Level Vs. True

I see a lot of talk about getting the machine “level” and making sure the furniture the X-Carve rests on is “level” and making sure the base is “level.”

Correct me if I’m wrong here, but I really don’t care if the thing is level at all. It could be on a 15º incline for all I care. What I care about is that the machine is True.

What that means is:
Are the Y Axis rails parallel to each other?
Are the Y Axis rails parallel to the wasteboard?
Are the Y Axis rails perpendicular to the X axis rail?
Is the X Axis rail parallel to the wasteboard?
Is the machine square?
Is the wasteboard lined up properly?
Is the wasteboard flat?
Is the Z axis perpendicular to the wasteboard both front/back AND left/right?
When you push the carriage front-back and left-right, does it stay in line with the wasteboard grid?
Are there low-spots or high-spots in the wasteboard?

The flatter you can get the surface that your X-Carve will rest on, and the squarer and truer you can get the machine to be, the happier you will be with it. It doesn’t really matter if the machine is tilted one way or another as long as it’s not so extreme that the motors can’t move the carriage. So put away your bubble level and get out your dial indicator and calipers and squares.

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Yep, that is the ticket. Square, true, and coplanar are the key things to work on when tuning a machine.

Some will just find it easier to use a level and Earth’s gravity as a standard to measure against in order to archive the afore mentioned… hence the reason for using “level” in their terminology.

Yeah but that can be quite misleading. Bubble levels have quite high tolerances in them. Your bed could be “level” and your gantry could be “level” but they could still be like 50 thou out of whack to each other. That’s enough to make it impossible to engrave something or make a cut that’s the same depth all the way from one side to the other.

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Correct. I agree, the more care taken in tuning a machine against better standards like machined flat surfaces and squares the better the machine will run.

These are what has enabled me to get the stock X-Carve tuned and milling some pretty precise stuff.

I was only pointing out that for some, especially those that are new to these concepts, a level and speed-square can be a cheap and quick way to get started in this world of CNC therefore reducing the barrier to entry and increasing the likelihood that they will take the plunge in the first place. Plus, the great pyramids of Giza were made square and true using pieces of string and a plumb-bob …

So, I would say the same as you @Mike only change it up a bit: If using a level, don’t expect high precision. If you do want high precision, then time, effort, and the right tools will go a long way to helping achieve that goal.


I agree all the way around but I would add one thing that most seem to fight so much. For every single project I do I mill a separate waste board then mount my aluminum to it for milling. I do it for my PCB milling, my stone work, every single project I do. Yes it take more time and it adds to costs and clean up overall. but my projects are milled on a surface that is flat to the spindle in all aspects. Once the pocket is milled the piece is mounted nd is flat in all respects to the travel of the mill and my cuts are true from side to side this way.

Having a tuned mill is the MOST important thing one can do for their mill to improve it of that there is no doubt and I sort of grin when I see guys freaking out about their tuning when they are measuring the “flatness” of MDF wasteboards… High on my lists of personal side projects is producing an affordable fixture plate for the 500 sized X Carve with tapped 1/4 20 holes every .5" in the full area of the wasteboard. Being cut out of toolplate with flatness of .015" per meter, this will give a true flat reference once placed on the mill instead of the MDF boards. But even then I am guessing a milled waste board for each project would go a long way to making up for the X Carve’s lack of adjustments for true tuning.

One promising change I am working with now though is just digitally probing the work piece on a standard piece of wood mounted to the metal bed that has been surfaced once. With the Planet CNC controller I use, the work piece can be probed and the high and low spots mapped and saved. Then as gcode is run the high and low spots are adjusted for and a level cut is made on uneven surfaces without the need to resurface and destroy the wooden waste board. But the draw back is the resurfacing of the boards is faster, but produces messy wood chips (not fun for an aluminum miller like me).

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If you’re doing a lot of aluminum, or any other expensive material where you want low tolerances, it makes all the sense in the world to do whatever you can eliminate variables in the machine.

I would LOVE a fixture plate for my X-Carve 500. Anything I can do to make the wasteboard flatter overall is a good thing in my book. I saw someone who had basically stacked MDF sheets underneath their X Carve so that the machine’s base rails were off the ground a bit (like 1mm) meaning the whole machine was now suspended from the MDF wasteboard and it supposedly took almost all the flex out of the machine. MDF is inexpensive so I might give that a shot. If it doesn’t work that well, at least I have some MDF to play with for other projects.

Just curious but - I mill my wasteboard flat and then use it again, and again and again and… you get the idea. How often have you discovered that a wasteboard that was milled flat once before is no longer true to the machine? I only re-mill when the surface gets ugly.

I have a full metal slotted bed on all my mills so I mill a flat waste board for every project for two reasons. First to make sure I have a 100% flat and level surface relative to the mill spindle. Secondly so I can screw down the aluminum parts I mill out instead of leaving tabs which I must later remove. 99.9% of everything I mill has a screw hole in it so i just use those to hold down the stock and milled pieces.

It might also be because I started my CNC milling with PCB milling which needs a perfectly flat and level surface to insure a good trace mill on the PCB. Maybe I just held that habit over into my aluminum milling. But I often do fine detail milling with very small endmills which do not like the surface to be uneven relative to the mill as they cut without breaking.

