Technical information
(1) Saws
When optimising parameters are set to allow the program to override the usual minimum trims this can (for some saw models) affect how the remaining trims and waste are dealt with.
Homag saws - Homag NPS400 V3 - as the fit of parts gets tighter the front trim is reduced leaving the rear trim intact. When the waste is less than rear trim the rear trim is reduced accordingly. The trim values written to the program file are set for the whole pattern and the rear trim is set to the smallest value occurring in the pattern.
Homag saws - Head retrim and rear crosscut trim - These trims usually must match for these saws but if the trim overrides apply this rule does not apply and the head retrim is set as the minimum of the actual head retrims and crosscuts trims.
Compumatic - On some of these saws the calculation is different because the rear trim can either be a fixed value or zero but not anything else.
Staggered head cuts - In some situations the reduced trim setting allows the optimiser to create a more complex pattern (staggered head) by overriding the trim value for the head portion of the board. In adjusting trims in this way the program attempts to adjust the trims on the head portions first before altering the trims on the main portion.
(2) Use of waste
Where there is more than enough waste to satisfy the override trims, waste is moved to the rear trim up to its maximum value. Any further waste then forms part of the front trim / falling waste, for example:-
Front & rear trims: 10mm. Override trims: 1mm (min)
Waste available Rear trim Front trim
2mm 1mm 1 mm
3mm 2mm 1 mm
4mm 3mm 1 mm
.....
11mm 10mm 1mm
12mm 10mm 2mm
More explanation of optimiser type
Optimiser type is set via Optimising parameters. Select the type appropriate to the task, for example, for timber the crosscut only optimiser is used. The options are:-
• Automatic selection
• Crosscut only (timber)
• Rip only (strips)
• Strip production
• Small quantity optimiser
• Medium quantity optimiser
• Medium quantity optimiser II
- Automatic selection - lets the program choose the best optimiser by analysing each part list; size of list, overall quantities etc. This does NOT cover Rip only, Crosscut only or Strip production.
- Small quantity - for small lists less than 300 pieces in total where the required quantity does not average more than 10 pieces per part.
- Medium quantity - for medium volume lists usually with an average part quantity between 10 and 50. The medium quantity optimiser is also used for lists where restrictions do not allow other optimiser to be used, for example, where exact quantities are required of a large volume list.
Rip only
For ripping along the length. For example, when cutting strips for stock or cutting worktops. Set the length to a constant value in the part list.
Mixed one dimensional lists - In some cases with one dimensional cutting it is preferable to place all the boards in a single working board list and the items to be cut in a single part list. The one dimensional optimisers automatically match the correct boards against each part. For example, with worktops there may be a set of basic strip widths from which the worktops are cut in varying lengths. Place all the parts in a single part list; a set of boards of different width are then selected:-
Boards Parts
1. 2440 x 300 A 750 x 300
2. 2440 x 700 B 650 x 300
3. 2440 x 900 C 320 x 700
D 420 x 900
E 800 x 900
F 630 x 700
G 480 x 700
The optimiser matches the 700mm parts with the 700mm width boards (strips), 900mm width parts with 900mm width boards (strips) and so on. If a part does not match a board width the part is cut from the next widest board.
Strip production
The strip production optimiser is designed for the production of strips where the ripping of boards and crosscutting of strips are separate operations.
In this style of production boards with common strips widths can be combined into a single rip pattern and strips with common crosscuts can be combined into a single crosscut pattern. This tends to maximise the book height for cutting at each stage.
There are two methods of strip production:-
Strip production optimiser - One book at a time
In this method each book is processed separately. The rips for the book are made then the strips from the book are crosscut immediately. For this method the patterns are produced as a set of alternating rip and crosscut patterns; one set for each book. This method is generally used for strip production when all the cutting occurs on one saw.
Strip production optimiser - Multiple books
In this method all the books are initially ripped and the strips are then crosscut as a separate operation. For this method all the rip patterns are shown first and the cross cut patterns are shown after all the rip patterns. This method is generally applicable where ripping is done on one saw and crosscutting occurs on a separate saw. For example, in a production line with two single saws and an edgebander for edging strips.
- Because of this unique way of working the strip optimiser does not deal with the sequencing of patterns and the Optimising parameter: Open Parts is not used
- Strips on rip only patterns are labelled with a strip reference (e.g. 'Strip/1'). The strip reference also appears as a board code on the associated crosscut patterns.
Crosscut only optimiser
For example with solid timber.
- Set the width to a constant value in the part list.
The crosscut only optimiser uses a limited number of parameter settings. These include: - Recut trim parameters, Recut processing parameters (Saw/Router combination or Recut device).
