I created a simple example pcb (bug.kicad_pcb) and exported the gerber files (
bug.zip).
In GerbView the pcb looks perfectly fine:
But at the JLCPCB gerbviewer (
) the silkscreen is broken:
Any ideas why this happens? Would it be a bad idea to just ignore the preview rendering?
Interestingly the other JLCPCB preview is fine:
The gerber viewer is for reference purpose only and may differ from the actual PCB product.
So I would assume that this is just a preview issue.
You don’t say what’s broken but I assume you mean the silkscreen lines that look like a face under JP1. I’m not seeing this on JLCPCB’s upload viewer or other online viewers. So it looks like a bug in JLCPCB’s gerbviewer. But one can only tell by looking at the layers, maybe it’s a stray pattern on another layer that got rendered.
Many people have found that the JLCPCB gerber viewer is buggy - but strangely when you upload an order the viewer used there is correct.
Why they have different viewers, I’ve no idea. Basically ignore the buggy viewer.
OK thanks, then I’ll just go ahead with my order.
Looking at the top silk gerber, where the arcs (G02) are, I don’t understand why KiCad outputs a G75 before each G02 arc:
G75*
G02X75000000Y-49800000I700000J0D01*
G01*
X75000000Y-51800000D02*
G75*
G02X74300000Y-51100000I0J700000D01*
G01*
X77100000Y-51100000D02*
G75*
G02X76400000Y-51800000I-700000J0D01*
G01*
X76400000Y-49800000D02*
G75*
G02X77100000Y-50500000I0J-700000D01*
G01*
D11*
Then googling for the gerber spec I find “G75 turns on 360° circular interpolation” e.g. page 47 here:
I would have guessed that 1-quadrant (90-degree) circular-arcs can be done with a simple G02 move (G74 mode) - why would G75 (360-degree mode) mode be used here?
anyway the I and J parameters of the G02 define where the center of the arc is (relative to the starting point), and the bug might be that they are considered unsigned numbers in G74 mode (G02 or G03 specifies CW or CCW arc) and signed in G75 mode. just a guess…
You should also check your gerbers with another standalone gerber viewer, for example gerbv.
I recently discovered the same issue with arc outlines where they rendered inverter. Kicad’s gerber viewer didn’t show any artifacts.
The one I like to use is hosted by PCBWay, a competitor, but it’s based on open source software and works very well.
https://www.pcbway.com/project/OnlineGerberViewer.html
or the author’s site:
thanks, that is an awesome viewer!
any reason you prefer the PCBway site over tracespace?
It was the first one I encountered so just habit. Anyway you’re not loading the server much. It spits out SVG which is rendered by your browser.
Yeah, the new JLCPCB gerber viewer has that bug, they know it, but they have not fixed it yet. They do say that it looks fine if you ask them, and indeed my pcb’s were fine.
Good to know. I went ahead and ordered the PCB and I’m now very surprised by the super detailed status report: 
Yes a couple of other fabs also provide a running status report of the production stage. The same UX principle as progress thermometers; customers are more satisfied when they perceive progress. 
VisualPlace is another gerber viewer I use on Windows it supports Kicad outputs for part positions and such also.
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.
