CNC Wisdom Part 2

Hi Everyone,

I previously posted HERE asking for some help getting started with the CNC Module.

User @sdj544 gave an amazing walk-through of many initial considerations.

I also found this awesome video in the SnapMaker Academy that has a bonus few Fusion tips: Fusion 360 CAD & CAM Tutorial for CNC Beginners

Following that guidance, I’ve generated a file and am at the (scary) ready to test stage:

The actual file is only the arch and letters, the green surrounding everything was colored by fusion.

I basically made a huge pocket around the letters and the inner pockets between them. I generated it all as one process with a 1.5 mm flat end mill.

Does anyone foresee issues with the settings I’ve tried?

Originally I was going to also mill the letters 0.5 to 1 mm down from the top of the stock (because I stained the original frame before processing). But I’m not sure that’s wise. Will it chip out the letters? Would that need to be done first?

Is there a way I can combine both of those operations into a single process or is that pushing it for a complete novice?

The height of the letters above the bottom of the pocket is 2.5 mm. Once I set up the origin, is there a way to convince SM the depth I want to go is 3 mm total (so the letters are 0.5 below the surface and the pocket is 3 mm below - if I even carve the 0.5 off the top of the letters))? Is that something I need to set up in fusion before I use post processing?

Thank you everyone and especially Sdj544 for your phenomenal reply to my other question.

I think your lead-out rate is too high. I generally put it same as lead-in. In reality now it might not make any difference with the free version, since one of the limitations is that it doesn’t use fast moves. Also for all but the start of the move it probably won’t be contacting the work piece. But as far as finish goes and minimizing deflection, keeping the speeds near to the same improves that. Probably can raise your plunge rate. Generally if my work speed is 400, than I do 300 lead-in/out, plunge 240 (for hardwoods like oak, maple, walnut). You didn’t state what type of wood you’re using.

You’ll also have to decide if 1.5mm gives you enough detail. All of your inside angles will be rounded to the 1.5mm dia. It should be fine, but that’s up to you. The outside edges will be sharp.

If you’re using a downcutting bit (and it isn’t dull), you’ll get a good finish without much tearing. I’ve done facing of the top both before and after cutting letters. It really doesn’t make much difference. You may still need to do some light sanding to remove tool marks and any rough fibers. Decreasing step-over to 1/4 to 1/3 of your bit size will lessen marks.
All of your heights and layers should be determined by your model/s in fusion and how you set up both the stock and heights as well as boundaries. So some of that needs to be done in the design tab, and some in the machining tab. Some can be done in both. You have to figure that out for your model.

You may find it easier to create two (or more) toolpaths. As long as they’re the same tool you can combine multiple toolpaths into one file and run them with one operation.
I’d suggest using to check that your g-code is doing what you expect. Then run a test pass on scrap wood (or just have plenty of wood you can sacrifice.)


Thank you SDJ! In truth I only changed a few of those settings from their default based on the SM Academy Video.

The wood I’ll be using is actually an oak plywood (hence the shallow depth, I only want to cut through the veneer and the first layer below it which comes to about 4 mm).

I made the model by extruding up from the SVG, but in terms of height being milled down, should I make a larger rectangle fusion and cut the model down into it? I plan to cut a piece of scrap tonight or tomorrow and I’ll post the result back here after incorporating your suggestions.

Again I truly appreciate your invaluable assistance!

From your picture it looks like you’ll be fine setting origin to top of piece.

A couple things you can do if you want. Set z 1mm high and depth 1mm deeper. It will cut air at first, but you can watch it following path and see what it’s doing before it starts cutting.
You can also just set the origin well above the work piece and watch what it does.


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Thank you for the suggestion. It’ll be a few extra days before I can test, I accidentally broke the bit before I even started by hitting go to origin before I set the origin : /. Waiting for new bits from Amazon.

Hi @sdj544,

So I was finally able to run my test after getting my replacement bits and incorporating your advice. As for a first test, it went pretty well (with 2 exceptions).

The first exception was I didn’t have enough clearance in the SVG between some of the letters and the lower arc. No biggie, I can fix that.

The one I would love your perspective on, is that my Facing operation didn’t work like I expected.

I followed your guidance and made 3 toolpaths (all using the 1.5 mm flat end mill).

The 1st carved out the holes in letters that had them.

The 2nd toolpath was supposed to face the letters every so slightly.

The 3rd carved out the outside pocket (due to the quick swap brackets I use there was some wobble on the Y axis here when the platform moved forward (towards the touchscreen) which affected quality in some places, so I need to rethink that as well or not use it for CNC).

The facing operation ran the proper path, but it did so just above the stock. There was enough room to slide the white card under the rotating bit without it getting chewed up, but probably not much more clearance.

I used virtually the same settings for all 3 operations (except for a lead-in/out rate 50 mm slower for the face operation because I forgot to change it).

One exception might be that this: I realized after the fact that I set the WCS origin to be on the tip of the T, which was 0.5 mm lower than the stock face. Perhaps this is what I did not account for? If its that simple, which of the various settings do I need to change?

Otherwise I want to sincerely thank you for your help so far SDJ. I’m thrilled with the first test and think I’ll be able to fine tune this pretty well in short order.


That’s looking really good for a first pass!

Checking for the right amount of clearance can be tricky. You should be able to measure the gaps between points in Fusion to check. Also problems like that should show up when you run a simulation in Fusion. But sometimes that’s just why you run a test.

I haven’t seen a quick change bracket that would hold up for the cnc work I do. It’s not worth the 5 minutes I’d save. Double check that there isn’t excessive play in either your y brackets or the head. It will deflect with pressure but shouldn’t easily rock.

As far as the path goes, I always set the origin to be at the top of the stock. If I’m changing bits I set it on the SM on a piece of the workpiece that I know won’t be milled.
The only thing I can see that might be giving you problems is how you’re selecting the bottom height. On a contour you can usually select either the top of a shape/or letter, or you can choose the base of it. Make sure that when you select it that you’re selecting which one will work for what you’re trying to do. That will affect the height range that it will mill.
When facing I sometimes run a pass that takes only .5mm or 1mm off. I’ll run it once and then depending on the results just run it again while lowering the work origin a bit. That may be .1mm or 1mm or somewhere in between. All depends on how the first pass turns out and what I’m going for.
Watch and make sure it’s not going to run into anything you don’t want it to when it goes that low.