I'm an electrical estimator and I am noticing an increasing frequency of PLC designs with fiber at 30% maturity. My normal methodology (at 100%) is to get quotes for all materials from the bill of materials and then assign a level of programming based on I/O point (usually 6 hours per.

How would YOU estimate these PLC's? At 30% there is little definition and the scope change between 30% and 100% can be huge.

What is the basis for your materials and equipment pricing? Your labor productivity? Your quantities?

In looking through the threads I see that many people discourage estimates based on I/O point? What is the other methodology used? I prefer deterministic models of estimating based on good drawings and some statistically significant data but this seems to be impossible with specialty systems/equipment and programming requirements.

Does anyone have a parametric that they use or any advice on how to create one?

 

I've never worked with an estimator nor have I given many estimates, but I will say as a programmer and machine troubleshooter that basing any estimate on IO count seems ridiculous to me. I have dozens of IO that literally requires 5-10 minutes worth of coding (Simple "housekeeping" stuff like pressure switches, etc that are just double checks). Alternatively I could literally spend days writing and debugging code on a certain mechanism that only requires 5-10 IO points (And maybe a servo motor or two to make things interesting...).

I'd work well with your programmer and come to some kind of mutual trust. Make sure he/she is not padding things and make sure you don't bust their chops.

I'm just curious, are you a machine integrator/seller or are you working for a company that does work for internal use?

KEJR

 

If we estimated PLC programming at 6 hours per point we would never get any orders.

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Bob