How to measure the length of straight seam steel pipes

1. Straight seam steel pipes can be measured using a grating ruler.
(1) The basic principle of measuring straight seam steel pipes using a grating ruler is as follows: Two fixed-length grating rulers are installed on the outer sides of both ends of the straight seam steel pipe. A rodless cylinder is used to move the grating rulers close to both ends of the steel pipe, and the length of the straight seam steel pipe is measured by utilizing the interference phenomenon of light.
(2) The characteristic of measuring straight seam steel pipes using a grating ruler is high accuracy. However, grating rulers are expensive and difficult to maintain, and are very sensitive to the effects of dust and site vibration.

2. Straight seam steel pipes can be measured using a camera.
(1) The principle of measuring straight seam steel pipes using a camera is to use image processing to measure the length of the steel pipe. The principle is to install a series of photoelectric switches at equal intervals on a certain section of the straight seam steel pipe conveyor roller, and add a light source and a camera on another section. When the steel pipe passes through this area, the length of the steel pipe can be determined by the position of the image captured by the camera at a certain photoelectric switch on the screen. 
(2) The advantage of using a camera to measure the length of straight seam steel pipes is that it allows for online measurement; the length data is obtained as the pipe passes through the measurement area without any intervals. The disadvantage is that without a dedicated light source, the pipe is susceptible to interference from external light. With a dedicated light source, the high brightness at the pipe end after chamfering leads to strong light reflection, easily causing reading errors.

3. Straight seam steel pipes can be measured using an encoder.
(1) The principle of encoder-measured straight seam steel pipes involves installing an encoder at the hydraulic cylinder. The cylinder pushes the steel pipe along a roller conveyor. A series of photoelectric switches is installed at equal intervals on the other side. When the pipe end touches a photoelectric switch after being pushed by the cylinder, the recorded encoder reading is used to calculate the cylinder's stroke, thus determining the pipe's length.
(2) The advantage of encoder-measured straight seam steel pipes is that the pipe needs to be raised during measurement. Furthermore, photoelectric switch detection also has errors, potentially requiring more thorough measurement.

4. Length Measurement of Straight Seam Steel Pipes Using an Improved Encoder
(1) The principle of measuring the length of straight seam steel pipes using an improved encoder is an indirect measurement method. The length of the steel pipe is indirectly measured by measuring the distance between the two end faces of the pipe and their respective reference points. A measuring carriage is set at each end of the steel pipe, initially at zero position, with a spacing of L. Then, the length of the measuring carriage is moved to the respective pipe end by a distance (L2, L3). L-L2-L3 is the length of the steel pipe.
(2) The improved encoder for measuring the length of straight seam steel pipes overcomes difficulties such as the large size of the steel pipe, the complex production environment, and the inability of the measuring mechanism to pass through the lower support frame of the steel pipe. This method is easy to operate, with a measurement accuracy within ±10mm and a repeatability of ≤5mm.