G76 Chamfer End of Thread

G76 Chamfer End of Thread

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Category : Fanuc Turn New Stuff

G76 Chamfer, this is another myth exploding article about the G76 threading cycle.

It’s so easy to use cycles like G76 day in day out and never really fully understand how they work.

I certainly did and then one day I thought “Fuck this I need to know more” 

That’s when I sorted out the number of passes thing. If you don’t know how to calculate the number of passes in a threading cycle then you should read the article above.

(G76 Chamfer) I want to talk about the P

G76 P011560 Q20 R.02
G76 X16.93 Z-25. P1534 Q485 F2.5

G76 Threading Cycle First Line
P01   One spring pass       15   Chamfer        60   Thread angle
Q       Minimum depth of cut
R       Finishing allowance

G76 Threading Cycle Second line

X         Core diameter of thread
Z         Thread end point
P         Depth of thread (as a radius no decimal point)
Q        Depth of first cut no decimal point.
F         Pitch of thread

Six Figure P Number Holy Shit

G76 P011560 Q20 R.02

First two digits are easy, spring cuts. No it’s not the latest haircut for April.

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G10 Using G10 on a Fanuc Type Control

G10

I am always amazed that so many companies still don’t use G10 in their CNC programs. If you know you know.

I must admit I fuckin hate a lot of the things that young people say like “can I get a Latte”. (Get behind this fuckin counter and make it yoursef if you want to “get it”).

Anyway I kind of like “If you know you know”

No G10… Is this you?

I am sure you have your reasons which I will accept. But if your reason is that you don’t understand it then that’s just not good enough.

So you make a part, it’s all setup and you need to break it down.

If you can fix the work holding in such a way that you can reload it in exactly the same place then you need G10.

Let me explain, watch this video to see how single point location works.

G10 No need to spend loads of money.

You could just bolt a sub plate to your machine table so that vices and chucks etc can have dowels to locate them.

But the main idea is that you can relocate your work holding in exactly the same place every time.

G10
Using G10 on a Fanuc Type Control

This is your work offset page on a Fanuc control.

G10

These figures are written in by hand or by automatic setting.

If you had written this line in your program.

G90 G10 L2 P1 X-440.500 Y-265.200 Z-443.00

They would have been written in automatically when you ran the program.

So the work offset page could have any values in G54 but as soon as you run your program this G10 command will replace them with its preset values.

Make Sure Your in Absolute

Try not to forget the G90 (Absolute) because you may accidentally be in G91 (Incremental). What would then happen is it would add these numbers to what is already in the work offset. Oh dear me.

In G90 it will always replace them.

You can write to G54 G55 G56 G57 G58 or G59 just by changing the P number.

G90 G10 L2 P1 X-140.600 Y-265.923 Z-400.00 (G54)

G90 G10 L2 P2 X-125.500 Y-236.865 Z-313.865 (G55)

G90 G10 L2 P3 X-800.500 Y-563.200 Z-125.00 (G56)

G90 G10 L2 P4 X-440.500 Y-265.200 Z-169.369 (G57)

G90 G10 L2 P5 X-440.500 Y-265.200 Z-123.568 (G58)

G90 G10 L2 P6 X-410.500 Y-235.200 Z-443.00 (G59)

The code above would setup all six work offsets.

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G01 G00 Basic CNC Programming ( G01 not GO1 )

G01 not GO1 Back to Basic CNC Programming

The letter O is only used for a programme number and a GOTO statement on a Fanuc Control. It’s important not to get it mixed up with the number Zero. So we should really say G zero one ( G01 not GO1 ).

So remember it’s G01 not GO1 (Zero not letter O)

G01 not GO1

A good solution is to miss it out where possible G1 not G01 etc.

This is part of a series of articles designed to cover basic CNC Programming.

When I first learnt to programme, before the First World War, I still remember how daunting the thick yellow Fanuc Manuals were. The Japanese were learning to speak English and we were learning to speak G Code.

Fanuc Manuals

Fanuc manuals are just like the yellow pages. A note here for you young people who might not know what yellow pages are (no it’s not like someone pissed on the photocopier)

Long before Google we had these thick yellow books and we used them to find stuff like if your mam needed to get the outside toilet unblocked or something.

None of this stuff was in the Fanuc manuals but you could easily get them mixed up cos they looked very similar.

I can honestly say when I was learning Basic CNC Programming I read the old 6M Fanuc manual from cover to cover. The Macro bit was just like another planet to me. Some things I had to read over and over again to understand.

Some of it was so badly written you kind of had to guess what they meant.

In the Beginning

Every now and then I used to go right back to the beginning and read the basic stuff again. Believe me, every time I would find something I didn’t know, mind you I didn’t know much then anyway.

Try it later and if it doesn’t work I’ll give you your money back.

Okay enough of this bullshit and verbiage let’s talk about G codes.

Geometric Code, that’s what the G stands for.

Useless information but anyway, now I’ve said it. Don’t tell your mates down the pub because you will probably bore them shitless.

I often begin my training courses by saying “you only need to know four G codes to programme a CNC, it really is that easy”

G0 G1 G2 G3

(Please smart arses don’t contact me.)

What that means is that you can get round any shape with straight lines G1 and circles G2 and G3. Oh and you need to quickly get to the part so use G0 rapid.

Yes and another note. You don’t need leading zeros.

G00 can be G0 (Never GO as in letter O)
G01 can be G1 (Never GO1 as in letter O)
G02 can be G2 (Never GO1 as in Letter O)
G03 can be G3 (Never GO1 as in letter O)

Read this if you want to know more.

