PRECISION INFEED OPTION
COMPUTERIZED CROWNER RETROFIT SYSTEM
RGB Engineering offers a program upgrade that will allow the computer hardware to be used to give the operator some "handwheel" manipulation for tilting (as opposed to sliding) the wheelhead for precise control of the infeed.
Virtually all roll grinders up until about 1960 utilized "slide" type infeed ways for feeding the wheel to the work. These were either cast iron ways, hardened steel against bronze, or sometimes special materials were used. Hydrostatic ways were not introduced until the middle sixties. Some machines employed a separate undercarriage (camber base) for "tilting" the wheel to achieve the fine accuracy required by the crown profiles. But the primary wheel feed that the operator controlled for shaping and finishing the roll was still the slide way infeed. The problem with this approach, which is well documented, is the classical "stick-slip" condition that makes it extremely difficult to feed the wheel in a uniform and precise manner. The wheel tends to move in discrete jumps rather than in a smooth motion. There is also the problem of excessive backlash with the acme feed screw, making it virtually impossible to feed the wheel "in" or "out" precise amounts.
It was because of this that Farrel Corporation developed their "tilt infeed" concept in 1959. Essentially, this consisted of a compound lever arrangement, superimposing both the crown and normal handwheel feed through the same pivoting wheelhead structure. Other roll grinder manufactures later achieved the same result with different versions of the concept (wedges, levers, etc). RGB Engineering can achieve the same benefits on these older style roll grinders, without major mechanical alterations, by utilizing the crown tilt axis for fine handwheel movements. This can be an important feature when grinding any type of roll where finish is critical, since the operator has much finer control than with slide infeed alone.
With the precision infeed option, the operation of the crowner control will be essentially the same as described, except that the screen outputs will be modified to include the precision infeed readouts. There will also be a separate screen used by the operator to monitor the precision wheel feed. Whichever display is active has no effect on the actual crown control, which continues to function normally. The operator can manually add or subtract precision distances to the infeed during the "crown" control mode by selecting this PI screen. Output will still be a positive reference which will be controlled by the LVDT servo system. The infeed will be superimposed on top of the crown profile, which has the effect of shifting the entire crown curve in or out depending on the direction of the feed.
The total amount of precision infeed available is the difference between the maximum amount of infeed (which is a function of the cam throw or ball screw travel, and the LVDT), and the amount of crown or concave selected. Therefore, if a large crown is being ground, only a small precision infeed component is available for PI control. Conversely, small crowns will allow almost all the infeed to be used for PI. It should be noted that the primary function of this feature is for fine control during finish or semi-finish grinding, or for limited amounts of rough grinding as with cold mill work rolls.
It is
possible to actuate this precision infeed feature using only the keyboard arrow
keys, but the
preferred method is via a small MPG (manual pulse generator)
handwheel mounted close to the operator's work station on the carriage, or in
front of the grinder for a TT. The photo shows a typical setup.
Other logical extensions of this option are the "continuous infeed" and "end infeed" automation features, which allow the wheel to be fed in at a constant rate (continuous infeed) to compensate for wheel wear, and a fixed amount after carriage reversal at each end of the roll face (end infeed) to initiate a fresh cut. Of course, the amount of infeed available for this purpose is dependent on how much is used for the crown and bed correction curve.