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I believe anyone familiar with cnc would agree 100% with what you are saying. My questions is how to achieve a truly flat surface to put the cnc machine on top of. A wooden table works acceptably when milling wooden signs and cutting out many things that do not rely on precision surface engraving. But engraving things such as pcb’s or engraving on aluminum when you are only cutting down to .017" it becomes a visible problem with the finished product. I have been engraving designs on aluminum and have had to search around the waste board for a area that is true enough to keep a uniform depth of cut. I am searching for a way to achieve a dead flat platform for the cnc to rest on which will go a long way to being able to true the machine so that the entire waste board is flat. With a dial indicator I have seen dips in my waste board of as much as .010". That doesn’t sound like much but when I am milling to a doc of .017 that is completely unacceptable.

Anyone have any suggestions on how to reduce the wave in my waste board. That .010" variation was after milling it flat with a 1/4" bit. I considered a piece of granite. I found a local supplier that could hook me up with a piece big enough for my 1000mm x-carve for a “just” $350.00 plus tax. Ouch!

I always face-mill a backboard before making any depth critical parts on XCarve. But over time, the wave in my XCarve waste board has become substantial. The shelves I have it sitting on are not flat or level. I’m sure that’s the root cause.

Anyway, today I got fed up and decided to do something about it. I thought about buying a slab of Mic6 aluminum or granite to set XCarve on. Also thought about building a torsion box. But in the end, as usual, I opted for a quick and dirty solution.

My XCarve is sitting on two sheets of 2’x4’x0.75" plywood. I decided to use pairs of M5 bolts and drywall screws in sort of a jam nut configuration to:

(1) first level the waste board by adjusting the height at the corners using the bolt-screw pairs

(2) then flatten the backboard in the area where I’m milling parts, by turning in six more M5 bolts to adjust the gap from bit to wastboard over the backboard area.

These bolts and screws are actually bending the wasteboard and frame to make it both more level and more flat. I do still use a backboard and mill it flat before making depth critical parts. But now, the backboard is out-of-flat by only about .01" rather than .100".

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An order of magnitude more flat is a pretty good result! Congrats! I love the ingenuity of this community.

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I’ve always heard the word trammed used to describe how “level” a machine is.

As a first step, you could use a gcode simulator like CutViewer or simulate in Fusion 360, to see if it is a problem with the tool paths or with the XCarve.

You’ll want to single step the sim through the trouble areas in the tool path and compare the rendering to the physical part.

But if the z-axis has slipped, then it would show up in all subsequent cutting for the job. Is that what you’re seeing?

I get similar things and have confirmed it is not in the g code. My guess those are areas where the bit is taking a full thickness cut, causing it to deflect so the cut depth is off. I call them “pencil lines”

Do you have a stiffening mod? That will help a lot with that issue.
I am still trying to figure out how to eliminate them completely.

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I have recently run into an issue with this very topic. I have noticed that my depth of cut tapers off as I move towards the center of the wasteboard. I made sure all my axis were lined up and everything was good prior to the first cut (this was about November when I upgraded from the 500X500 to the 1000X1000). This is a recent development, so I put a 4 foot level across my waste board and noticed a gap that has formed in the center to slightly more than 1/8 of an inch. Has anyone else experienced this and my first thought of fixing this issue would be to slide spacers or washers in the middle support rail under the waste board. Are there other methods to repair without planning out my wasteboard? Those gridlines are very vital to me which is why I am so meticulous on the front end ensuring everything is square and true.

Great topic and discussion. For the furniture the machine rests on, I think “stable” is the key attribute (hence tortion boxes). You can then true the wasteboard and know the table won’t be flexing or warping it.

Look for cabinet shops that sell granite or marble countertops. Sooner or later they will have a piece with a flaw that they can’t use. I found one large enough to fit under my 1000mm X Carve that was 1 1/4 inches thick. They even cut it to size and it cost me a total of $60.00.

Wood moves with weather changes. That’s why doors and windows stick and sheet rock has cracks at different times of the year. I don’t care how well built your table is that you pout your machine on, it will move. When it does, the X Carve will follow it. When it does your waste board is no longer perfectly flat and your precision goes out the window. You will find that when cutting out a part that is .75 thick with a .75 inch depth of cut will cut out part of your project fine, too deep on other parts, and not all the way through on others. So you find yourself cutting out parts that are .75 thick with a dept of cut that is .77 deep which cuts into your waste board in some places and barely scratches it in others.

Putting your machine on a 1 1/4 inch thick chunk of marble or granite along with proper tramming of the spindle and insuring that your Y axis rails are parallel with each other and the same height, will leave the “Wave” to the Home Coming Queen in the Parade and removed from youi X Carve. Your table will still move but the granite/marble won’t. At that point, the only problems you should see with your waste board is possible swelling from excessive humidity especially if you are using MDF. Normally a quick resurfacing will resolve that issue.

So stay away from companies that have a thousand granite slabs sitting outside. They won’t work with you. Look for a local smaller shop that cuts and installs them. They will occasionally have pieces that may be chipped or cut wrong. They are too big to put in the dumpster or too ugly to sell. They just want to get rid of them. Who cares if it is pink and black, all you will see is the edges and isn’t a extremely well aligned machine worth it. I have had mine on a slab for about 2 years now and it hasn’t moved at all but I am certain that my table has.