When there is a high level of variant involved with your processes it can be really hard to stay in control of quantity. If you're experiencing this, the best thing you can do is install a digitised weight control system into your factory. When I was having a similar problem, I implemented a weight control solution from Hartford control
Essentially, the system combines average quantity law and Statistical Process Control to ensure optimum control and effective line management. Since using this software I've noticed an improvement in wastage, increased control and increased compliance. If you're having an issue with wastage then something like this can help you to keep better control, as it will give you automatic adjustment advice. Getting this type of software installed may be an investment, but I think you'll notice a marked improvement in your quantity control.