you to assimilate the concepts efficiently. The job sheets should be performed one after another since the content of a given job sheet builds up on the knowledge acquired in the previous one. Manual objectives When you have completed this manual, you will be familiar with gear drives and their roles in industrial applications. You will know how to properly install gear drives and the importance of following specific protocols. You will be able to identify the main components of gear drive systems in industrial installations. Safety considerations Safety symbols that may be used in this manual and on the equipment are listed in the Safety and Common Symbols table at the beginning of the manual. Safety procedures related to the tasks that you will be asked to perform are indicated in each exercise. Make sure that you are wearing appropriate protective equipment when performing the tasks. You should never perform a task if you have any reason to think that a manipulation could be dangerous for you or your teammates. Prerequisite As a prerequisite to this course, you should have read the manual titled Introduction to Mechanical Drive Systems. System of units Units are expressed using the International System of Units (SI). Festo Didactic C IX

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11 To the Instructor You will find in this Instructor Guide all the elements included in the Student Manual together with the answers to all questions, results of measurements, graphs, explanations, suggestions, and, in some cases, instructions to help you guide the students through their learning process. All the information that applies to you is placed between markers and appears in red. Accuracy of measurements The numerical results of the hands-on exercises may differ from one student to another. For this reason, the results and answers given in this manual should be considered as a guide. Students who correctly performed the exercises should expect to demonstrate the principles involved and make observations and measurements similar to those given as answers. Before a student begins a Job Sheet, ensure that the equipment is in good condition and does not represent any risk when used. When a student has to complete a setup that is partially already mounted, ensure that the setup corresponds to the job description. When the jobs are performed in teams, ensure that each student has and installs a padlock when performing the Lockout/Tagout procedure. Festo Didactic C XI

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13 Sample Extracted from Job Sheets - Instructor

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15 Information Job Sheet 3 Backlash Adjustment Backlash Backlash is the clearance between mating teeth. It is measured on the pitch circle as the amount by which the width of a tooth space exceeds the thickness of the engaged tooth (Figure 16). Excessive backlash can cause wear on the teeth and it is particularly detrimental on reversing mechanisms. On the other hand, insufficient backlash may cause excessive wear and noise. A correct backlash ensures a smooth meshing and allows for proper lubrication and thermal expansion of the teeth. Figure 16. Backlash. Backlash is adjusted by varying the distance between the shafts. The distance between the shaft centers is calculated as follows: CC = dd 1 + dd 2 2 (3-1) where CC is the distance between the shaft centers dd 1 is the pitch diameter of the driving gear is the pitch diameter of the driven gear dd 2 The backlash value should remain within a certain range. This range is a function of the module and distance between the shaft centers. Table 5 shows recommended backlash values for gears with small modules, rotating at a pitch line velocity lower than 8 m/s. The minimum and maximum backlash values are usually available from the manufacturers. Festo Didactic C 23

16 Job Sheet 3 Backlash Adjustment Table 5. Recommended backlash for spur gears (pitch line velocity lower than 8 m/s). Module Min. backlash (mm) Max. backlash (mm) 1.5 or less Direct backlash measurement One common method to measure the backlash between two gears is by direct measurement using a dial indicator. Figure 17 shows how to set a dial indicator for backlash measurement. The backlash is measured on the pitch circle of the gear. Figure 17. Backlash measurement. Figure 17 shows an ideal setup, however, several factors can influence the accuracy of backlash measurement. A damaged or worn out indicator point could induce an unwanted measurement error. Differences between the gear teeth could also influence measurement. The cosine error effect can also affect the measurement. Cosine error effect Sometimes there is not enough clearance to put the dial indicator spindle at a 90 angle with the tooth. When this occurs, a type of measurement error called the cosine error effect can lead to an overestimated backlash. Figure 18 shows how the angle with the tooth may influence the measurement. The measurement error can be understood using a square triangle and basic geometry. 24 Festo Didactic C

17 Job Sheet 3 Backlash Adjustment When the spindle is at an angle with the line perpendicular to the tooth surface, the displacement reading on the indicator is larger than the actual vertical displacement. Instead of the vertical distance, the dial measures the length of the hypotenuse of the square triangle shown in Figure 18. Fortunately, the vertical displacement can be calculated as follows, using the measurement angle and the measured value: bb = c cos θθ (3-2) where θθ is the angle between the line perpendicular to the tooth and the spindle. bb the actual vertical displacement cc is the measured distance on the dial indicator. Although the error for small angles is likely to be negligible, it is important to be aware of this type of measurement error and use a compensation factor, if required. Table 6 gives examples of correction factors for different angles. Figure 18. Backlash measurement error due to the cosine error effect. Table 6. Correction factor for a cosine effect error. θθ Correction factor (cccccc θθ) Dial indicator modification Another factor to keep in mind with dial indicators; do not replace the indicator spindle or tip with a longer one. Although this could seem convenient to reach some locations, a longer spindle cuts the accuracy of the measuring instrument. This could induce an additional error on the final measurement. Festo Didactic C 25

