Logic for Wire Rod Mill.

[rajsiyer]

Hi guys, My next project is a wire-rod mill control system. It is actually a cut to length line, fixed at the end of a finishing mill for 6,12,16,20,25 & 32 mm diameter steel rods of the type called re-bars which are used for reinforcement of concrete in construction. This kind of steel is called TMT bars in India. I'd like to hear other's experiences if at all available to take care of pitfalls to be anticipated in a work of this nature. Basically, the finishing stands have a shaft-encoder each and the ends of the bars are being detected by a HMD or hot metal detector. Required length of the cut pieces are put into the PLC from SCADA(InTouch probably). PLC also measures the speed of the hot rod before and after cutting and suitably sets the speed for a pinch roll arrangement to pull away the cut section. Delays for the PLC cycle time, the time taken for the flying shear(cutting mechanism) are all taken into account to decide the time offset at which the PLC outputs a signal to the flying shear so that the cut length is of the length required length within a tolerance of a few mm. There is also a quenching tank through which white hot metal(900 degs passes and emerges with a dark surface(@200 degs. celsius). A problem arising out of this is that a Hot metal detector placed on the low temp. end of the quenching tank will not work. So I'd like to know what the steel industry elsewhere in the world does in the same situation. Thanks a million to anybody who could offer a few words of help. Raj S. Iyer

[BobLfoot]

The last steel shearing job I did was with cold roll bars between 1&3/8 and 2&1/2 inches diameter. We used an encoder off from one of the pinch wheels. We had to decel and accel for the stationary shear to cut. For your application how about this. Put your shear knife on a flying table. At the end of the table have a grounding sensor which the bar completes the circuit when it touches it. The table which was moving very slowly accels and matches the rod speed when the gound circuit closes. The shear then drops and the table accels forward to seperate the rod and pushes it off the table at a 90 degree angle. Once the billet clears the table it reverses direction back to the pick up position and waits for the slug to touch ground again. If you use V slot wheels and palce the shear on a servo bed then one bed can cut all sizes and lengths. just a wild thought.