GB2043300A - Engraving apparatus and method - Google Patents

Abstract

A workpiece is engraved by a tool caused to move stepwise in directions transverse to a workpiece. Signals controlling the tool are derived from a computer or an intelligent computer peripheral such as a keyboard/video unit including an interactive programme. Preferably the signals are pulses driving stepping motors. <IMAGE>

Description

SPECIFICATION Engraving apparatus and method This invention relates to engraving.

It is known to engrave a workpiece with a pantographic form of engraving apparatus in which a rotating engraving spindle is caused to move, via a pantograph linkage, in accordance with a stylus moving over a reference symbol or shape or other copy.

It is an object of the present invention to provide engraving apparatus which does not require mechanical reference copy and hence provides faster and more versatile engraving resulting in greater output at lower cost.

In accordance with the present invention engraving apparatus has engraving means which can engrave a workpiece under the control of signals derived from a computer or an intelligent computer peripheral.

A preferred peripheral is a keyboard/video unit.

Alternatively a magnetic tape could be used to record keyboard information and replay it to a control unit for the engraving apparatus. Punched tape or card, magnetic drum or disc or central processorforfeeding in instructions could also be used.

Preferably the engraving means is an engraving spindle movable along three co-ordinates under the control of stepping motors so that the outlines of the engraved symbols are formed by steps not immediately apparent in the finished engraving without magnification. The precision achieved by the stepping action gives a high quality to the finished engraving which is not marred by the nearly invisible steps.

The versatility of engraving is enhanced by the fact that the parameters of any selected symbol (such as height, width, slope, and style) can be selected at a keyboard. Thus the font and size can be changed and can differ as between one symbol and the next if so required or between one workpiece and the next.

One form of the invention will now be described with reference to the accompanying drawing in which: Figure lisa layout diagram of one form of engraving apparatus according to the invention; Figure 2 is a typical engraved symbol indicating controllable parameters; and Figure 3 is an enlarged view of the edge of a part of the engraved symbol of Figure 2.

In Figure 1 a worktable 10 is shown having above it an engraving spindle 11 with a bearing box 12, the spindle being driven via constant length belt and motor (not shown) on an arm X.

The box 12 is movable along the arm X (to give an X-axis movement) under the control of a stepping motor SMX. The arm X is carried on a counterbalancing spring (not shown) in a block 13 which is movable along a base Y (to give a Y-axis movement) under the control of a stepping motor SMY, and the arm Xis movable in the direction Z between arms 14 of the block 13 under the control of a stepping motor SMZ.

The motors SMX, SMY and SMZ receive control signals along respective lines LX, LY and LZ from a control unit 15. The signals are in the form of pulses each of which causes the appropriate stepping motor to create a linear movement of the spindle 11 of, typically, 0.01 mm for each pulse.

The unit 15 is arranged to accept instructions from an interactive video unit and keyboard 16/17 along a line 18. These instructions are converted by unit 15 into pulse trains, appropriately timed and phased, along lines LX, LY and LZ to cause engraving operations to be carried out.

To use the apparatus above described the following operations are performed: 1. A workpiece is placed on the table.

2. An operator at the keyboard defines the parameters of a string of symbols (or a single symbol or other copy) to be engraved. This takes place as responses to an interactive computer programme.

3. The operator causes the string of defined symbols to appear on the screen for checking.

4. If required the operator can now define the parameters of a second string of symbols.

5. With responses to the interactive programme completed and checked, the operator then instructs execution of engraving.

6. Whilst engraving is taking place the operator may set up instructions for engraving a further workpiece. In this way a saving in operational time is achieved.

In Figure 2 the engraved letter "J" is shown. This has a width "W", a height "H" and a slope represented by the angle "S". The thickness "T" of the letter is determined by the diameter of the spindle 11. The depth of engraving can be controlled at the motor SMZ.

In Figure 3, a magnification of the part of the letter "J" is shown. It is seen that the outline of the letter is formed as arcs 32 arising from movement of the centre-line of spindle 11 along a stepped path having a "tread" 30 and a "riser" 31. Typically each "tread" may be .010 mm (or one step from the stepping motor SMX) and each "riser" may be .060 mm (or six steps from the stepping motor SMY). By adjusting the "tread" to "riser" ratio the angle "S" may be adjusted. Of course, as the curved foot of the letter "J" is reached then the "tread" to "riser" ratio must change to introduce the curved shape.

Apparatus according to the invention could be arranged to cut out symbols from a workpiece as well as engrave them by arranging for a spindle to cut round the outline of letters and through the workpiece.

Symbols may be cut which are wider than the engraving tool by arranging for multiple passes of the engraving tool with displacement between passes.

When compared with the known pantographic engraving apparatus, apparatus according to the invention provides many advantages, for example: 1) There is no call to manually set up a symbol to be engraved for following by the pantograph stylus.

2) No inaccuracy can arise from unsteady and erroneous manual operation of a stylus and hence a low level of skill is required.

3) Faster engraving is obtained.

4) Parameters are available instantaneously and hence no stocks of copy are required.

5) Overlapping operations (such as setting up engraving instructions for a subsequent engraving operation whilst a first engraving operation is taking place) give greater output.

The stepping motors SMX, SMY, SMZ could be replaced wholly or individually by DC Servo motors.

Claims (9)

1. Engraving apparatus having engraving means arranged to engrave a workpiece under the control of signals derived from a computer or an intelligent computer peripheral.

2. Apparatus as claimed in claim 1 in which said peripheral is a keyboard/video unit including an interactive programme.

3. Apparatus as claimed in claim 1 or 2 including a control unit sending pulses to stepping motors controlling the movement of said engraving means.

4. Apparatus as claimed in claim 3 in which said stepping motors are arranged to move the engraving means along X, Y and Z co-ordinates.

5. Apparatus as claimed in any preceding claim including facilities to define copy parameters of height, slope, width and style.

6. Engraving apparatus substantially as hereinbefore described with reference to Figure 1 of the drawings.

7. A method of engraving predetermined copy on a workpiece comprising the steps of: securing said workpiece, causing an engraving tool to enter the workpiece at a selected position; .. moving said tool transversely in steps from the point of entry into the workpiece to effect engraving under the control of pulse signals derived from a computer or an intelligentcomputertermin- al; and ... causing thewengraving tool to leave said workpiece.

8. A method of engraving according to claim 7 substantially as hereinbefore described with reference to the drawings.

9. An engraved workpiece made in accordance with the method of claim 7 or claim 8 or made with apparatus as claimed in any one of claims 1 to 6.