FlatCAM practical tutorial: clean non copper area – Part 3

When you mill a PCB traces probably remain some islands of copper, and here can stay a floating potential that can create disturbances, so if you make a high-frequency PCB, It’s better to remove them.
Remember, you can put the area on the ground and fix the problem.

Next, go to remove islands of copper. To remove the island, you can follow two approaches; the first is to use NCC Tool (Clear N-copper) directly. You will now remove all copper in the area you select, or first do isolation (look at the previous chapter).

Clear residual non copper area

I continue from the previous part; here is a screen with some arrows to identify the islands

and we are going to remove the islands, and you must select the more external geometry generated

• PCB_PCF8574_03_copperBottom.gbl_iso1
• PCB_PCF8574_03_copperBottom.gbl_iso2
• PCB_PCF8574_03_copperBottom.gbl_iso3 <– more external

Select more external geometry and click on the NCC Tool button; a panel Non-Copper Clearing is shown

As you can see in the upper part (red arrow), you can select the Gerber or Geometry this choice because you can land on this panel via menù also with Tool --> Non-Copper Clearing.

Single tool without change

Then, we can select one or more tools (blue arrow); in this example, we continue with the same tool used with the Copper isolation, so when you set a Tool Dia you put 0.55 or other value as you put in the previous Copper Isolation.

Then you can put a correct Cut Z (but in the generation of GCode, you must reinsert It), the default value is 0,05, but I usually put 0,07 or better 0,08.

Overlap Rate have the same behavior explained in the last part.

For this specified situation, the margin (yellow arrow) is set to 0.2, but we remove It because we will extend the area to be sure that no residue remains.

Method: now, here you can select a method of geometry generation; the standard is the creation of concentric border and is in line with the previous work (in the next paragraph, I’m going to explain the various method).

Connect: simple try to do all without stop milling, create a long continuous line;
Countour: first, create a border to prevent insufficient margin;
Rest. M.: is used with the multi-size tool; we will explain it better next.
Offset: dislike margin here you can add a safe area not from all but only from copper to prevent problems.

Reference:

• Itself: is applied to the Gerber or Geometry selected upper;
• Area Selection: you can select a specified area;
• Reference Object: you can select another object different from reference object selected upper.

We are going to do it all with area selection, then when you click on Generate geometry button (pay attention to the error in the left bottom of the window), nothing append, and you must select the area.

The step to follow are:

1. click on the angle of the region you want select;
2. click to the end of area;
3. repeat for all areas you want clean;
4. when you finish click with right mouse button and the action start.

With the same tool, all line is parallel and concentric, and you maintain the same device for all.

Multiple tool with different size

You can select a tool with a bigger diameter for the big area and a little more tool for the angle: you must add the tool on the upper grid and insert the more little diameter tool in the “default” tool.

In Tool Table, I add two tools, one with 2mm diameter (for rough remove) and the classic 0,55mm. You must select Rest M. and select all tools in the table, then Generate Geometry. Select area as explained and the result is here

In the bigger area, you can see a line generated by a tool of 2mm at the margin of 0,55mm.

Mill all with Non-Copper Clearing

Now restore the pcf8574 project after basic import (Part 1), then select PCB_PCF8574_03_copperBottom.gbl, and on the Gerber object panel, select the NCC Tool button.

Now we must pay attention to margin, this value It’s important to get good work.

You must select PCB_PCF8574_03_copperBottom.gbl on Object and Itself as Reference.

Now here is a result without margin (margin set to 0).

Without margin outside the border of Gerber, some part of work isn’t covered, here a result with a 2mm margin

Now, as shown upper, you can add multi-tools with Rest M. parameter, so if you add a 2mm tool and a 0,55mm tool on the table tool (remember to add the tool with lesser diameter to default) and select Rest M. you obtain an element like so:

Result

Here is the result with the use of the same tool

Thanks

1. FlatCAM practical tutorial: introduction, installation and import
2. FlatCAM practical tutorial: copper traces geometry
3. FlatCAM practical tutorial: clean non copper area
4. FlatCAM practical tutorial: silkscreen geometry
5. FlatCAM practical tutorial: contour
6. FlatCAM practical tutorial: gcode and PCB milling

You can find Gerber, fritzing, images, and FlatCAM project files here.