CMMs are used extensively in manufacturing, especially in the automotive, aerospace, and defense sectors. They are used to inspect machined and molded parts, such as engine blocks, pistons, cylinder heads, transmission housings and gears, sheet metal, brake cylinders, plastic moldings, headlights, and windows.

DMIS enables companies to save on costly development overhead by providing a common format for part inspection programs that works across different CMM brands. This also yields flexibility by enabling a manufacturer to use inspection equipment that is immediately available, rather than waiting for a specific machine to become free. This is why companies like Ford, Daimler-Chrysler, Volkswagon, and John Deere^* have been strong supporters of DMIS standardization.

Overview
DMIS is a strategic technology that enables a manufacturing organization to apply an inspection program across a range of inspection machines from different vendors. Depending on the machine, DMIS Part 1 may be used either as translation file format between a CAD system and the CMM's native proprietary inspection language, or as a native programming language for direct execution on the CMM.

DMIS Part 1, then, defines a structure for offline or batch mode processing of inspection operations. In other words, all of the operations that will be required to perform a part inspection are generated and sequenced into a file (or a group of related files), and that file is passed to the CMM. The CMM then reads this file, possibly translates it into its native language (if it does not execute DMIS directly), and executes the file in its entirety. During execution, the CMM writes inspection result output to another file. Once execution has completed, a reporting or analysis program can read this output file to process the inspection results.

The related DMIS Part 2 standard defines a format for online connection of inspection applications.

A Syntax Specification
DMIS Part 1 focuses on the specification of a common syntax that defines the features to be measured (holes, flat surfaces, slots, etc), the tolerances to be applied (flatness, runout, position, orientation, etc), and the measurement inspection sequence (moves, probed measurements, sensor orientation, etc). DMIS Part 1 contains support for various measurement technologies, including touch trigger, contact scanning, video, and laser scanning data probing. Part 1 also supports synchronized multiple carriage motion and measurement.

The syntax follows some basic, regular patterns:

MAJOR/MINOR,value,value,value,MINOR,value,value
-or-
X(label) = MAJOR/MINOR,value,value,value,MINOR,value,value

Labels are used as names for a broad range of elements, including features, tolerances, sensors, rotary tables, carriages, coordinate systems, devices, and more. Each such element has its own label type. Major words break down functionalities into various categories; while minor words specify a sub-category, or identify the format and meaning of parameters which follow. Expressions may be used anywhere that a value is expected.

For each major word, the Part 1 standard defines the syntax (allowable statement structure), that is, the parameters that may follow the major word. It also defines the semantics (meaning and effect of statements and parameters), that is, the acceptable range of values for the parameters and their meaning during execution.

For example, a circle feature would be described similar to the following:

F(label)=FEAT/CIRCLE,var_1,var_2,i,j,k,diam

var_1  can be INNER or OUTER
var_2  can be CART,x,y,z or POL,r,a,h
label  is the label name for the feature, which can be 1-64 characters
INNER  indicates that the inside of a feature is being measured (ie. a hole)
OUTER  indicates that the outside of a feature is being measured (ie. a boss)
x,y,z  are the cartesian coordinates of the circle center, based on the coordinate system
r,a,h  are the polar (ie. cylindrical) coordinates of the circle center, based on the coordinate system
i,j,k  are the direction vectors for the normal of the plane in which the circle lies
diam   is the diameter of the circle

Document Overview
The DMIS 5.0 standard is a soft-cover, soft-bound document consisting of 679 pages. The document comprises the following sections:

1. Scope
2. Conformance
3. Normative References
4. Terms and Definitions
5. Language Reference
6. Statement Reference
Appendices
A. DMIS Example Code Segments
B. Descriptive Figures
C. Standard Characterization File
D. Characterization File Extensions
E. Scanning Reference
F. Tolerance Application

Language Reference
Section 5 contains the Language Reference. This provides broad, general requirements for use of the DMIS language. It defines syntactic requirements, such as the allowable characters in a variable name or label, describes establishment of a part coordinate system, explains feature measurement point data access, discusses multiple carriage machines and sensor selection, and provides much more detail about the proper structure and content of a DMIS program.

