G96, G97 and How To Calculate Surface Speeds

G96, G97 and How To Calculate Surface Speeds

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Basic Turning

Basic Turning
G96 Hamsters Large wheel Small wheel
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Basic Turning, in the early days of CNC Turning G96 was one of the things that really made a massive difference.

It meant that instead of having to turn a part at a fixed speed and feed, the part could be programmed in G96 which was a constant surface speed.

Where diameters changed, particularly when facing, it made a massive improvement to tool life and surface finish as well as speeding up the whole process.

G97 Speed In RPM

In Basic Turning when you program G97 your machine will start the chuck up at a speed in RPM. So if you program.
G97 S1500 M3
Your chuck will start revolving clockwise at 1500 rpm.

G97 for Drilling Tapping and Screwcutting

When drillingĀ  a hole you are on the centreline of the machine so you just want plain old simple RPM.

When tapping or spot drilling it’s the same.

Screw Threading (G76) can only be done in G97

G96

G96 however means meters per minute. This is a surface speed.
G96 S200 M3
Your machine would start up at a surface speed of 200 meters a minute. Now your RPM would depend on where on the diameter the tool was positioned.

Basic Turning

If the tool was positionedĀ  at a 100mm diameter it would be as if the tool were able to run around this diameter atĀ  a speed 200 meters a minute.
It’s a bit like being on a running machine if you ran at 200 meters a minute and placed various diameters under your feet the large ones would turn at slow rpm and the small ones would turn at high rpm. (Just like the hamsters above)

Basic Turning

Ā That’s why on a manual lathe it is hard to face a large diameter without changing speed half way.

Neeeeeoooooooowwww

You know when you face a part on a CNC Lathe and you hear that change in pitch? It’s the spindle increasing in RPM as it gets closer to the center of the part.

When it gets to the center your spindle is flat out so the G50 becomes crucial.

The G50 restricts the speed of the machine.

G50 S2000 machine will go no higher than 2000 rpm.

 

G96 G97 hamster on a Wheel

Did you have a pet hamster as a child?

I know it’s a random question but bear with me there is a point to this.

Well maybe you still have a Hamster and that’s not a problem. Time you fuckin grew up but it’s not for me to judge.

Anyway I did and his name was Harold WilsonĀ (British Prime Minister at the time).

Well I bought my hamster loads of different wheels to play on just like the one above.

My hamster suffered with depression on account of being stuck in a cage all day and not having a girlfriend oh and he had a lot of credit card debts too.

These wheels varied in diameter from about 6 inches to a massive 2 foot one. They kept him happy all night. He was so tired he slept all day.

Harold could only run so fast but I noticed when he was on the small 6 inch wheel it absolutely whizzed around. Now on the big two foot diameter one it took him ages just to get it to spin around once.

Basic Turning
G96 G97 all about hamsters

Harold Had G96

A CNC machine in G96 will give a lovely finish because the surface speed always remains the same.

So even though Harold ran at 200 metres a minute (this is fuckin lightening speed for a hamster)

The wheels ran at different RPM depending on what diameter they were.

Harold Was a Clever Bastard

Oh by the way Harold had a tail (unlike other hamsters) and a maths qualification.

He knew that if he multiplied the diameter of the wheel by .00312 it would give him the circumference of whatever wheel he was running on in meters.

200 mm wheel (.00312 x 200 = .6864)

All he now needed to do was divide this answer into the speed he was running at and he would know how many RPM his wheel was revolving at.

If he was running at 200 meters a minute not only would he be fuckin knackered but the wheel would be running at 291 rpm

200 / .6864 = 291

Basic Turning Manual Machining

Using a manual machine you have to compromise. At the outside your speed is too fast and when you get to the centre you are too slow.

Manual Lathe


On a CNC lathe we would normally program in mm per revolution as well because the speed is changing all the time so we need our feed to be locked into the speed.
With a machining centre our cutter is always revolving at the same speed so the feed can be constant in mm per minute.

Someone out there will be thinking “what happens in G96 when you get to the centre of the part”. Well the spindle will be flat out!

