Kalahari – Minimum Crib Edge.

Kalahari – Minimum Crib Edge.



It is now possible to set a minimum thickness on the oval calculated. This is useful for polishers where a sharp edge is to be avoided.



When Kalahari calculates the oval, the oval has to run between the Knife edge / Blank size (whichever is smaller) and the shape. In some cases, this is not possible so then a trepan circle is used which is the minimum size uncut (MSU) diameter plus an allowance.



In order to achieve a minimum crib edge the Knife diameter calculation has been altered to be the diameter at the necessary minimum thickness. If the minimum thickness at the new knife diameter is less than the necessary minimum thickness then an oval is not possible. If it is then a search is made for a suitable oval which again may not be possible as the margin between the shape and the knife diameter has been reduced.



Note that lens thickness is not increased. The lens thickness remains optimised to the shape. The use of a minimum crib edge will reduce the number of ovals calculated and hence the number of trepan circles will increase.



If the trepan circle exceeds the minimum knife diameter then a warning is given and the lens thickness can be increased for this.