PETROQUIMICA BASICA Y NUESTRO FIADO(S), REFERENTES A RESPONDER DE LOS

The in-feed when machining contours (finishing) requires specific movements to access and leave the programmed contours. We use contour with milling tool radius compensation as well as program straight line repetition with approach and exit conditions: G41/G45 G71,G72, G73, G01, G00, G23

Remark on the programmed workpart contour:

The following must be observed when programming the external contour of the workpart:

In the vicinity of the horizontal jaw holding the workpart, the contour corresponds to that of the raw part. The contour cannot be followed in this area because the jaws are in contact with the workpart; the tool must be moved up and kept clear when passing here. The clearance motion is achieved by adding the quadrant points P1, P5, P8 and P12 as auxiliary points.

The external contour of the workpart should be followed in down cut milling with the tool radius compensation, whereby the Z-motions for approaching, in-feed and leaving the workpart are inserted within the compensated contour.

Here, the following special characteristic of milling tool radius compensation with Z-in-feed must be observed: When the compensated contour is being calculated, the compensation function inserts additional motions into the compensated contour at the external corners in order to move the tool around the respective corner. In most types of controls these additional motions comprise a circular arc centered on the external corner – as is also implemented in MTS controls. In some control models, however, an external corner is created with the tool travelling past the corner tangentially by a distance greater than or equal to the milling tool radius, followed by a linear movement to the corresponding tangential approach travel to the contour element connecting to the external corner, or, in the case of corner angles equal to or greater than 90°, the tool is moved towards the intersection along this approach path.

If a permitted in-feed motion in Z-direction which does not change the compensated contour is carried out at an external corner of this type, the following question arises:

Is the in-feed motion carried out before or after the circular arc inserted by the milling tool compensation function?

As in most CNC controls, this in-feed motion is carried out before the additional motions.

If this rule is applied to our programming example task, carrying out the Z-direction in-feed before the compensation arc motion towards point P8 would lead to a collision with the vice jaws. For this reason, the auxiliary point P7 must be added to the contour to prevent the Z-in-feed at P8 causing a collision. To make the programmed coordinates easier to understand, a point P6 located symmetrically to the Y-axis is also added. The compensation is activated at point P0 and de-activated when leaving point P12 to access P13.

After the tool change, the new tool T0202, a slot-milling tool, is moved to position P0.

Using the graphical contour editor for programming (WOP), we shall describe the following contour passing through points P0 to P13. This will introduce you to the essential functions of WOP.

Please note:

Due to the workpart clamping position, care must be taken to avoid collisions between the tool and the vice jaws during approach and leaving motions.

There are several methods of creating contours with WOP, one of these is described below.

The contour description starts at point PS (top left) on the arc of radius R1 centered on P2. However, this point is not annotated on the drawing. We therefore have to divide a circle of radius R12 centered on P2 into 4 equal quadrants. In this way, the coordinates of the auxiliary point (P1) are determined as being X=42,0 und Y=54,0 and these can then be inserted into the contour description

The approach instructions for point (P1) are entered via the dialog programming function.

N0102 G00 X+048.000 Y+055.000 (P0)

N0104 G00 Z-045.000 M08

Press to call up the graphical contour editing mode. The blue cross shows the programmed actual workpart position (P1) which has not yet been accessed due to the tool compensation calculations. Press to call up the geometry input selection menu.

The first step is to enter the center (P2) of the counterclockwise arc of radius R12. Use the “Arc counterclockwise “ function (G73) to select the corresponding menu

Command: G73 <Arc counterclockwise>

Next, the absolute coordinates of the center of the arc, (P2), must be entered:

Input I + 054.000 J + 043.200

It is not necessary to calculate the radius, since this is calculated automatically on the basis of the starting coordinates.

The arc, which has no defined end point, is initially drawn as a full circle.

Now conclude the input by pressing , because the end point of the arc is not given in the drawing.

Note that tangential transitions are now also permitted after the first contour element has been input.

Command: G71 <Tangential straight line>

In the drawing, the counter-clockwise arc connects to a tangential straight line of undefined length.

Therefore an undefined straight line with a tangential transition is selected.

It is not possible to enter any other values, as there are no corresponding dimensions in the drawing.

No input is required here.

As the position of this straight line of the contour is not yet defined, only tangential transitions can be entered for the following entries.

Command: G72 <Tangential arc clockwise>

Next, the absolute coordinates of the center (P3) of the clockwise arc of radius R26 must be entered.

Input: I + 060.000

J + 000.000

B + 026.000

Now the straight line between the arcs is uniquely identified by reference to the two circles now displayed and is shown in the graphic display. The end of the second arc is not defined in the drawing, so that its coordinates cannot be entered.

Confirm and conclude your entries by pressing the key.

Command: G71 <Tangential straight line>

Here, again, a tangential connecting straight line of undefined length must be specified.

It is not possible to enter any other values, as there are no corresponding dimensions in the drawing.

No input is required here.

Command: G73 <Tangential arc counter-

clockwise >

The absolute coordinates of the end point (P5) and the center (P4) of the counterclockwise, tangentially connected arc of radius R12 are entered.

The position of the end point (P5) is calculated by dividing the corresponding circle into quadrants Input: Xe + 042.000

Ye - 043.200

Input: I + 054.000 J - 043.200

Confirm your entries by pressing the key.

Change over to the following menu by selecting function key “DIN” : G00, G01,G02, G03

Command: G00 <Linear rapid traverse> To keep the tool free of the workpart, a rapid linear

traverse to point (P6) is carried out.

