Chris Emerson wrote: > My board house[1] has complained about my gerbers having "negative > plots" and "composite layers". My fab (http://basista.de) had similar complains. (I use the last pre-HID snapshot). After a bit of discussion it boiled down to two independent issues: a) Different layers get the same name by the %LN command In my case: $ grep LN PCB*.gbr PCB_ModulPID_back.gbr:%LNGROUP_0*% PCB_ModulPID_back.gbr:%LNCUTS*% PCB_ModulPID_back.gbr:%LNTRACKS*% PCB_ModulPID_backmask.gbr:%LNGROUP_7*% PCB_ModulPID_fab.gbr:%LNGROUP_7*% PCB_ModulPID_front.gbr:%LNGROUP_1*% PCB_ModulPID_front.gbr:%LNCUTS*% PCB_ModulPID_front.gbr:%LNTRACKS*% PCB_ModulPID_frontmask.gbr:%LNGROUP_7*% PCB_ModulPID_frontpaste.gbr:%LNGROUP_7*% PCB_ModulPID_frontsilk.gbr:%LNGROUP_7*% PCB_ModulPID_frontsilk.gbr:%LNCUTS*% PCB_ModulPID_group8.gbr:%LNGROUP_7*% b) shapes that are supposed to be subtracted from the polygons are put into seperate layers, all named LNCUTS. Apparently, my fab joins all gerbers into one big file. Subsequently the operator has to figure which LNCUT layer corresponds to which ordinary layer. I guess, the first issue is a bug, while the second needs to be dealt with according to the pecularities of the actual board house. > 1) (Main question) How can I tell if my gerbers are negative and/or > composite so I can check? Check the gerbers for the token %LNCUTS% If you have polygons defined, they most likely will induce cutouts. > 2) What can I do to affect whether pcb uses negative and/or composite > outputs? Don't use polygons. However, with Basista I got away with simply removing the lines that contain the LNCUTS command. The shapes are still correctly definied to be negative because the command %LPC*% is issued. But now the shapes to be cut out are in the same layer as the polygon. This conforms to Gerber format RS274X. Consequently the gerber tools of my board house will import it correctly without human intervention. > Is that what the "Invert positive/negative" tick box on the > printing page does, at least for the negative stuff? This is supposed invert everything. Thank you for bringing up the topic. I almost forgot to post it to the mailing list. ---<(kaimartin)>--- -- Kai-Martin Knaak kmk@xxxxxxxxxxxxxxx Blog: http://lilalaser.de/blog
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