Jan 29, 2020
New:  CYCLE/TURN lathe post-processor command for OD and ID rough stock removal.  Similar to the G71 command provided by some CNC lathe controllers, this automatically generates the rough turning passes needed to remove excess stock during turning and boring operations.  See the post-processor documentation for the CYCLE command for a full description.


Jan 21, 2020
Recently added:  LETTER post-processor command:  Mill/engrave alphanumeric strings.


Jan 12, 2020
If anyone would like to try any of the following applications, contact me at aptfan@frenetec.com.  All I ask is that you let me know about any bugs/problems and suggestions for improvement.  The post-processor currently supports mills and lathes for the Centroid, Fanuc, Haas and Tormach controllers.  Follow the links below to browse the applications' documentation.

APT360 pre-processor
APT360 post-processor
Post-processor options file
NC plotter
APT source file template
APT command file

I can also provide a copy of the APT360 compiler (apt360.exe for Windows) if you need it.  I built if from the free source code as described earlier (see https://sourceforge.net/p/aptos/apt360/ci/master/tree)  and fixed a bug pertaining to defining a point as a location in a PATERN.

The editor is not ready for public consumption.


Jan 11, 2020
TRACUT and COPY cutter location transformations are stored in the "enhanced" binary cutter location file PRO.TAP (along with all other cutter location records).  If your APT program uses either TRACUT or COPY you must post-process the file PRO.TAP rather than CL.TAP.  To determine which file to post-process just scan either CL.TAP or PRO.TAP for TRACUT and COPY record types (see below for the record type definition).  If the scanned file contains either record then PRO.TAP must be used.  Technically TRACUT and COPY are post-processor commands so you can use CL.TAP if you provide your own implementations.


Sep 24, 2019
I have been sidetracked by other projects so it has been a while.  Something I have been meaning to do is document the record structure of the APT360 binary cutter location file, CL.TAP.  Hopefully this information will be of help to anyone wishing to write their own post-processor.  Note:  This information is for the Windows platform and is the best of my knowledge up to this date.  It is not exhaustive as I certainly have not tested every feature of the APT language.  Please contact me if anything is incorrect, has been omitted, or if something could use further explanation.

Each record begins with a block that identifies and describes the record.  Following the block is the data associated with the record.  This pattern repeats for the rest of the records in the file.  The structure of the block is as follows:

RECNO (4-byte integer):  This record's record number.
COUNT (4-byte integer):   Count of 8 byte entries in this record's data (8 * count = the length of the data in bytes).
RECTYPE (4-byte integer):  The record type.
SUBTYPE (4-byte integer):  The record subtype.
DATA (8 * count bytes):  The record's data.

The record types (RECTYPE) that I have discovered are:

1000: The record number (RECNO in the CLPRNT file) and the Input Sequence Number (ISN).  The ISN is in the SUBTYPE field.  All other record types are preceded by a 1000 record.  Hint:  Every APT program line can be identified by its ISN number in the CLPRNT file.

2000:  Post-processor commands.  The specific command is in the SUBTYPE field.  The record's DATA is formatted to match the commands' parameters which, in turn, are specific to the post-processor implementation.  As such, I cannot document each command here.  Suffice it to say that the data can contain bytes that are characters, integers mapped to APT minor words, and Doubles.

3000:  I believe this describes any nested surface definitions such as LINE, CIRCLE, etc.  SUBTYPE is either not used or I have not determined how it is used.  The specific surface type is identified by a 4-byte integer beginning at byte 8 in the DATA.  The surface's name is in bytes 24-31.  The subscript used with the surface's name is a double-precision floating point number (i.e. a Double) at byte 32.  The remainder of the data are Doubles and are the canonical values of the specific surface type.

4000:  Unknown

5000:  For lack of a better description this is an actual cutter location record.  SUBTYPE identifies the source of the cutter location.  So far I have discovered  SUBTYPEs:  FROM (3), GODLTA (4), GOTO (5) and SRFCNTD (6).  The DATA may contain a surface name, subscript, point coordinates and tool axis vectors.

6000:  I believe this describes DNTCUT/CUT (SUBTYPE=1) and OUTTOL/INTOL commands (SUBTYPEs 4 and 5), and cutter shape definition data (6).

7000:  Unknown

8000:  Unknown

9000:  So far this looks like a MULTAX record when SUBTYPE=2.  ON or OFF is a 4-byte integer at byte 0 in the DATA.

13000:  So far I have discovered 2 uses:  SUBTYPE=3 is a warning/error, although I don't follow the when's and why's of their usage.  SUBTYPE=4 is a CLPRNT and the 4-byte integer at byte 0 of the DATA identifies the option value, if any.

14000: The FINI record.

As for the APT vocabulary, post-processor words and their values can be found here.  Minor words and their values can be found here.


