Juan,
IMHO that would be a major problem for accuracy to have you then move all
of those designators in your "unintelligent" dxf file.
Most PCB CAD systems make it so the Ref Des is really an intelligent item.
That means that whenever you move a Ref Des it automatically highlights the part it is associated with.
This makes it a lot easier to make sure you are moving the right Ref Des close to the right part.
It really is in the PCB Design tool that this should be done, or you are
greatly increasing the chance for error. DXF file is not really the place to have to be moving designators
around on a dense design. It is too easy with dense boards to make a mistake that way.
That is why others have also suggested that the PCB design tool really needs to have a dedicated assembly
layer with the intelligent Ref Des on it and the work of positioning those Ref Des should be the
done in that tool, whoever ends up doing it. The PCB designer doesn't have to be the one do this
or even cleaning up silkscreen positions, but it should be done in the PCB CAD tool.
If that cannot be done then, yes errors can happen easily, and it really creates much more
work in the end, rather than just doing it in the appropriate tool for the job.
Bob
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of Juan Vega
Sent: Wednesday, April 02, 2014 9:52 AM
To: [log in to unmask]
Subject: Re: [DC] Assembly standard + best practices
Thanks James and all of you.
I really appreciate your help, it has given me much knowledge.
I will explain a little further why I ask your opinion.
In the PCB design process that we have at this time is:
1 Mechanical guy come up with the position of connectors, dimensions etc. etc in PCB.
2 Then the Design Engineer, make out the layout, layout review, route the PCB and so on.
3 The design review it's done, and if there are not changes needed, it is approved.
4 Then the design engineer send a DXF file to the ME (it contains the silkscreen layer information [reference designator and the body components description]).
5 When the ME receives that, he start adding 3D models and relocating texts that can move due the conversion from DXF to the format of his software (Solid Edge, ProE, Solid Works).
To date that was the common process here.
But recently, there was pointed by our assembler some ambiguities in our assembly drawings(due the high density of components), due some reference designators pointed to other component that does not belong to. Immediately, there was pointed out for co-workers that we need to place all the reference designators inside the component body in our drawing (but that will be at step 5 of my above listed). That will be accomplished by taking the same DXF that DE sends on step 4 of above, and then the ME start moving every ref des to the inside of component body. For me it represents a lot of work for the ME (unnecessary), and as told in some of the emails, it should be done in the PCB cad file by adding the assy layer in a mechanical layer (and adding reference designator in that layer for assembly drawing purposes, inside the component).
And to avoid ambiguities, the assembler should use the pick and place file that we send with every design.
Best regards!!
Juan Vega | Product Enngineer | Branson Ultrasonics Emerson Industrial Automation | Lote #4 Carretera Nacional KM 8.5 Modulo Industrial America | Nuevo Laredo| Tamaulipas | 88277 | Mexico T + 011 52 867 711 0821 | F + 011 52 867 711 0811 [log in to unmask]
-----Original Message-----
From: DesignerCouncil [mailto:[log in to unmask]] On Behalf Of James Head
Sent: Wednesday, April 02, 2014 3:46 AM
To: [log in to unmask]
Subject: Re: [DC] Assembly standard + best practices
Yes to having separate Assembly Drawing Layer and Silkscreen Layers.
We use Tom's new product: PCB Library Expert to create all footprints since it handles all the Silkscreen and Assembly drawing requirements. If you go to the PCB Libraries website you will find Tom's guidelines linked in the forum.
One thing I will say is add notes to the Silkscreen and Assembly layers that get included with any gerber outputs.
On the Silkscreen say:
"DO NOT USE THIS LAYER TO CREATE PLACEMENT PROGRAMS"
On the Assembly Drawing say:
"DO NOT USE THIS LAYER AS A SILKSCREEN"
Believe it or not but in past one assembler decided to ignore the centroid co-ordinate csv file and assembly drawing I provided and thought they'd create the assembly program themselves using the Silkscreen as they'd done with all the other customers in the past - and miss-interpreted silkscreen idents with the result two resistors were swapped around.
Also I had one PCB fabricator ignore the gerber files that had "Silkscreen" in their names and written on the layers and used the Assembly gerber file instead for the silkscreen.
Both of these companies are "middle tier" suppliers!
James
James Head BEng CID+ MIIE MIET
Senior PCB CAD Engineer
Crowcon Detection Instruments Limited
2 Blacklands Way
Abingdon Business Park
ABINGDON
OX14 1DY
Telephone: 01235 557700 extension 289
Fax: 07092024504
E-mail: [log in to unmask]
********************************************************
The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. If you are not the addressee, any disclosure, reproduction, copying, distribution, or other dissemination or use of this communication is strictly prohibited. If you have received this transmission in error please notify the sender immediately and then delete this e-mail.
E-mail transmission cannot be guaranteed to be secure or error free as information could be intercepted, corrupted lost, destroyed, arrive late or incomplete, or contain viruses.
The sender therefore does not accept liability for any errors or omissions in the contents of this message which arise as a result of e-mail transmission. If verification is required please request a hard copy version.
********************************************************
______________________________________________________________________
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
---------------------------------------------------------------------------------
This e-mail and any files transmitted with it are the property of Kimchuk Inc. and is solely for the use of the individual or entity to whom this e-mail is addressed. If you are not one of the named recipients or otherwise have reason to be believe that you have received this message in error, please notify the sender and delete this message immediately from your computer. Any other use, retention, dissemination, forwarding, printing, or copying of this e-mail is strictly prohibited.
______________________________________________________________________
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
---------------------------------------------------------------------------------
|
