small amounts, but are using a high rate dispense valve to do the job. An auger, a vertical valve, a horizontal valve with a flow restrictor, or a smaller valve would help to improve accuracy and control.
If the timing number is below 5, you are operating in a range were it is difficult for the blender to perform well.
The LAG time parameter adds time to every dispense. This is to compensate for the time at the beginning of a dispense when the solenoid valve shifts and air pressure builds, before the valve starts to move. LAG times are always set slightly longer then the necessary minimum. If a calculated dispense time is very short, the Lag time that is added, while small, may interfere with accuracy, and cause an over dispense.
PERCENTAGE ERRORS: (DATA line 1)
When looking at errors of percentage of color or additive dispensed, look further.
1.First, look for indications of "retries". Retries are evidence of a problem that will also cause percentage errors.
When FIRST time dispense, (DATA line 3), does not equal FINAL dispense, (DATA line 1), one or more retries have occurred. This means the hopper ran out of material, or the flow rate is so erratic that the first dispense was short for no good reason. Parameters _RT and _RP determine what shortage error is necessary to force a retry.
Inconsistent loading resulting in large variations in hopper material level can cause retries.
Excessive vibration can also cause bad weight readings, which can cause unwarranted retries. If the BAILOUT line is printing occasionally, then vibration is most likely causing this. Increasing the BAILOUT parameter should fix this.
A LAG time set too high may cause retries to overshoot their mark resulting in over dispensing.
2.Second, look at ACTUAL weight dispensed (DATA line 1).
Color, for example, is a percentage of the natural. In the example above, Natural is 1908.3 grams, so color, at 4 percent of Natural, is targeted to be 76.3 grams. In fact, 77.6 was dispensed. The error is 1.3 grams, well within the expected accuracy of a 1 inch auger feeder.
The actual GRAM error of a dispense is more meaningful then the percentage error. Mechanical devices are not perfect. The most we can expect from them is to operate within a reasonable range of accuracy. This range is better defined by an error expressed in grams, rather them percentage.
Page 76