I've primarily used MyData equipment, personally, and, optically centered devices definitely take longer than mechanically centered parts on a MyData, owing to the construction of the machine. With a fixed upward looking camera, the head has to pick the part, move to the camera, and move to placement...where as, with the mechanically centered devices, the head picks the part, and centers it while moving to the placement location.
However, I viewed a number of other machines at IPC/APEX this year, and I've found that optical centering is getting better and better, and faster and faster. A number of machines have lasers mounted on the head, and do optical centering in line with pick/place; rarely moving to the upward looking camera. Other machines have the upward looking camera located between the pick area and placement area, so that the head loses minimal time passing over the camera on it's way to placement. Image processing speeds have increased dramatically over the years as well, so that the centering process can be conducted nearly in line with the pick/place operation.
Higher mass components can often have slower pick/place times, as adjusted in line with manufacturing, if they're causing issues on the machine, as well; adding another dimension into establishing a time model.
With all that said, narrowing an exact time/placement for each different component group could be one of those things that becomes more difficult than it's worth. A 9-pin BGA (or LGA) should take slightly less time in image processing than, say, a 1000 pin BGA...or, a 1000p BGA with non-symetrical ball patterns. Do you have one price for small, medium, and large BGA's? Another price for heavy IC's, another price for chip components, etc, etc? Do you account for tool changeover (if applicable on your equipment) between the size groups? Do you account for slower placements/picks as components require it?
In my mind, the solution to the above is to determine a base cost/component for running your machines, based upon the average efficiency of the machines, and your operating costs for the machines (direct and indirect labor, estimates of MRO purchases for maintenance, cost of the machines, etc). If you determine that your average placement rate is, say, 15,000 cph; and you calculate the cost to run the machine at that rate, you'll have a pretty good benchmark. Then, you just need to review your cph rates at whatever interval is desired (per job, per week, per month, per quarter, per half, per year), and keep an eye on your fixed costs.
About the only time I'd think you'd need to look at it in more detail is if you're trying to shave every penny off of a job for a huge win, or for a continuous cost savings policy with a customer.
cheers, ..rob
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