The precision retaining ability of robots is an obstacle for the popularization of domestic robots. Compared with imported robots, the poor precision retaining ability of domestic robots is one of the main gaps between them in technology and process performance.
In fact, the factory precision of domestic robots is not much worse than that of imported robots, and even the static precision index of some robots is higher than that of imported robots. However, the precision of domestic robots declines rapidly after leaving the factory, and some robots need to replace the parts or recalibrate after half a year of use. In contrast, the precision of imported robots remains high after years of use.
Generally speaking, under normal conditions of use, the robot's precision is not static, but it will fluctuate and decline. As long as it does not exceed the range of precision requirements, it is considered that the robot's precision retention ability is still good.
The precision of domestic robots can hardly be guaranteed within the limit after a period of use. To solve this problem, we must find out the main factors that affect the precision of the robot, and then act accordingly to make improvement.
Among them, the loss of hardware structures such as the wear of harmonic reducer, the deformation of connecting rod and the decrease of joint rigidity are the main reasons for the poor precision retaining ability of robots.
From the point of view of robot precision decline, the fundamental reason is abnormal wear of moving parts, which may be caused by unreasonable design, manufacture and use.
The harmonic reducer in the robot transmission system is the joint of the robot, just as the gearbox is to the automobile, which controls the power output and operation precision of the robot. Therefore, in the improvement of robot's precision retaining ability, harmonic reducer is undoubtedly a crucial breakthrough point.
If taking the foreign high-end brand HD as the standard, through the horizontal evaluation test of the precision retaining ability of harmonic reducers on the market, the output end of the reducer is subject to constant torque (average allowable load torque) and rotating speed for continuous operation test. According to the test results, it can be found that, with the increase of test time, the transmission precision presents a trend of first getting worse and then getting better; as time continues to increase, the transmission precision fluctuates within a certain range. (The figure below is the horizontal evaluation test of Haozhi)
Precision retaining ability test for harmonic reducers of mainstream brands
In the precision retaining ability test for harmonic reducers of mainstream market brands, Haozhi's product is the closest to the HD product both in terms of initial precision and precision retaining ability.
Key factors of precision retaining ability for harmonic reducers
To ensure the precision of the robot, the precision of the harmonic reducer must be very high, which is closely related to the design, material selection, and technology of the harmonic reducer. This is also why Haozhi's harmonic reducer can match the HD product.
After thoroughly studying the IH gear tooth profile, "Harmonic Gear Transmission", "Harmonic Gear Transmission Theory and Design" and curve mapping theory, Haozhi forward designed and developed the SP harmonic gear and convex contour for its harmonic reducer, which also obtained national invention patent. The SP gear tooth profile ensures that the number of teeth meshed simultaneously exceeds 30% of the total number of teeth.
The meshing of the rigid and flexible gears of the harmonic reducer will also lead to constant wear, which will affect the precision retaining ability of the robot. The rigid gear of Haozhi's reducer adopts imported cast iron with high strength and excellent lubrication performance, which guarantees precision and longevity as well as reduces the noise value of the product.
The wear speed of harmonic reducer is directly influenced by the finish and precision of tooth surface. In order to reduce wear speed, the gear machining precision level of Haozhi's products is strictly controlled within Level 6, and the surface finish is controlled within Ra0.4.
Real photo of the tooth surface of Haozhi's harmonic reducer
The company independently develops the special flaw detection instrument to overcome technical barriers in the industry and ensure product quality.
In addition, in order to ensure the consistency and stability of products when leaving the factory, the key dimensions of all parts and components of Haozhi are strictly selected, and each product after assembly is monitored by spectrum, truly achieving the full closed-loop control of the assembly process.Improve the lubrication effect and reduce the wear of transmission parts
The lubrication effect of tooth surface is another key factor of gear wear. Based on lubrication theory and years of grease application experience, Haozhi has developed a special grease. The grease produces a winding oil film on the transmission parts, which reduces the wear of the transmission parts, improves the oil film strength and reduces the temperature rise at the same time.
In addition, because the uniquely formulated grease contains nanoscale spherical particles with a diameter of about one twentieth of the molecular diameter, it can penetrate into every corner between parts without causing viscosity changes. The nanoscale particles play the role of fine bearings, and make use of the bearing effect to change sliding friction into rolling friction, thus reducing the wear speed of transmission parts to the greatest extent.
State of abrasive particles under abnormal wearState of abrasive particles under normal wear
In 2014, Haozhi entered the field of robotics and officially started the research and development of harmonic reducer. After five years of theoretical research and practice exploration of robot's gear reducer, Haozhi has continuously broken through the bottlenecks of material restrictions, tooth profile, convex contour and other design blockages and lubrication technology.
At present, Haozhi has developed two series (double-wave and three-wave), 10 specifications (11, 14, 17, 20, 25, 32, 40, 45, 50, 58), 6 large reduction ratios (30, 50, 80, 100, 120, 160) and a full range of robot joint modules. The company's harmonic reducer product line continues to expand to meet different needs in different fields.