Ever carved something that has several toolpaths to perform and after carving a couple of toolpaths you then find that the material at your Z-Zero location for all toolpaths is now GONE!!! Early in my experiences with my CNC I found that this had occurred on a couple of occasions. I had to come up with some creative way to be able to Z-Zero the remaining toolpaths to save my projects.
When creating your projects and toolpaths in your design stage you must keep in mind --- will there always be material remaining at the Z-Zero location for all toolpaths to be able to complete project?
If anyone wishes to comment/add please feel free to do so!!!
Sharkcutup
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That's why I always zero to the table (spoilboard surface). I have a point just off the bed that is fixed in XY but adjustable in Z (to account for when I plane the spoilboard) which I zero to for every job.
Of course you have to be very accurate with your material thickness that way but I never have to worry about anything else.
I must admit I'm always a bit puzzled why zeroing off the material surface seems to the most common method but I don't do a huge amount of 3D work so perhaps there is a reason why because of that.
... I must admit I'm always a bit puzzled why zeroing off the material surface seems to the most common method but I don't do a huge amount of 3D work so perhaps there is a reason why because of that.
The main reason I zero off the material surface is because as I started out I had very limited means of adjusting the material thickness and little reason to do that. Most of my cutting was cuts into the material from the top (signs, etc.) or cuts all the way through the material (cutouts, etc.)
I've done it so much now that changing zero to the spoilboard surface brings back that anxious feeling of the unknown!
Tex — Crooked Wood Products
Now there's a man with an open mind – you can feel the breeze from here.
I almost always zero off the top. Just habit, for the most part, since I usually know my material thickness to within a fraction of a millimetre. But yes, there are occasions where the reference is either gone or inconvenient. Then I zero off the spoilboard, but it is a challenge to remember the change in routine. So I try to label the toolpaths appropriately in those cases.
A similar issue that I ran into this morning was with the "Catch-all Tray". When designing my own 2-sided jobs, I always flip on the Y axis because that's my long axis. This file flips on the X, and I almost missed it. I had already saved the toolpaths and was doing a final check. Good thing! I went back to the file and changed the flip direction. Now the back-side toolpaths cut through the material! I finally determined it was because the drive rails are (of course) directional. Changing the flip direction left the drive rail directions the same way, but they were now reversed compared to the material. So I changed back to a X flip, and all is well. Side A is cutting now, so I'll have to be sure to flip in the correct dimension!
Just goes to show that habit can bite you where it hurts!
Side A is cutting now, so I'll have to be sure to flip in the correct dimension!
Just goes to show that habit can bite you where it hurts!
If your using asymmetric dowels then you can't flip it the wrong way
I use both methods, it really depends on the project I am working on, I don't find it difficult to remember which I am using as there are plenty of opportunities to remind yourself, add something to the toolpaths works, just a couple of letters is enough so either sb or ms.
You can also make notes of anything important or that you think you might forget,
In over a decade of CNC with many 100's of projects under my belt, never once zeroed from the board, always material.
Have never thought much about it, just don't see the need to re-invent the wheel and experiment with something that has always worked well for me. Also abandoned the touchplate long ago, fell into disuse when I found that I can zero with a piece of paper just as good if not better, and alot quicker too. Also never home my machine, when I start a project I set it where it needs to be then press center x/y then zero .. Homing takes so long and its completely unnecessary for me and actually, needless wear & tear on the machine itself.
If its something I make alot of don't even need to do that, I just save the location and recall it at will, index the position then all I have to do is zero the z, which [almost] always has to be done.
My habits are not recommended for novices [not that I am Joe Pro or anything], better to fall into good accepted practices then work your way into time saving tweaks once experience is accumulated. I know alot of by the book guys recoil at some of my practices, I don't see them as wrong and me right or vice versa, takes all kinds and I have a mindset and lifestyle really of figuring out the best most efficient systems to save time and effort.
I guess everyone uses the methods they are most comfortable with. I always initialize the machine after a power down. It is an industry standard recommendation. I also always set Z-zero to the spoilboarrd whenever possible. Once it's set it never has to be reset unless the spoilboard is surfaced. Even after powering down the machine but I always check it. After mounting my project board to the spoilboard, I set X-Y zero to the location that is set in the software (Aspire). Usually at the center of the board or lower left corner. In WinCNC it's called using offsets or temporary location settings. This is a very quick and easy procedure I follow unless the project dictates otherwise. Also I always verify the X Y Z settings before running the gcode file (JIC). A few minutes spent verifying can save time and material in the long run.
If your using asymmetric dowels then you can't flip it the wrong way
Martin, that's a great example of another habit. In Todd's file the dowel positions were actually set asymmetrically, and I changed them. That was partly due to the material I had to work with (off-cut from the thermo-kinetic sculpture) but mainly habit. But I take your point, and should try doing it the asymmetric method, as it reduces potential error.
In over a decade of CNC with many 100's of projects under my belt, never once zeroed from the board, always material.
Have never thought much about it, just don't see the need to re-invent the wheel and experiment with something that has always worked well for me. Also abandoned the touchplate long ago, fell into disuse when I found that I can zero with a piece of paper just as good if not better, and alot quicker too. Also never home my machine, when I start a project I set it where it needs to be then press center x/y then zero .. Homing takes so long and its completely unnecessary for me and actually, needless wear & tear on the machine itself.