Could be a problem. That’s where your G50 comes in to restrict the speed. Very important! CNC Basics G50

cnc turning basics
G50 Warning

Watch the video

See how surface speeds are translated to speeds in RPM. There are many converters online that you can use for this and I do recommend their use. It will also mean you don’t have to watch my tedious video.
When I train people at the CNC Training Centre my emphasis is on understanding not memorising. I usually start by saying ā€œplease don’t remember all the things I am telling youā€.

Ā In the early days training students in Basic Turning I remember them saying to me the next day that they had G codes floating around in their head from the lessons the day before.

Basic Turning
G96 and G97


What I really mean is that the most important thing is to understand what the machine can do and the concepts of programming and Basic Turning.
You could say ā€œI know there is a G code that makes the machine run in RPMā€ so all you need is a list of G codes.

If you can be bothered to work through the simple maths above. It will help you to fully understand how G96 is works.

Here is a list of Basic Turning G Codes.

The ones you use every day you will remember whether you want to or not.

G96 Whoopee It’s amazing

So use G96 for everything.

Except for:

  • Drilling.
  • Tapping
  • Threading (Screw cutting)
  • Cutting the Lawn

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CNC Milling M Codes List For Beginners

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CNC Milling M Codes
List of M Codes for a CNC Milling Machine

Download CNC Milling M Code List

This is my list of CNC Milling M Codes and you will notice there aren’t many.

That’s because you don’t actually need many.

M Codes are used to turn things on and off on a CNC Milling Machine. Sometimes known as miscellaneous functions.

A typical M Code would be M03 which would start your spindle forwards.

M04 would be reverse and guess what?

M05 is stop the spindle.

There, you learned three already.

You don’t need the extra zero so I advise you leave it out, program M3 M4 M5.

It really doesn’t matter but….. You could be wasting memory space or wearing out the tips of your fingers.

Here’s what I think about leading zeros.

M codes are the Snow Leopards of CNC Machining

Snow Leopards are Solitary Animals

Snow Leopards only ever get together to mate, they don’t even have a Christmas party or get pissed on a stag night.

With M codes they hate being on the same line of code. If they are then they will fight to the death.

Tigers Playing

Please note no animals were hurt in the making of this post.

There are exceptions to this rule, M Codes that is, but please don’t overload yourself with this at the moment.

Just trust me.

The first one in the block usually wins but I can’tĀ  guarantee it. So you could get some crazy shit happening.

G90 M8 G0 G54 X0 Y0 S1500 M3;

You wouldn’t even get an alarm on most controls and it may just obey the first M Code it sees and ignore the last one.

The other thing to note with M Codes is that it makes no difference where they are in a block of code.

So if you put your M Code at the front of a block of code.

M3 S1500 G0 X0 Y0;

Or the end.

G0 X0 Y0 S1500 M3 ;

The spindle will start according to the logic of the machine not where the M Code is in the block of code.

The Boring CNC Milling M Codes

That’s my list of M Codes the rest are really boring doing stuff like changing gear ranges and stuff.

Download CNC Milling M Code List

Sorry I’m being flippant again.

CNC Milling M CodesĀ Where Are The Rest?

Sorry you can’t have them. The reason for this is that they are different depending on what machine they are on.

CNC Milling M Codes
Hand Em Over

For example this beast is a Mazak Megaturn

CNC Milling M Codes
Mazak Megaturn

It Has a Gearbox.

To change gear you program M41 M42 and M43 for the different gears

M40 is neutral. Now on machines with gearboxes they do normally use these same M Codes.

However they can be different.

M10….. mmmm well that’s normally a clamp.

I think you get the picture. It is up to the machine tool builder.

It is best to get a specific set of M Codes from your machine manual.

The manual by the way is that book that nobody ever reads, it’s usually at the bottom of a bent up old filing cabinet.

Please Don’t Read It

I’ll read it for you then charge you a shit load of money for training.

Click here for CNC Training

Joking aside please don’t be arsed to learn a load of M Codes you will probably never use.

Well Commented Programs

Try to put M Code descriptions in your program. That way you won’t need to keep looking them up. A part transfer on a CNC Lathe is a good example, there are an absolute shit load of em.

