Flat milling the wasteboard

I’ve seen many post that kind of discuss this, but is there any step by step tutorial scenario? I can’t find that, and I am clearly doing something wrong. I have what I think is the proper bit:

# CNC Spoilboard Surfacing Router Bit, 1/4 inch Shank Carbide Tipped Surface Planing Bottom Cleaning Cutter Slab Flattening Router Bit, Wood Milling Cutter Planer Woodworking Tool

I created a giant rectangle in Fusion and created a “face” tool path that looks like it should be doing the proper thing. Exported the .cnc and loaded it into the A350. The bit wanders back and forth and I can clearly see that the wasteboard isn’t level. But as the tool wanders back and forth, in the areas where it does cut the board, it leaves very slight ridges between the passes. The tool is only moving about half the width of the cutting head, between rows. I can’t really figure out how the cut isn’t even, despite probably not being deep enough, since parts of the board aren’t touched.

How is your tool path? Left to right? (along the x-axis) or back to forth? (along the y-axis)?

Did you tram your setup?

There’s a chance the tool head is slightly rotated in one direction which causes this.

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Tool path is back and forth across the x-axis, which was the default, so I figured it was the more common technique.

I don’t know what it means to “tram” my setup.

How can I tell if the tool head is slightly rotated and is there anything that can be done about it?

This is the end result:

It seems as if the ridges are created on just the return sweep, but I can’t be 100% sure. Any advice on how to fix/ adjust for this is greatly appreciated.

You can use parallel in fusion 360 and add perpendicular passes.
I’d also set the stepover to 1/3 the width of the bit.
What I did was set up for a .5mm step-down pass, but raised the z-origin so it was only cutting .2mm to start. (I wanted to shave off as little as possible, and time wasn’t an issue) Then I ran it and determined that it still needed one more pass .2 lower. (There were untouched areas) I actually ended up running the 2nd pass twice (at same height) just to make sure there wasn’t any deflection. Don’t know if it made a difference or not.

Are you suggesting the parallel (I’m not 100% sure I understand why that should make a difference, but I’ll try anything to get a better understanding of this stuff) instead of the face path, or in addition?

I created a rectangle and extruded it one cm. Then I added .5mm of extra stock on top. Used a face path to trim it down the half millimeter. The tool is about an inch across, but I used 1cm side steps. I know the cut looks deep, in the photo. But on the far edge (outside the photo), it was barely touching.

I still have a little room to play with. Worse case scenario, I cut a new board. Such is the price of education.

I will play with the parallel, and perhaps just cutting in the Y direction, if that’s configurable, might fix this if it’s an artifact of the tool being a bit less than flat.

How can I configure it to cut in from the side, rather than trying to plunge, in the corner?

Instead of. Just because it will do a perpendicular path in the same gcode output.
You could also do face twice and change the angle 90º.

Your approach is sound. It looked like you were doing half passes, but hard to tell.

I attached a piece of plywood to the top of mine. (It was what I had, all things being equal I’d prefer mdf) My bed is pretty flat. It was only when I was doing some marble with only .1 engraving depth that I started to have problems where one side wasn’t engraving.

You can use scallop and start from the inside.


Basically, to make sure that everything is square and as parallel as possible. For example the x-axis and build plate you can align this way: Milling the cnc wasteboard flat (or so I thought): mis-aligned z-axis modules - #16 by brent113

If you read through that topic, you’ll also see I made the mistake of not doing it and due to making the mistake of turning of the machine and restarting, the x-axis and the carriage got aligned differently. The most important thing is that you have a reliable/reproducable way to align them.
If you ever run your tool head in the bed hard, break a bit, change tool heads, there’s a reasonable chance that both z-axis might might shift slightly compared to each other, and then it’s not aligned anymore. The same applies in the Y-direction but that’s not that easy to do without additional rails or something.

