Download PDF - Gear Technology magazine

More documents

Recommendations

Info

The Design and Manufacture of Machined Plastic Gears Part I Design Parameters of Plastic Gears by John H. Chen and frank M. IUMbe The Poly.mer Corporation Reading, Pennsylvania 19603 ABSTRACT The use of Plastic Gearing is increasing steadily in. new products. This is due in part to the availability of recent design data. Fatigue stress of plastic gears as a function of diametra! pitch. pressure angle, pitch line velocity, lubrication and life cycles are described based ot! test information. Design procedures for plastic gears are presented. Introduction The use of machined plastic gears is increasing in industrial power transmission applications, Cast or extruded gear materials of 50 mm to over 2 meter (2"-84") in diameter are machined to desired dimensions and gear tooth forms. Nylons and acetals are the most widely used thermoplastic gear materials. They offer resiliency, resistance to wear and corrosion, noise reduction, vibration suppression. lightweight and minimum maintenance. This increased use is due in part to the availability of new data in design parameters, manufacturing and installation techniques to optimize utilization of the materials and to prevent premature failures. Some 'test data on plastic gears are the results of earlier publications}H) Plastic gears are sensitive to frictional heat and hysteresis loss, which causes softening, expansion and deflection of the gear teeth. Tooth interference. caused by AUTHORS: DR...JOHN H. CHEN is Project Leader for The Polymer Corp. where he hasbeen employed since 1968. During this time he has been involved in various aspects of product development and application testing of ihermoplasiics. Dr. Chen received his BSME from Taiwan College of Engineering and his Dr. -lng. degree from the Technical University of Aachen, West Germany. He is the author of over 30 technical papers in the field of plastic engineering. and holds patents in.manufacturing methods of nylon parts. Additionally he is a member of the American Society of Mechanical Engineers, American Society of Testing Materials. Society of Plastics Engineers. and a committee member .of the American Gear Mcmufacturers Association on "Design Guide for Plastics Gearing .• MR. FRANK M. JUARBE has been with Polymer Corp. for the past ten years as Product Manager uihere he has been invol'ved in. the deuelopment of Cut Tooth Plastic Gearing and Sprockets. Prior to his work at Polymer. he has over twenty years experience in related engineering fields. Mr. [uarbe is a member of the American Gear Manufacturers Association. and the American Society of Mec:hanicai Engineers. deflection and creep, can lead to different types of damage due to the viscoelastic nature of plastic gears.(S) For better heat dispersion and to reduce contact stress. plastic gears 31'e usually mated with metal gears. To measure plastic gear temperature in operation. a techmque utilizing an infrared radiometer was developed(6l and friction heat and hysteresis loss were inv,estigatedY" 7) Al!though plastic/steel contacts show rather low friction(8)a~d some plastic gears can be operated Without lubrication, the lubrication also has a considerableeffect on the performance .of the plastic gears.(9) The ,tooth deflection of p.1'asticgears and low Hertizan stress of plastic/steel contacts results in generally higher gear contact ratio and smooth rotation of plastic and steel gear mates. A model to assess gear contact ratios of plastic / steel gear mates was proposed PO) A larger backlash allowance required for plastic/steel gear mates was suggested,(S) Factors which influence performance of plastic gears are, Ito an 'extent, clarified by the works mentioned above and others. However. design data. available to meet power transmission of plastic gears is still. insufficient for most applications. The purpose of this paper is to fill part of this gap by presenting some pertinent design parameters based on experiments, which were conducted at conditions dose to typical field applications. Design parameters as functions of diametrical pitch, tooth form, lubrication, pitch line velocity, stress levels and life cycles using cast type 6 nylon and other plastic gears are presented. Experiments Test Gears Industrial experience indicates that anionically polymerized cast type 6 nylon is one of the highest strength unreinforced thermoplastic gear materials available. The typical. test material contains molybdenum disulphide for improved lubricity and wear resistance. Impact modified Nylon 6/6 and ultra high molecular weight polyethylene (UHrvlWPE) are known to be very t.oughand resistant to fatigue and notch sensitivity. The letter starting resin has a molecular weight ·o.f 2-5 million by solution viscosity test. Polyacetal (melt viscosity 3360 poise). which features strength and low moisture absorption was also selected for this test, Physica~ properties of these four thermoplastic test gear materials are summarized in Table 1. 18 Gear Technology
Maag Gear Inspection Genter Model SP-42. Full GNG setup, operation and analysis of involute, profile, helix. pitch and runout in one setup. From 0" to 16.5" diameter gears including bevels and worms. "". ..,..;" Jff.Jt Lorenz Gear Shaping Machine Model LS-1 80 MP-Tronic. Full GNG including 5.9" vertical adjustment of stroking positions during one cycle. 7" diameter, 2.35" stroke. ........ Geared to excellence " / The names Maag and Lorenz mean excellence throughout a full range of products. Gear hobbing, disc-cutter shaping. rack cutter shaping - models from 0.250" to 46 feet diameter Gear grinding - models from O.BOO"to 197" diameter Gear Checking - models from 0" to 197" diameter i'f"..... MAAG GEARWHEEL COMPANY, LTO. LORENZ COMPANY, LTD. P.O. Box 8023 LOIIINZ P.O. Box 1556 Zurich,Switzerland );, ITTUNOIIN [). 7505 Ettlingen, west Germany Exclusive U.S.A. General Sales Agent. Miller Associates, Inc .• P.O. Box 304. New Berlin, Wisconsin 53151 Telephone: (414) 785-1111, Telefax: (414) 785-1115 CIRCLE A-l0 ON READER REPLYCARD 'f I "'I.r\ J ~;
Page 1 and 2: Th',e Journal of Gear Manufa'ctu,ri
Page 3: Can, you I. answe'r' th,ese 2. lio,
Page 7 and 8: Photo by JennIfer Short This issue,
Page 9 and 10: Gear Tooth Scoring Design Considera
Page 11 and 12: occur when a critical total tempera
Page 13 and 14: I.Ḷ 500 300 i /' V / V / t- V t>
Page 15 and 16: Table 2 Pili I[ln teeth: 25 Pinion
Page 17 and 18: ! Gear 1 ~~~ .. J!EIL Autamatlic Ge
Page 19: IYII I' Here', die reatOII wby ,.,.
Page 23 and 24: in the direction that it acts as a.
Page 25 and 26: TABLE .3 TOOTH FORM FACTOR v 1 No .
Page 27 and 28: ț CNC Shaving Cutter Grinding Mach
Page 29 and 30: TABLE 5. UFE FACTOR Kl OF MOS2 FILL
Page 31 and 32: A new and beHer way to broach blind
Page 33 and 34: " ,ACl'UAL L[AII'jr '01' HELII - ,'
Page 35 and 36: where the check is made relative to
Page 37 and 38: o WOBBLE Fig. 7 - Analytical inspec
Page 39 and 40: AN INVOLUTE ClilECKII'IG F HIlER WI
Page 41 and 42: 1 I I ~" d c 1 o ~, o ! e oo o I ~
Page 43 and 44: I -.~ + ". 1 ' . ..- ___ . ,_,' .I~
Page 45 and 46: THO'1 HOB MOUNTING ERRORS MULTIPLE
Page 47 and 48: ALTERNATELY WIDE ANID NARROW FEED S
Page 49 and 50: dueing that area (scallop) of the g
Page 51: ILLITRON'S, IMO,DEL 9400 CNC GEAR I

Download PDF - Gear Technology magazine

Create successful ePaper yourself

Delete template?

Save as template?