estimating small machine controls design and programming

interested

Guest
I
I believe that estimating (well, that is) is the most difficult task in the engineering field. Do any of you have insight to share on some lessons learned over the years and some pointers to offer in small machine controls design and programming estimating? My experience has been limited to repetiton of similar designs. I now want to stretch my legs a bit and delve into other areas. The easiest way into a new area is with smaller projects but, obviously as the budget gets smaller...the more crucial the estimate (not enough cushion).
What are some of the "rules of thumb" that some of you have proven or disproven over time?
I look forward to your comments.
 
Document in your bid very clearly what you have allowed for and more importantly what you have not allowed for. Then if you are comfortable in doing a job for the quoted price, there should not be a problem. Alan Case
 
As Alan says, Its not how you do the job that makes or breaks it as much as your specification of work in the first place.
For small projects, especially on the controls design side, it is not too difficult to 'scratch out' a design and get pretty close with the material estimation. How long it takes is down to you!
 
I keep track of how much time and money it took to actually do a job vs what I quoted. I break projects down by spec review, developing I/O count, selecting components, drafting, building, programming, staging, shipping, startup and training. In each section there are suprises. It usually takes longer than you think. If you've done something before, the next one should be similar. If you've gone through a learning curve, the next one should take less time. Keep good records.
 
Unfortunately, there is no substitute for experience. That's why estimating is usually done by senior individuals. You have to know how long things took last time, be able to identify similarities and differences between projects, factor in learining curve and competence of the staff available, and so on and so on.

As a rough guide, I use a certain number of hours per drawing, a certain number of hours for preparing Bills of Material and ordering parts, a certain number of hours for customizing a standard control loop to special requirements, and so on and so on. Then I use a fudge factor based on special complications. Even if I were willing to provide competitive info on an open forum by giving you these numbers, it wouldn't help you much because your capabilities, project complexity, etc. are different than mine.

If all else fails, figure out how long you think it will take, multiply by two, and double that number. The result won't be too far off.
 

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