Gah, need zero width poly, but get warning even for polys with non-zero width!

On 7/8/2016 7:48 AM, Jonatan Magnusson wrote:

Hi

 

I need to draw polys with very specific form. It's a capacity sensor that requires fingers to have a specific width, height and no rounding in the ends.

 

First I thought I could trace them using regular wires and change the cap, but cap can't be changed from round to flat for god knows what reason (it only works for arcs, but it also works for arcs with next to no curving...).

 

So I used polygons instead. Problem is that if I draw a polygon with width of 1 mm from side to side the final width will be 1 mm + the trace width. Plus the corners will be rounded.

 

Obvious solution: set polygon width to zero. So I happily created the poly and everything looks great. Time to create Gerber for production. Then I get a warning that zero-width polygons are not allowed!

 

I kind of understand why: zero-width would mean that the poly would be built using an infinite amount of zero-width lines to fill the poly. Not good.

 

So I try to set the poly width to a very small value. Yet the DRC keeps complaining of zero width polygon! I increased the poly width to 0.1 mm just for testing, but DRC still complains!

 

Two questions: why does DRC keep complaining even if I change the trace width of the poly, and how do I best draw figures with very precise requirements in Eagle?

 

--

To view any images and attachments in this post, visit:

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Hi Jonathan,

I hope you're doing well. What you see in the CAM processor is just a

warning not a hard stop to the zero width polygon. EAGLE is just letting

you know that zero width polygons might take a while to process because

these generate lots of data(your understanding of the inifinite amount

of wires is mostly correct, the reality is that 0 in EAGLE is really

0.03um). If the polygons are relatively small then they won't have that

much of an impact on the CAM processor. With that said the rule of thumb

for polygon width is use the largest width possible that will give

acceptable results.

Now the DRC complaint, can be ignored because the board manufacturer

will generally turn that whole feature into a solid shape so the width

in the polygon is a DRC error that you can usually approve. However, if

your board house complains then you'll have to set the width to whatever

the minimum width required is.

hth,

Jorge Garcia

Cadsoft Support

On 7/8/2016 7:48 AM, Jonatan Magnusson wrote:

Hi

 

I need to draw polys with very specific form. It's a capacity sensor that requires fingers to have a specific width, height and no rounding in the ends.

 

First I thought I could trace them using regular wires and change the cap, but cap can't be changed from round to flat for god knows what reason (it only works for arcs, but it also works for arcs with next to no curving...).

 

So I used polygons instead. Problem is that if I draw a polygon with width of 1 mm from side to side the final width will be 1 mm + the trace width. Plus the corners will be rounded.

 

Obvious solution: set polygon width to zero. So I happily created the poly and everything looks great. Time to create Gerber for production. Then I get a warning that zero-width polygons are not allowed!

 

I kind of understand why: zero-width would mean that the poly would be built using an infinite amount of zero-width lines to fill the poly. Not good.

 

So I try to set the poly width to a very small value. Yet the DRC keeps complaining of zero width polygon! I increased the poly width to 0.1 mm just for testing, but DRC still complains!

 

Two questions: why does DRC keep complaining even if I change the trace width of the poly, and how do I best draw figures with very precise requirements in Eagle?

 

--

To view any images and attachments in this post, visit:

https://www.element14.com/community/message/201039

 

Hi Jonathan,

I hope you're doing well. What you see in the CAM processor is just a

warning not a hard stop to the zero width polygon. EAGLE is just letting

you know that zero width polygons might take a while to process because

these generate lots of data(your understanding of the inifinite amount

of wires is mostly correct, the reality is that 0 in EAGLE is really

0.03um). If the polygons are relatively small then they won't have that

much of an impact on the CAM processor. With that said the rule of thumb

for polygon width is use the largest width possible that will give

acceptable results.

Now the DRC complaint, can be ignored because the board manufacturer

will generally turn that whole feature into a solid shape so the width

in the polygon is a DRC error that you can usually approve. However, if

your board house complains then you'll have to set the width to whatever

the minimum width required is.

hth,

Jorge Garcia

Cadsoft Support