A good one this.
For absolute full on dedicated design time I usually add another 50% of the design time for the "You never know factor"
So the famous 2 weeks becomes 3. But this is 100% dedicated hours.
Usually, lots of interruptions occur, and I mean lots.
So as in time to completion I usually double the result too. :)
I suppose we are kind of lucky here because all our designs are our own products, i.e. not working for third parties, so things are easier and flexible.
Paul.
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: marted́ 8 settembre 2015 22:37
To: [log in to unmask]
Subject: Re: [DC] Estimating PCB Design time
Hi Bill,
I often feel the same way. One thing I have found to be true - it is human nature to think we can get things done quicker than we actually can.
Some of the software companies have attempted to include some estimators in their software. They're not too bad, but they don't take everything into account.
There's also the "Team Work" factor that is going to be different in every situation. When you review data, layout parameters, and restrictions or regulations, it will impact a completion date. However, it is time that has to be spent to get a good design.
There are so many variables to every board design, the best any of us can do is get close. That's probably why "Two Weeks" often works within a company. When you're "Bidding" the job, you have to be a little closer or eat the extra time. So, similar to what others have done, I took some lessons from many other designers through the years and came up with a formula that works pretty good for me. I'll warn you - there are many variables in this. Also, since I have a library of parts, I can get the part areas fairly quickly.
Things you need:
1- BOM with list of all parts.
2- Footprint sizes or datasheets with component mechanical size information.
3- Board surface area that is usable.
4- Spread sheet to define:
a - Total # of each type of footprint used.
b- Total area (in sq mils or sq mm - only choose one) of each type of footprint used. (Include Test Points.)
(Use courtyard area.)
c- Total # of pins - per part & for all parts.
d- Total usable board area in sq mils or sq mm (match to parts) for both top and bottom.
From the above information, calculate times for:
A- Density - [Total usable area / Total component area needed]
0.1 to 0.35 is Low (You can probably save some money and trim the board after layout);
0.36 to 0.6 is Medium;
0.61 to 0.85 is High; (I see most boards in this area today. May need blind & buried vias.)
0.86 - 0.97 is Very Difficult. (Will need blind & buried vias and may need more board space.)
0.98 and up will need more board space or fewer parts.
B- Part Placement [# of parts / #/hr you can do] Base "#/hr" off of your experience and board Density.
Note: I use 24-30 (#/hr) for Low & Medium density & 12-16 for High & VD depending on other variables.
C- Pin Connectivity {# of pins / #/hr you can do] Also base "#/hr" off of experience and board Density.
Note: I use 24-30 (#/hr) for Low & Medium density & 12-16 for High & VD depending on other variables.
D- Documentation
New - Full docs, ODB++ setup, GERBER, Panel(s)? = 2-3 days with checking.
Change Existing - Modifications to originals & Checking = 1-2 days.
Can be minimized if others are doing or assisting with the documentation = 1 day or less.
Time to complete = [(B+C)*A)+D] Note: "A" can be halved if Low or Med Density.
As you can see, it's not as exact as some would like to see. It does get me within the 10% range on most estimates. I use the spreadsheet to show the details of what needs to be done and to negotiate what may or may not be needed. It also helps when parts want to be added in at a later time. I can put them in the calculator to show the actual impact an addition can have on the density and how it impacts the overall design.
IF I need to create new part footprints or schematic symbols or link them in the program, I will add this in separately. I have found that in every EDA package I've worked with, it takes an average of 5 minutes per pin to create a footprint or symbol. And that's with the help of wizards. (You gota' check the footprints after they are created!)
Hope that helps. It's similar to calculations that others do. I just get a bit more detailed about it.
Cherie Litson, IPC-CID+/CMIT
Litson1 Consulting
PCB Design Solutions & Training
206-619-8844_ [log in to unmask] (mailto:[log in to unmask])
In a message dated 9/8/2015 8:36:23 A.M. Pacific Daylight Time, [log in to unmask] writes:
Does anyone have a spreadsheet or program for estimating design time in hours for printed circuit design in an engineering environment? How do you go about estimating the time it takes to do a design? What factors affect your ability to be efficient and quick designing with minimum errors?
I would assume that service bureau shops would have to have a way to handle this for every job they get in to do.
Any help or guidance would be appreciated... Thank you.
OBTW - If you are like me, you might think PCB design work estimation is something like asking Michelangelo to give an accurate estimate on when he would finish painting the frescos on the ceiling in the Sistine Chapel...
https://en.wikipedia.org/wiki/Sistine_Chapel
(Or more simply... when I'm going to finish my next sculpture...
:)www.facebook.com/BillBrooksSculpture )
I'm reminded of the movie 'The Money Pit' where they asked the plumber how long it would take to re-pipe the house... His answer was always the same... "Two Weeks" :) I would love to hear your comments and experiences...
:)
William Brooks, CID+
Printed Circuit Designer
2747 Loker Ave West
Carlsbad, CA 92010-6603
760-930-7212
Fax: 760.918.8332
Mobile: 760.216.0170
E-mail: [log in to unmask]
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