Lets Get On with It

G00 or G0 commands a rapid move. That means the axis will be flat out. Maximum foot to the floor, shit off a stick as we say in the Midlands.

A common mistake with rapid moves is to assume that the axis will all move in a straight line like a bullet from a gun.

Not true. Because each axis is flat out one axis may arrive before the other. The rapid on your X axis could be slower than your Z. Anyway you get what I mean.

Why do I need to know this?

Easy because if something is in the way then you might hit it. That is if you assume the movement is a straight line.

Now lets see.

Move down in Z

G0 Z5.

G01 not GO1

Then a nice straight line G0 X130. Z-30.

G01 not GO1

But meanwhile in the real world

G01 not GO1

It’s obvious really.

Just think for a moment:

If both X and Z rapid motors ran at the same speed. Then each axis will move the same amount until one reaches its destination.

Looks like this.

G01 not GO1

Z has 30mm to move in total so they will both move 30mm. This will make a 45 degree line.

Ah but X is not finished yet. X will carry on and finish its move in a straight line.

G01 not GO1

If something is in the path of your rapid move you may need to programme your axis separately to be sure not to hit anything.

G00 X130. Z-30.

Could be:

G00 X130. ;
Z-30.;

G01 not GO1

Please don’t repeat the G00 (you know it will piss me off).

Now G01 ( G01 not GO1  )

G01 is a linear feed. It means feed in a straight line. Just like stretching a piece of string between two points. It can be just one axis or two simultaneous axis. You can even programme X Y and Z all in one line of code.

So this is what really separates a CNC from a manual machine. Remember how hard it was to machine an angle on a manual milling machine? Or a taper on a lathe.

You do?

Well on a CNC Machine we just programme the end point. It will then machine a straight line from it’s current position to the programmed point

If your machine was at X50. Y0 and you programmed a line

G01 X55. Y-200. ;

You would get an angle.

Ok what’s wrong in this picture?

Just to see if you are not a robot?

Yes congratulations but what is wrong with the line.

G01 X55. Y-200. ;

The Feed-rate

Yes with G01 you need a feed-rate. Don’t repeat the feed-rate, you only need another feed-rate when you want to change it.

G01 X55. Y-200. F100. ;

Don’t forget you can programme X Y and Z together and it will still be a straight line just like you tied a piece of string between the start and end point.

F100. means feed at 100mm per minute.

CNC Turning

On a manual lathe you would have to set up a compound slide to just machine an angle.

Basic CNC Programming

Mmm very skillful and I’m sure it’s loads of fun.

On a CNC Lathe this is just one line of code and some Basic CNC Programming!!

What About 3 Axis Rapid?

Yes you can programme 3 axis together in rapid move. It’s definitely the quickest way to get to the part.

G0 X50. Y20. Z3.

I would definitely advise using it but, and there always is one, just be real careful nothing is in the way. Don’t blame me I’ll just say I never  met you.

Oh just one more thing as Columbo would say.

You could use a very high feed instead of a rapid move. That way you really would guarantee a straight line. I’ve never done this but it just came to me in a flash.

So there you have it G0 is rapid ( never GO letter O).

G1 is linear feed, remember G01 not GO1 (Not letter O)

Thank you for reading my article ( Basic CNC Programming G01 not GO1 )

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G84 Rigid Tapping Program Example

G84 Rigid Tapping Program Example

For On-site CNC Training Contact David: 0783 858 407

G84 is a tapping canned cycle.

G84 taps holes.

This simple part has four M12 holes, drilled, countersunk and tapped. The datum is the centre of the part so the holes positions are.

X55. Y55.
X-55. Y55.
X-55. Y-55.
X55. Y-55.

G84 Rigid Tapping Program Example

G84 Rigid Tapping Program Example

Here is the CNC code

G84 Rigid Tapping Program Example

The machine first moves to X-55. Y-55. and rapids the Z axis to 3mm above the part.

G84 Rigid Tapping Program Example

The G95 selects feed per revolution which means we only need to program the tap pitch for the feed-rate.

See full rigid tap G84 Rigid Tapping Program Example

The M29 engages the rigid tapping mode and the S800 is the speed. (It does not start the spindle)

It then rapids the Z axis down to 1mm above the part R1.

The G84 Cycle instructs it to tap a hole 17.mm deep (Z-17.) at a feed of 1.75mm per revolution (F1.75) 

So it feeds at 1.75mm per revolution with the spindle turning clockwise to depth.

At the bottom of the hole it reverses the spindle and feeds back to the initial point.

This initial point was in the line.

G84 Rigid Tapping Program Example

This is because of the G98.

If it were G99 it would return to 1mm above the job (R1.)

See explanation of G98 and G99

Once the cycle is active each time it sees a position it repeats the tapping process.

When the G80 is programmed it no longer taps holes.

Single block and feedhold do not work in a tapping cycle.

Why? You ask.

IT BUSTS THE TAP

Now watch the video to see it all in action (not breaking the tap).

Thanks

If you have been affected by any of the issues in this post or need CNC Counselling then contact me.

If you want to learn to program CNC Milling Machines

Look no further Contact CNC Training Centre

 

 

 


G0 Cancels Canned Cycles

G0 Cancels Canned Cycles, this is not a news flash it’s always been the case.

G0 Cancels Canned Cycles

O0001(G28 Example)
(PROGRAMMED BY ANDY MURRAY)
G21 G90 G40

T01 M06(20MM ENDMILL)

G90 G0 G54 X200. Y0 S1500 M3
G43 Z3. H1 M8
G81 G98 Z-5. R1. F100.
X100.
X50.
G0 X25. (No hole drilled here cycle would be cancelled)
G80 (This also cancels the cycle)

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