Can I avoid the "Zeroing" process with a fence?

How To
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I have a Shapeoko Pro XXL with BitSetter, BitZero and BitRunner. I use my machine for a lot of small/one time jobs and find that going through the BitZero probing process each time I power up is very time consuming compared to the time to run the job. It seems to me that if I always start a job at the same x,y position, there should be a way to avoid the zeroing process. The machine knows it’s abosolute x,y position after homing, it knows the bit’s z position after the BitSetter process, the Hybrid Table does not move, and the software knows the diameter of the bit and the thickness of the material being cut. That should be all the information that is needed to calculate the 0,0,0 position for the job.

For simple jobs, I would like to be able to start the machine with the 1/4" end mill already mounted, clamp my stock against the fence, start the job and walk away. If there is a way to do this, please let me know.

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My experience is that the homing process is not perfectly reproducible. I see variations on the order of about 1/2 mm, so if you can live with that level of accuracy, then you can skip the zeroing process.

I wanted to do the same, so I set up a fence at the SW rapid position. If I’m just doing a surface engraving on a piece, I don’t worry about the error in position, but I wouldn’t rely on it for a piece that takes longer than one session.

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I think this might be a problem. It doesn’t know the bit’s Z position after the BitSetter.

I also am not sure how it would know the thickness of the stock you are putting on the machine. Is it always exactly the same?

If the absolute X,Y position is very important (ie: there’s no room in the stock for a slight error), then @mhotchin 's point would also cause issues.

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On any given project, I believe the SPXXL will remember the X, Y positioning even if you shut it down at night. BUT, for some reason in the back of my head I always first thing Rapid to the X, Y position and check it. After that I am good for the day, barring any mishaps. In that case I’ll check it again.
First project of the day, I will set the Z-zero even after I run the x,y corner probe or any Bit change. I guess this is some sort of OCD or something. I just don’t want to mess my machine up.

That is my opinion should anyone care.

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If the homing process is only accurate to +/- 1/2 mm, that would be an issue for some projects, but could be tolerated in many others. I think the machine knows the z position after BitSetter process. Your point may be that it doesn’t know the z position of the stock. The thickness of the stock is specified in CC, but maybe it isn’t passed to the controller in the G code. That would be an issue. I don’t know much about G code, but I guess I should learn it. The controller would also need to know the z position of the Hybrid Table, but if that is not a stored value, then it would not be able to calculate the stock z zero position either. Perhaps what I am looking for is an enhancement that is not standard to the CNC world. But, it would certainly be a very desirable enhancement from my point of view.

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After you set up x and y the position is persistent over power cycles. As others said the accuracy of a homing cycle is not perfect. The z is also persistant over power cycles.

Stock for multiple parts must be exact. If your stock is consistent then after first part is set up go into cm and uncheck bitsetter if the job is a single tool. You do not need to send configuration just close configuration window.

At the end of each job the router moves to the back center and stops. Place your material near that area to avoid excessive movement to start a repeat job.

If each repeat job has multiple tools you are stuck leaving the BitSetter checked.

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I am certain the machine does not know the position of the endmill tip after the BitSetter operation.

The machine might know that the Z axis had to travel downwards 34mm to trigger the BitSetter switch, but the switch could be three feet below the Z axis or 6” below the Z axis. It doesn’t know. Similarly your baseboard/spoilboard could be 1 foot below your router or 2”. So telling it the height of your stock is not going to tell it where to go.

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Thanks to everyone who replied to this post. The information has been very helpful. Based on the information, I came up with a process that I feel will save me significant time on small projects. I documented the process and tested it on my machine. the process is more complex than I wanted, but still is more efficient than what I was doing before. It’s probably difficult for anyone but me to follow this, but if you see anything that looks wrong or could be improved, please let me know. Here it is:

  • Power up machine & connect to computer
  • Initialize machine
  • If job requires precise x,y accuracy, go through full BitZero process with probe, else continue
    • If tool change required, change tool & resume, else resume*
    • “Jog”,”Rapid Position”, “Rapid Current XY” & “Rapid Current Z+6mm”
    • Check position
    • If not as expected, go through full BitZero process with probe, else continue
    • Position material against fence & clamp
      -If material is different thickness than last job, set z zero with BitZero, else continue
      -“Run”, If Warning: “Zero not set”, “Continue with Zero not set”, else continue
    • “Load New File”, “Start”,”Start”
    • Message:”Tool Change Required”, “Resume”
  • If tool change not needed, BitSetter process can be avoided by going to “Settings” and “Disable BitSetter”
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Hey David,

This process looks okay, but as written it looks like if the Rapid didn’t work, and your stock is different, you’ll do two BitZero processes when only one is required.

