Before we run any G-Code program, we need to tell the machine where our part zero is.
A Part Zero is simply a bunch of numbers that offset the axis to give the machine a new coordinate point to work from.

Work Offsets is one of the most basic pieces of knowledge any machinist must-have.

Let us account for all the basic coordinate systems and definitions, available in a generic CNC machine

• Machine Home and (Absolute) Machine Coordinates
• Work Offset Coordinates
• Tool Length Offsets

Machine Home and Machine Coordinates: G53

Machine Coordinates (or Absolute Coordinates) is the absolute and constant representation of the machine axis position.
These coordinates never change between Machine Restarts and must remain such. In fact, there is often no way for an operator to adjust the Absolute Machine Axis Home position.

Machine Home is simply that magical place where all Machine Coordinates should become Zero.

To Home the Machine is to start a machine operation, that will move all Axis to their soft limit position where X, Y, and Z-axis reading will be set to zero.

Homing must be done every time you restart your machine. Without it machine does not know where is the position of its table or spindle.

When homed your machine coordinates will read X=0 Y=0 and Z=0 and it is going to look like this:

The point where Machine X and Y intersect is called Table Home Position and the one where the Machine Z-axis starts from is called Spindle Home.

Now, there is no agreement between machine tool manufacturers on where the machine home should be.

Canned cycles are used every time we need to drill, ream or tap holes on our CNC machine

Standard Fanuc G-Code language supports more than a dozen canned cycles.

The most common cycles that will cover 99.9% of your g-Code CNC programming work are:

Subsequent holes

You can drill additional holes After your canned cycle has been initiated.
Any line with X Y position will be treated as another hole position.

Each position can have its own Retract value, feed rate and retract height modifier.

G80 - Canned Cycle Cancel Code

After all the holes of the canned cycle have been drilled, it is required to call G80 code in order to cancel the current cycle.

In this tutorial we are going to explore different options and techniques when programming cutter movement.

Lets begin with a simple part shown in a drawing below.

Basically it is a rectangular piece 4.00x2.00
For the purpose of simplicity lets make the depth of our profile (z- dimention) 0.75"

We are going to use a 0.5" dia endmill, again because it is a very common size and is easy to do basic math with.

I took a liberty of puting locations for our part/toolpath, so it is easy to extract numbers from the drawing just by looking at it.

Notice the green rectangle. This rectangle represents the path that the center of the tool will have to take to produce the part with required dimentions.
The thing is: because endmills have certain diameter, the center of the tool must be always offset by its radius.

There are two ways of doing that.

At my day job I am starting to do more and more manual programming.

Which i do not realy like, but since am at it anyway i have decided to keep piling little articles about G-Code programming into this new category.
This way when i forget things again i will be able to quicly refresh my memory.

Program Start

O0001 (COMMENT OR PROGRAM NAME)

Starting safety blocks

(G20 IMPERIAL UNITS, G21-METRIC)
(G17 XY ARC PLANE, G18-XZ, G19-YZ)
(G40 CANCEL TOOL RADIUS COMPENSATION)
(G49 CANCEL TOOL LENGTH OFFSET)
(G80 CANCEL CANNED CyCLE)
(G90 ABSOLUTE POSITIONING MODE)

G20 G17 G40 G49 G80 G90

Tool Change Routine

(T14 - call 2.5" Face mill)
(M6 - Perform tool change)
(G0 - rapid feedrate)
(G55-G59 - Choose Work Offset)
(X, Y - Command a Position to move to)
(S - choose spindle speed)
(M03 - Turn spindle on Clockwise, M04 - Counter-clock wise)

T14 M6
G0 G54 G90 X{X} Y{Y} S{SPEED} M03;

Apply Tool length offset at retract height, Turn on Coolant

(G43 H14 Z2.0 - All codes must be in the same line Apply cutter length offset from record #14 to cuttent tool, move to 2.0 above work at the same time )
(M8 - Turn on Coolant)

G0 G43 H14 Z2.0 M8

Rapid tool to plunge height

G0 Z{Z_PLUNGE}

Plunge to cutting depth at plunge feedrate

G01 Z{Z_DEPTH} F{F_PLUNGE}

Make a straight cut in xy direction at cutting feedrate

G1 X{X_POS} Y{Y_POS} F{F_FEED}

Retract to plunge height at either rapid or retract feedrate

G1 Z{Z_PLUNGE}

Retract to rapid height, turn off colant

(M09 - Turn OFF coolant)

G0 Z{Z_RETRACT} M09

Retract to tool change height, turn off spindle

(G28 G91 Z0 - all coes must be in the same line, move Z axis to HOME POSITION through a reference point)
(G91 Z0 - Causes reference point to be the current location, thus sending axis straight up )
(M05 - Turn off spindle)

G0 G28 G91 Z0 M05

Perform Next tool change or end program

M30(end program)

Normally i can't keep secrets and announce what i am working on.

