Estimating engineering time on machine design

I'd just like to compare notes with a few machine designers about how they figure time on machine design tasks. I personally find that about 1 1/4 hours per fabricated part is minimum to estimate for design (3D) and detailing (2D), and that's really a very conservative minimum. 1 3/4 hours to 2 hours is probably more realistic unless the task is very straightforward. Then one has to figure in time for changes and time to do assembly drawings. It's certainly not nearly as simple as that, and there are a lot of variables that can drive an estimate drastically one way or another, but that's where I begin. How about you? I'm just looking for general approach "rules of thumb" as contrast to how I start off.
Thanks for any feedback
Mark 'Sporky' Stapleton Watermark Design, LLC www.h2omarkdesign.com

When I estimate any design I like to 1st take into account the customer. If I've worked with this client before and have a feel for how they do things, if they change their mind alot, if their requests are somewhat "Grey" or "Clear" and how much interpretation is involved trying to put their idea on a screen. This has helped me tremendously overtime in avoiding going over my man-hour budgets.
And as far as estimating the time to complete a design, be liberal about it when 1st coming up with the numbers then go back over and see if any parts such as a square plate that doesn't take but 15min to model, dim, and plot out can soak up some of the more complicated parts time usage.
But 2hrs is the average I estimate for anypart that has more than one bend, or more than 4 taps or drills...
K.Josey
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Don't forget competitive quoting and ordering time for the parts also.....this can eat up most of a few days.

Anthony wrote:
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It's a good point. Even though I'm doing this as an adjunct to a machine shop who will actually build the machine I've got to take into consideration what time the shop will require me to spend on such tasks as this. We need to have a very detailed and clear definition of task scope. Thanks for the comment.
'Sporky'