But in essence, if for example you found that the left side of your bed was consistently 1mm higher than the right side, then that might be an indication that both z-axis weren’t aligned perfectly.

Finally, there’s the chance there is some play on the x-axis (if you wiggle your toolhead it might move a bit forwards/backwards or left to right). If you wiggle hard enough it will anyway, the machine isn’t that stiff :wink: So whenever you make a cut, due to the resistance it might be pushed crooked just a tiny little bit. As your bit is 1" wide, a very small deflection like that can cause a little ridge already.

So how big are those ridges? Based on the picture it doesn’t look that big.
As already mentioned by @sdj544 running a second perpendicular pass on it, or do a spiral from the center outward might clean that up already.

Finally, you will almost always see a toolpath if you look closely enough especially just after you ran your job.

And then, for your wasteboard, if there is a 0.05mm ridge, that won’t really matter and for all practical purposes your wasteboard will be flat. The most relevant thing to look out for is that you can reproduce the parallellism between your x-axis and the carriage in a reproducible way so that when you’re changing toolheads etc you don’t come to the conclusion you should mill it flat again.

Obviously, since you already milled it now; the easies way is to get them aligned again is to just push the x-axis down onto the board (possibly with a 123-block or spirit level or something else that you know is flat in between as the toolhead won’t allow you to push it down completely).

I ran another facing, in the Y direction. Then, just for good measure, ran it again at the same height and the bed is much improved. One of these days I might actually understand what I’m doing.

I understand, now. I just purchased the 1-2-3 blocks. Are you just manually pushing the z-axis down onto them?

Yes indeed

But you must do it with the power off. When powered on, the stepper motors keep them fixed in their location.

So power off, push towards the reference location and turn back on.

Just a tought - Is a M18 not possible too?

Good idea, Yes, should be possible as well. I think you should always home G28 after tramming then. Not sure if G28 also reenables the steppers or you need to execute an M17 first.

I am planning to mill my wasteboard. I have a couple of questions for you as I see you tried it with a similar surfacing mill.
What were the spindle speed and cutting feed rate?
The bed for me is off by 0.1 to 0.2 mm. Is it worth milling?
Thanks in advance :slight_smile:

With a 1" bit on plywood I’ve had good success using a feed rate of 400mm/m and a spindle speed of 12000 with a .2mm step down. It’s always easy to increase or decrease speed on hand controller. Use your ears. It will tell you when it’s pushing too hard.

As far as is it worth milling goes, that’s up to you. My bed is also within .2mm. I’ve found it unnecessary for most carving (reliefs, signs etc.) The only time I’ve used it is when my cutting depth is close to how much is off by. If I’m carving marble I’m only going .2-.3mm deep, so that error really shows up. With a sign that’s 2-4mm deep, it’s not noticeable.

I don’t recall the cutting speed, but it wasn’t crazy slow or crazy fast. You are looking to trim as little as possible, so faster speeds are possible, I suppose. The deeper you cut the slower you might want to move. Spindle speed was 12k.

As for the need… It depends on your project. Even with the waste board “level” and tramming the machine, etc. I still have a big enough difference in areas that I can detect it. Most of my projects, so far, are cutting out shapes, so I just go a bit deeper into the waste board in some areas and that gets the job done. If you are looking at 3D milling, you might see more issues with an uneven waste board.

Thank you @sdj544 and @rlrcstr. I realized that it’s probably not possible to have a true wasteboard even after milling the top surface if I switch modules. For time being, I will just mill the face of my work pieces after mounting on wasteboard to ensure flat starting surface.

Some people have had more success ‘tramming’ their x-axis.
Mine seems to do pretty well as is and is consistent even when changing beds.
(I made sure to mark the direction and position of extra piece of plywood I milled.)
You can do a search for tramming and find more in depth info, but the basic idea is taking two identical objects (engineers blocks are the pro way, but soda cans are pretty consistent) and lowering and adjusting the x-axis so the height from the wasteboard is identical on both ends.