I have created and run with carbide motion my flattening tool path. Total depth 3/16 and depth per pass 1/16 and after the multiple passes it is not enough. Do I create a new toolpath by resetting the z axis and running the same program or is there a better and faster way?
Resetting the Z is probably the fastest way. You can do it with a bit of math, you donât have to probe for the new Z value.
Go to the âSet Zerosâ page, take the existing Z value, and subtract ADD 0.1875 (3/16"). Type in the new value and hit âEnterâ. Done. You donât have to set the Z physically in any spot, this works no matter where it is.
As an aside, this is one of the reason I now prefer metric - the math is easier!
Now just re-run the already loaded program. Since you are only working the top surface, it doesnât matter that the new stock thickness doesnât match the original thickness in the project.
Of course, this assumes you want to run the entire existing program. If you want to make changes, you can edit the project and the toolpaths, but you can still use this technique to set the Z rather than probing. Or use the original Z, and change the project to have a new start depth.
EDIT: âaddâ, not âsubtractâ. Doh!
You mean âaddâ. The current Z will be 3/16" higher when your new zero moves down.
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@mhotchin and @Tod1d have good advise. However there is a simpler way that I do it and do no math. I would jog off the material and use the jog function and lower the Z to zero (assuming you used top of material). Then jog down the amount you want to remove, in your case 1/16", and set z zero. Simply start your same file again and you will remove 1/16" of an inch. This works when you get close and dont want to remove more material then necessary.
The use of math is a very logical way but many times mistakes are made in the calculation conversion from 1/16" to decimal of 0.0625".
In your case removing 3/16" of material must mean you had a very rough cut board. For things like surfacing your spoilboard that is relatively flat to start with I like to put pencil marks all over the surface. Run your first surfacing program with the removal of whatever amount you want. Then look at your spoilboard and see if any pencil marks still remain. If all pencil marks are gone you are done. If you still have pencil marks then jog over to where the pencil marks are and lower your Z with the jog and use the paper method to set your new Z. Run your leveling program and if all pencil marks are gone you are through. If still pencil marks then repeat until you have no pencil marks left. This will result is minimal amount of material removal of your spoilboard.
@mhotchin and @Tod1d method work better for a lot of material removal. Depending on how wide your material is removing 3/16" of material might be better on a different machine like a planner on a sled with the material shimmed to minimize removal on one side to get it flat and then running the material back through the planner if you want two parallel sides.
To expand on that, I will note that an equal amount of material should be removed from the opposite side.
I wrote up a bit on this at:
Instead of re-measuring the Z, why not just increase the total depth and reduce the number of passes? So, if you started with 3/16 but need to take an additional 1/16 off, set the total depth of cut to 4/16=1/4 and have it done in one pass.
In this case, since you want to take off a different amount, I agree that editing the project file and using that makes sense.
I find changing the Z is faster when you are taking off the same amount each time.
I want to thank everyone for their help and guidance. What gets to me is the vocabulary. So many terms to try to understand in a partical sense. I downloaded a few published list and they help some. For those experienced they take those terms for granted, but not for a newbe. I finally sat down with a pencil and paper and drew out what was happening. All based upon what the machine knows and what I am telling it. Like when you deal with the top of the wood and how it is different when you already have a carving and need to carve another within it. I am not there yet, but enjoying the journey. As a retired shop teacher I go back to remember my lesson plans and how to teach something my students know nothing about. I am now doing that for myself.
Again think you all for taking the time to help, most appreciated.
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The community has worked up a glossary here:
Thatâs exactly what this forum is for, helping members. We all started somewhere and had to learn like you are now. Donât wait too long to ask a question, the sooner you ask and get it resolved, the sooner you can get back to running the cnc for projects!
ok more questions:
- I am using a Shapeoko XXL with Carbide Create. I have a BitZero V2 and it works great, however if I want to use it on the spoilboard that little raised protion on the bottom will not let it sit flat so wonât that throw off the Z zero measurement. I thought I read where you turn it upside down to do this,
- I donât have an accurate way to measure the thickness of the wood I am using. So if I set the Z axis on the spoilboard to zero then set the probe on the top of the wood, wonât that difference be the thickness of the wood???
- Now I want to use my new 1/2 inch roundover bit on the contour. I have the tabs set, so do I cut out the project then use the roundover bit because the tabs are still holding the project in place. Or is there a better way to do this?
- I so appreciate the help. pastor
- If you are probing all three axis (X -Y - Z), you âhookâ the Bitzero on the stock. If you are measuring Z only, you place the BitZero entirely on top of the stock. CM expects this, and internally uses two different values for the thickness of the BitZero.
- If you use Machine Co-Ordinates, this is true. You get Machine co-ordinates by clicking on the text âPositionâ. It will toggle back and forth between the two.
- Using a round-over bit on the CNC is a bit of an advanced topic. It can be done, but requires specifics on both the bit (must not have a bearing), and creating the toolpath for it.
- You are welcome!
For the round-over bit, using one with a bearing with a router or router table is usually simpler.
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The way I do it is pretty simple. I zero off the highest point in my stock and take off .5mm for hardwoods with a 3/4" Onsrud 40-141. I estimate the number of mm I need to take off, multiply that by two and add a couple of extra to figure out how many toolpaths I need to copy. Then I edit each of the toolpaths to start the Z .5 mm lower for each successive pass. Then I can just successively run the passes until everything is level with no need to reset the Z. The Onsrud bit leaves a very smooth finish in hardwood which requires very little sanding or hand planing. It also doesnât clog up the way some carbide insert bits can which is why I prefer to use it for smaller projects.
I have a Bitzero, but I never use it as I find it just isnât consistent enough for my needs. I always zero on the stock using the paper method. For through cuts I zero on the spoilboard and then zero again on the top of the stock. The difference between the two is your stock thickness. For subsequent bits I zero on the top of the stock leaving the stock thickness alone. Do this correctly and you will never cut into your spoilboard with perfect through cuts every time (assuming your spoilboard is true).
I thank you, I like simple and you confirmed that for me.
I appreciate you taking the time to respond.
I understand logic and when you realize this machine only does what you tell
it to do then it becomes manageable. Thank you again most appreciated.