[jlawton]

Was kind of hoping there was a CAM topic entry here for FlatCAM, I'm just a "johnny-come-lately" with one of these Chinese 3018 GRBL 1.1h machines (like a Genmitsu/Sainsmart), I'm generating double-sided PCB layouts with KiCAD (using freeRouting the autrorouter, and whatever its "native" trace width is) and FlatCAM, and trying to make sure I can account for all the mistakes I made today. Actually I'm pretty happy so far but I was watching the following YouTube describing how to set up for the engraving part, and I'm pretty sure he said 3 passes at 25%:



so it came as very much a surprise that when the engraving bit was attempting to isolate the traces from each other, there was basically zero trace width left [and no I didn't enable autoleveling, I don't quite understand it (I'd sure appreciate it if someone could link a decent description) and the largest board dimension is only 3" anyway]. This was with the "blue steel" engraving bits from Amazon, I noticed there were a few more of a slightly different nature sent with the machine itself, and somehow I would up with a third package of 10 as well. I "assume" these are all 0.1 mm width and 30 degrees and other than the color they all look the same. What would be absolutely terrific would be if someone could give me a reasonably accurate formula explaining the relationship between "native" trace width, degrees of bit angle, # of passes, % retrace and final trace width, or if you don't have that if you could just give me settings that "seem to work OK" for you, and maybe what else to watch out for in order to get consistent results?

[CitizenOfDreams]

The key to successful PCB engraving is consistent depth of cut. The cutter needs to go deep enough to remove the copper, but no deeper than that. If the cutter goes too deep, the cut becomes too wide (and the copper traces become too narrow, or even disappear completely).

Problem is, even a 3-inch board will have enough height variations to completely mess up the engraving. No matter how much you try to level the table or flatten the board, it will never be flat enough.

Commercial PCB prototyping machines use "depth rings" to keep the cutter at a constant depth. Hobbyists like us use surface probing. A program such as Autoleveller probes the PCB surface and adjusts the G-code for any height variations.

Once you figure out how to make consistent cuts, adjust the bit diameter in your CAM program to match the actual cut width. A "0.1mm" V-cutter will probably cut about 0.12-0.13mm.

Here is my recent work. I have yet to figure out how to spread the solder mask perfectly.

[hfjbuis]

Calculating the trace width is pretty complicated. It depends on the runout of your mill, the form of the tip (flat or curved) and the angle of the tool bit. For what I have seen, most PCB millers set the cutting depth by trial and error.
You can calculate the change of the trace width (when milling deeper than the radius of the tip) using this formula:
dW = change in width
tan = tangent of the angle
Angle = the angle of the tool bit. Depending on your calculator settings, this angle must be in degrees (common) or radians.
dW = 2 X tan( Angle / 2)

For a 30° tool bit this is 2 X tan (30/2) = 2 X tan(15) = 2 X 0.26 = 0.53 mm / mm
so for every mm you lower a 30° tool bit, the milled trace gets 0.53 mm wider.

[jlawton]

You can calculate the change of the trace width (when milling deeper than the radius of the tip) using this formula:
dW = change in width
tan = tangent of the angle
Angle = the angle of the tool bit. Depending on your calculator settings, this angle must be in degrees (common) or radians.
dW = 2 X tan( Angle / 2)

That's all fine, but those aren't the parameters I'm being asked to set up! I'm supposed to enter "passes" (cnt) and "overlap" (%) as well as depth.
What do those first two parameters even mean, and should I endeavor to involve either or both of them in the engraving process, or simply
choose some "default" value to "get them out of the way", and in either case what value would that be? And is there a formula that incorporates
them as well?

[hfjbuis]

I am building my PCB router so i have no experience.

The overlap means how much of the previous pass is milled again.
Depth means how deep the cutter is milling. It should be as shallow as possible so that just the copper layer is milled away.
Passes (I gues) is how many passes it should do to mill the requested depth. A cutting depth op 0.05 mm/pass is quit normal. To cut 0.015 mm it would require 3 passes.