Input: Ye - 048.000

Confirm your entries by pressing the key. Press to call up the next rapid traverse set.

Command: G00 <Linear rapid traverse> To prevent a collision with the jaws when approaching

(P7), we start a rapid traverse to the return position Z-30, which is above the clamping jaw.

Input: Ze - 030.000

Confirm your entries by pressing the key. Press to call up the next rapid traverse set.

Command: G00 <Linear rapid traverse> The tool is then moved across the jaw in a rapid traverse

to point (P7).

Input: Xe - 042.000

Confirm your entries by pressing the key. Press to call up the next rapid traverse set.

Command: G00 <Linear rapid traverse>

The appropriate quadrant end point is used as starting point of the counter-clockwise arc of radius R12 centered on (P9).

This point (P8) is approached by a rapid traverse. Input: Xe - 042.000

Ye - 043.200

Confirm your entries by pressing the key. Press to call up the next rapid traverse set.

Command: G01 <Linear milling traverse>

Here, the tool depth is set to Z-45 while it is still outside of the workpart.

Input: Ze - 045.000

Confirm your entries by pressing the key Press to call up the next rapid traverse set.

Command: G73 <Arc counter-clockwise>

The absolute coordinates I… J… for the center (P9) of the counter-clockwise arc of radius R12 are entered. Input: I - 054.000

J - 043.200

Confirm your entries by pressing the key.

Command: G71 <Tangential straight line>

Here, again, a tangential connecting straight line of undefined length must be specified.

Command: G72 <Tangential arc clockwise>

Next, the absolute coordinates of the center (P10) of the clockwise arc of radius R26 must be entered.

The hitherto undefined straight line joining this arc tangentially with its given orientation has now been uniquely defined.

Input: I - 060.000

J + 000.000

B + 026.000

Confirm your entries by pressing the key.

Command: G71 <Tangential straight line>

Here, again, a tangential connecting straight line of undefined length must be specified.

Command: G73 <Tangential arc

counter-clockwise >

The absolute coordinates of the end point (P12) and the center (P11) of the counterclockwise, tangentially connected arc of radius R12 are entered.

Input: Xe - 042.000

Ye + 043.200

Input: I - 054.000

J + 043.200

Confirm your entries by pressing the key.

Change over to the following menu: G00, G01,G02, G03

Command: G00 <Linear rapid traverse

Specify point (P13). Input: Ye + 048.000

Command: G00 <Linear rapid traverse>

In order to prevent a collision with the jaws, a rapid traverse to (P13) is made, i. e. to position Z-30. Input: Ze - 030.000

Confirm your entries by pressing the key.

Command: G00 <Linear rapid traverse>

The tool is then moved across the jaw in a rapid traverse to point (P0).

Input: Xe + 042.000

Confirm your entries by pressing the key.

Command: G01 <Linear milling traverse> Now the starting point (P1) is approached by a rapid

traverse.

Input: Xe + 042.000

Ye + 043.200

Command: G01 <Linear milling traverse>

Now the depth Z – 62 of the second contour-milling run is entered.

Input: Ze - 062.000

Confirm your entries by pressing the key. The contour is defined by the geometry and can be saved by pressing key .

Exit the WOP by pressing the key.

You have now been shown some of the basic functions of contour programming with the graphical user interface (WOP). The contour was described in a simple geometrical manner. At the same time, an NC program was generated in background.

The next step is to program two sub-program repetitions with the second in-feed depth. After that, the contour is completed before being processed by the CNC simulator.

Note: If the tool radius compensation is activated, the control must read in a certain number of NC records before it is able to calculate the milling tool path. This means that the programmed NC records are processed out of step. Depending on the pre-read depth setting of the controls, the delay will amount to one or more NC traverse records.

It is advisable to write this part of the NC program with WOP and then to simulate it.

An alternative would be to work without tool radius compensation when interactively writing the program and then to activate the compensation function in a second program run.

Processing the contour by repeating subprograms

Press to call up the NC editor. The straight line of our NC program generated by WOP is already

inserted. The milling straight line must be

supplemented by a repetition of the subprogram and the de-activating of tool radius compensation

Individual milling work straight lines are repeated with the aid of subprogram repetition <G23> (dialog programming). Press to change back to interactive programming and then simulate the program right up to NC record N0122

N0106 G41 X+042.000 Y+043.200 G45 A+007.000 G01 N0108 G73 I+054.000 J+043.200 O0070 N0110 G71 O0000 N0112 G72 I+060.000 J+000.000 O0070 B+026.000 O0000 N0114 G71 O0000 N0116 G73 X+042.000 Y-043.200 I+054.000 J-043.200 O0070 O0000 N0118 G00 Y-048.000 N0120 G00 Z-030.000 N0122 G00 X-042.000 N0124 G00 X-042.000 Y-043.200 N0126 G01 Z-045.000 N0128 G73 I-054.000 J-043.200 O0070 N0130 G71 O0000

N0132 G72 I-060.000 J+000.000 O0070 B+026.000 O0000 N0134 G71 O0000 N0136 G73 X-042.000 Y+043.200 I-054.000 J+043.200 O0070 O0000 N0138 G00 Y+048.000 N0140 G00 Z-030.000 N0142 G00 X+042.000 N0144 G01 X+042.000 Y+043.200 N0146 G01 Z-062.000 N0148 G23 O0108 Q0124 N0150 G01 Z-062.000 N0152 G23 O0128 Q0144 N0154 G40 G46 A+002.000 N0156 G00 Z+005.000