Funny how we all start off from different points. When I first started 15 years ago I always zeroed to the spoilboard but after a few months I switched to the material surface as 90% of people were doing it that way around on the forum and, as a newbie, I thought I must be doing something wrong. I switched back later when I had the confidence to realise that it was just personal preference rather than something anyone was doing wrong.
I very rarely home my machine either. Another thing I picked up as got more confident. These days I only re-home it if I know I moved something while the machine was turned off.
I still use a touch off but it's a fixed one rather than a plate so it's very fast to do. As so much of my work is single bit jobs it basically means I can go days at a time without ever setting the z-zero. Generally it's the bit wearing out which necessitates setting the z-zero.
In over a decade of CNC with many 100's of projects under my belt, never once zeroed from the board, always material.
Have never thought much about it, just don't see the need to re-invent the wheel and experiment with something that has always worked well for me. Also abandoned the touchplate long ago, fell into disuse when I found that I can zero with a piece of paper just as good if not better, and alot quicker too. Also never home my machine, when I start a project I set it where it needs to be then press center x/y then zero .. Homing takes so long and its completely unnecessary for me and actually, needless wear & tear on the machine itself.
Funny how we all start off from different points. When I first started 15 years ago I always zeroed to the spoilboard but after a few months I switched to the material surface as 90% of people were doing it that way around on the forum and, as a newbie, I thought I must be doing something wrong. I switched back later when I had the confidence to realise that it was just personal preference rather than something anyone was doing wrong.
I very rarely home my machine either. Another thing I picked up as got more confident. These days I only re-home it if I know I moved something while the machine was turned off.
I still use a touch off but it's a fixed one rather than a plate so it's very fast to do. As so much of my work is single bit jobs it basically means I can go days at a time without ever setting the z-zero. Generally it's the bit wearing out which necessitates setting the z-zero.
Yeah I know multi tool machines have quick touch plates that are handy, I used it until I started using a drag bit which can't use the plate ,, So after I saw the beauty of the slip of paper I converted and sold the plate. For rough passes I just eyeball it, I don't want the margins so tight that the rough pass bites into the finish.Roughing itself I often do without.
Homing to me is a completely unnecessary extra step, only time I use it is if something locks up, once in a blue moon the Z will refuse to raise to the proper height, rehoming usually solves the problem.
Jim Mcgrew mentored me when I first started, was all Greek to me at that point. He walked me through just cutting out my first name over the phone, had me zero from the top, been doing it like that every since - Conceivably I could run into a situation where its better or even necessary to zero from the bed but haven't yet.
While I am in confession mode, a couple more practices of mine that some by the book pros wince at. Early on I have heard:
* Never use the same .tap file twice
i not only use them twice when I need to, I have used them dozens of times. When you are making an identical with the same bit and same material, I don't see any reason not to. You simply index the position on the spoilboard, save it as a "home position" [in win cnc, which allows 10 of these] Then every time you want to make one, put the same material in the same position, make sure you have the same type bit and zero it, recall the home position and boom, start cutting.
If I had to recreate the file from scratch and initialize the machine, that would be an extra 5 minutes at least, maybe more and 100% unnecessary.
* Never, ever walk away from the machine while cutting
Opinions vary on this and yes, I am aware that some guys have had some bad fire incidents while not around the machine, including the highly experienced Mcgrew if I recall correctly.
I do it all the time, sometimes for hours. Part of the beauty of CNC to me is to multi-task, to set it doing a job while I go on about whatever it is I'm doing that day. Were I to restrict myself to the garage for hours and hours no exception ,,,, That would be unacceptable to me, so I take what I deem to be a very slight risk of something major going wrong while I am away, so far so good.
Some guys use net cams so they can at least keep an eye on the machine when away, and always a good idea to have a smoke alarm and an extinguisher handy. I have come home to broken bits and once a project broke lose of the holddown and was ruined, but nothing I could have done about those if I was there anyhow.
In the 2 incidents I can recall on the CAM forum, both were caused by sparks being sucked up into the vac hose, starting a dust fire.
Wow! Never thought I'd get this much of a response from a comment!
Interesting habits and/or preferences!!!
My intention was for the newbies to understand/realize that it is not always a good idea to use Surface Material as a Z-Zero location because that material may not always be there throughout the entire project carving stages.
Thank You All for making this forum what it is!!!
Sharkcutup
V-Carve Pro Tips, Gadget Tips & Videos
YouTube Channel - Sharkcutup CNC
V-Carve Pro 12.004
I haven't been doing this as long as you Xxray but I have never heard of someone saying not to use the same tap file twice, I am the same as you & do it quite often when I have more than one of something to cut, sometimes directly after cutting the first one & sometimes at a latter date.
As for your other comment then each to his own, you understand the possible problems so at least you have given it some thought.
personally, I like to be about just in case something does go wrong so I am always in the workshop when the machine is running, I don't babysit it because even if I did there is no way I would be able to react quickly enough to save a project
There is always plenty to do in the workshop so for me it doesn't stop me from getting on with life, I do periodically check it on a long carve, feel motors, spindle for heat, make sure the water pump is running etc but that is probably a throw back to my time watchkeeping on machinery in the RN