But this time is different.

I can only tell you that i am working on a unique feature in our android version

Nobody has done anything like that. I can only tell you that i will be adding more tools for aiding manual programming on the control.

Check back soon. Like my facebook page to get the latest updates on our many projects.

The link is on the right :)

HSM or High Speed Machining is becoming more and more popular each day.
Many of us have seen those youtube videos where endmlls remove large amounts of material at high speeds/feeds.

While definitions of HSM may vary between tool manufacturers and even individual shops, the physics behind it remain the same.

In this article i would like to explore flat endmills.

HSM is not about ramping up your speed/feed overrides to 200% and puling out your smartphone to record another youtube-worth video.

What is HSM?

HSM is a complex of programming, machining and tooling techniques aimed at radical increase of productivity.

Programming

The cornerstone of HSM is low radial and high axial engagement of an endmill with the workpiece.

There are many CAD/CAM systems that allow you to create HSM tool-paths. Mastercam's Dynamic milling and SurfCAM's Truemill are some of them.

When radial cutter engagement with the material is smaller than the radius of the tool an interesting thing happens.
Chip load- the distance the tool advances per cutter revolution per tooth- does not equal the actual chip thickness anymore.
Chip thinning mainly happens at radial engagements below 30% of the diameter.

In order to get compensated chipload you need to multiply recommended by manufacturer chipload by the chip thinning factor.

Usual Radial Engagement for HSM toolpaths however is between 5 and 15%.

Axial depth of cut varies depending on geometry, but

Radial Chip Thinning HSMAdvisor Screenshot

Sevaral weeks ago i saw a post on CNCZone.

A HSMadvisor user Peter Neil used it to calculate cutting conditions for cutting a block of pre-hardened stainless steel.
His machine was Tormach.

Here is an exact copy-paste from that forum post:
_____________________________________________________________________________________

Did a test cut on the Tormach today using feeds & speeds from the latest version of the excellent HSM advisor.
To make it interesting, I did the cut using some 1.2085 pre-hard Stainless Steel as I have plenty of stock of it and have a job in mind for this, and wanted to see how it cut on the Tormach.
The material is like a stainless P20, at 16% Chrome/1% Nickel & 0.5% Sulphur (which makes it slightly free-er machining) and is hardened to around 33-35 Rockwell C, so I used the HSM advisor guidelines for machining P20 rather than Stainless. Cutter was a 10mm 4-flute Carbide TiAlN coated EM.

So...... ticking the HSM/Chip thinning option I got a speed of 5120 and feed of 2214mm/minute( 87 IPM). I used a DOC of 10mm and WOC of 0.5mm/0.020" - and turned off the flood cooling to machine it completely dry. The finish pass on the 1st level was 15mm DOC and 0.5mm WOC and slightly lower speeds/feeds.

Loaded up a 40mm x 63mm block , pressed the start button, and it went from this....





...to this!

Using Peck Cycle is often needed when drilling deep holes.
When using proper feed and speed no peck is required at depths of up to 3xDia for regular or 5xDia for High-Performance Parabolic drills.
At depths up to 10x, up to 5 pecks are required for regular  drills and up to 3 for Parabolic.
Anything over 10x Dia requires constant pecking of 0.5-1x Dia for regular drills and 1.5-2 Dia for Parabolic.

Since for programming you need a peck amount. Here are the numbers:

Of course our HSMAdvisor Speed and Feed Calculator suggests not only the Speeds and Feeds but also the proper peck depth for various drill types and depths of the hole.
It in fact was the first machinist calculator to do so. This feature was much later borrowed by our competition.

And here is a pretty image showing Peck VS Hole Depth for regular twist drill:

This not only means that peck amount should be different for different styles of drills and depths of holes.
But also that peck distance should be different for different stages of drilling the same hole.
Ideally we should start the hole with large pecks, that continually reduce as the hole gets deeper and deeper.

Let's find out how we can apply this knowledge when programming our toolpaths.
This is format for normal Pecking:

Renishaw OTS tool probe cycle for HAAS can set both length and diameter offsets.

Too bad there is no choice: it only puts absolute measured diameter of the tool into D- diameter offset and makes wear offset=0

But if your programming is done with the center of the cutter, then you actually only need the difference between actual and programmed diameters of the tool.

I.E.: When probing 5/8Dia end mill, we get D=0.6248. You would normally have to subtract 5/8 from it and leave the -0.0002 difference.

But there is an easier way

Here is a list of Okuma G and M codes i got from the manual

Note Some codes may not be supported by your machine, all information is given as is and i dont give a ... if you break something.

Information given here is correct to the best of my knowlege