How to write G41 in CNC

Im not a cnc professional or even a learning cnc operator,Im a student, currently studing my fourth year in mechanical engineering, Im required to study cnc as part of my syllabus. Im a newbe to cnc.
Can somebody please explain G41 syntax used for tool offset.

Let's say during a side milling operation, a 40mm diameter tool is used, so an offset is specified using a syntax as follows:

G41 D4

From what I understand from the above syntax is that, D must be followed by a number obtained by dividing the tool diameter by 10. Am I right? I've seen another example where a 25mm diameter tool was used and the D there was followed by 2 and not 2.5 (25 divided by 10). How come?

Can you please explain how the number that must be followed by "D" must be obtained.
Thank you.

somanna said:

Im not a cnc professional or even a learning cnc operator,Im a student, currently studing my fourth year in mechanical engineering, Im required to study cnc as part of my syllabus. Im a newbe to cnc.
Can somebody please explain G41 syntax used for tool offset.

Let's say during a side milling operation, a 40mm diameter tool is used, so an offset is specified using a syntax as follows:

G41 D4

From what I understand from the above syntax is that, D must be followed by a number obtained by dividing the tool diameter by 10. Am I right? I've seen another example where a 25mm diameter tool was used and the D there was followed by 2 and not 2.5 (25 divided by 10). How come?

Can you please explain how the number that must be followed by "D" must be obtained.
Thank you.

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D4 is tool offset number 4 got nothing to do with diameter of the tool
G0 G40 X0. Y0.
G1 G41 D4 X1.0 F10.0
.
going to X1.0 using the D4 tool offset amount which if 0.25 center of tool would be at X.75 (.75 + .25 = 1.0)
cnc just does the math it adds the D4 offset to the coordinate position. you should have a tool offset screen sometimes separate columns for H and D and sometimes not
it sometimes just goes
1 .1000
2 -.0050
3
4
H1 and D2 might be for one tool its not always H1 and D1 for same tool depends on control
.
some cnc always use H1 and D2 for tool currently in spindle which changes when tool is changed
cause a variable like #2001 can be used like
#2001=#2001+.001
#2001 on some cnc is same as H1 so gcode can be used to modify the H1 value in the program so there can be advantage to only using H1 and D2 cause the #200? number is different between H1 and D2 and H3 and D4 etc

The D # can be anything you want it to be. Common practice is to have it match the tool #. When the controller sees a G41 D3 in the program it looks in the tool offset table at the value entered in D3 and applies it to the cutting. You can have multiple D#s for the same tool so you can adjust different features independently of each other.

somanna said:

...From what I understand from the above syntax is that, D must be followed by a number obtained by dividing the tool diameter by 10. Am I right?

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Only if your ending position happens to be 1/10 your tool diameter.

G1 G41 D4 X50 Y20.

This would be a linear move ending at X50 Y20 using the offset value in register D4.

there are advantages if control only uses H1 and D2
.
i often use a program loop to modify H1 so
1st pass is .001 higher
2nd pass at .0000
.
relatively easy to program a loop and if #2001 is same as H1 you can program a change to H1 in the program
.
can do the same for D2 its just a different number maybe #2002

D is diameter compensation. G41 activates the diameter compensation and is used when the tool is to the left of the matl in relation to the direction of travel of the cutter. G42 is used when the cutter is to the right of the matl in relation to the direction of travel. G40 deactivates both.

Both must be called with machine movement.

In your example the value in D4 would adjust the programmed profile by the amount in D4.

ie: If you're milling the outside of a profile and its too big by .002, you would add -.001 (or -.002 depending on control parameters) to the value in D4. This would adjust the profile by .001 smaller per side, or .002 total.

Hope this helps.

somanna said:

Im not a cnc professional or even a learning cnc operator,Im a student, currently studing my fourth year in mechanical engineering, Im required to study cnc as part of my syllabus. Im a newbe to cnc.

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And people wonder why India is doing so well.

litlerob1 said:

And people wonder why India is doing so well.

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in China multinational companies often pay extra for people with college degrees. a shop machinist might have a engineering degree as well as read and write many languages preferably one language being English or the language the multinational companies bosses usually speak
.
basically instead of $3./hr they might pay $4./hr to the shop machinist who is also a engineer. obviously with currency differences and cost of living its like paying $24./hr instead of $18./hr to have a shop full of smarter people. dont know many shops in USA full of college degree engineers working as a shop machinist who also read and write Chinese as well as English

India is not China.

DMF_TomB said:

in China multinational companies often pay extra for people with college degrees. a shop machinist might have a engineering degree as well as read and write many languages preferably one language being English or the language the multinational companies bosses usually speak
.
basically instead of $3./hr they might pay $4./hr to the shop machinist who is also a engineer. obviously with currency differences and cost of living its like paying $24./hr instead of $18./hr to have a shop full of smarter people. dont know many shops in USA full of college degree engineers working as a shop machinist who also read and write Chinese as well as English

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I’m sure just about every shop in the US would love to have machinists with advanced degrees in engineering and the ability to speak multiple languages. We just can’t find them and couldn’t afford them if we did. The few that are like that are smart enough to either work for themselves (and that is a debatable option), or work in higher paying careers

Spruewell said:

I’m sure just about every shop in the US would love to have machinists with advanced degrees in engineering and the ability to speak multiple languages. We just can’t find them and couldn’t afford them if we did. The few that are like that are smart enough to either work for themselves (and that is a debatable option), or work in higher paying careers

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when i say $24./hr for engineer working as a machinist compared to $18./hr perhaps i should raise that to $34./hr compared to $26./hr (adjust the numbers to whatever works)
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the purpose being when wages are high enough you can get people to work a job that ordinarily wouldn't
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i dont believe in a millisecond there is a shortage of any workers. it called company doesnt want to train people problem. about 40 year ago i got hired out of high school by a company with a apprentice training program and they were training over 100 people every year for jobs. 3 or 4 year apprenticeship. its called company has the ability to plan years into the future. same so called "new" problem been around for thousands of years
.
only problem i ever saw with engineers working as machinist is some dirty jobs they felt were beneath them and they would be embarrassed to be caught working those jobs. sort of like you might have trouble with a engineer being a garbage man on a garbage truck he would be embarrassed to admit he was doing that no matter what the wage. mostly to his family if they knew he was doing that. how do you think a garbage man came to be called a sanitation engineer

cameraman said:

India is not China.

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I'm not confused, about Geography, or Finances.

many places have engineers work in the trades for a few months in each trade as a learning experience. obviously engineers need to learn the trade too and are not experts in machining just cause they are a engineer.
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actually i would consider it a good sign engineer wants to understand programming rather than just do the time and not learn anything from the experience
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a common error with G41 is movement asked is less than the tool comp. that is if you say move to right .100 and tool comp was -.200 it actually would more away or other way. hard to describe. some cnc when tool comp called must move toward line or arc being machined or you get error message. often had to move start where no tool comp active farther away so when tool comp called it moves toward the line or arc
.
usually get a hard to understand error message when wear comp is too high like D2 -.150 but movement asked is .100

litlerob1 said:

I'm not confused, about Geography, or Finances.

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lol

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India is a very special case as it has refused foreign investment for many decades and remains a very controversial subject (foreign investment/ development from outside sources) within India (Still today).


BBC world service/ news does a good job of covering business news internationally and does a good job of hosting round table discussions with key people from those/various countries, so it's a bit more direct/ less filtered.