Papers by Gorazd Hlebanja
Feature modelling and manufacturing with a CAD-CAM system
MATEC Web of Conferences, 2019
Plastic materials can be used for various gears and gear mechanisms due to their qualities, like ... more Plastic materials can be used for various gears and gear mechanisms due to their qualities, like wear resistance when running dry, low noise, vibration damping, low inertia, low manufacturing cost, etc. However, they also expose with temperature connected problems like rapidly decreasing load, thermal expansion and accuracy of moulded gears. Therefore, it is a challenge to produce gears with adequate accuracy and durability to serve in contemporary mechatronic applications in automotive, in medical equipment and many other industries. Such materials are POM, PA6, PA66, PEEK, reinforced plastic materials, etc. and steel. Proper combination of such materials can result in long and reliable operation of such mechanisms. On the other hand, S-gears offer improved properties in comparison to involute (Egears), which essentially comprise lower contact pressure, less sliding and frictional losses, stronger root and improved oil film when lubricated. The goal is development of advanced power...
Investigation of the Computer-Aided Drafting
CIRP Annals, 1985
The workshop drawing represents the basic document for forming the part spectrum data base for pr... more The workshop drawing represents the basic document for forming the part spectrum data base for process planning and the generation of the NC - tapes. The paper reports on a unified approach to develop a software for computer-aided drafting on a common basis with the CAPP and CAM including the computer-aided part classification. The proposal is based on the binary matrix of primitives in CSG presentation. The organisation and the operations on the sets of contours are explained in detail. It is shown how this approach is used in computer-aided drafting.
New Trends in Technologies: Control, Management, Computational Intelligence and Network Systems, 2010
MATEC Web of Conferences
Search for an improved gear tooth flank shape arose from heavy industry problems rolling mills. O... more Search for an improved gear tooth flank shape arose from heavy industry problems rolling mills. Original involute gears suffered severe flank damages. So, better gear teeth flanks should improve contact circumstances, decrease the flank pressure, and enhance a lubrication film. This was achieved by a curved, pole symmetric path of contact by purely graphical methods. And the developed gears, proven in heavy industry applications, showed highly improved properties. Specimens of both gear geometries, which were made of tempered and nitrided alloy steel, were tested on an FZG testing machine, and results confirmed the theoretical foundations of S-gears. Then it was necessary to replace the graphical method by a numerical one and to define the tool. So, the rack profile was defined by a pole symmetric parabolic-type function, which in turn defined the path of contact and finally gears with an arbitrary number of teeth. Many applications were developed with S-gear shape, e.g., helical, c...
Influence of the tooth flank shape on wear for a steel-POM gar pair
International Conference on Gears 2022
S-gears: From Metal to Polymer Solution
The paper addresses the gradual development of S-gears from a heavy industry start up to the pres... more The paper addresses the gradual development of S-gears from a heavy industry start up to the present state with polymer gears. The curved and half symmetric path of contact implies a concave-convex contact in a vicinity of the meshing start (and end), higher reduced radii of curvature and improved lubrication conditions. Specimens of both gear geometries, which were made of tempered and nitrided alloyed steel, were tested on an FZG testing machine, and results confirmed the theoretical foundations of S-gears. Lastly, the rack profile is defined by a parabolic-type function, which in turn defines the path of contact and finally gears with arbitrary number of teeth. This concept is considered for polymer gears as well. A special testing machine was built to enable testing of small plastic involute (E-) and S-gears. Initial results combining gear pairs made of polyacetal and nylon confirm the theory of S-gears. Improved performance of S-gears, compared to E-gears, is based on the fact ...