5. Language reference
  5.1 Syntax and Structure
       DMIS command and definition statements
       Programming comments
       Operator input
       Data output
       Program structure
       File structure
       Programming considerations
  5.2 Execution and control
       Declaration statements
       Definition statements
       Program statement sequences
       High Level Language (HLL)
  5.3 Mathematics
       Operators
       Features
       Tolerances
       Datums
       Coordinate systems
       Measurement uncertainty
  5.4 Equipment control
       Machine parameters
       Rotary tables
       Sensors and sensor-related
       Carriages
       Motion control
       Measurement control
  5.5 Characterization file

DMIS 4.0 major words include the following:

ACLRAT	VA()=ALGDEF	varname=ASSIGN
BADTST	BOUND	CALIB
CALL	CASE	CI()=CLMPID
CS()=CLMPSN	CLOSE	SG()=CMPNTGRP
CONST	CR()=CRGDEF	CRMODE
CROSCL	CRSLCT	CC()=CUTCOM
CZ()=CZONE	CZSLCT	DATDEF
D()/DA()=DATSET	DECL	DECPL
DELETE	DID()=DEVICE	DFTCAS
DISPLY	DMEHW	DI()=DMEID
DMESW	DS()=DMESWI	DV()=DMESWV
DMIS	DMISMD	DMISMN
DO	ELSE	ENDAT
ENDCAS	ENDDO	ENDFIL
ENDGO	ENDIF	ENDMAC
ENDMES	ENDSEL	ENDXTN
EQUATE	ERROR	EVAL
SX()=EXTENS	EXTFIL	F()/FA()=FEAT
FEDRAT	VF()=FILDEF	FILNAM
FINPOS	FI()=FIXTID	FS()=FIXTSN
FLY	FROM	GECOMP
GEOALG	G()=GEOM	GOHOME
GOTARG	GOTO	GSA()=GROUP
IF	INCLUD	ITERAT
JUMPTO	VL()=LITDEF	D()/DA()=LOCATE
LI()=LOTID	M()=MACRO	MA()=MATDEF
MEAS	MD()=MFGDEV	MODE
varname=OBTAIN	OPEN	OP()=OPERID
OUTPUT	PN()=PARTID	PR()=PARTRV
PS()=PARTSN	PL()=PLANID	POP
PRCOMP	PV()=PREVOP	PC()=PROCID
varname=PROMPT	PSTHRU	PTBUFF
PTMEAS	PUSH	Q()=QISDEF
RAPID	READ	RECALL
RM()=REFMNT	R()=REPORT	RESUME
RMEAS	ROTAB	D()/DA()=ROTATE
RT()=ROTDEF	ROTSET	SAVE
SCAN	SCNMOD	SCNPLN
SCNSET	SELECT	SS()=SENSOR
S()/SA()=SNSDEF	SNSET	SGS()=SNSGRP
SNSLCT	SNSMNT	TECOMP
TEXT	TH()=THLDEF	T()/TA()=TOL
TL()=TOOLDF	D()/DA()=TRANS	UNITS
varname=VALUE	V()=VFORM	VW()=WINDEF
WKPLAN	SW()=WRIST	WRITE
XTERN	XTRACT

Minor Words
Several of the major words, most notably CONST, FEAT, SENS, and TOL, each contain numerous pages enumerating the supported minor words (statement variations) for each statement type.

For instance, the FEAT major word section of DMIS 4.0 describes the following feature types:

ARC	GEOM	PLANE
CIRCLE	GCURVE	POINT
CONE	GSURF	RCTNGL
CPARLN	LINE	SPHERE
CYLNDR	OBJECT	TORUS
EDGEPT	PARPLN
ELLIPS	PATERN

Sample Pages
Several sample pages from Section 5 and Section 6 of the DMIS 5.0 ANSI standards document may be viewed using the free Adobe Acrobat Reader. (Used by permission.)

Related Information
See also the DMIS Part 2 standard.

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