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19 Job Sheet 3 Backlash Adjustment OBJECTIVE Measure the backlash between the teeth of two gears; Adjust the backlash of a gear drive within the recommended range. PROCEDURE Equipment required Refer to the Equipment Utilization Chart in Appendix A for the list of equipment required for this job. Safety procedures Before proceeding with this job, make sure to complete the following checklist. You are wearing safety glasses. You are wearing safety shoes. You are not wearing anything that might get caught such as tie, jewelry, or loose clothes. If your hair is long, tie it out of the way. The working area is clean and free of oil. The floor is not wet. Your sleeves are rolled up. 1. Perform the Lockout/Tagout procedure. a Refer to Appendix B if necessary. Festo Didactic C 27

20 Job Sheet 3 Backlash Adjustment Setup You will use the same setup as Job Sheet 2 and add a dial indicator on a flat bar to measure the backlash of a gear drive. 2. Fix six T-slotted extrusions to the universal base as shown in Figure cm 42.5 cm 24 cm 30 cm Figure 19. Setup. 3. Install the gear drive as shown in Figure 19. Make sure to: Check the motor for soft foot and correct it, if necessary; Install and align couplings; Perform vertical and horizontal angular alignment of the gears; a Perform parallel alignment of the gears. Refer to Job Sheet 2 if necessary. Backlash measurement You will make a comparison measurement with a dial indicator to measure the backlash of the gear drive. Dial indicator setup 4. The dial indicator has a magnetic base and must be installed on the flat bar. To be able to measure the backlash of the gear drive, the indicator base should as close as possible to the driven gear. Use M X 20 mm screws, flat washers, and T-nuts to secure the flat bar as shown in Figure 19. Secure the dial indicator on the flat bar using its magnetic base. 5. With a soapstone marker, mark the tooth you will use to measure the backlash. Always use the same tooth to verify the backlash. 28 Festo Didactic C

21 Job Sheet 3 Backlash Adjustment 6. Place the indicator tip on the tooth of the driven gear. The spindle must be as perpendicular as possible to the tooth surface. 7. Secure the dial indicator using the support adjusting screws. Comparison measurement 8. Block the driving gear with one hand. 9. Make sure the teeth of both gears come in contact. Rotate the dial face of the indicator to set it to zero. 10. Rotate the driven gear until the tooth that was in contact with the driving gear touches the other tooth. Be careful not to move the driving gear. You must place the driven gear so as the dial indicator reads zero when the tooth touches one of the teeth of the driving gear and it reads a positive displacement when you turn the driven gear so has the tooth touches another tooth of the driving gear. Record the backlash value below. Backlash: 11. Refer to Table 5 and determine the recommended backlash range for the actual setup. Recommended backlash range: Between 0.08 mm and 0.13 mm 12. Compare the measured backlash to the recommended range. If the backlash is outside this range, adjust it using the following procedure. Backlash adjustment 13. Loosen the screws of the pillow block bearings supporting the driven shaft. 14. Move the pillow block bearings to increase or decrease the shafts center distance, depending if the backlash is too small or too large. 15. Tighten the pillow block bearings screws. 16. Perform vertical angular alignment of the gears. 17. Perform parallel alignment of the gears. 18. Measure the backlash again. Repeat this procedure until the backlash is within the recommended range. Festo Didactic C 29

22 Job Sheet 3 Backlash Adjustment Remove the dial indicator from the enclosure before testing your setup. 19. Ask the instructor to check your work. Start-up procedure 20. Remove the lockout and tagout devices from the main switch. 21. Close the safety guard and install a lockout device in the padlock eyes. 22. Turn the power on by setting the main switch to the I (on) position. Make sure the power light on the control panel is turned on. 23. Press the safety reset button. Testing the system You will start the motor and vary its speed to make sure the system works properly. 24. Start the motor by pressing the start button on the variable frequency drive. Then, set the frequency of the drive to 15 Hz. Make sure the system works properly. 25. Increase the motor speed in steps of 10 Hz until you reach 50 Hz. Make sure there are no abnormal sounds or vibrations. 26. Turn off the motor and then turn off the system by setting the main switch to the O (off) position. 27. Remove the lockout device from the padlock eyes and open the safety guard. Wait for the motor to completely stop before removing the lockout device and opening the safety guard. 28. Perform the Lockout/Tagout procedure. 29. Disassemble the setup and return the components to the storage location. Name: Date: Instructor's approval: 30 Festo Didactic C

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