Advanced Lifetime Tests of Plastic Gears with E- and S-Geometry
Preizkušanje vzdržljivosti površin pri kotalno drsnem trenju in majhnih hitrostih Testing of Surface Endurance in Rolling-Sliding Friction at Low Velocities
Kotalno-drsni stik je eden od osnovnih načinov, s katerim sta v oprijemu dve površini, poznamo ga... more Kotalno-drsni stik je eden od osnovnih načinov, s katerim sta v oprijemu dve površini, poznamo ga pri najrazličnejših sestavih. Še posebej zanimivi so taki stiki, če je proces počasen, ker se v tem primeru mehanizem bistveno razlikuje od hitrih stikov tako po načinu tvorjenja oljnega filma kakor po mehanizmu obrabe. Najbolj značilni so počasni zobniški prenosniki, kakršne uporabljamo npr. pri cementnih mlinih, v naftni industriji, pri prenosnikih za dvigalne naprave itn. Taki počasni zobniki so izpostavljeni procesu obrabe, zaradi česar se spremeni oblika zobnih bokov, s tem pa se poslabšajo kinematične lastnosti. Ker gre praviloma za večje komponente, je odpravljanje takih napak še težje in dražje. Postopek za dimenzioniranje zobnikov pri takih delovnih razmerah tudi še ni dobro definiran, zato so tovrstne raziskave toliko bolj upravičene. Ker je zmanjševanje trenja in vsakovrstne obrabe v bistvu pomemben gospodarski problem, so bile v zadnjih desetletjih izvedene in se še vedno iz...
Recent Advances in Gearing, 2021
The chapter starts with the theory defining S-gears and their properties and compares S- and invo... more The chapter starts with the theory defining S-gears and their properties and compares S- and involute gears. Most of the text deals with cylindric spur gears. S-gears are defined with the half-symmetric rack profile, which then uniquely defines the path of contact and gears. Reshaping of the gear flanks for external and internal gear pairs is presented here and thermal behavior discussed and compared with the involute gears. Experimental verification of S-gears theory, especially durability and thermal behavior of importance for plastic gears is presented. So, in this chapter a material combination of interest was alloy steel and POM (which was only heat stabilized). The chapter presents some specific information about this. And finally, the planocentric gearbox focused on high-tech industry (e.g., robotics) is presented. The problem is how to achieve required properties. So, all possible analytical tools should be used to minimize backlash and many other parameters which is also pr...
The planocentric gear boxes, devices for large transmission ratios, primarily applied in automati... more The planocentric gear boxes, devices for large transmission ratios, primarily applied in automation and mechatronic industry, decrease rotational movement and increase torque to the largest possible extent in the smallest available space. The paper discusses several planocentric gear boxes in common use in this context. Several solutions are patented. Due to industrial interest for such devices authors propose another solution which improves some characteristics of the existing devices.
Parabolic Worm-Gearing Contact Circumstances
Recently proposed parabolic type worm-gearing is distinguished by a convex-concave contact which ... more Recently proposed parabolic type worm-gearing is distinguished by a convex-concave contact which in general implies higher load capability, improved reduced radii of curvature along the path of contact, and thus better sliding circumstances, which means lower friction and power losses. The worm tooth shape is defined in the axial section by a generalized parabola, which enables progressive curvatures of profiles and implies a convex-concave contact through the entire contact area. The corresponding shape profile implies a progressively curved path of contact and thus a closer fit and correspondingly thicker oil film and better lubrication already in the contact start area. From the basic worm profile in the axial plane, the worm flank surface and the mating worm gear profile and flank surface are derived. Kinematic circumstances are discussed, disclosing the emergence of contact lines (surfaces). The essential characteristics of the proposed worm-gearing are that its entire teeth fl...
Optimization of Planocentric Gear Train Characteristics with CA-Tools
The planocentric gearboxes are characterized by the coaxial input and output shafts and large tra... more The planocentric gearboxes are characterized by the coaxial input and output shafts and large transmission ratios, which can be achieved based on a ring gear with internal gearing in combination with usually two planet gears with external gearing, where the difference in the numbers of teeth between the gear ring and the planet gears is small, preferably amounting one. The proposed solution is based on the S-shaped tooth flank geometry. Since the required gear train characteristics impose strict limitations (e.g. near zero backlash) on the assembled product, it is necessary to simulate its tolerance behaviour. So, a professional or proprietary developed CA tools are necessary to deal with such analyses, e.g. KissSoft. Properties of a such gear train can be successfully modified in this way. A sophisticated testing rig was developed to verify actual gear train characteristics, and to test its short-term and long-term behaviour. Backlash, stiffness, kinematic error, and dynamic behavi...
