CNC Programming Safely Using Decimal Point

CNC Programming Safely (Decimal Points)

CNC Programming Safely is very important. This post explains about the role of the decimal point.

Decimal points who needs em eh?

On Fanuc controls and Haas controls depending on the setting of a parameter if you input something like X20 it can be taken in two ways.

(1) X20 is taken as a movement in X of 20mm this is like a calculator and some controls will convert this to 20.000 for you.

(2) X20 is taken as 20 microns which would be .020

The difference between 20mm and .02mm is massive would you agree?

This also works on feed rates so you could be waiting a long time. Or the other way around you end up with a pile of broken tools.

The most dangerous one is with offsets this will definitely cause a collision.

I remember those things in comic books where you have to find the difference between two pictures. The difference with a CNC Machine is it can cost you your job if you don’t spot the missing decimal point.

Even at five years old I couldn’t really be arsed. I remember swearing for the first time and thinking “fuck this, pass the water pistol”

Sorry this is not true, obviously I was swearing long before my fifth birthday.

Please contact me with the answers to the quiz above (that way I’ll know never to offer you a job)

Decimal Points

Now you could go diving for your manuals and check your parameters and settings. I don’t actually recommend that right now.

Think of people like me and all those applications engineers who work here there and everywhere.

It maybe that in your company you have machines set in different ways and that’s gonna be real confusing.

It is obviously a good idea to have all your machines working in a similar manner if possible.

So in order to do your CNC Programming Safely I recommend that you make a rule when you are inputting code.

Always include a decimal point regardless of the control settings.

That way whatever your machine setup you will still get the right movements and offset adjustments.

Never Use a Decimal Point (CNC Programming Safely)

M codes
S Codes
G codes although there are exceptions such as G54.1
H numbers
T codes
L
N numbers
O (Programme numbers)
P  address

And if you do you will get an alarm. There are exceptions to these rules but you would need to check your programming manual.

Use a Decimal Point (CNC Programming Safely)

B   address
C   address
D  address
E   address
F   code
I   address
J   address
K  address
Q  address
R  address
U  address
V  address
W address
X  address
Y  address
Z  address

I have trained people who insist on programming X0.0 and that is ok if it helps you to remember the decimal point. Even though on X0 it would make no difference but rules are rules.
Just remember that if you change companies it will be very hard to break the habit if you are not inputting decimal points.

It’s a bit like keep putting your hands down your trousers. When your at home it’s a minor bollocking from the wife.

Try it in public and you’ll end up on the sex offenders register.

Those using CAD/CAM systems it is quite easy to change your post processor to always output decimal points too.

Here is the Fanuc parameter that you can alter.

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