Reciprocating screw is a kind of screw that can make the slider reciprocate without changing the rotation direction of the spindle. Reciprocating screw is a form of three-dimensional cam pair, which is characterized by two thread grooves with the same pitch and opposite rotation directions. The two ends are connected by a transition curve. Through the rotation of the screw, the lateral surface of the spiral groove pushes the slider placed in the spiral groove to do axial reciprocating motion.
Ball screw is an ideal product to convert rotary motion into linear motion or linear motion into rotary motion. Ball screw is the most commonly used transmission element in tool machinery and precision machinery. Its main function is to convert rotary motion into linear motion or torque into axial repetitive force, which has the characteristics of high precision, reversibility and high efficiency. Ball screw is widely used in various industrial equipment and precision instruments because of its small friction resistance!
1 1 ball screw specifications and selection points;
1 to determine the positioning accuracy.
2, through the motor and screw speed requirements to determine.
3. Check the nut size to determine the stroke of the screw shaft end and related data.
4. Determine the average axial force and rotational speed by load and velocity distribution (acceleration and deceleration).
5. Determine the pre-pressure by the average axial force.
6, life, axial load, speed to determine the dynamic rated load.
7, basic dynamic rated load, lead, critical speed, DmN value limit to determine the screw diameter and nut form.
8. Stiffness is determined by outer diameter, nut, preload and load (machine design).
9, environmental temperature, the total length of the nut to determine the thermal change and lead accumulation.
10, screw stiffness and thermal displacement to determine the pretension.
1 1, the maximum speed of the machine tool, the temperature rise time and the specifications of the lead screw determine the driving torque and specifications of the motor.
The nominal diameter of the ball screw is the outer diameter of the screw. Common specifications are 12, 14, 16, 20, 25, 32, 40, 50, 63, 80, 100, 120, but please note that among these specifications, Please refer to the manufacturer's product samples for specific values. Only two concepts are explained here: dynamic rated load and static rated load. The former refers to the rated axial load in motion, while the latter refers to the rated axial load at rest. Just refer to the former when designing. It should be noted that the rated load is not the maximum load, and the smaller the ratio of the actual load to the rated load, the higher the theoretical life of the lead screw. Suggestion: Try to choose the diameter 16~63.
There are two concepts about the length of the ball screw, one is the full length and the other is the thread length. Some manufacturers only calculate the full length, but some manufacturers need to provide the thread length. Thread length also has two parts, one is the total thread length and the other is the effective stroke. The former refers to the total length of the threaded part, while the latter refers to the theoretical maximum length of the nut's linear motion, and the threaded length = effective stroke+nut length+design margin (if it is necessary to install the protective cover, the compressed length of the protective cover should also be considered, generally calculated as 65438+ 0/8 of the maximum length of the protective cover).
When designing and drawing, the total length of the lead screw can be roughly accumulated according to the following parameters: total length of the lead screw = effective stroke+nut length+design allowance+supporting length at both ends (bearing width+lock nut width+allowance)+power input connection length (if coupling is used, it is roughly half of coupling length+allowance). It is particularly important to note that if the length is too long (more than 3 meters) or the aspect ratio is too large (more than 70), it is best to consult the sales staff of the manufacturer in advance whether it can be produced. Generally speaking, the maximum length of conventional products of domestic manufacturers is 3m, and that of special products is16m; that of conventional products of foreign manufacturers is 6m, and that of special products is 22m. Of course, it's not that domestic manufacturers can't produce longer ones, but the price of customized products is ridiculously high. Suggestion: Try to choose the length within 6 meters, and it is more cost-effective to use rack and pinion if it exceeds the length.