The ECE R117 standard was formally issued on February 20, 2023. This standard specifies the wore tire preparations equipment and buffing requirement for test procedure for measurement the adhesion on wet surfaces of tires in worn state. The release of this standard has received extensive attention from tire manufacturers, with the most critical wore tire preparation machine becoming the focus. What kind of equipment can meet the wore tire requirements of the standard? What needs to pay attention about the machine? The following is explanation according to the customer inquiries combined with TMSI tire grinding machine.
a) In order to increase the worn tire fabrication efficiency, the tire buffing machine should be equipped with tire auto inflation system. The inflation system is used for rapid inflation and deflation, and needs to keep air pressure stabilization during tire rotation. The inflation system includes pressure detection and pressure control system. Tire can be automatically inflated after putting in position. During buffing process, the tire pressure can be monitored and recorded real time. According to the requirement, the accuracy of tire pressure shall be ±5Kpa. And the tire pressure shall be always maintained to be setting pressure during buffing.
b) The rim shall be rigid enough to ensure the deflection of bead seat in any direction less than 0.13mm when it runs in setting pressure. The forged aluminum rim is used with the high-strength shaft to ensure the circumferential accuracy when the tire is loaded to buffing stone by the radial force; otherwise, the problems of bias grinding and uneven depth of circumferential grinding may occur.
c) The temperature of the tire tread shall be monitored during buffing, and the temperature can’t be greater than 110℃. The tire buffing equipment shall be equipped with surface temperature measuring sensor, the common type is the contactless infrared temperature sensor. Secondly, the buffing recipe should be setup according to the tire dimension and rubber material, the feeding amount shall be adjusted (the more feeding amount, the higher the buffing efficiency will be, but the temperature of tire surface will rise accordingly). The most important is that the tire buffing equipment shall be equipped with cooling system which can physically cool the tire surface, and remove the rubber crumbs attached on the tread. TMSI uses a high-efficient vortex cooling technology which can effectively control the temperature of tire surface within 100℃.
d) The groove depth in each measurement point reaches the target groove depth. The final groove depth at each individual measurement point of the central zone should be 2mm ± 0.4mm, the average groove depth over all measurement should be 2mm ± 0.2mm, The final groove depth in the shoulder zone should not be greater than 2mm. The final contour in tire shoulder shall be a curve which transits from the main groove to the tire shoulder on both sides.
This requirement is most important and difficult to meet. Firstly, the buffing equipment should have profile measurement to get the profile data for tire tread and groove. Secondly, it shall have ability to define and edit the target contour by the user or create target contour auto automatic. Besides, the machine control system and mechanical structure can perform buffing according to the target contour. TMSI tire buffing machine has X/Y coordinate system, which can work with the buffing stone swing system to ensure the transition of the curve.
e) The average of 3 arithmetic mean height of absolute values of the roughness profile of the final surface should not exceed 20um. Some standard request tire surface roughness Ra≤10μm. This is another important requirement for preparation of the worn tire, which is related to actual effect of the wet slip test. This parameter is decided by the roughness of the buffing stone and the buffing uniformity. The buffing stone of TMSI machine is made of steel wheel coated with emery, which can ensure the buffing effect and service life.
The five items above basically cover the key requirements of preparation equipment of worn tire. Besides, many functions of the tire buffing equipment may affect the safety and efficiency of tire buffing. For example, the sound insulation room, automatic tire lifting device, dust collection device, etc.
Anyway, the worn tire preparation equipment is an important tool for wore tire adhesion measuring on wet surfaces. High-precision tire buffing machine can not only improve tire grinding accuracy but also enhance grinding efficiency, which can ensure to provide enough wore tire for test and the test accuracy for measurement the adhesion on wet surfaces of tires in worn state.
