For cold rolled strip coiler, the design principle is that the inner strip does not produce plastic deformation during coiling. For hot rolled strip coiler, it is required that the first few turns of the strip produce a certain degree of plastic deformation, so as to get a neat and compact strip. Taking into account the characteristics of both cold and hot coiling processes, according to the elastoplastic bending theory, the following relationship should be satisfied between the diameter of the reel and the thickness and mechanical properties of the coil strip.

　In addition, due to the limitations of the strength of the reel and the operation line, the diameter of the reel should not be too small or too large. D=(150-200)hmax can be taken at the time of coiling of a cold strip. Non-ferrous metal belt winding when taking D = (120-170) hmax. 305 ¢, commonly used drum size series, ¢, 450, 510, ¢, ¢610 mm. For the strip with large thickness and low yield limit, the diameter of the reel smaller than the calculated value of equation 12-1 is allowed for the strip with correction equipment in the next step of uncoiling. If the thickness range of the coiled strip is very large, it shall adopt the scheme of replaceable reel or machinable sleeve, and change the diameter of the reel according to the thickness and process requirements of the strip, so as to prevent the thick strip from plastic deformation on the small-diameter reel or the thin strip coil from collapsing due to excessive internal hole. Under the condition of hot coiling, the diameter D of the reel is usually selected between (700-850)mm. For the production of wide strip steel, D with 762mm is the most common.The length of the working part of the drum barrel should be equal to or slightly greater than the length of the roll barrel.