They are everywhere. If you put a meaning to each one in brackets it will make proving the program out really easy. Oh and if you have a CAM system then change your post processor to output them for you.

M11 (OPEN CHUCK)

M10 (OPEN CHUCK)

etc etc

I had a boss once who actually learnt sines and cosines of angles.

Cosines of Angles

Holy shit I mean it’s impressive and I must add in 1975 it was actually worth doing because we didn’t even have calculators.

Hope you enjoyed reading my article on CNC Milling M Codes.

Please remember that it keeps me occupied and while I’m writing these articles I am not holding you up in the supermarkets queue trying to find a coupon for 10p off my incontinence briefs.

Download CNC Milling M Code List

 

 

 

 


Hyundai Wia L 300LC CNC Lathe

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Very solid nice big Hyundai Wia CNC two axis lathe with Guide i, what more could you want?

Hyundai Wia

You know like when you have been on holiday eating loads of fancy food and you get home and all you fancy is a nice simple chips n egg?

Staple diet of my childhood. Anyway that is what this machine is. It’s the chips n egg of the CNC Lathe world.

Having just worked on a Nomura sliding head that’s as complicated as a nuclear reactor (are they complicated, I don’t know?) Anyway it just seems nice to come back to some nice simple stuff.

This is a no messing sturdy beast, none of your namby pamby driven tool shit.

No Y axis, and no stupid sub spindle to mess about with. G12.1 forget it. C axis no way.

Happy days, easy training job simple two axis CNC Lathe with a Fanuc i series control. Oh and it’s got Guide i too. I’m gonna love this.

Hyundai Wia With Guide i

Seem to get loads of these lately an I’m kind of getting to like them mmm maybe not. There’s loads of good stuff mixed in with some bad shit.

Sorry I’m rambling.

Guide i Did You Know?

Well I certainly didn’t. Anyway it’s got this button called alter.

Fanuc Guide i

Always wondered what it did so today after some deep breathing exercises I plucked up the courage to press it. Put on a mask, gloves and full PPE.

Safety shoes, check.
Incontinence briefs, check.
Crash helmet, check.

Bingo I pressed it.

Guess what it did…….

Nothing, jack shit, fuck all.

Ah but wait don’t go off to some other boring stupid website with naked chicks or naked dudes. No no no.

After much deliberation me and my new bestie (James) tried every combination.

Anyway if you highlight an M code and then press the beast. Guess what it comes up with a list of all your M codes, all their meanings and you get to pick one.

Fanuc Guide i

Woopee, err, not. Well I suppose it must have a use. If you didn’t know the M code you needed I suppose it could be good.

Now I lost a good 10 minutes of my life trying to sort out what this button did and I’m not impressed.

No matter how totally bladdered my mates are at the pub tonight I wont be able to impress them with this one.

Anyway enough said, I bet someone at Fanuc got promoted after inventing this exceptional, programming aid. A close runner up to the Fanuc PROGRAM RESTART button as another contender for the “this button is fuckin useless” award 2023.

Guide i Did You Know

Honestly this one really is worth reading. When you want to call a sub-program and you are not sure what number it is this one helps.

PressĀ  Fanuc Guide i

Then from the screen move over to subprogram.

Fanuc Guide i

This takes you into the directory and from here you can select your subprogram. It will insert this into your program complete with the M98. And if you use names for your programs then it puts it in those nice little V shaped brackets. What do you call those funny brackets by the way. Does anyone out there know?

Guide i

Names For Programs

Using names for programs is cool. When you are an old school pre-septuagenarian git like me it seems real 21st century. Saves on all those shitty four digit numbers and bracketed descriptions.

This is mine above <FACE-GUIDEI>, certainly save on typos. I recon if you get into the habit of using this it could be very useful.

Guide i

If this sub program call feature is on Trust pilot I will give it 6 out of ten or maybe 7.

So bloody shit-faced convoluted to find. I mean who the fuck would think right I’ll press this button called FIGURE I mean it’s bound to take me somewhere where I can input my sub programs straight from the folder they are in.

Enough said.

