How I would have designed the concept...
I would have designed this so that all of the pieces around the window are made at essentially the same time. That is, all pieces would be developed in a single pass. Each of the four lines would have a forward-mitre, a backward-mitre and a straight-cut. (I'll explain later how each is selected.)
TRANSFER POSITIONS
LINE A B C D
Left-Side -- / ----- \ ----- | --->
Right-Side -- \ ----- / ----- | --->
Upper-Side -- / ----- \ ----- | --->
Lower-Side -- \ ----- / ----- | --->
.
One drive for the left/right sides, and one drive for the upper/lower sides.
Raw stock is driven by a knurled wheel made of hardened steel; one (maybe two) under each line. ("knurled" is not the right word for what I'm thinking of... I'm thinking of sharp teeth.)
Positive friction is developed by applying pressure with the rollers on the upper side of the piece. The knurled wheel should be in contact with the blind-side of the piece.
Individual clamps for each of the four lines. When a piece arrives at the appropriate mark, the clamp for that piece closes, and the upper roller is raised from that piece.
Because you indicated that some of the dimensions might be slightly different (this is especially true in retro-fits) you need to be able to make a slight offset adjustment to one piece or the other. Because you have the measurents, the program can calculate the difference. Once both pieces arrive at the minimum mark, close the clamp on the shorter piece and raise the upper roller on that piece. Then inch the other piece forward to the appropriate position. The clamped piece doesn't move. Then close that clamp. Lower the roller that you raised, then make the cut. When the cut is done you are ready to move to the next cut.
The left-hand piece and the right-hand piece are made from the same raw stock. The thing that makes one a left-hand piece and the other a right-hand piece is the particular mitre-cuts that are made relative to the shape of the channeling.
If there are no mitre-cuts then there is no difference between the two.
Now, it might be the case that all four pieces around the window use the same raw stock. Or, the upper and lower pieces might be different from the side pieces (which are from the same raw stock), and the upper and lower pieces might even be different from each other. Additionally, some designs might call for straight-cuts, or mitre-cuts, or a combination of both.
All of that was only for the purpose of describing all of the possibilities.
Now, as far as accomplishing the goal in a single pass...
Just for the sake of example, let's assume that all of the pieces use the same raw stock, and that all joints are mitred, and that there is no offset in the dimensions of any pair of pieces.
(The following describes making the cuts with only two lines. It could just as well be done using all four lines in half the time.)
Two pieces are loaded up to some appropriate start position and then the process is started.
Both pieces move in together up to some predetermined mark for the first cut. One piece receives a forward-mitre-cut, the other receives a backward-mitre-cut.
Both pieces move in together up to the next cut-mark. Now the complementary mitres are made.
These might be either the sides or the upper/lower pieces. In either case, these pieces are done. They can be removed by hand or they will be ejected when the raw stock pieces are advanced.
Both pieces of the remaining raw stock move in just a bit for the next cut. After the cut is made, the small pieces of material just ahead of the cuts are waste. They will be pushed out when the stock advances.
Then the stock advances for the final cuts.
The same type of scheme applies if the upper and lower pieces are different from the sides, and possibly each other.
All of the pieces start at the appropriate position. They all move ahead to the appropriate position for the initial cut. <== This position is determined by the particular cut - more later.
After the initial cut, the left/right side drive brings the stock to the next cut-mark. The clamps close.
Meanwhile, the upper/lower drive brings those pieces to the next cut-mark. Those clamps close.
The punch cycles. All four cuts are made at the same time. The clamps release and the stock advances to the next position.
Now, as far as controlling which cut is selected... and doing so with a single press...
There is a technique in punching where particular punches are selected for use in a single punch-die operation. The die contains all of the punches, but only the selected one(s) is(are) used.
I can't remember if I'm using the correct terminology... so I'll just call it a "transfer". In software parlance the effect would be called a mask. In this case it is not a filtering-mask as much as a selecting-mask.
The "transfer" mechanism can be designed to select individual punches or patterns of punches.
Anyway, it works like this...
The transfer has a "neutral-position". While in that position, the press can cycle all day long without actually performing a single punch-cycle. If you then place the transfer over a particular punch, then, when the press cycles, that punch cycles.
First...
There are two transfers; one associated with the left/right sides, and one with the upper/lower sides. The cut patterns are configured to provide complementary cuts.
In the figure below, Position-B is the neutral-position.
If you need to use the cut patterns under "A" for the left/right side, then the associated transfer is shifted to Position-A.
At the same time, you might need to use the straight-cut for the upper/lower sides. In that case, that transfer is shifted to Position-D.
When the press cycles, the left/right sides are punched according to the cut pattern under "A". The upper/lower sides are punched according to the pattern under "D".
LEFT/RIGHT
TRANSFER POSITIONS
LINE (A) B C D
Left-Side --(/)----- \ ----- | --->
Right-Side --(\)----- / ----- | --->
Upper-Side -- / ----- \ -----(|)--->
Lower-Side -- \ ----- / -----(|)--->
LINE A B C (D)
UPPER/LOWER
TRANSFER POSITIONS
.
Now, what this means is that when you advance the stock to the next cut position, you need to advance it relative to the particular cut-pattern. You need to know the distances between the punches so that the program can make the appropriate adjustment.
Of course, all of this would mean a complete re-build of your system.
However, in terms of moving the material accurately in your current system, I believe that the knurled drive wheel would serve you best. And leave the encoders on the drives. I sure hope that your drive shaft is geared way down... so that it takes many motor turns to develop a single drive-wheel turn. Since you said that speed is not an issue, the more motor-turns the better.
And make damned sure that you use appropriate ramping to counter the inertial effects.
Mike,
Simply add an "r" to "late" to make "later".
You "r" late 'cuz you showed up "later".
"Latter" is the opposite of "former", as in previous.
Think of "pie" when you write "piece"... as in
piece of
pie.