NC Drill File Codes - APCircuits

NC Drill File Format

Control Codes
Document Number: ANSI/IPC-NC-349
PCB/CAD systems are usually set to ANSI/ICP-NC-349 (Excellon defaults).

Computer Numerical Control for Drillers and Routers

%	Rewind and Stop
X#Y#	Move and Drill
T#	Tool Selection
M30	End of Program
M00	End of Program
M25	Beginning of Pattern
M31	Beginning of Pattern
M01	End of Pattern
M02 X#Y#	Repeat Pattern
R#M02X#Y#	Multiple Repeat Pattern
M02 X#Y# M70	Swap Axis
M02 X#Y# M80	Mirror Image X Axis
M02 X#Y# M90	Mirror Image Y Axis
M08	End of Step and Repeat
N#	Block Sequence Number
/	Block Delete
R#X#Y#	Repeat Hole
G05, G81	Select Drill Mode
G04 X#	Variable Dwell (ignored)
G90	Absolute Mode
G91	Incremental Mode
G92 X#Y#	Set Zero
G93 X#Y#	Set Zero
M48	Program Header to first "%"
M47	Operator Message CRT Display
M71	Metric Mode
M72	English-Imperial Mode
Snn	Spindle Speed (RPM)
Fnn	Z axis feed speed (IPM)

Maximum drill block length is 100 characters, English (inch) or Metric (mm), Leading or Trailing Zeros, Incremental or Absolute modes are supported. Maximum m.n format supported is 2.4

NC Drilling File and Gerber file Similarities

An NC drilling file is very similar in nature to that of the Gerber file. The main differences are the absence of control codes in the NC drill file. The drill assumes that each X/Y pair is a hole location and the drill will plunge at each X/Y coordinate that is listed in the file. The NC drill file contains delineators that identify groups of X/Y coordinates to be drilled with a specific Tool Size.

The delineator is "T"+#, the ‘#’ is cross referenced to a customer supplied list. There is no sorting necessary or specific sequence required when identifying the T code.

T1 for instance could be a .2550" while T2 could be a .0200" etc. There is provision for header comments in the drill file as well.

Many CAD systems such as Tango, Orcad, and Protel for Windows place the T code sizes in the header of the NC drill file just before the Start of Data marker "%".