Durability testing and characterization of POM gears
Engineering Failure Analysis
Abstract Polymer gears are widely used in various power train applications, depending on the inpu... more Abstract Polymer gears are widely used in various power train applications, depending on the input requirements such as weight, noise emissions, load, operating temperature, load cycles, price of the product, etc. Power train systems often use polymers due to their advantageous properties. An optimal material combination should be selected during design to meet the above listed input requirements. The paper contributes to the understanding of wear mechanism in a time sequence from the start up to failed gear, where steel/POM gear pair material is of interest. Gear geometry, quality, testing arrangement and procedure are disclosed in this context. Propagating flank wear is observed by a 3D optical scanning device. Spot temperature of meshing gears is recorded during testing and presented in the study. The paper novelty is the approach for wear characterization throughout the POM gear lifetime. The contribution is the development of a procedure for defining wear progression across the entire tooth flank profile depending on test timescale. Additionally, wear coefficients are calculated according to VDI 2736 guidelines to improve the understanding of the wear progress during the entire service life of the gear pair.
Experimental failure analysis of S-polymer gears
Engineering Failure Analysis
Abstract A comprehensive experimental failure analysis of S-polymer gears is presented in this st... more Abstract A comprehensive experimental failure analysis of S-polymer gears is presented in this study. The analysed gears, made of two often used polymers (POM and PA66) in gear manufacturing, were machined using the standardised cutting tool, and then tested on a custom made gear testing device which allows a continuous torque setting by using a drive and braking asynchronous electric motors. The experimental testing has been done under different external loading of the gear pair (torque) until the occurrence of final failure, which has appeared in three different types: tooth root fracture, tooth deformation, or tooth melting. The obtained experimental results for S-gears are also compared to the results of standardised involute E-gears. This comparison has shown that S-gears demonstrate better load capacity than E-gears in the case of high loading and softer gear material (POM), where the increased temperature may involve the melting of gear teeth.
IOP Conference Series: Materials Science and Engineering
There are many plastic materials (POM, PA66, PEEK, …) and material combinations available. The qu... more There are many plastic materials (POM, PA66, PEEK, …) and material combinations available. The question is which combination is the correct one. It depends on many factors, like expected durability and price, means of production, e.g. injection moulding or cutting, lubrication, microstructure, fillers, etc. The available data bases and data sheets do not present conclusive results. So, it is of the utmost importance for a company to produce effective tests which could present correct results for each individual case. The gear tooth flank profile could be also optimized. S-gear shape is characterized by a convex concave contact in meshing start and end areas. This implies improved properties in comparison to involute gears, like lower contact pressure, less sliding and lower frictional losses, stronger root and improved oil film when lubricated. The paper presents some material properties for the combinations which were tested on the fatigue test benches, presents testing rigs, refer...
Development of Gears from the Antiquity to the Present Time
Recent Advances in Gearing, 2021
The development of human civilization was made possible by mechanical tools, especially those tha... more The development of human civilization was made possible by mechanical tools, especially those that served to transmit power. And soon in this development, devices with teeth appeared. Gears were simple wooden aids for many centuries, but the evidences of complex mechanical devices of antiquity exist. Water- and animal-powered devices were used during the Middle Ages. The Renaissance accelerated the development of science and technology. And soon after a steam engine was invented, which supplied more energy as it was possible until then. Later, the combustion engine, the turbines, and electric motors also accelerated the development of mechanical transmissions. Today we find complex mechanical transmissions in industrial plants, in high-performance machine tools and robots, as well as in consumer devices, with increasing demands toward higher loads, lower vibration, lower maintenance, no additional lubrication, etc. So, gears are a crucial part of such devices, and their development ...
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Papers by Gorazd Hlebanja