FlatCam has a manual that should get you started by using de proposed defaults: 4.1. Isolation Routing — FlatCAM 8 documentation

[jlawton]

That's some beautiful work. But I'm confused, there are comms packages like the paid version of Ultimate CNC (I saw it somewhere else for free, maybe Chilipeppr?) that look like they run
autolevelling as a separate "machine operation". It looks as if inside the machine it uses some G38 commands which sets up a grid based on XY that then "behind the scenes fixes" the Z
value...or at least it LOOKS like what might be going on! Can you explain this or link me to an explanation? FlatCAM itself is already complex enough, I wouldn't want to feed IT into ANYTHING that has to try and reverse-engineer its output, I couldn't EVER trust it to get it right!

[jlawton]

Unfortunately FlatCAM is in version 8.994 beta, they really haven't made any updates to the documentation since FlatCAM 8, and any similarity between the documentation and the released
beta is entirely accidental! (Or I wouldn't be here!)

[hfjbuis]

I have a few video's that show how to mill a PCB.

For starting, I will use the free versions. FlatCam is often mentioned as a way to go, so I will give it a try as soon as my PCB router is ready.

But whatever software you select, it will take time to get it working.



https://forum.electricunicycle.org/t...op-cnc-router/

[jlawton]

I will be studying all of those intently, thank you! I would say in my experience FlatCAM "delivers the goods" in terms of being CAPABLE of great results, but in my opinion both the documentation and "learning curve" leave much to be desired. For example you wind up plowing through quite a bit about "setup parameters" before you HAPPEN to learn there's a whole set of screens where you can set up the "default" values that appear, and then make them what YOU want, rather than having to change every default every time you encounter them. That's certainly a GOOD thing, but right now there's no way to learn it's already there...

And by the way I've already laid out most of my concerns about setting up track width, but I also have a feeling that I don't REALLY know what the ACTUAL parameters are of the three boxes of ten engraver bits I already own...I know how to tell "30 degrees" but there seem to be quite a few variations on "tip type" and NONE of the containers I have are marked, neither (in my opinion) are the descriptions of the ones available online on Amazon or AliExpress! If anyone has any kind of "part # cross-reference" that tells me if these are supposed to be considered rounded tip or pointed or what the width is, it might really help because I couldn't really tell you what's sitting in my machine or next to it, and I would really like to "nail that down" because that could be a big component of not getting the results I expect with the settings I'm borrowing from a video. Thank you hfjbuis for your help!

[deadlykitten]

hey citizen, what is this ? and it works, doesn't it ? i am not into electronics

[CitizenOfDreams]

hey citizen, what is this ? and it works, doesn't it ?

It is a flashlight. And yes, it works.

[jlawton]

This sounds interesting, I just went on https://www.precisebits.com/products...oreengrave.asp and read the following:

"30° V-tip tools are NOT intended for metal engraving, or PCB trace isolation"

That's an interesting statement, considering that's the first place I'VE ever read saying that's NOT what's supposed to be used...yes I'm a "newbie" or whatever,
and maybe this is mostly marketing, but I dropped his support email address a little message asking to explain himself...if he has something that delivers more
predictable results I'd certainly like to know more about it...

[CitizenOfDreams]

This sounds interesting, I just went on https://www.precisebits.com/products...oreengrave.asp and read the following:

"30° V-tip tools are NOT intended for metal engraving, or PCB trace isolation"

I don't think they had that warning when I was using PreciseBits cutters several years ago. But I agree, 45° and 60° tips are more suitable for trace isolation. Anything sharper than that is just too fragile.

[jlawton]

CitizenOfDreams, you seem to have experience with this PreciseBits outfit...

So he got back to me with the following link: https://www.precisebits.com/products...d_stub_125.asp

What do you think about this tip EM2E8-0039-15V? (It IS 30 degrees I believe) Do I need MELube ( https://www.precisebits.com/products...als/MELube.asp )?

