[airbrush]

Hi,

I finally have my home cnc machine up and running. I'm a little confused on where you should zero out your machine.
For example, you zero to the top of your stock and start cutting a rough pass. So you wouldn't be cutting away the spot you just zero to? So how could you do a tool change and rezero if that material is gone?

I guess what i'm saying is zero also considered your point you have to start cutting from?

I have a touch plate and autozero script setup in mach, will be using bobcad/cam v26.

thx

[BurrMan]

You can use the touch plate, then keep track of the math that moves to workpiece zero.

You can zero your "machine" at touchplate and then create a g54 work offset for the stock. If you do it that way, you will have to pay attention to your post and how you move to machine zero with work loaded.

I dont know mach well, but i think using machs auto zero and touchplate can be setup as a 3rd move, seperate from machine and work offset zero. Ideally, you want machime zero to be a far up and away point of the machine, not down on the table.

[airbrush]

well i'm not talking about machine zero...just the whole process of how you start your cuts. Haven't really seen any videos describing how you go through the passes. Most have been, load your stock, zero to the top of the stock and start cutting....
Just looking for info on how most people go about it.

[jrmach]

well i'm not talking about machine zero...just the whole process of how you start your cuts. Haven't really seen any videos describing how you go through the passes. Most have been, load your stock, zero to the top of the stock and start cutting....
Just looking for info on how most people go about it.

Well,there are a dozen ways.A lot well depend on your machine,your controller,and personal preference.
The best way to learn is look at the documentation for the above mentioned,and or go to the specific forums.
If you have a Haas,I can tell you how I do it,otherwise,,,,,,,,,
maybe I not understand ????
Have you been here https://www.youtube.com/user/Depoalo...view=0&sort=dd

[The Engine Guy]

Hi,

I finally have my home cnc machine up and running. I'm a little confused on where you should zero out your machine.
For example, you zero to the top of your stock and start cutting a rough pass. So you wouldn't be cutting away the spot you just zero to? So how could you do a tool change and rezero if that material is gone?

I guess what i'm saying is zero also considered your point you have to start cutting from?

I have a touch plate and autozero script setup in mach, will be using bobcad/cam v26.

thx

You seem to be confusing Machine Zero with Part Zero, two different things.

Machine Zero is where your machine is "Homed" to on your Home/Limit switches, that is Machine Zero, normally done at start up by clicking the "Reference All" button in Mach3 beside the DROs.

Once that is done you are good to go and setup your fixture/vise and stock, once your stock is in position you can use Mach3 to "touch off" say the bottom left corner of the stock with an edge finder of some description, you could even use a tool or a ground piece of bar but you need to be able to accurately measure the diameter so your measurements will be as accurate as possible.
Then check that the numbers input into your choice of "Work Offset" eg G54, G55, G56 etc are correct.

Now you can set up your tools, it is always best to do ALL your tools off the same "Top of job" which is your Part Zero = Z0 in your G code. When ALL your tool lengths are setup you can if you want go to your Tool Table in Mach3 and write down all the tool lengths, now you can input those tools into your Tool Library, you don`t have to do this but if the tool information in BobCAD is the same as that in Mach3 then your simulations will be spot on accurate, much easier in the long run
You should never need to re-zero anything once you start machining your part, all that is done in the Cad-CAM for you, once the code is generated all you should need to do is change tools if you don`t have an ATC.

Also you should make sure that you have both your Cad-CAM and your actual CNC machine setup the same so that if you are going to always use the "touch off bottom left corner" method at the machine then you should always draw your part in BobCAD in exactly the same place, that is with the bottom left corner of your stock at X0Y0 on the screen and the top of the stock at Z0, then it will be exactly the same as what is clamped to the bed of your CNC

Personally I always set my stock to X0Y0Z0 in the centre of my Part, just my preference, I find it the easiest method for me, may not suit you, use whatever is best for you but ALWAYS, ALWAYS set ALL tooling, stock etc before anything else.
I have a touch plate system on one of my Mills that has an ATC so I just load it up with the tools for the job and I have a number of small Tool Change programs written and I just choose one that has the same tool numbers as I have in the carousel, press start and let the program run through all the tools and that`s it, job done, you can do the same sort of program even without an ATC by putting an M00 in the code at the tool change so the machine stops at the tool change, if you want to have the bed move out of the way to your Machine Zero and your spindle up to it`s highest point while you change a tool (Often easier with the fixture/stock out of the way) then put these lines of code in before the M00 :-

G28G91Z0
G28G91X0Y0

What that will do is move the Z axis up first and the X and Y will not move until the Z has reached the top and stopped, then the X and Y axis will move together to machine Zero.

This is a bit safer than other methods as the Z axis is always at it`s highest point before anything else moves, it also removes the need to jog the Z axis up in order to change the tool assuming the script you are using doesn`t do it for you, some don`t.

Hope that is of some help

Regards
Rob
:rainfro: :rainfro: :rainfro:

[BurrMan]

Now you can set up your tools, it is always best to do ALL your tools off the same "Top of job" which is your Part Zero = Z0 in your G code. :

Hi Rob, there is a caveat..... A lot of "hobby" users don't/cant set a tool as "ALWAYS"..... In other words, the chuck up the tool in the spindle and need to rezero the tool between operations at toolchanges....

