Precision Probing

I am new to the forum, so forgive me if there are any errors.

Currently, I am working on my first major product with the Shapeoko, which requires double sided machining. This requires a job, and precision homing.

I am using the touch probe and getting decent results 90% of the time. However, I was wondering if we can add a feature, that probes each Axis, a set number of times, and compares the values against each other, and if it is outside of a tolerance, it notifies you.

This would help with minor differences in movement of the probe by accident, or a slight bend material with an overhang, causing the zero to be incorrect.

Let me know if you have any questions, or if this idea doesn’t make sense.

Probing and finding the workpiece is quite a complex subject that old machinists can talk about for a looong time.

One common way to deal with the repeatability issue is to not change the workpiece home position each time but instead to use locating dowels / pins jig etc. to allow you to flip the workpiece within a known co-ordinate system, this frequently then just requires an adjustment to Z zero. Winston Moy has a few videos about this on his YT channel.

Re-measuring each time you relocate the part is going to require you to be able to accurately place the part parallel to the X, Y axes and then accurately re-measure, if the sides of the part are not perfectly square and vertical this just won’t work out and it’s possible to chase your tail for quite a while trying to figure out what’s wrong.

3 Likes

I am using pins on my jig to locate the piece, like you mentioned and like Winston Moy uses. Let me give you an example.

I make the initial cut out of Baltic Birch Ply wood, I remove the piece and use pins in the piece to locate it on a piece of MDF. This MDF jig is then set square to the X/Y axis using a fence that has been squared to the machine. Now the Zero position for the G-Code is measured off the MDF jig in a corner. Again this provides an accurate result, within a few thousands, using a Makita Router.

But what I am requesting is a simple, pop up message if it measures the zero point of any axis twice and the difference between the first and the second are larger than a given value. This would just be a last minute check, to make sure the probe hasn’t shifted slightly, due to human error.

I can see that being helpful, I’ve found that the probe is light enough to be easily moved, even by it’s own wire and this would be faster than a manual check.

This would be a setting one can select in Carbide Motion, so it can be enabled when needed or wanted.

I’ve found probing to be much more accurate the slower the probe cycle. I get very repeatable results with a fast probe (now you’ve got a good idea where the probe actually is so the probe distance can be short) and then a very slow probe again. Homing by default works on a “seek” then “fine” method, you can do the same on a probe. I haven’t found a need to average, multiple slow probes get me the same answer (well sub .001")

4 Likes

Completely agree. I use a very quick 5 probe sequence for my Z and toolchange macros. A fast seek then a series of progressively slower alternating probes to dial it in. Could easily be implemented in X & Y too.

2 Likes

one quick question, i got the touch probe for my shapeoko 3 xxl and the flange screw will go into the screw hole but it will not tighten, is there any other way to ground the alligator clip?

Source a nut for the other side?

If that’s not an option let us know at support@carbide3d.com and we’ll work this out with you.

will the probe work if i just try to install it on the screw hole at the bottom. Because i have already tried other screw for the same side and it does not work. But the bottom part the screws it barely held so i think i should be fine. will this work?

Yes, a corner should work — just make sure you get a good ground.