There are ways to make your approach work a little better, particularly if you use the newer versions of Carbide Motion which support macros/quick actions.

If you made your fence so that the origin (lower left corner) had enough clearance for an overhanging BitZero, then it is possible to get you to the following scenario.

  1. Initialize and change bit if appropriate
  2. Fix and clamp your stock
  3. Click the quick action/macro that sends your router to the origin of your fence with Z at a useful height for probing your typical stock with the BitZero
  4. Do a X/Y/Z BiZero probe
  5. Run the job
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Are the Pro endstops really as inaccurate as claimed?? If so, that’s pretty disappointing.

At +/- 0.5mm accuracy, doesn’t that make it nearly impossible to run machining from both sides of the part if you can’t depend on you zero being at the same place when you start the job for the second side?

Doesn’t that mean that you can accurately tile a larger workpiece?

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I just finished running half-a-dozen parts on my Pro, re-homing constantly and everything was cut to match the files and was consistent and fit fine, even when running a profile which didn’t do anything but cut out dogbones w/ a 1/8" downcut endmill, detailing after a 1/4" downcut.

Anyone who has consistency issues w/ their homing switches should check the machine mechanically — if everything checks out mechanically, they should contact support@carbide3d.com

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Thanks Gerry,

The process as written does not include the branches after it is determined that I need to do the full BitZero process, so I didn’t intend to do it more than once.

I just started using my machine a few weeks ago. I downloaded CM at that time. I will have to check if there is a newer version. I know nothing about macros or quick actions. I seem to be missing an information channel. Where should I have learned about those things?

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Apparently, quick actions are only in the beta at this stage: https://carbide3d.com/carbidemotion/beta

I haven’t used it myself or upgraded CM for a while (mostly because of the increased popups and prompts).

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Since there seems to be some questions about the accuracy and consistency of the initialization (homing) process. I decided to measure the accuracy on my Shapeoko Pro XXL.

I placed the .25" probe in my router and established a 0,0,0 position near the SW corner of my Hybrid Table with the probe .035" above the table. I offset a fence exactly 1.000" from the x=0, y=0 position as a reference. I then jogged z up to the stops and x,y back to the NE corner of the table. On the first set of measurements, I kept power on and did not reinitialize the machine. I jogged the probe back to the 0,0,0 position and then measured the position of the probe relative the fence and table top. I repeated this process 6 times and recorded the results.

On the second set of measurements I followed the same process, but between measurements I cycled power on/off and reinitialized the machine after powerup. Again I recorded the results of the 6 passes.

The results are that the average deviation was X=0.001", Y=0.003", Z=0.001" for the 6 readings taken without reinitialization. The largest deviation was Y=0.005".

For the case where the machine was power cycled and reinitialized after each measurement, average deviation was X=0.002", Y=0.002", Z=0.000". The largest deviation was Y=0.004".

My conclusion is that my machine comes back to the 0,0,0 position pretty accurately independent of whether it goes through a power cycle and reinitialization or not. Michael Hotchin mentioned deviations on the order of .5 mm in his post. That would be a deviation of about .020", which is far more than I saw in my tests. Perhaps my accuracy will get worse as my machine ages. But, I feel comfortable using a fence to avoid having to go through the full BitZero process for most of the work I do with my machine.

I was also curious how accurate the BitZero process is to establish a 0,0,0 reference. I decided to test this by performing the BitZero process and measuring the position of the probe relative to the corner of the work piece. To do this, I established a fence that was offset from my work piece by exactly 0.750" in the X and Y directions. I then performed the BitZero process, removed the work piece, moved the router probe to the 0,0,0 position, and measured the distance from the probe to the fence and table top. I followed this process 6 times and recorded the results.

The average deviation was X=0.002", Y=0.003", Z=0.001". The largest deviation was X=0.005" and Y=0.005". This was disappointing to me. I expected this tool/process would be very accurate and consistent. I wonder if the problem is that the BitZero tool seems to move as it is being probed, even if you try to hold it against the work piece? Perhaps others have more information about this.

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Will Adams did I see some where that you ,wrote a post showing all the steps along with pictures of the carbide motion screen it takes to get ready to run acut file and to do a tool change with the bit setter and touch probe.I would like to print a copy of it for reference
Thanks Jeff peters.

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Perhaps this one?

or:

Did a bunch of screen grabs at:

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