Hello Guest it is May 15, 2021, 05:19:55 PM

### Author Topic: G81 Question  (Read 3462 times)

0 Members and 1 Guest are viewing this topic.

• 82
##### G81 Question
« on: December 30, 2006, 10:08:12 AM »
When I run my program i get the following errors

" R less than Z in cycle in xy plane on line #8"
here is the actula line of code
N45 G81  X0.4771  Y1.1648  Z0.5000  R0.0000  F3.00

If R specifies the up position and
Z specifies the drill position
shouldn't r be less than z with mill head going down to larger numbers  (ie 0 at the top)
did i miss a concept in my programming.

#### Brian Barker

• 3,864
##### Re: G81 Question
« Reply #1 on: December 30, 2006, 10:39:08 AM »
Z is the depth of the hole and R is the distance that you would like to rapid too.. R must be greater then Z
Fixing problems one post at a time

www.newfangledsolutions.com
www.machsupport.com

• 82
##### Re: G81 Question
« Reply #2 on: December 30, 2006, 12:21:52 PM »
Brian - still troubled.

assuming i set my (r) rapid position at 0.0  (mill head far up) and my drill depth (Z) at 5.0 inches (downward).
then R would be less than Z.

am i missing something here.  should down (into the material) be going negative.

on my mill (sherline) the head moves in z  not the knee (material).  am i looking at this wrong.

Feeling real stupid here.

#### fer_mayrl

• 453
##### Re: G81 Question
« Reply #3 on: December 30, 2006, 03:14:13 PM »
1. rapid height should not be at 0.0, that would leave a line where the drill marks the surface when traveling from hole to hole.
2. 5 inches downward would make it Z-5.0. On most machines, (and i think its better this way) when your tool moves into your material, regardless of what is moving (spindle or table) the move is negative, if the material is moving away from the tool, then the move is possitive.
So your line of code should turn out to be like this:

N45 G81  X0.4771  Y1.1648  Z-0.5000  R0.1000  F3.00

So R=0.1 is greater than Z=-0.5

This code will drill a hole at X=0.4771 and Y=1.1648, at a depth of 0.5 inches (z=-0.5), at a feed of 3 inches per minute, when the hole is done, the tool will rapid back at 0.1 over the material. and will be ready to rapid to another hole location. (all this providing the Z movement is negative when the tool goes into the material)

Hope that helps
Regards
Fernando

• 82
##### Re: G81 Question
« Reply #4 on: December 30, 2006, 03:54:27 PM »
thanks that is the concept i was missing.
top of material is zero,
INTO material is negative,
ABOVE material is positive.

I had the last two reversed

#### Brian Barker

• 3,864
##### Re: G81 Question
« Reply #5 on: December 30, 2006, 05:49:41 PM »
Looks like you are all set now

(Look at G98 and G99 for more info on how the R is used)
Fixing problems one post at a time

www.newfangledsolutions.com
www.machsupport.com