For this, he needs the touchoff plate to be accessible to the current job. If he cant set machine zero at the touchoff plate, then I would suggest setting his tool Z level zero at the plate, then jog up and touch off zero at the part, keeping track of the Z jog. Then at toolchange, he can re zero a new tool at the plate, then jog up the Z the amount before and reset his mach 3 zero there....

Most have been, load your stock, zero to the top of the stock and start cutting....
Just looking for info on how most people go about it.

Probably because that part of the process will vary widely, as jrmach pointed out....

Probably better said is, "How do YOU want to do it? If you answer that, then a video can be made to show you how to do that.....

If you are just asking for a "poll" type of thing, then I should probably drop off....

[minicncuser]

The way I do it is top down for engraving and art stuff most of the time unless like you say I removed my top then I set my 0 off my table and program with that in mind. For just cutting I do like my 0 off table. A bunch of ways to do the same thing you will find what works best for you and the software your using

[The Engine Guy]

Hi Rob, there is a caveat..... A lot of "hobby" users don't/cant set a tool as "ALWAYS"..... In other words, the chuck up the tool in the spindle and need to rezero the tool between operations at toolchanges....

For this, he needs the touchoff plate to be accessible to the current job. If he cant set machine zero at the touchoff plate, then I would suggest setting his tool Z level zero at the plate, then jog up and touch off zero at the part, keeping track of the Z jog. Then at toolchange, he can re zero a new tool at the plate, then jog up the Z the amount before and reset his mach 3 zero there....



Probably because that part of the process will vary widely, as jrmach pointed out....

Probably better said is, "How do YOU want to do it? If you answer that, then a video can be made to show you how to do that.....

If you are just asking for a "poll" type of thing, then I should probably drop off....

Ha ha, nicely put Burr, sorry but it isn`t my fault if the user is either short of cash or just too tight to have more than one tool holder, my machines have the old R8 taper spindles but I went out and bought adapters that fit the R8 and take those lovely "Easy Change" tool holders from Coventry Tooling, they are available in the USA and not as expensive as one might think, once bought and fitted they are so great to use I simply couldn`t/wouldn`t live without them

Yes, agreed, I never have the touch off plate on the part, it is on a small steel block at one end of the bed held there by some very small but very powerful "rare earth" magnets (I can`t spell or pronounce the proper name) so there is never a need to be doing tools on the part, as the OP rightly says once you have done some machining on the stock the original setting point has disappeared

The tool length setting is the difference between the "Master" tool and the rest of the tools, doesn`t matter where the plate is as long as you rightly say it is accessible and isn`t moved during the operation/job, which is why mine is on the magnets so I can move it around the bed depending on what fixtures/vises/stock are being used, only once did I have a full bed and had to resort to putting the block plate on the Z axis slideway behind the bed Crazy things we have to do eh? ?

Regards
Rob
:rainfro: :Rainfro: :rainfro:

[jrmach]

Yet,there are a half a dozen more ways than already mentioned.

[airbrush]

Hi Rob, there is a caveat..... A lot of "hobby" users don't/cant set a tool as "ALWAYS"..... In other words, the chuck up the tool in the spindle and need to rezero the tool between operations at toolchanges....

For this, he needs the touchoff plate to be accessible to the current job. If he cant set machine zero at the touchoff plate, then I would suggest setting his tool Z level zero at the plate, then jog up and touch off zero at the part, keeping track of the Z jog. Then at toolchange, he can re zero a new tool at the plate, then jog up the Z the amount before and reset his mach 3 zero there....
.

Thx, yes this makes more sense to me. Gets me thinking that I should have two touch plates then. One I can keep on the table and one to touch off the top of the part initially...then just keeping track of my xyz 'machine' coordinates of where I want to start cutting.

More will become clear as I get into the process.

Keep in mind I am a hobbyist and have not yet cut anything with this machine.

thx

[airbrush]

I guess this is what i'm looking for...

https://www.youtube.com/watch?v=p1xH...KM0tl&index=13

[minicncuser]

Now that's kind of neat.

[BurrMan]

Well, all the parts except where you stick your fingers in the working area....

[jrmach]

That would never Fly for my machine.

[The Engine Guy]

Thx, yes this makes more sense to me. Gets me thinking that I should have two touch plates then. One I can keep on the table and one to touch off the top of the part initially...then just keeping track of my xyz 'machine' coordinates of where I want to start cutting.

More will become clear as I get into the process.

Keep in mind I am a hobbyist and have not yet cut anything with this machine.

thx

My apologies, I had wrongly assumed that you did have two plates as in the video as that is pretty much the standard

I have two plates, and just like in the video use the second one for setting the Z0 work offset with the Master tool, after that all tools measured will be either longer or shorter in the tool table and will just follow on always going to the right height.

Once again my apologies for not going through that area of the procedure, picture is worth a thousand words and the video really does say it all

Regards
Rob
:rainfro: :rainfro: :rainfro: