CNC machine tools linear guide: high precision and long life maintenance

CNC machine tools linear guide: high precision and long life maintenance

First, the installation accuracy: lay the foundation for precision "first step"

datum calibration

installation before the laser interferometer to detect the machine base flatness (error ≤ 0.01mm / m), an automotive mold factory due to the base is not flat leading to the guide rail distortion, machining the workpiece flatness exceeds the difference of 0.03mm, regrind the base after the recovery of the accuracy of 0.005mm. 0.005mm after regrinding the base.

The parallelism of the two guide rails should be controlled within 0.005mm (available marble platform + micrometer calibration), otherwise the table will generate lateral force when running, accelerating the wear of the guide rail.

Bolt torque control

diagonal order in 3 times to tighten the guide rail mounting bolts (such as M8 bolt torque 20-25N・m), a machining center due to uneven screwing bolts, local deformation of the guide rail caused by the table stalling, adjusted running current fluctuations from 15% down to 5%.

Lubrication management: the core strategy to reduce wear and tear

Grease selection and cycle

Ordinary working conditions: use lithium grease (such as Klüber NBU 15), replenish the oil once every 100 hours of operation, an automated production line according to this maintenance, the life of the guideway is extended from 3 years to 7 years.

High-speed scenarios: switch to low-viscosity oil mist lubrication (such as Mobil DTE 24), through the compressed air will be sprayed to the surface of the guide rail oil mist, a high-speed milling equipment used, the coefficient of friction from 0.005 down to 0.002, heat reduction of 40%.

Lubrication "three taboos"

taboos excessive oil injection: grease filling more than 1/3 of the slider cavity will increase the operating resistance, a machine tool due to excessive oil injection, servo motor load increased by 20%, significant waste of energy consumption.

Avoid mixed use: different base oil lubricating grease mixing is easy to produce gelatinous substances, a device mistakenly calcium-based grease mixed with lithium-based grease, 6 months within the guide rail abnormal wear.

Third, clean protection: the key to resist environmental erosion

dust and debris protection

installation of dust scraper (such as THK's Z-shaped scraper), a woodworking machine tool installed, the guideway groove dust accumulation reduced by 90%, the maintenance cycle from 1 time a month to 3 months.

High-dust environments use fully sealed guideways (e.g. NSK LE series) with IP65 protection, so a foundry machine extended its guideway replacement cycle from one to three years.

Rust and corrosion control

Humid environment regular application of rust preventive oil (such as WD-40), a coastal area of machine tool guideway through the weekly rust treatment, the probability of rust from 40% to 5%.

Immediately after contact with corrosive media (such as cutting fluid), wipe with anhydrous ethanol, a gear processing plant because of the lack of timely cleaning, the surface of the guide rail rust spots, resulting in table movement jam.

Load and speed control: avoiding overload wear

Dynamic load management

Avoid exceeding the rated dynamic load of the guideway when cutting (such as THK HRW series rated load 5000N), a gantry milling machine overloaded machining, the guideway raceway appeared to be indentation, the machining surface roughness from Ra1.6 to Ra6.3.

Heavy-duty scenarios using double-row roller guideway (such as the INA SLW series), a press to change to the After a press was retrofitted, the load capacity was increased by 3 times and the guideway life was extended from 2 to 6 years.

Acceleration and deceleration control

set smooth acceleration and deceleration curves during high-speed operation (such as acceleration ≤ 1m/s²), a lithium battery wafer cutting equipment due to emergency stops and starts, the guideway slider wear increased by 0.01mm per month, after optimizing the parameters, the wear rate decreased by 70%.

V. Thermal deformation control: the invisible key to precision maintenance

Temperature monitoring and heat dissipation

Installation of temperature sensors (accuracy ± 1 ℃), a machining center guideway temperature exceeds 50 ℃ automatically start the cooling fan, to avoid gap changes due to thermal expansion (20 ℃ temperature difference of 1m guideway deformation of 0.023mm).

High-speed machining with a cooling channel guide rail (such as Germany Rexroth temperature-controlled guide rail), a device through the circulation of oil cooling, guide rail temperature fluctuations control in ± 2 ℃, 4 hours of continuous processing size deviation <0.005mm.

Thermal balance design

The distance between the motor and the guideway is ≥100mm, which reduces the heat conduction of the motor. After adjusting the layout of a CNC lathe, the temperature of the guideway is reduced from 60℃ to 45℃, and the thermal deformation error is reduced by 60%.

Sixth, regular testing and preventive maintenance

Accuracy review project

annual laser interferometer to detect the straightness of the guide rail (standard ≤ 0.005mm / m), a mold factory found that the straightness of the guide rail deteriorated to 0.01mm / m, grinding and repairing in a timely manner, to avoid loss of workpiece scrap.

Use a micrometer to detect the parallelism of slide operation (error ≤ 0.01mm), a certain equipment due to excessive parallelism led to abnormal wear of the screw, after adjusting the maintenance cost reduction of 8,000 yuan.

Wear and tear assessment

with a ruler to detect the gap between the guide rail and the slider (normal ≤ 0.005mm), more than 0.02mm when you need to replace the slider, an automated production line according to this standard maintenance, there is no downtime due to the guide rail problem.

VII, typical fault emergency treatment

running stagnation

Immediately stop the machine to check the guideway grooves whether there are foreign objects (such as iron filings, grease dry junction), a machine tool due to chips embedded in the guideway, forcibly run resulting in damage to the slider, the correct approach is to use compressed air blowing after applying a new lubricating grease.

Abnormal noise

If a "clicking" sound is emitted, the ball may be worn (e.g., after 5,000 hours of operation), and the guideway needs to be disassembled to check the surface of the ball, and a certain machine therefore replaces the ball ahead of time to avoid further damage to the raceway.