HEIDENHAIN ND 920 User Manual

User´s Manual

Position Display Units for Milling Machines

11/ 95

Position display (ND 920: only two axes)

REF

R- inch

PGM

HEIDENHAIN

Status

Keyboard (ND 920 has no Z key)

display:

inch

PGM REF R+ R–

Inch display is active

Distance-to-go display is active

Program input is active Reference marks have been crossed Radius compensation R+ is active

Radius compensation R– is active

Datum point number

Message field

Distance-to-go display (traversing to zero)

Input field

For incremental dimensions (only with distance-to-go and program input)

Tool compensation

SPEC

FCT

SPEC

PGM

FCT

GOTO

HOLD

MOD

ENT

POS

PGM

GOTO

Call radius compensation for the current tool Special functions (probing functions,

hole patterns, rectangular pocket) Program input

Select datum

Go directly to parameters or program steps Page in program or parameter list/

select function

•••

Select coordinate axis

Numerical input Reset all axes to zero,

functions for Program Input Decimal point

Change sign or parameter

HOLD

POS

MOD

ENT

Clear entry/cancel operating mode

Hold current position/output measured values Select/deselect parameter list,

activate RS-232-C Confirm entry

This manual is for ND display units with the

following software numbers or higher:

ND 920 (2 axes) 246 112 05

ND 960 (3 axes) 246 112 05

NDP 960 (3 axes, panel mount) 246 112 05

About this manual

This manual is divided into two parts:

Part I: Operating Instructions

• Fundamentals of positioning

• ND functions

Part II: Installation and Specifications

• Mounting the display unit on the machine

• Description of operating parameters

• Switching inputs, switching outputs

Part I: Operating Instructions

Fundamentals 4 Switch-On, Crossing Over the Reference Marks 9 Switching Between Operating Modes 9 Datum Setting 10

Datum setting with the tool 11 Datum setting with the KT Edge Finder 13 Resetting all axes to zero 18

Holding Positions 19 Tool Compensation 21 Moving the Axes with Distance-To-Go 22 Bolt Hole Circles and Bolt Circle Segments 24 Linear Hole Patterns 27 Rectangular Pocket 30 Scaling Factors 33 Program Input 34 Program Output over RS-232-C Interface 37 Error Messages 38

Part I: Operating Instructions

Part II: Installation and Specifications 39

Fundamentals

You can skip this chapter if you are already familiar with coordinate systems, incremental and absolute dimensions, nominal positions, actual positions and distance-to-go.

Coordinate system

To describe the geometry of a workpiece, the

Fundamentals

system is used. The Cartesian coordinate system consists of three mutually perpendicular axes X, Y and Z. The point of intersection of these axes is called the datum or origin of the coordinate system.

Think of the axes as scales with divisions (usually in millimeters) which allow us to fix points in space referenced to the datum.

To determine positions on a workpiece, the coordinate system is “laid” onto the workpiece.

The machine axes are parallel to the axes of the coordinate system. The Z axis is normally the tool axis.

Cartesian*

coordinate

–X

Graduation

Datum or origin

–Z

–Y

*) Named in honor of the French mathematician and philosopher

René Descartes (1596 to 1650)

Datum setting

The workpiece drawing is used as the basis for machining the workpiece. To enable the dimensions in the drawing to be converted into traverse distances of machine axes X, Y and Z, each drawing dimension requires a datum or reference point on the workpiece (since a position can only be defined in relationship to another position).

The workpiece drawing always indicates one absolute datum (the datum for absolute dimensions). However, it may contain additional relative datums.

In the context of a numerical position display unit,

datum setting

means bringing the workpiece and the tool into a defined position in relation to each other and then setting the axis displays to the value which corresponds to that position. This establishes a fixed relationship between the actual positions of the axes and the displayed positions.

1225

750

320

150 0

-150

300±0,1

-250

-125

-216,5

250

125

216,5

250

216,5 125

-125

-216,5

Relative datums

-250

Fundamentals

You can set up to 99 absolute datum points and store them in nonvolatile memory.

Absolute datum

325

450

700

900

950

Absolute workpiece positions

Each position on the workpiece is uniquely defined by its absolute coordinates.

Example Absolute coordinates of position

Fundamentals

If you are working according to a workpiece drawing with absolute dimensions, you are moving the tool to the coordinates.

