Cnc wood - needs leveling before i can start job

hi, i did everything right, and cnc’ing is just 1mm, but half the board must be 1mm lower than the rest using a pine board, (frustrating to watch only 1/2 the image being cnc engraved).

@sdj544 is there a way (if i know the size of the print) to level the piece of wood before i start the print? ideally i want to go down 1mm before i start.
willing to do a blank separate print and reset the machine and settings, before i start my job, but have no idea how to do a blank.
maybe a picture of a black area, and just expand it to the size i want?

looking for guidance so i do it the right way.

having so much fun with the snapmaker and learning so quickly, (for anyone else, the enclosure is well worth it - i thought it was a bit rich, but when i saw the quality and how much it helps (light, dust outside, smells outside) can’t recommend it enough.

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You want to carve the wasteboard, to get it flat right?- You could easily make a square in Luban to carve.

not quite, it is my understanding the waste board is under the piece of wood i want to carve (wasteboard is flat)

but thankyou, you have given me the answer - why i didn’t see the rectangle tool on the left and work it out is beyond me (i am laughing about it now), thanks @xchrisd , and also thanks for the photo :slight_smile: it helped a lot

The waste board is probably flat. But there is a chance that the alignment with the rails./bed isn’t perfect. Thus it might result in the perception that your stock is also crooked.

So to be sure, you should make sure your waste board and cnc tool head are perfectly aligned. A good way to do so is to mill the surface of your waste board.

The next step is to always mill away the first mm of your stock too. (or measure carefully that it’s perfectly flat as sometimes you do want maintain the original surface)

In short: you should explicitly validate the alignment of your cnc head and waste board. If you don’t, you may end up making your stock that was perfectly flat, skewed.

Maybe this was obvious to you, but it wasn’t clear from just reading the posts.

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no, it wasn’t obvious brvdboss, thanks for the hint :slight_smile:

I ended up creating a few different sized rectangles for basic sizes of wood i tend to use.
I did them with my largest bit, 1/4", with .5mm step down. Exported the gcode and labeled them appropriately, Surface_100x100, Surface_200x100, Surface_200x100 etc
Now when i need them I can just grab one and go. If I find it didn’t take off enough I lower my z origin by .5mm and then run it again.
-S

thanks @sdj544 , that fills in the blanks of exactly what i was looking for :slight_smile: for anyone else, rectangle box filled in setting :slight_smile:

@sdj544 if it is not too much trouble, your largest bit - what is it called (i have bought all the drill bits - i think it might be “ball end mill” 3.175mm
you said step down 0.5mm (for harder woods it might change) but the speed and density you have been using?

background - (before i got your advice) was using the “v” bit at 0.5mm @ 720 and it created a mess (wood became very furry - bits sticking up, and didn’t feel nice and smooth).
would just save me so much time experimenting - a starting point to see what works would be awesome.

I’m using a flat end mill.
For surfacing you want a flat bit.
While it’s possible to do it with other bits it will take forever because what’s called the stepover (how far the bit moves for every pass or how much each pass overlaps) has to be really small.
You can mill with a 3.175 flat end mill like the one that came with the SM, but I bought a flat end mill that’s 1/4" (6.35mm) so I could cover more area. For that I also had to buy a new collet (the part that clamps around the bit when you screw the nut down). The standard collet that come with the SM is 1/8" (3.175mm). SM uses ER11 collets. For any new size bits you’ll need a matching collet. Fortunately you can get a set cheap. Even better is that you’ll probably really only need the 1/4" one. (the majority of bits have either 1/8" or 1/4" shank)
For harder woods (oak,maple) I use a .5mm step down. For softer woods I can sometimes get away with 1mm. 340mm/m work speed and 240mm/m plunge speed seems to be best combo of speed and smoothness and not straining the motor. Listen as it’s cutting and you’ll get a feel for it but it’s pretty obvious when the motor is straining and working too hard.
I’m not sure why Luban uses fill density. (maybe because it’s a terribly designed program)
Every other program uses percentage or an actual measurement to set stepover. I leave it at 4 when I use Luban, but generally I use Fusion or Easel to create my tool paths. I can choose travel direction in those and I prefer to be able to have my tool paths travel parallel to the grain. In those I use 50% or 33% depending on how nice and smooth I need it. 33% if it needs to be a finished surface I’m going to sand. 50% if it just needs to be level to start.
Hope this all makes sense and helps.
(was going to be a much shorter response originally)
-S

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If you really want to push it further and test & validate. This video gives a quite good overview of all the things you can do to tune your device for cnc usage: https://youtu.be/P4VverLXpCI
It’s for a shapeoko, yet the principles are mostly the same.

The above all assumes that the device itself is perfectly squared and aligned. If not (and for example the cnc module is a little bit off) you still may end up with an uneven waste board surface. (And have created something like a saw-tooth pattern on the surface).

There are also specific surfacing router bits (google for surfacing router bits) available. Those cover a much bigger area, but I’m not sure if those are suitable for the snapmaker (very high spindle speed & limited power of the motor) plus heavy “top” of the bit which can causes more “wobble”.

As sdj544 mentioned, the flat end mill is best for this operation. (of those included with the device)

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thankyou @sdj544 and @brvdboss the info is very informative and it will take me a few reads to absorb it all :slight_smile: the video you gave i look forward to watching (even though it is a different machine)
i will look into fusion or easel later (need to get my head around this info first) :grinning: thanks -s

thanks guys

from Nazar

@sdj544 looking into software (it looks awesome) of fusion and easel, and it looks better in every way.
just so we are on the same page and for anyone else looking at this post - is this the software you are using?

fusion 360 - free to use for hobbyists (as long as it is non commercial) https://www.autodesk.com.au/products/fusion-360/personal

easel from inventables (free program) - https://www.inventables.com/technologies/easel

video (13 mins) that shows what we are missing with Luban - https://www.instructables.com/id/Fusion-360-CAM-Tutorial-for-CNC-Beginners/

(for anyone visiting) took me a bit to work out, please like the post so others see it :grinning:

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thanks sdj544, :grinning: the like confirms the SW - thanks

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