On-the-Fly Z-axis adjustment

[russ]

Hey guys, quick question...

Is there a way to adjust the z-axis depth on the fly during mid project?

I have had several situations where say for example I run a clearance path with a 1/4 or 1/2 inch end mill and then when I go to do the pocket cut with a 1/8 inch, it is proud of clearance path (or inset further) by a couple thousands of an inch.  Is there a way to make easy adjustments?  The puck is used to zero the z on both toolpaths but there is a slight variation in cut depths.

Thanks guys!

[aluomala]

You can pause the operation (using the controller) and then drop the z-axis down (in .5mm increments on "fast" setting, or .1mm increments on "slow" setting (the blue circle "fast/slow" button on the B18 controller) and then when you are ready to resume, hit the pause button again and, as per the manual:

3- After making the adjustments, press Run/Pause to continue the file operation.
a. The display will show a Restore Position? prompt.
i. Press OK to resume using the modified settings.
ii. Press Cancel to resume using the previous settings.

I keep a copy of the manual handy, since I don't find this step particularly intuitive: to me "Restore position?" would indicate I want to discard any changes I just made (using the controller), so hitting OK doesn't seem to be the preferred option, but what do I know? Perhaps having prompt that read "Continue using new position?" (or similar wording) would make more sense, but my opinion and $5 won't even get you a cup of coffee nowadays...

Allan

[johnb]

Maybe if it just said "Re-Store Position" instead of "Restore Position" it would more accurately reflect what's going to happen here...

[Bob]

Jun 14, 2019 22:10:31 GMT -5 russ said:

Hey guys, quick question...

Is there a way to adjust the z-axis depth on the fly during mid project?

I have had several situations where say for example I run a clearance path with a 1/4 or 1/2 inch end mill and then when I go to do the pocket cut with a 1/8 inch, it is proud of clearance path (or inset further) by a couple thousands of an inch.  Is there a way to make easy adjustments?  The puck is used to zero the z on both toolpaths but there is a slight variation in cut depths.

Thanks guys!

Russ,
When changing the z after a tool change, the puck is only as accurate as the surface it's on. When using the puck, I am careful to touch off in exactly the same spot each time, clean the surface of the wood, and gently hold down the puck with the same amount of pressure used for the initial setup. In general: Keep all variables as unchanged as possible. This has given consistent tool changing results for me.
 
Remember what Bill Tell always said, "Be accurate!"

Bob

[johnb]

Jun 16, 2019 20:50:49 GMT -5 Bob said:

Which brings the following thought to mind...it would appear that, if you're doing some piece of complex 3-D work, you might well reach a point where you need a tool change and the original Z set no longer exists (it's "up in the air" somewhere) and there's no co-planar surface to that on which to place your puck. It seems that this would be a situation in which you'd want to set your Z at the spoilboard for the project from the get go.

I'm kind of at a loss as to why there's so much interest/emphasis on setting Z at the top of the material. The Axiom manual emphasizes this, and I can certainly understand that it might produce more consistent V-Carving and pocketing toolpaths, but, at the same time, when the emphasis is on "what's left" rather than "what's removed", using the spoilboard height is going to give you more consistent tabbing and/or onion skin etc. 

Comments?

[Gary Campbell]

A few thoughts from the cheap seats....
Like John I am similarly confounded with the emphasis or popularity on setting the Z reference to the top of material, vs the spoilboard/table surface.

I do however question the "more consistent" statement and would off that in the long run the table surface is much more consistent. That said, if you have inconsistent material thickness, and/or don't measure the thickness accurately, good results are easier to come by when top of material reference is used, especially with inexperienced users.

The fact that the original surface can be machined off or that material will most assuredly move upwards when doing a large pocket or a 3D relief, will negate any advantage of "simplicity" that could be gained by top of material Z reference.

Truth is that neither our CAD/CAM programs or the machines themselves are capable of making a math mistake. The material thickness that is entered by the user is virtually the only place where errors can occur when Z depth errors happen. The accuracy that we as operators can expect to achieve is totally dependent on our ability to input material sizes accurately.

[Axiom Tool Group]

We generally put the emphasis on the top of the material...for new users, as an attempt to prevent costly errors.

If you were to accidentally overlook the settings within the software and have a tool-path setup for the Bottom of the material, but have touched off at the machine on Top of the material....then you'll simply cut the air above the piece.

However, if that's reversed and you select the Top but use the Bottom at the machine, then the machine may plunge the tooling through your material into the spoil boards...or if no spoil boards are being used either the fixture or the aluminum table.

*While is is generally at risk for new users...it happens with those of use with plenty of experience as well*


In house, we regularly use inconsistent thickness materials (barn board for instance) and use the spoil board surface as the Z-0 location....and agree that this is the best, most consistent option. We just stress that what ever fits your application...try to use the same setup between jobs to avoid those potential costly mistakes.

[johnb]

Job Sheets with checkboxes listing all relevant steps, tools, X-Y origin location, Z origin location, files names to be run in sequence (with tool change notes and a reminder to re-HOME and re-set Z to top/bottom of work), etc etc are a handy thing and a good habit for any user (newbie or experienced).

After a long day in the shop and a night's sleep, you'll at least know "where you left off" when you come back to the machine in the morning.

[aluomala]

I am used to using the bottom-left corner as my X0Y0 and generally use an area around there to zero off my z-height. I say "an area around there" because I use hold-down clamps and almost always use the corners as hold down points. I will usually put a pencil mark (an "X" with a circle around it) and use that, and a piece of paper (waxed or otherwise) for each toolchange.

I have also learned, with uneven stock particularly, that it is a good idea to use the lowest point as your z0 height (not neccesarily the area where it's lowest, just find the lowest height). I do a lot of 3D carving, and I have had a few pieces ruined, or at the least looking odd with a flat spot in it, from not doing this, and that area (the lowest point that ends up with a flat area) doesn't get any material removed during both the roughing and finishing passes, and it it happens to be the highest point of my model, it doesns't get cut at all. I used to try to make my wood stock as flat at possible, but after a lot of work trying to achieve that, I realized that I spent a lot of time flattening it perfectly, only to have 99% of that work go into my dust collector. "Good enough for government work!" is my motto when doing 3D carving (getting the wood prepared). I generally leave at least .05" on the bottom (I don't cut all the way through, or "cookie cutter", my projects, since I have found that the wood will release a lot of tension as it's cut all the way through, curling up, and I have damaged a lot of nice pieces doing that (2-sided tape doesn't work all that well on rough wood). After I have finished my cuts, if it will fit into my 13" planer, I cut around the piece with my bandsaw, leaving enough material to support it to go through the planer and remove almost all the wood on the back (I hold it up to the light to see if I can see light) and then finish it with my 16/32" drum sander (to avoid having fine edges of my piece ripped out by the planer... don't ask how I know that).

Sorry for the long response, but I thought it might help someone who does the same type of work I do.

Allan

[buildswithbrian]

my thoughts have always been use the Z reference for what is appropriate for the job,
off the top of the material for "most" 2D work, is the simplest and guarantees pockets, grooves etc. to
be at an accurate depth, of course assuming you are not surfacing the entire piece, and where the normal
tolerances of material thickness do not need to be taken into account.

and I absolutely agree that the smarter choice is "Z off the spoil-board" with 3D work
for the reasons both JohnB and Gary describe.
you set the Z parameters while designing in CAM to fit the job at hand, just like all the other variables.


the only absolute rule is their is no absolute rule.