Relative workpiece positions

A position can also be defined relative to the previous nominal position. The datum for the dimension is then located at the previous nominal position. Such coordinates are termed incremental coordinates or chain dimensions. Incremental coordinates are indicated by a preceding

I. Example Relative coordinate of position referenced to

If you are working according to a workpiece drawing with incremental dimensions, you are moving the tool by the dimensions.

Sign for incremental dimensioning

A relative dimension has a positive sign when the axis is moved in the positive direction, and a negative sign when it is moved in the negative

direction.

X = 10 mm Y = 5 mm Z = 0 mm

position :

IX = 10 mm IY = 10 mm

Nominal position, actual position and distance-to-go The position to which the tool is to move is called the nominal position

). The position at which the tool is actually located at any given

( moment is called the actual position (I). The distance from the nominal position to the actual position is called the distance-to-go (

Sign for distance-to-go

When you are using the distance-to-go display, the nominal position becomes the relative datum (display value 0). The distance-to-go is therefore negative when you move in the positive axis direction, and positive when you move in the negative axis direction.

Fundamentals

Position encoders

The position encoders on the machine convert the movements of the machine axes into electrical signals. The ND display unit evaluates these signals, determines the actual position of the machine axes and displays the position as a numerical value.

Workpiece

If the power is interrupted, the relationship between the machine axis positions and the calculated actual positions is lost. The reference

Fundamentals

marks on the position encoders and the REF reference mark evaluation feature enable the ND to quickly re-establish this relationship again when the power is restored.

Reference marks

The scales of the position encoders contain one or more reference marks. When a reference mark is crossed over, a signal is generated which identifies that position as a reference point (scale datum = machine datum).

When this reference mark is crossed over, the ND's reference mark evaluation feature (REF) restores the relationship between axis slide positions and display values which you last defined by setting the datum. If the linear encoders have distance-coded reference marks, you only need to move the machine axes a maximum of 20 mm to do this.

Position encoder

Scale in Distance-coded linear encoder reference marks

Reference mark

Switch-On, Crossing Over the Reference Marks

Switching Between Operating Modes

➨➨

➨ 1

➨➨

REF ? ENT ...CL

ENT

PASS OVER REF.

Crossing over the reference marks stores the last relationship between axis slide positions and display values for all datum points (99 per axis) in nonvolatile memory.

Note that if you choose clearing the dialog REF ? with the CL key), this relationship will be lost if the power is interrupted or when the unit is switched off.

Turn on power (switch located on rear panel). REF and decimal points in status display blink.

Press ENT before crossing reference marks

Cross over the reference marks in all axes (in any sequence). Each axis display becomes active when its reference mark is crossed over.

not

to cross over the reference marks (by

You can switch between the operating modes Distance-To-Go, Special Functions, Program Input, Set Tool Datum, Hold Position and Parameter Input at any time simply by pressing another operating mode key.

Switch-On, Crossing Over the Reference Marks

Datum Setting

Datum setting with the tool

Only after crossing over the reference marks can you set new datums or activate existing ones.

Datum Setting

There are several ways to set datums: Touch the workpiece with the tool and then set the desired datum

(see example). You can also touch two edges and set the centerline between them as a datum, or touch four points on a circle and set the circle center as the datum. The tool data of the tool used for this are automatically considered (see “Tool Compensation”).

Probe the workpiece with the edge finder and then set the desired datum. You can also probe two edges and set the centerline between them as a datum (see examples), or probe four points on a circle and set the circle center as the datum. The display unit will automatically consider the stylus radius and length if their values are entered in parameters P25 and P26 (see “Operating Parameters”).

After you have set a datum it can be activated as follows:

DATUM NUMBER =

If you want to save the datum points in nonvolatile memory, you must first cross over the reference marks.

Select datum setting.

ENT

Enter the number of the datum point, for example 12.

Example

Working plane X / Y Tool axis Z Tool radius R = 5 mm Axis sequence for X – Y – Z

datum setting

R = 5 mm

Select the datum point number.

Touch workpiece edge .

SPEC

FCT

Select special functions.

Select PROBING FUNCTION.

PROBING FUNCTION ?

ENT

Confirm selection.

Select PROBE EDGE.

PROBE EDGE ?

ENT

Confirm selection.

PROBE X

Select the X axis (if not already selected).

•

ENT

The X position is captured.

POS. MEASURED X =

ENT

Enter the position value for the datum. Tool radius compensation is automatically accounted for.

PROBE X

Select the X axis.

