Bosch 6000 User's Guide download pdf (Page 174)

Chapter 5. Custom Profiling

159

mechanical configurations will tolerate such abrupt changes, and the controller will accept

such a program; however, it is generally good practice to design paths with smooth direction

changes. This may be done by designing a path using arcs to round corners.

X Vel

Time

X Vel

Time

Possible

Stall

Figure A (Segment Example) Figure B (Stall Example)

Using the C Axis

(4-axis products only)

The C axis is an axis whose position changes in a manner linearly related to the direction of

travel in X and Y (i.e., the path direction). The C axis would be used in applications that

require a work piece or tool to remain tangent or perpendicular to the path direction. Examples

would be: a knife always pointing into the cut, or a welding head staying normal to the weld.

The magnitude of the C axis resolution refers to the number of steps of C axis position

change for 360 degrees of direction change in the X-Y plane. This number may be the same

as, or different from the C axis motor resolution, allowing any gearing that is convenient for

the mechanics. If the C axis load is to be driven directly, the C axis resolution should be the

same as the C axis motor resolution. This will cause the C axis motor and load to rotate once

when a circle is drawn by the X and Y axes. If the C axis load is to be geared (e.g., 5:1), the

C axis resolution specifications should be five times the C axis motor resolution. This will

cause the actual motor to rotate five times and the load to rotate once when a circle is drawn by

the X and Y axes.

The number may be positive or negative, allowing greater flexibility in C axis motor

mounting orientation. If the sign is positive, the C axis will rotate in the positive direction

when CCW arcs are drawn. If the sign is negative, the C axis will rotate in the negative

direction when counter-clockwise arcs are drawn.

The C axis is assumed to be in the proper position when path execution begins. It will

change position only as the direction of travel changes. The program must position the C

axis before the path is executed. This can be done with the HOM command or a GO to a

position.

Because the C axis position changes linearly with the direction of X-Y travel, it is important

to avoid path definitions which result in an abrupt direction change between segments. The

segment boundary considerations for the C axis are similar to those for the X and Y axes,

except that abrupt direction changes will result in abrupt C axis position changes. The X and

Y axis would only suffer large accelerations, which may cause a stall in steppers or exceed the

maximum position error (SMPER value) in servos. The C axis will suffer impossibly high

velocity commands, causing stall and position loss in steppers or position error in servos.

Using the P Axis

(4-axis products only)

The P axis is an axis whose position and velocity are proportional to the position and velocity

traveled by the load along the path generated by X and Y. It can be used as the Z axis in

helical interpolation, or to control other motion which must be proportional to the X-Y path

motion. The proportionality of the P axis is specified as a ratio, with a range of ±0.001 to

±1000. The sign of the ratio determines which direction the motor will turn. The magnitude

specifies the ratio of P axis travel to path travel, regardless of path direction or segment type.

This ratio is essentially a position ratio, but because the ratio is maintained at every instant it

also becomes a velocity ratio.

The P axis only responds to the distance traveled along the path, and is not affected by

direction changes in the path. The only caution that must be observed comes when a high

ratio is specified. In this case, path velocity and acceleration are amplified, which may result

in impossible velocities or stalls (steppers) or excessive position error (servos).

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Bosch 6000 User's Guide Page 174

Comments to this Manuals

Bosch 6000 User's Guide Page 174

Comments to this Manuals

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