Excellent advise from Montague. The lateral delt machine was not designed to be a compound unit, though it can be used for one with some programs. Work the mind, along with the muscles...they are connected. This applies strongly to true BB'ing.
If a weight is too heavy to start with, the traps will come into play strongly. Even with normal light DB lateral raises, the traps come into play. Even stronger when the DB's continue over head, beyond shoulder height. The whole point is not to rush to use more and more weight every workout.
The progressive overload system require a steady increase in exercise poundage, but not before you can handle the present exercise poundage with reasonable control. If working in the 8-12 rep range, be sure in hit the 12th rep before adding weight the next workout and dropping back to the original 8 reps. Progressing reps is just as important as progressing weight.
Another factor may be that the pads are too far up on the elbows/arm, shifting more of the workload to the traps. Try having the pads resting on the very end of the elbows. Not so easy though, not too many of those lateral machines are that adjustable. If you have longer arms than normal, there may be a problem getting the correct leverage for the delts. Most exercise machines are designed for a normal height of 5'10 or so. Good luck.
