With the arrival of winter, the environmental temperature drops significantly. As high-precision machining equipment, CNC drilling and milling machines are susceptible to low temperature effects on their mechanical components, hydraulic systems, electrical components, etc., leading to accuracy fluctuations and even malfunctions. To ensure that the equipment can maintain processing accuracy comparable to new machines in low temperature environments, the following usage and maintenance specifications must be strictly followed.

Before starting up: fully preheat and eliminate temperature difference stress

At low temperatures, the temperature of each component of the equipment is consistent with the ambient temperature. Direct start-up can easily generate thermal stress due to excessive temperature differences, which can affect transmission accuracy and structural stability. Before starting up, the following preheating steps need to be completed:

Equipment overall preheating: After connecting the main power supply, do not immediately start the spindle or perform feed operations. First, turn on the equipment control system and let the heater (if any) in the electrical cabinet run for 15-30 minutes to raise the temperature inside the control cabinet to above 15 ℃. For equipment without automatic preheating function, the lubricating oil pump can be manually turned on to circulate the lubricating oil in the oil circuit for 5-10 minutes, preheating transmission components such as guide rails and lead screws.

Spindle directional preheating: Start the spindle and set it to idle at low speed (such as 500-800r/min) for 20-30 minutes. During this period, the spindle direction can be changed every 5 minutes to ensure uniform heating of the spindle bearings and avoid increased radial runout caused by local temperature differences. Simultaneously observe the temperature changes of the spindle and wait for the temperature to stabilize before proceeding with high-speed machining.

Coordinate axis no-load operation: Manually control the X, Y, Z and other coordinate axes, and perform 10-15 full stroke reciprocating motions at a rated feed rate of 50% -70%. Preheat the screw and guide rail pair through the heat generated by motion friction, eliminate clearance errors at low temperatures, and check the smoothness of the motion of each coordinate axis for any jamming, abnormal noise, etc.

Running: Parameter adjustment, optimization of processing technology

In low-temperature environments, the viscosity of lubricating oil increases and the coefficient of thermal expansion and contraction of materials changes. Therefore, targeted adjustments need to be made to processing parameters and processes to ensure processing accuracy

Cutting parameter adaptation: Compared to normal temperature environment, the cutting force will slightly increase at low temperature. It is necessary to appropriately reduce the cutting speed (about 10% -15%) and increase the feed rate (about 5% -10%) to avoid poor chip discharge or increased tool wear caused by low cutting temperature.

Lubricating oil and coolant management: Replace with low-temperature specialized lubricating oil to ensure good fluidity and lubrication performance even at low temperatures. The coolant needs to be replaced with an antifreeze type, and its freezing point should be at least 5 ℃ lower than the local low ambient temperature to avoid the coolant freezing and blocking the pipeline or freezing and cracking the water tank. At the same time, regularly check the coolant concentration and maintain it at 8% -10% to prevent excessive concentration at low temperatures from affecting the cooling effect.

Workpiece clamping and alignment: Workpieces may undergo slight deformation due to temperature changes at low temperatures. Before clamping, the workpiece should be placed in an environment that is close to the temperature of the equipment workbench (at least 2 hours) to avoid clamping errors caused by temperature differences between the workpiece and the workbench. The method of taking the average of multiple measurements is used to reduce the impact of temperature fluctuations on measurement accuracy during timing.

After processing: clean in a timely manner and take protective measures

After the processing is completed, the cleaning and protection of the equipment are key steps to prevent low-temperature damage and maintain accuracy:

Equipment cleaning: After turning off the spindle and feed system, immediately clean the workbench, guide surface, spindle taper hole, and other areas of chips and coolant residue. For the guide rail surface, a cotton cloth dipped in a small amount of low-temperature lubricating oil can be used to wipe it, forming a protective film to prevent the guide rail from rusting or being scratched by chips at low temperatures. The spindle taper hole needs to be cleaned with a dedicated cleaning rod, coated with anti rust oil, and then installed with a spindle protective sleeve.

Pipeline and oil tank maintenance: After turning off the lubricating oil pump and coolant pump, check for leaks in the oil and water circuits. If the equipment is not used for a long time (more than 24 hours), all the coolant in the coolant tank should be drained and stored in a sealed container to avoid freezing, expansion, and damage to the water tank. The lubricating oil circuit needs to be kept unobstructed. The lubricating oil pump can be manually operated to fill the oil circuit with lubricating oil before turning off the main power.

#Warm reminder#

Maintaining the accuracy of CNC drilling and milling machines in low-temperature environments is a systematic task that requires operators to strictly follow the above specifications, while making personalized adjustments based on the specific model and user manual of the equipment. Only by maintaining and managing every detail well can we ensure that the equipment can continuously and stably output high-precision machining results in winter.