HELP: PCB quality degrades from start to finish

[psychoul]

By the way, I created a small software to create the g-code for smoothing the surface. It runs in your browser so you don't have download anything. I hope it's useful to you.

[Jay C]

I typically mill at .003" for depth of cut to go through .5oz copper and .005" for 1oz. Any deeper and you are into the substrate. How did you board turn out after you leveled the area?

-Jay

[psychoul]

Hey Jay,

Well the board turned out better than before. On monday I will do the soldering and see if everything works!

However, I still have concerns about the quality of the board. First, I used a 60deg tool with milling at .006". However, using a multimeter, I could see that some lines, even though seemed OK, failed the continuity test. I didn't want to dig any deeper with this tool, since that meant it would mill even bigger tracks. So I changed the bit to 30deg and run it again (on the same board) having it to dig deeper (I think about .008"). Now the continuity test seems ok but I will be sure once the board is working.

I am attaching some pictures. Also notice the bad quality of the cut. The copper seems like its torn out of its place instead of a clean cut. Maybe I have large feed/Spindle_RPM ratio?

Thanks

[eaglezsoar]

I would like to ask what machine you are using? From the picture that shows the spindle
the CNC machine looks like a beauty. I think that when they talk about carpet tape they are not talking about the thick double sided tape but rather the wide, thin stuff that is protected on both sides with paper you peel off. You should be able to find carpet tape
at any home improvement store. It is not much thicker than a sheet of paper.

[psychoul]

Thanks,
We got the machine from here Welcome to World of CNC | Marchant Dice Ltd

[Jay C]

Actually I use the stuff from Lowes and it is "thick" compared to turner's tape which is only as thick as a piece of paper.

I think that when they talk about carpet tape they are not talking about the thick double sided tape but rather the wide, thin stuff that is protected on both sides with paper you peel off. You should be able to find carpet tape
at any home improvement store. It is not much thicker than a sheet of paper.

[Jay C]

I am attaching some pictures. Also notice the bad quality of the cut. The copper seems like its torn out of its place instead of a clean cut. Maybe I have large feed/Spindle_RPM ratio?

Thanks

I have my isolation set so that there are at least two passes per line. Experience showed me that it's easier and more reliable.

On 1/16" board 1oz copper my settings are:
Milling depth: -0.062"
Spot Drill: -0.005"

Isolation:
Default: 0.001"
Max: 0.016"
Step 0.002"

Tool size: 0.003" (this is the precise bit etching tool)

And Z depth: -0.008"

X/Y feed 35ipm
Z feed 5ipm

FWIW,
Jay

[Drools]

Just a quick comment on your Z axis. Is there any other bracing on the bottom of the axis? From the pics shown it is hard to tell but it looks like you are using the linear rails as the only support for the for the bottom piece of extrusion.
A over picture of the machine might help.

[psychoul]

Isolation:
Default: 0.001"
Max: 0.016"
Step 0.002"

Tool size: 0.003" (this is the precise bit etching tool)

And Z depth: -0.008"

Hey Jay thanks for the settings. I will use your isolation numbers on my next experiment. Isn't Tool size a bit too small? Isn't that the size of the track your bit is engraving on the surface? So far I was using something like 0.009

Also what RPM are you using?

Just a quick comment on your Z axis. Is there any other bracing on the bottom of the axis? From the pics shown it is hard to tell but it looks like you are using the linear rails as the only support for the for the bottom piece of extrusion.
A over picture of the machine might help.

Hey drools thanks for you comment but I am afraid my knowledge is still young on CNC so I can't really understand the question

[Jay C]

RPM I use 16-20K RPM on my Bosch Colt. Yes I undersize my tool so it makes more overlap when etching, and I use the largest trace widths to make sure my traces are not impacted.

[Drools]

Just looking for an over-all picture of the machine.

[psychoul]

RPM I use 16-20K RPM on my Bosch Colt. Yes I undersize my tool so it makes more overlap when etching, and I use the largest trace widths to make sure my traces are not impacted.

Oh I see. What line width do you set in EAGLE? Also what distance between lines? I use 15mils for both those settings.

Also about the RPM, I will have to look up the specs of the spindle to see what I am using...