I don't know what to make of this information...I'm not really having problems breaking tips (as far as I know)...I may be having trouble with tip "chatter" (excess vibration) but I don't
really know that either...or maybe I ought to be looking at a different spindle motor with better bearings (not sleeve)...I'm operating in an environment that I'm not exactly expert in, so
almost everything I look at is basically filled with FUD (fear, uncertainty and doubt)...then again the ONLY "unknown" left is the isolation routing, ALL the other "issues" I've had are
the result of known causes...

And as far as links he sent me another one that I didn't have, I don't think there's much in it I haven't already "picked up" somewhere but it's nice to have anyway:

https://altrish.co.uk/wp-content/upl.../flatcam-1.pdf

[CitizenOfDreams]

jlawton, I only used the V-tip tools (EM2E8-0625 series) from PreciseBits. Haven't tried the "tapered stub" ones. I did not use MELube either.

Those PreciseBits V-tip cutters did work beatifully. However, I felt like my machine was not capable of taking full advantage of those (rather expensive) tools. So eventually I switched to cheap Chinese pyramid shaped cutters off eBay.

The "chatter" you are talking about is probably caused by the cheap spindle motor. It may have unacceptably high runout. Or it may be poorly balanced. Try reducing the RPMs (together with the feed rate) and see if the vibration goes away.

Most important of all, don't give up. If other people could successfully make PCBs with their cheap Chinese machines, so can you. :wave:

[jlawton]

I can't say I AM having "chatter" because, guess what, I don't have anything I can trust to measure it! But just about everybody I talk to is themselves talking about "excess spindle runout
in Chinese mills" so I guess it's extremely common. Do you have any direct advice, or do I just start looking under rocks for 775-compatible motors sporting ball bearings? Is my ER11
collet set (Genmitsu) OK or is it also suspect?

Also could you enlighten me a bit about V-tip versus tapered stub, if you know something? I think I need to change part #s to get the former, again for SW compatibility, it would be worth
a few bucks to make sure this project doesn't get TOO far off track, but I hear what you're saying about the Chinese tools being "good enough", but I can go back after I get predictable results.

[jlawton]

Guess I got that wrong, all PreciseBits seems to have in 0.1mm tip is tapered stub. Also after tearing into it I'm less than certain that the motor on my rig is NOT already ball bearing (now whether those bearings are any good is a different kettle of fish). But in all likelihood a 2 flute 0.1mm tapered tip bit has to present a more constant load, so in application probably less runout than the Chinese half-cone? Seems like it would be worth a try anyhow.

[joeavaerage]

Hi,
I use these:

https://www.ebay.com/itm/381533819973

They are 60 degree bits and I get many boards out of them and $4.00 each. I have nominated a tool tip diameter of 0.175mm and a step over of 0.09mm
in my Gcode generator. I use Autoleveller.

I make dozens of boards a month, almost all surface mount with a self imposed minimum trace width, and isolation width between traces of 0.2mm.

Craig

[jlawton]

Hi Craig,

What's a "stepover", is that the same as overlap except in distance instead of %? Are you at all familiar with FlatCAM, what's YOUR gcode generator? I'm looking for someone to look at the video I linked at the start and explain if there's some reason THOSE settings aren't going to work with my layouts. Do you have a link to how Autoleveller works so maybe I could understand it? Does it have to modify the gcode files themselves before they go to the machine? (If it does I despair of anything being able to correctly modify the gcode coming out of FlatCAM, I'm not sure why but they'll find some way to make it incompatible.)

You don't have to answer EVERYTHING I asked, but it would be great if you could just make one or two layers of the smoke dissipate...

Jeff

[joeavaerage]

Hi,

What's a "stepover", is that the same as overlap except in distance instead of %?

Yes,that is correct, so approx 60% overlap.

I have used FlatCam but was not impressed.

I use PCB-to-Gcode , the User Language Program of EAGLE.

Autoleveller – CNC Millings, Levelled

Does it have to modify the gcode files themselves before they go to the machine?

Yes.

It sounds to me that you have to set the tool tip diameter as wide as you do because FlatCAM is not applying a tool width offset.

Craig