Balls from the ball guide off the main causes and solutions
I. Installation errors lead to uneven force on the balls
Reason:
guide rail installation parallelism is too poor (such as the parallelism of the two rails > 0.02mm), resulting in the slider running skewed, the balls bear lateral force and fall off. An automated production line due to the parallelism of the guide rail 0.03mm, 3 months after the operation of the ball from the groove of the slider off.
Insufficient verticality of the support base (such as verticality > 0.01mm), the slider tilted extrusion of the ball, a CNC lathe, so the ball crushed off.
Solution:
Calibrate the parallelism of the guide rail with laser interferometer to within 0.005mm, and adjust it with 0.01mm stainless steel spacer during installation;
Test the perpendicularity of the support base with a ruler + micrometer, and grind the installation surface to within 0.005mm.
Second, lubrication failure triggered by ball dry grinding off
Reason:
grease type error (such as high-speed scenes using ordinary lithium grease), a high-speed engraving machine due to high grease viscosity, ball friction heat sintering off.
Lubrication cycle is too long (such as more than 200 hours without oil replenishment), the ball and the raceway direct friction wear, a 24-hour running production line so every six months off the ball.
Solution:
Choose low viscosity oil mist lubrication (such as Mobil DTE 24) for high-speed scenarios, and use molybdenum disulfide grease for low-speed and heavy-duty;
Set automatic lubrication cycle: inject oil every 100 hours for normal working conditions, and every 50 hours for high-speed working conditions.
Overloaded operation crushes ball raceway
Cause:
Load exceeds the rated dynamic load of the guideway (e.g., rated at 5,000N but carrying 8,000N), and the ball of the guideway of a press craters due to overloading, and eventually falls off.
Instantaneous impact load (such as workpiece collision table), a machine tool tool impact on the table during tool change, resulting in the slider ball crumbling off.
Solution:
selection according to 1.5 times the safety factor load calculation, heavy load scenarios with double row roller guide (such as INA SLW series);
installation of buffer devices (such as hydraulic dampers), reduce the impact load, a stamping equipment retrofitted with a 90% reduction in the failure of the ball off.
Fourth, foreign matter invasion stuck ball
Cause:
dust or iron chips into the guideway groove, a woodworking machine tool due to the accumulation of wood shavings, the ball is stuck when running, forcibly move to cause the ball to fall off.
Cutting fluid infiltration into the guide, the grease is diluted failure, a gear processing machine tool so that the ball rust off.
Solution:
Install dust-proof scraper (e.g. THK Z-shaped scraper), and use fully sealed guideway (IP65 protection) for high dust environment;
Clean with anhydrous ethanol immediately after contact with liquid, and apply waterproof grease (e.g. Klüber BE 41-152).
V. Long-term wear and tear leads to large gap
Reason:
The guide rail has been used for more than 5000 hours without replacement, and the diameter of the ball is worn out by 0.02mm, and the gap increases and then falls off. An automobile production line guide after 8000 hours of operation, the ball due to excessive clearance from the slider thrown out.
Pre-tensioning force decay (such as spring pre-tensioning force is insufficient), the slider loosened resulting in uneven force ball shedding.
Solution:
Every 2000 hours with a ruler to detect the ball gap (normal ≤ 0.005mm), more than 0.02mm when the replacement of the slider;
Regularly check the pre-tensioning spring tension, a device through the monthly calibration of pre-tensioning force, the ball off the failure to reduce 70%.
Sixth, design defects or material problems
Reason:
guideway radius of curvature and ball mismatch (such as curvature is too small), a low-priced guideway due to design defects, running 1000 hours after the ball peeling.
Insufficient material strength (such as the surface hardness of the raceway <HRC58), a non-standard guide due to poor quenching process, the ball crushed after the raceway fall off.
Solution:
Select brand guide rail (such as THK, HIWIN), ask for the curvature of the raceway test report;
acceptance of the Rockwell hardness tester to test the hardness of the raceway, to ensure that ≥ HRC58, reject non-standard poor quality products.
Emergency treatment and prevention strategy
shedding emergency:
found that the ball off immediately stop, with a magnet to adsorb the scattered ball, check the raceway whether there are scratches (depth > 0.01mm need to replace the guide).
Regular inspection:
weekly flashlight irradiation guide groove, observe the ball surface luster (dark or spots indicate wear);
listening to the running noise (abnormal "click" sound suggests ball damage).
Lifetime management:
Replace the guide rail according to the cumulative running distance: every 1000km for normal working conditions, and every 500km for high speed and heavy load.
Summarize: shedding prevention "three principles"
Installation precision: calibrate the parallelism/verticality with the instrument, control the error within 0.01mm;
Lubrication in place: select grease according to the working conditions, regular oiling to avoid dry grinding;
Load control: avoid overloading and impact, choose brand guide rail to ensure the strength of the material.
By following the above strategies, the risk of ball shedding can be reduced by more than 80%, and the continuous operation of the equipment can be guaranteed.
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