Jan 31, 2018

I got sidetracked on the above when I began reviewing my implementation of some of the post-processor words I have implemented.  For example I went too far with the CLEARP implementation and decided to align it with Irvin Kral's definition.  In short he defined it as specifying a plane parallel only with the XY plane, relegating it effective only to the Z-axis.  As a result my post-processor now supports RETRCT for a mill only.

I also reviewed my planned implementation of the CLRSRF command.  The documentation does not specify what it should do and Irvin Kral does not cover it in his book so I'm wondering if anyone has any input on the subject.  Should it just rapid to the specified surface using the shortest distance from the current cutter location?  Does anyone think it is a "must have" option?


Jan 26, 2018

For the past few days I have been attempting to learn how to get web crawlers to index this page and re-index it regularly.  It seems to me that those in control of such matters are constantly changing the rules.

Today I started the design of (for lack of better terminology) the "Post-processor Vocabulary Word Assistant."  Similar to the Geometric Definition Assistant it will provide syntax help for post-processor words with parameters.  For example, when "COOLNT/" is typed a window will pop up and display the syntax of the coolant command and the parameters that the post-processor supports, such as "ON" and "OFF".  As another example typing "CYCLE/" will display the syntax of the various cycle commands (such as drill, tap, etc.) and their parameters.


Jan 19, 2018

More screen shots of some of the editor features:

APT Studio File options

APT Studio Edit options

APT Studio Geometric Definition Assistant
This last image shows the Geometric Definition Assistant.  It pops up whenever a geometric definition is typed and is followed by a forward slash.  In this image "circle/" was typed and the user can select one of the eleven possible circle definitions.  Click the up and down arrows or use the up and down arrow keys on the keyboard to iterate through the possible definitions.  Pressing the TAB key inserts text which is a commented template for that definition.


Jan 17, 2018

APT Studio is an integrated development environment for creating, compiling, post-processing and plotting APT programs.  Some of the features are:


Here's a couple of screen shots of the integrated editor and plotter:

The APT Studio editor

The APT Studio 3D line plotter


Jan 16, 2018

Welcome to my APT home page!  Here I, and hopefully other APT fans, will discuss all things APT.  I will also talk about some of the APT related projects I have been working on the past few months.  I'm just getting started so relax and check back occasionally.  Please feel free to contact me at aptfan@frenetec.com.

But first, what is APT?  APT is an acronym for Automatically Programmed Tool, or some variant thereof.  It is a computer language for programming Numerically Controlled (NC) machine tools and other devices.  If I remember my history correctly, the project began in the 1950's as a joint effort between MIT and the Air Force to help solve the complexities of programming the newly burgeoning industry of computer controlled machine tools, otherwise known as NC machine tools.

I have been amazed by what APT can accomplish ever since my introduction to NC back in the mid 1970's.  My first career was as a machinist for Texas Instruments.  I worked in the Short Order and Non-metallic shops where I was assigned to change part stock and push the buttons on an old 2 1/2 axis Cincinnati milling machine.  If you happen to remember machines that old you will recall that the Z-axis was controlled via cams and set screws.  Also, the floor mounted controller read a punched tape that fed through the tape reader and rolled up on wheels behind a clear polycarbonate door on the front of the controller.  Eventually I was one of the group programming the shop's newer CNC tools.  I have always been grateful that TI gave me the opportunity to expand my skill set as both a machinist and APT programmer.  That's where I fell in love with programming in general and have been doing so ever since.

So why this web page dedicated to APT?  I feel that it is worth paying homage to such a great technological leap forward at a time when manufacturing industrial might and computers were being integrated, all right here in the great country of the USA.  I also fear that APT programming and programmers are being forgotten and that such valuable skills and resources will be lost with the passage of time.  CAM is the reigning king today as the industry has taken mighty technological leaps forward.  APT may be a dinosaur but it is still around, doing all sorts of amazing calculations and helping to machine amazing parts on even more amazing tools.

I wish to express my thanks to the group of individuals that ported the IBM 360 version of APT to Unix and Windows.  I obtained the freely distributable source code (a project entitled "Aptos", which is available for download at https://sourceforge.net/p/aptos/apt360/ci/master/tree) and compiled it with Microsoft's Visual Studio Express 2015.  As I recall I had to tweak a couple of headers and fixed a bug related to defining a point as a member of a pattern, but so far I've had good luck with the port.  I have not pushed the code to its limits by any means, as I've been busy with developing projects related to making it easier to use, but so far it seems to work very well.  There are a couple of known issues with it, which are are documented in the README file included with the source code, but I have not found them to be an impediment.  So thanks Aptos folks for your hard work and dedication to APT!

Up to this point I have written a post-processor targeting Fanuc controllers for mills and lathes, a synonym parser (because the APT port does not support synonyms), an editor and a 3D line plotter.  My target environment is Microsoft Windows and all coding is done in C#.

Update:  The post-processor now additionally supports Centroid M-Series mill and T-Series lathe.