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]
____________________________________________________________________________
_
Scanned by IBM Email Security Management Services powered by MessageLabs.
For more information please visit http://www.ers.ibm.com
This email is intended only for the use of the party to which it is
addressed and may contain information that is privileged, confidential, or
protected by law. If you are not the intended recipient you are hereby notified
that any dissemination, copying or distribution of the email or its
contents is strictly prohibited. If you have received this message in error,
please notify us immediately, by replying to the message and deleting it from
your computer.
WARNING: Internet communications are not assured to be secure or clear of
inaccuracies as information could be intercepted, corrupted, lost,
destroyed, arrive late or incomplete, or contain viruses. Therefore, we do not
accept responsibility for any errors or omissions that are present in this
email, or any attachment, that have arisen as a result of e-mail transmission.
____________________________________________________________________________
_
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
----------------------------------------------------------------------------
-----
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV
16.0.
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET
DesignerCouncil NOMAIL/(MAIL)
For additional information, or contact Keach Sasamori at [log in to unmask] or
847-615-7100 ext.2815
----------------------------------------------------------------------------
-----
______________________________________________________________________
This email has been scanned by the Symantec Email Security.cloud service.
For more information please contact helpdesk at x2960 or [log in to unmask]
______________________________________________________________________
---------------------------------------------------------------------------------
DesignerCouncil Mail List provided as a free service by IPC using LISTSERV 16.0.
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF DesignerCouncil.
To temporarily stop/(restart) delivery of DesignerCouncil send: SET DesignerCouncil NOMAIL/(MAIL)
For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815
---------------------------------------------------------------------------------
|
