Fanuc Display (Relative Position) is used only by the operator.
You can reset Fanuc Display (Relative Position) just like you would on a manual machine with a DRO. So use it for setting or even measurements. One thing to remember is it will not retain it’s position when you turn the machine off. The control in the video is a Fanuc 18i on a big vertical lathe but all other Fanuc controls are similar.
This is a video explaining cutter compensation in CNC programming.
You will come across various terms to describe this such as:
Tool cutter comp.
CNC cutter comp.
G41 G42 cutter compensation.
Cutter diameter compensation.
Cutter radius compensation.
Heidenhain RL RR.
Cutter compensation is referred to as cutter diameter compensation and cutter radius compensation
Haas cutter compensation, Fanuc cutter compensation and Mazak cutter compensation all work in the same way.
Although Heidenhain cutter compensation or Heidenhain cutter comp looks different. In the programme it functions in exactly the same way.
In the parameters or settings of your control you can set up your system to use the radius or the diameter of your cutting tool.
This means that when you input the data for your cutting tool in your offset table you can use the diameter or the radius of the tool. This depends on your settings.
When people talk about cutter compensation G code they may say “cutter comp G code” it’s often shortened.
(Cutter compensation G code)
The G codes used in this video are:
G41 cutter compensation left
G42 cutter compensation right
G40 G code to cancel cutter compensation
This Video shows you :
How to program G41.
How to program G42.
CNC cutter compensation examples.
Cutter compensation Heidenhain style.
Heidenhain RL RR.
We always recommend that you climb mill so you will be using G41 most of the time.
Milling the outside of a square using G41.
Milling the inside of a square using G41.
Milling the inside of a square using G42 (should you want to conventional mill).
Milling the outside of a square using G42 (should you want to conventional mill)
The rules when using compensation on a CNC Milling machine.
This is simple on a square sided figure or a simple radius. Anything more complex and it’s a nightmare.
I just heard some smart arse say “Ah well my CAD system takes care of that”.
So it should my friend but, and there is a but:
What will you do when your cutter wears?
What if you want to use a different size cutter?
The cutter may not run true.
What if the cutter is not exactly size?
In the old days of paper tape and Corned Beef we as programmers would write several programmes.
This was so that we could re-grind the milling cutters in fixed increments. A different programme could be used each time the tool was changed.
Sorry I can’t talk about this much longer as I still have the nightmares (mainly about corned beef sandwiches).
Anyway enough of that. So when we machine our first profile we can add some on to the tool radius in the offset file. When we check the part we can adjust the offset and re-cut the profile to achieve an accurate result.
The Rules:
Shape must be continuous and consistent.
You can’t cut along a line and then go back along it.
It’s important to allow more than the tool radius when entering tool compensation. The same applies when you come out of tool compensation.
Internal corner radii and steps must be greater than the tool radius.
Always allow more than the radius because when you adjust it it may be larger than the actual tool you are using.
Don’t ask
For example if you have a 12mm endmill but you have .2mm in the wear compensation. The machine thinks that the tool is 12.4mm in diameter.
You can’t do this in cutter comp:
You would have to apply one cut in G41 and cancel with G40 then do another cut in G42 and cancel with G40:
You do not need leading or trailing zeros in a CNC program (see below):
O0001(G81 DEMO) G21 G90 G40 T01 M06 (20.0 MM DIA X 90 POINT SPOT DRILL) G90 G00 G54 X12.64 Y88.00 S2546 M03 G43 H01 Z15.00 M08 G0 Z100.00 Z1.00 G01 Z-0.1
Without leading Zero is exactly the same. (Trust me it won’t self destruct or start world war 3) O1(G81 DEMO) G21 G90 G40 T1 M6 (20.0 MM DIA X 90 POINT SPOT DRILL) G90 G0 G54 X12.64 Y88. S2546 M3 G43 H1 Z15. M8 G0 Z100. Z1. G1 Z-.1
Try to keep your code consistent. As I mentioned before try to make all programs look the same.
Leading Trailing Zeros, if you are short of memory (not as in forgetful) this can save loads of space, and you might be surprised how small the memory is on some CNC machines, some have the memory of a fish.
CNC Programming
The main thing is that you are happy with the layout of your program.
If you are not consistent with your approach it can cause a lot of problems.
Please remember that when you are typing code into the machine it will take you considerably longer to type G01 X0.200 Y0.200 F100.00 than G1 X.2 Y.2. It could wear out your fingers or give you multi RSI.
A Haas control will automatically add leading zeros but just try to ignore it. Maybe Mr Haas likes to see them.
I recently got to train someone on one of these, a Webster & Bennett with Fanuc 10t Control.
It’s what I crudely call a big bastard. But bastard it is not, it can definitely machine some big shit
Like this monster.
Don’t ask me what it is or I would have to kill you. Joking aside I think it’s a water valve. Beware these jacuzzis use a lot of water,
The machine is a Webster & Bennett vertical borer and I think the Fanuc 10t control was possibly a retro fit.
When these start whizzing around even a few RPM it can scare the living shit out of even the most seasoned engineer. And me, well I,m more seasoned than a piece of Nando’s chicken.
G50 on a Webster & Bennett Your Best Friend
Anyway joking aside your best buddy now is definitely G50 get this wrong and it’s fuckin world war three.
Imagine the scenario, you program G96 S180 M3. Spin at 180m/min. Not too fast but…. what if the tool is sat in the middle of the part.
Machine says “come on lads happy days foot to the floor flat out joy riding” and it fucks off like two teenage boys in a stolen Lamborghini.
So without aG50, or the wrong speed, this beast will accelerate to it’s maximum rpm.
Oh and did I Mention it’s harder to stop than a P & O Criuise Ship with 4000 obese pensioners on board?
