Question:
Under what circumstances does the Cam template give the error message XYPosChangeLimit?
Answer:
The error message XYPosChangeLimit is generated by the Cam template under the following circumstances:
Max. number of cam points /task cycle is exceeded:
The cam function block L_CamData (interval time of the cam template: 2 ms) can skip max. 20 cam points per task cycle. If more than 20 cam base points are skipped due to a too high master speed, a jump in the x-position setpoint or due to an unexpected setting of the s-offset value, XYPosChangeLimit-error message will be displayed.
Concrete remedies:
- Reduction of the base points in the CamDesigner
- If the absolute data model is used in the cam data: Do not arrange the points in an optimum way for partial reduction of the closely followed points.
The y-position cannot be displayed by the phase difference signal:
The y-position assigned to the x-position is not processes as 32-Bit-value in the signal flow of the cam template. The cam function block displays a phase difference signal (_v-signal), whose integration enables the y-position to be presented. If the y-position changes within one task cycle (2 ms) by more than +/- 65534 [incr.] (=32767 [incr./ms]), this y-position jump cannot be displayed within the 2 ms cycle by the phase difference signal, but it requires several program cycles. This results in an inconsistency between x- and y-position, which is shown by the XYPosChangeLimit-error message.
In practice, phase difference signals of the described dimension cannot be handled by drives (16384 [incr./ms] = 15000 [rpm]) and the drive system cannot trigger them to move.
Concrete remedy:
- Reduction of the cam's rate of rise for the selected cam in the CamDesigner
y-stretching-/-compression factor >100% leads to an overspeed:
In case of stretching / compression it is not the y-position which is directly stretched, but the corresponding phase difference signal - as described before. It is represented in the value range of -32768 ... +32767 [incr./ms] as a 16-Bit-value. If the given cam is evaluated with a y-stretching / compression factor >100 %, the 16-Bit-display area can be exceeded when the phase difference signal is evaluated. This results in an inconsistence between x- and stretched --position shown by the XYPosChangeLimit-error message.
In practice, phase difference signals of the described dimension cannot be handled by drives (16384 [incr./ms] = 15000 [rpm]) and the drive system cannot trigger them to move.
Concrete remedies:
- Reduction of the y-stretching / compression factor (template-variable g_nYStretchCompress_a)
- Reduction of the cam's rate of rise for the selected cam in the CamDesigner
Moreover, in all mentioned cases the following remedies can be used, which are also able to eliminate the cause for the XYPosChangeLimit-error message.
General remedies:
- Reduction of the master speed
- Activation of the x-offset-adjustment device via a profile generator (g_bRfgXOffsetEnable = TRUE)
- In case of external master speed selection (g_bVertShaftExtEnable = TRUE, g_bTypeOfVertShaftExt = TRUE): Reduction of the resulting x-stretching-/-compression factor (g_nXStretchCompressNum_a / g_nXStretchCompressDen_a
- In case of x-touch-probe-correction: Reduction of the correction influence via g_nXTpMakeUpLeeway_v resp. connecting the ramp generator via g_bRfgXTpEnable = TRUE and parameter setting via C3649 and C3650)