The Machine David The Machine

Oh yea, some stuff I like on this machine.

Absolute encoders, no stupid zero return. Switch it on wait a few minutes press the standby button and you are good to go.

No open and close the door shit, no rotate the turret shit no no no just switch the beast on. Lovely.

Clever that is, my tellies at home are the same, can safely say I never had to zero return any of my many 50″ tellies. One in every room by the way except for the shit-house.

No open and close the door shit, no rotate the turret shit no no no just switch the beast on. Lovely.

Gear Change

Now I knew this thing had a gearbox but I couldn’t get the thing to change gear. Well actually you don’t need to. Just select a speed in G97 and it gets the right gear. What’s all the fuss you ask? Well if you are in G96 and it’s in low gear. Imagine you are facing off a part, well it will get to 1000 revs and just stay there.

Anyway the technique is as follow

You will get low gear

G97 S500 M3
G96 S200

You will get high gear

G97 S1200 M3
G96 S200

The G97 will make the machine select the correct gear.

Hand wheel Hyundai Wia

The jog and hand wheel are the same mode just press this button.

Hyundai Wia

When an increment is selected the button will start to flash indicating that You are in hand-wheel mode.

Hyundai Wia

There is a slight delay in starting the jog mode so be patient. A couple of times I thought it wasn’t working and started playing around with other buttons.

Turret Index

Turret will only index in manual mode when the X axis is at zero return. It is probably better to use MDI as it doesn’t mind where it is. Obviously take a good look at the surroundings before pressing cycle start.

Indexing the turret is done with these buttons. Hold in the middle one and press either of the outside ones to move turret clockwise or counter-clockwise. Press and hold for continuous rotation, Top red number is station number.

Hyundai Wia

Don’t forget when you index the turret the tool is not active, the Fanuc control will only display last tool used in MDI or inĀ  program.

Start Spindle Hyundai Wia

As with most Fanuc controlled machines you will have to set a speed in MDI before you can start the machine manually. Once the speed is set use these buttons. Press and hold central button and your direction to start spindle manually,

Hyundai Wia

If you press forward or reverse without the central button the machine will jog the axis at the programmed speed. You can also do this with the door open. lucky you.

Hyundai Wia

Rapid does not work at all with the door open.

The jog feed potentiometer will stop all movement in rapid if set to it’s lowest position, It needs just one notch to make rapid work. A little trick, you only make this mistake once. A call to some smart arsed service engineer who says “did you try moving the dial one click?”

Zero Return

Select zero return then press direction key. One press and you don’t need to keep your finger on the button, This machine has a tailstock so keep an eye out for it when referencing the Z axis,

You can set both axis going together.

I like the door locks on this machine because they release on their own, There is no button to open and close, I like that,

A Room With a View

The viewing window is a bit small but I suppose its a good safety thing when you have a big chuck spinning at 3000 RPM.

One very concerning thing is the fact that there is no safety back kick plate on the chuck pedals, This is a 2022 machine so I would have thought it would have one.

It means you can accidentally press the pedal and open the chuck!! Holy fuckin shit.

We decided to put the pedal under the bench so you couldn’t press it by accident.

Guide i Again

Every time I use guide i I find something new that I like about it. Me and Guide i are definitely in a love hate relationship.

This time I found the two things above.

Fixed Forms

I recon with some work using Fixed forms is a good quick way of programming, Given time you could get a really good library of things.

This would make program creation very quick. Multi screen editing is also good on Guide i. You can have several programs open together and switch between them when editing.

This also means no pesky background edit where you get locked in a fuckin time warp and nothing works until you find the escape button (BG END)

Graphics Graphics Sodding Graphics

Graphics are still pretty shitty, When you alter the rotation or size of the part you lose everything and have to start again.

How annoying is that. I mean I should be used to it by now.

Come on Fanuc this is 2024 not 1981. There is no speed control on the graphics either so it’s all over in a flash.

Not sure on this one can somebody explain? Some controls have a speed control on graphics and some don’t!!

Hyundai Wia Tool Measure

Tool measurement with the tool arm uses the hand-wheel to drive tool towards the probe. Never been a great fan of this way of setting tools but I suppose it’s still better than cut and measure.

