Plated and Non-Plated Slots and Cutouts

I solved it, I had to enlarge the area so the minimum milling diameter can mill it.
Thanks :slight_smile:

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Hi @js_qat,

Welcome to the community!

Indeed, technically it’s not a problem to manufacture non-plated slots smaller than 1.6 mm. The same tools (special nibbling drills) are used for both plated and non-plated slots / elongated holes.

The reason why we do not support non-plated slots < 1.6 mm: The manufacturing of an elongated hole with a nibbling drill is an extremely time-consuming process. In contrast to a conventional milling segment, the nibbling drill must plunge into the material hundreds of times. Using a 1.6 mm milling tool would be much more efficient.

In the past, we often experienced that non-plated slots were used to realize large “conventional” milling sections (e.g. to realize user defined subpanels). In most cases, these sections could just as well have been milled with a 1.6- or 2.4-mm milling tool achieving the same functionality.

In our experience, non-plated slots in components tend to be the exception, which is why we have decided that this restriction is permissible.

However, we will consider allowing non-plated slots (maybe length and amount depending on the board size) to a limited extent. In this case we will inform about it here.

Best regards,

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Missing: the minimum width of non-round holes and similar cutouts. In this detail from one of my boards the cutout is supposed to be the same width as the hole to its left.
Also there’s this extra ring of no-copper space around one end of the cut (presumably the location where the milling tool enters the board?) which is somewhat annoying because if we really do need that empty space I’d like a way to control which end of the cutout has it.

Screenshot from 2022-04-25 10-50-08

Here’s (mostly) the same view in kicad:
Screenshot from 2022-04-25 10-52-01

Hi @MatthiasU ,

Welcome to the community!

We have moved your post, as your question is better addressed in this thread.

Our system has made a mistake here. As I have already written above, non-plated slots are normally converted into inner milling paths by our system. In a further step, we select (if possible) a suitable milling tool (1.6 or 2.4 mm) to mill the cut-out. This conversion does not seem to have worked properly in your project. What you see in your upper screenshot (blue color) is not a milling path, but a non-plated slot. As a consequence – but not intended – our system has removed nearby copper (analogue to conventional NPTHs, see here) but only in the area of the starting point.

Would it be possible to draw these elongated holes with a diameter >= 1.6 mm on the EdgeCuts layer?

Best regards,

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Thank you for the prompt reply. That works better, except that one of the four cuts I placed is now shown as plated for no good reason.

Hello @MatthiasU ,

I have sent you a PN, also with a few more project-specific comments.

I will later include this case (intended milling path is shown as a plated-through slot) in the article.

Short version: If the start or end point of slot is located in copper, it is classified as plated through and will be manufactured with a nibble drill.

Best regards,


I have a question regarding slots files. I’m using Allegro PCB editor, and this tool does not allow me to create slots and drills in a single file - it’s creating sepparate Excellons for circular holes (drills), and for slots (route).

What should I do in such case? From the gerber filename guide I see there is just one file for plated holes, and other for non plated holes. Any option for a router file?


By my shorter millings i get plated slots instead of millings paths. I tried to change the thickness but this does not helps.

Hi @karol-itworky-com ,

welcome to the community!

Sorry for getting back to you so late. We are currently working on the possibility of uploading more than two drill files. As soon as this is possible, I will get back to you!

EDIT: Upload of multiple files of the same layer are possible now! Please also see our Article about Traditional Gerber

Best regards,

Hi @julian ,

welcome to the community!

Our system classified these intended milling segments as plated slots, as they fulfill all criteria (length <= 15 mm & 0.7 mm <= diameter <= 2.8 mm & located in copper)

If you clear the copper in the area of each segment, they should be recognized as conventional milling sections. Note: To avoid the milling tool cutting through copper (risk of unwanted short circuits), there shouldn’t be any tracks or surfaces within 300 µm around the milling path.

Best regards,

Hello Manuel,

Thank you for your fast answer. Did you also know how to change this in eagle. To change a line to the outline of the line.

Thank you


I got this warning message in the board inspector:

The related part of the board are:

Can someone explain me what is the issue ?
The Gerber files are produced by Fritzing. (If this helps)



I’m running into an issue. My design includes two small cutouts that I can make 1.6mm wide (they should be 1.4mm per the specs, but it’s not critical), so should be OK. However, they are on one side of the board and seem understood as part of the ‘outer milling’ - and the online tool complains as they are not 2.4mm wide.

Any chance of making such a design works ? (an earlier revision of the design with 1.4mm cutouts could be made by a well-known competitor, but I’d rather switch to a more local manufacturer).

Thanks in advance & cordially,

Seems Aisler has changed the behaviour. I tried both versions, both are working.
I named the layer for the milling gerber data as board.milling.ger
This naming of the milling layer is not documented by Aisler in the Article about Traditional Gerber

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Usually, the milling paths are combined with the outline data.

It is also possible, as you described, as a separate milling layer and Gerber file. :slight_smile:

Hey. I’m using Target 3001, and I’m trying to place milling paths. In Target 3001 they are displayed, like it can be seen in the picture.

In the upload Aisler portal, the milling is not shown.
Screenshot 2023-01-18 132354
Is there a manual where I can find how to do it?

Im not familiar with Target but have you checked if you used the appropriate layer and made sure the milling path is at least 1.6mm wide?

The layer in Target 3001 is 25 and I use it. I also tried several line widths, for example 0.3, 1.6, 3.1 mm. This doesn’t change the layout in Aisler.

I have talked to the support, and they suggested me to draw the milling paths in layer 23. The line width should be at least 2.5 mm. It is also important that the milled sections do not touch the contour of the blank or panel.

Hola, ¿Lo resolviste? tengo el mismo problema. Me aparece el mensaje de Rutas de fresado exterior faltantes y/o incompletas