PEELSIM™ simulates peeling of peeler blocks for veneer.
It calculates average green veneer yields and peeling times for various block classes and combinations of lathe type, veneer thickness and peeler-core diameter. The latter combinations are referred to as peeling methods.
Blocks are allocated to various diameter classes, and also to quality classes determined by taper, sweep and other characteristics.
For the results to be useful, the program must be calibrated against production data and/or test results.
The benefit is that sets of yields and peeling times can be developed for a variety of block classes and peeling methods that match actual operating results, are consistent within themselves, and give accurate information as to the relative effects of small changes. Thus the results can be used with confidence to optimize plywood, LVL or similar operations.
The program simulates the peeling of each block that is described in the data in turn, by each of the peeling methods that are specified. It then allocates each block to a block class, accumulates the results and calculates average yields and peeling times for each block class and peeling method.
The program first calculates the axis and diameter of the largest "veneer cylinder" that will fit into the block full length. The green veneer that develops from within this cylinder is classified as heartwood, light saps, heavy saps or random width. Any veneer that comes from outside the veneer cylinder is classified as roundup veneer. Factors supplied by the user are then applied to the calculated yields to determine actual yields of various green veneer types.
The program makes corrections for the veneer that develops from the region next to the core when the veneer ribbon is clipped to full sheets, and to allow for the veneer being a spiral that is created as the knife moves in.
The user may specify diameter ranges for "grade zones" within blocks. These are concentric cylinders, with the same axis of rotation as the veneer cylinder. In addition to being classified as described above, veneer is classified by the grade zone that it develops from. The purpose is to allow subsequent specification of green-to-dry veneer yields that depend on the grade zone that the veneer came from. It also predicts volume of light- and heavy-sap veneer, depending on the thickness of the sap ring.
Overall veneer yield reduction factors may be specified for "cylinder" veneer and "roundup" veneer separately, and a diameter reduction constant and factor may be specified which applies to the diameter of the veneer cylinder.
Veneer-loss factors may also be specified for each grade zone, to account for losses from the inner zones due to curl and defect, depending on the core diameter.
Finally veneer yields may be adjusted by adjusting the factors that are supplied to convert calculated veneer yields to actual yields of various green veneer types. These factors do not have to add up to 1.0.
To test the yield table that is generated, the user may provide a table of block counts for each block class and peeling method. The program will calculate the corresponding green veneer type productions, for comparison with production or test run results.
For the program to calculate peeling times, the user must specify the load time per block, the rotation speed of the lathe, if it is a conventional lathe, or the ribbon speed, otherwise, the maximum tray speed and capacity, the clipper speed for fishtail and strip, and for full sheets. The peeling process is divided into phases that depend on whether the lathe speed, tray speed or clipper speed is limiting. The calculated time per block is the load time plus the times for each phase.
PEELSIM™ may be run in simulation mode with only one peeling method allowed per run. The totals of the veneer products, chips and cores, and lathe and clipper times for all blocks are accumulated. Alternatively it may be run in data generation mode, in which a database containing veneer, core and chip yields, and lathe and clipper times per block, is generated for each block class.