Touch workpiece edge .

•

Datum Setting

ENT

POS. MEASURED Y =

ENT

Datum Setting

PROBE Y

The Y position is captured.

Enter the position value for the datum in the Y axis. Tool radius compensation is automatically considered.

Select the Z axis.

Touch the workpiece with the tool.

ENT

The Z position is captured.

POS. MEASURED Z =

ENT

SPEC

FCT

Enter the position value for the datum in the Z axis.

When you have set the datum, leave the probing function.

Datum setting with the KT edge finder

Your display unit offers the following probing functions:

PROBE EDGE Set workpiece edge as datum

PROBE MIDPOINT Set centerline between two workpiece edges

as datum

PROBE CIRCLE Set a circle center as datum

The probing functions can be accessed in operating mode SPEC FCT.

The HEIDENHAIN KT 120 edge finder only functions with electrically conductive workpieces.

Before you can use the edge finder you must enter the stylus diameter in parameter P25 and the stylus length in P26 (see “Operating Parameters”).

The stylus dimensions you enter are considered during all probing operations.

PROBE EDGE and PROBE MIDPOINT are described on the following pages.

The sequence for PROBE CIRCLE is similar; however, you must probe four points before the circle center can be calculated. The circle center can then be set as the new datum.

Datum Setting

Probing a workpiece edge and setting it as a datum

The probed edge is parallel to the Y axis. For all coordinates of a datum you can probe workpiece edges and surfaces as described below and set them as datums.

Datum Setting

PROBING FUNCTION ?

PROBE EDGE ?

SPEC

FCT

ENT

•

Select the datum number.

Select special functions.

Select PROBING FUNCTION.

Confirm selection.

Select PROBE EDGE.

Confirm selection PROBE EDGE.

PROBE X

POS.MEASURED X =

ENT

Select the X axis (if not already selected).

Move the edge finder towards the workpiece edge until the LED in the edge finder lights up. The position of the edge is now displayed.

Retract the edge finder from the workpiece.

Set the position value (for example 52) to this edge.

Datum Setting

SPEC

FCT

Leave the probing functions, or select a new axis.

Probing workpiece edges and setting the centerline as a datum

The probed edges should be parallel to the Y axis.

You can follow these instructions for any centerlines.

Datum Setting

PROBING FUNCTION ?

PROBE MIDPOINT ?

SPEC

FCT

ENT

•

Select the datum number.

Select special functions.

Select PROBING FUNCTION.

Confirm selection.

Select PROBE MIDPOINT.

Confirm selection.

1. PROBE POS. X

2. PROBE POS. X

POS.MEASURED X =

SPEC

FCT

ENT

2 6

Select X axis (if not already selected).

Move the edge finder against workpiece edge until the LED in the edge finder lights up. The position of the edge is now displayed.

Enter the position value for the centerline (for example 26).

Leave the probing functions, or select a new axis.

Datum Setting

Resetting all axes to zero

To reset all axes to zero, simply press the key shown below. Note that when you do this, the last actual position becomes the relative datum and is not stored (incremental positioning). The status display then shows “– –” instead of the datum number. Any datum points already set remain in memory. You can activate these by entering the corresponding datum point number.

Datum Setting

This key resets all axis position displays to zero.

Holding Positions

Your display unit has the capability to hold or “freeze” position values. The tool can be repositioned without affecting the display. You can then assign a new value to the stored position.

Example

Drill in the Z axis, measure the depth and set the datum to this depth.

Move to the desired position and drill in Z direction .

Holding Positions

HOLD

POS

KEEP Z POS. ?

ENT

•

Hold the position.

Store (hold) the position of the Z axis.

The HOLD POS key may have a different function. See the section "Measured value output with the HOLD POS key".

SET POS. Z =

ENT

Holding Positions

KEEP Z POS. ?

HOLD

POS

Retract tool to position and measure position Z

Set datum ZT (for example 20).

Leave HOLD POS or store position of another axis.

Tool Compensation

You can enter the tool axis, the tool length and the tool diameter for the current tool.

Press the tool compensation key.

TOOL DIAMETER =

2 0

TOOL LENGTH =

TOOL AXIS =

Enter the tool diameter (for example 20 mm), and confirm with the arrow down key.

Enter the tool length (for example 200 mm),

and confirm with the arrow down key.

Enter the tool axis and end the function.

Tool Compensation

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HEIDENHAIN ND 920 User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual