Seems like the design wasn’t tested on slippery stock.
I think they do the extra X&Y outer probes to take the diameter of the bit into account.
A soft solution for people who don’t like the movement might be to allow the probe diameter to be entered into Carbide Motion and just have it do the “push against the stock” probes. Oh, to better support the Raspberry Pi of course
All that aside and all things being equal, the BitZero should function correctly. If the connectivity between the probe and the hole is poor, it will affect accuracy if unnoticed, or time out if pushed too far and requiring everything to be re-initialised. This wouldn’t necessarily be an issue with the v1.
Thanks for the lesson, though
(William Adams (Carbide 3D))
Split this topic
With respect to Z, the only position the machine knows is the vertical position of the spindle. It knows this because it’s been sending it up and down instructions from the last time it was “homed”.
So long as the up and down instructions have resulted in movement, and it’s not been driven into something that prevented movement, it’s pretty sure it knows where the spindle should be.
However, it has no knowledge of where the BitZero is, or how long the thing in the spindle is.
In truth, you could pull off the spoilboard, suspend the machine on legs, and put a 1 metre dowel in the spindle and put the BitZero on the floor. It wouldn’t know it was a metre away. Just that the spindle is a fixed number of “ticks” from the homing position.
So if you took out that 1 metre long dowel and put in a 10cm bit, and then tried to run your job, it would have no idea where the bit was cutting. Just that you told it to move the spindle to a particular position for your project’s zero.
Soo… long story short - the Shapeoko has no idea where the zero physically is in space. Just where the spindle was when you said “this is zero”.
This could randomly be true. If you look at the cutting end of your typical endmill, you can see that it isn’t a circle, but the cutting teeth are arranged in a circle. So, while it cuts a circle it isn’t actually a completely round end. Right?
The dowel does have a completely round end.
So, when doing a zero trip around the inside of that BitZero depression, an endmill may exactly touch at its radius, but then it may be oriented in such a way that it touches in between cutting edges and that would be a smaller radius. The zero may be off.
A dowel doesn’t have that smaller radius. It is round. It zeros inside that depression the same everywhere it touches. See?
You’re correct, though. I should have been a bit more specific and try to keep it simple.
As far as I understand it, the BitZero does what it should do, but at any time the bit (or dowel) is changed, the Z height needs to be re-zeroed. The X and Y should remain the same unless you move or change the workpiece, unless you’ve got a guide in place for repetitive work, for example.
I think CM does know. If there is a requirement to change the cutting bit during a project, you’d need a separate toolpath for each bit, and re-adjust the Z height before each new cut. With a BitSetter installed, CM understands the bit change, prompts for it, then pings it over to the BitSetter to re-zero the Z height before continuing with the next toolpath.
Again (me being pedantic, this time!) I don’t think it will matter. If the BitZero is doing it’s job properly (and only the designer of the BitZero can confirm this, really) it should find the corner of the workpiece, irrespective of how big the dowel is (as long as it fits inside the hole!) The cutting bit can be larger or smaller than the probe, because it’s the toolpath that determines where the cuts are made, based on the tools geometry. To extrapolate on @CrookedWoodTex comment, using a dowel will provide a more accurate corner of the workpiece than an endmill.
Well, I commented, but it was not discussed further.
Your discussion here seems more like a critique of the design of the BitZero-2. @Gerry is correct; the different dowel sizes are a convenience so you can do your zeroing without changing collets.
One thing to be sure you do is wipe down the contact surfaces occasionally. Sawdust is an insulator, the zero “hole” will catch dust, and you will get into a re-initialization situation quickly.
The only thing further I have is that you should get the BitSetter without hesitation. You can use CM without it (by zeroing traditionally), but CM will still have a few innocuous prompts about zeroing and changing bits, etc. Just don’t activate BitSetter in the Settings.
Referring to the situation where one did not have a BitSetter.
Actually, I disable my BitSetter (and clear all offsets) when I use a 1" diameter surfacing bit. It won’t physically fit my BitSetter in its standard configuration. (There is a thread here about adding a large diameter disc to the plunger for that situation.)