HEIDENHAIN ND 760 User Manual

User’s Manual

ND 760 E

Position Display Units for EDM

English (en) 1/2002

Status display:

SET = Datum setting REF = Blinking:

Traverse the reference points. On continuously: Reference points

have been traversed. D = SHIFT function 1 2 Datum 1 or 2

Inch = Display in inches SCL = Scaling factor

->II<- = Touch-off / Centerline

ND 760 E Position Display Unit (for 3 axes)

HEIDENHAIN

Keys

• Select coordinate axis

• Select axis-specific operating parameters

Trigger points 1 and 2 before reaching the erosion depth

Trigger point with respect to MIN position

Keys

Numerical input

• Select datum 1 or 2

• Page backward in the list of special functions

• Page backward in the parameter list

• Cancel entry

• Reset the operating mode

• Zero the selected axis (if activated with P80)

• Select parameter: CL plus two-digit number

• Select the special functions

- Probe for center line

- mm/inch switchover

- Parameter entry

• Page forward in the list of special functions

Add key for the erosion depth

TP3, TP4 Additional switching points, defined with respect to the top of the workpiece = 0

Trigger point for start position (HOME)

Trigger point for the erosion depth

Switchover from actual position display to MIN position display

• Change algebraic sign

• Call the most recent dialog

• In the parameter list: change the parameters

SHIFT key Use of double-function keys

• Confirm entry

• Page forward in the parameter list

This Manual describes the ND 760 E position display unit with the following software number or higher:

Part I Operating Instructions

ND 760 E for three axes 366 590-01

About this manual

This manual is divided into two parts:

Part I: Operating Instructions

 Fundamentals of positioning  ND functions

Part II: Installation and Specifications

 Description of operating parameters  Switching inputs, switching outputs

Fundamentals 6

Switch-on, Traversing the Reference Marks 12

Datum Setting 13

Working with a Scaling Factor 16

MIN Position Display in the EDM Axis 17

Programming the Trigger Points 18

Add Key 19

Description of Switching Output Functions 20

Error Messages 23

Part II Installation and Page 25 Specifications and following

Part I Operating Instructions

Fundamentals

The ND 760 E position display unit was conceived for use on electrical discharge machines (EDM).

The following functions support operation with EDMs:

 7 switching outputs for the EDM axis

Fundamentals

 Display of the MIN position, the distance-to-go, and the

total depth in the EDM axis. Because of the quick up-anddown motion of the EDM axis, HEIDENHAIN recommends displaying only the last minimum position value.

 Simple compensation of the erosion depth with the aid of an

add key.

 Simple setup function for finding the center line between

two edges.

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.

Graduation

Coordinate system

To describe the geometry of a workpiece, the Cartesian* coordinate 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.

*) Named in honor of the French mathematician and philosopher

René Descartes (1596 to 1650)

–X

Datum or origin

–Z

–Y

Fundamentals

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).

Fundamentals

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.

You can set up to 9 absolute datum points and store them in nonvolatile memory.

1225

750

320

Absolute datum

700

125

216,5

900

950

250

216,5 125

-125

-216,5

Relative datums

250

-250

-125

-216,5

150

-150

300±0,1

325

450

Absolute workpiece positions

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

Example Absolute coordinates of position

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

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 2 referenced to

position 1

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.

IX = 10 mm IY = 10 mm

Fundamentals

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 (

Fundamentals

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.

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 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 these reference marks are 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 need to move the machine axes a maximum of only 20 mm to do this.

Position encoder

Scale in Distance-coded linear encoder reference marks

Reference marks

Fundamentals

Switch-on, Traversing the Reference Marks

0 è 1

ENT...CL

ENT

Crossing over the reference marks stores the most recently defined assignment of display values to axis slide positions for datum points 1 and 2 in nonvolatile memory.

Note that if you choose not to traverse the reference marks (by clearing the dialog ENT ... CL with the CL key), this relationship will be lost if the

Switch-on, Traversing the Reference Marks

power is interrupted or when the unit is switched off.

If you wish to use multipoint axis error compensation, you must traverse the reference marks (see Multipoint axis error compensation)!

Turn on power (switch located on rear panel). REF in the status display starts blinking.

Confirm reference traverse mode. REF indicator stops blinking and stays on. Decimal points blink.

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

Datum Setting

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

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

In P70, you can select:  Two datum points: The selected datum point

is displayed via 1 or 2

 Nine datum points: The selected datum point

is displayed in the uppermost axis via d1 to d9.

You set a datum by first pressing the corresponding axis key and then entering a numerical value. To transfer the new datum, press the ENT key. The CL key can be used to clear an incorrect entry.

To call a datum you have set, proceed as follows:

You have set two datum points in P70:

Select datum 1 or 2.

You have set nine datum points in P70:

Press the datum key (d starts blinking).

ENT

Enter a datum number (1 to 9).

Datum Setting

Probing workpiece edges to find a centerline datum

The edges to be probed run parallel to the Y axis.

Follow the procedure below for all centerlines between two edges.

Datum Setting

PROBE MIDP.

1ST POS X (appears only briefly)

SPEC

FCT

ENT

Select a datum number (see page 13).

Select the special functions.

Confirm the probe centerline function. SET lights.

Select the X axis (if not already selected). The >❘❘<- status symbol starts blinking.

Touch the workpiece edge 1 with the tool.

X = 0

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