You can index the turret with the arm down so beware. Jog and rapid don’t work when the arm is down so that’s good.

No lights on the probe! What no lights on the probe, that’s annoying. When you make contact with the probe the axis just stops, There is no light so you are not sure it has stopped.

It does jump to the correct offset for you and it zeros the wear, Good because not all machines do that.

Big Chuck

It is a big 12 station turret but with a large chuck therefore adjacent tools can easily cause a problem so beware.

Take a look below the tool you are using as it approaches the chuck. Better still bring em in manually just to check before running.

I know you are never supposed to have the jaws above the chuck outside but that’s difficult with hard jaws but it’s really important to watch out for this one.

Big Fanuc Guide i Screen

All men love big TV’s, why is that? I know I do.

Anyway this machine a has a big “fuck off” screen. Big screen means more keys are visible happy days.

Means you don’t have to keep using arrow keys to find butttons.

QWERTY keyboard too, What utter luxury.

Hyundai Wia Easy to Use

All in all I liked the interface on this Hyundai Wia machine, Pretty easy to get it to do most things. Not too many frustrations. Apart from the slight delay on some buttons like the jog, I’d prefer to be able to index the turret anywhere and I don’t like using the Hand-Wheel to measure tools. A light to indicate when you are touching the probe wouldn’t go a miss either.

Tool Change Position

This Hyundai Wia has G30 P2 which you can set a position in parameter 1241 and have a second Zero Return position (G30 P2 U0 w0)

Personally I wouldn’t use it. You will need loads of different tool change positions on a machine this big. Otherwise you’ll be travelling a mile to get to small jobs.

I set it up to use local sub routines. This means I can call program 500 in any program and it can be a unique tool change position. Read this.

My tool change position is local to this program so you can change it for every job.

Hyundai Wia

 

 


G92 Threading Single Line Method

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G92 threading Cycle is something that concerns me. It’s sadly neglected. Now I know you’re probably saying “no one uses that old shit anymore”

Well you could be wrong.

G92 ThreadingĀ works exactly the same as G76 except you need to programme every pass. This would be a pain in the arse but hear me out.

The Haas G76 cycle does not have any facility for a spring pass. This is where you add extra cuts at the end of a threading cycle to take out any metal left from the tool pushing off.

On a Fanuc control you can put these extra spring passes in as part of the G76 cycle.

Read this if you need to know more.

If you want this on your Haas control or an old Fanuc control then you can do this.

G76 X16.93 Z-25. K1.534 D.485 F2.5

G92 X16.93 Z-25.
X16.93
X16.93

Just add the G92 after your G76 cycle and whatever X figure you want to go to.

The G92 is modal so you will need a G0 move to cancel it. The code above would give you three spring passes.

Here is a load more interesting stuff.

I hope you have enjoyed reading this article.

Thanks for watching and reading

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Haas SL15 CNC Lathe

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30 five star ratings on Google (just saying)

 

Today I got to train someone on a Haas SL15 Lathe, it had live tooling and a sub spindle.

Haas SL15

It also had a bar-feed.

Not worked on one of these for a while. Tell me why on earth don’t other companies look at the pragmatic approach that Haas take to CNC Machining and copy it?

Say what you like about Haas machines but they have an incredible knack of shattering the bullshit and making stuff easy.

Here are two massive ones.

G112

G112 tricks the Haas SL15 CNC Lathe into thinking it’s a machining centre and that it can mill.

It’s like gender identity for CNC Machines. But, and this is the “for fuck sake bit”, on most machines you have to program it like a machining centre but then when your done you need to double X and switch all the Y’s for C’s.

Sounds simple but in practice it’s a shit storm, specially when programming G2 and G3.

Here is an article about it.

When Mr Haas invented the Haas SL15 CNC Lathe he must have looked at this and laughed. Here is a really clever idea. We’ll trick the machine into thinking it’s a machining centre and here is the clever bit. We’ll keep up the facade.

So you make a milling program (XY) and then……. you leave it that way. How incredibly clever is that?? Mmmmmm

“Read More”

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