Let me provide some context behind the decision to introduce step consumption capability in Process Manufacturing  Dynamics AX2012.
Discrete manufacturing almost always involves linear consumption of ingredients - four tires are required to put together a car. Whereas in process manufactured products consumption can be linear and it can also be non-linear. As the home brewers know 5 Kg of malt gives 12 litres of beer and 10 Kg of malt gives 24 litres of beer but the bitterness is more in smaller lot, so if you want to keep same bitterness in bigger lots you need to add some extra malt, how much extra is non-linear - based on experience. Another industrial example will be use of carbon as a catalyst in plasticizer manufacturing. You can use 1 Kg of carbon to make up to 5 kiloliters of phthalates. Then you need 2 Kg of carbon up to 8 Kilo litres of phthalate (of course, it’s a different matter that phthalates are banned in many regions for some products, so you shouldn’t really be making them).

Many such reactions have non-linear consumption across different industries but sometimes it's not essential to capture them in an ERP and at other times it is possible but cost intensive to capture and maintain the formulae. This is where step consumption comes useful. Setting up Bills of material is fairly straightforward when compared to setting up formulae. It isn't because  formulae setup in AX is not user friendly, it's just because the number of parameters required to setup a formulae are many more. In order to setup formulae with non-linear consumption in previous versions, the only possibility will be to setup many different formulae where every detail is same except the quantity of the ingredient that is consumed non-linearly. Since this would be extremely cumbersome in itself and furthermore because process manufacturers needed multiple set of versions - master formula, production formula,  distributed formula, batch card formula and so on, we decided to introduce the concept of step consumption into AX2012.

So for the non-linear consumption of malt, you will create two lines in the formula for malt product. On one line you will setup linear consumption, 5 kg for 12 litre, 10 kg for 24 litres and so on. On the second line you can change the formula to "STEP" on the setup tab. This will make the step consumption grid available. Here you can specify that an extra 0.1 kg of malt is needed when finished beer quantity is between 12 and 24 litres and an extra 0.15 kg of malt is needed when finished beer quantity is more than 24 litres and so on. So, this gives you flexibility to setup non-linear consumption in the same formula.

Formula lines

Fomrula lines setup tab

During production estimation system will look at the finished quantity of beer you want to manufacture and will automatically calculate the correct quantity of malt needed. In case of carbon example above, it can be achieved by using just one line on the formula lines for carbon where you can setup step consumption of carbon of 1 kg up to 5 KL and then of 2 kg between 5 - 8 KL and so on.

Hopefully this will be useful for your scenarios. In case you have suggestions for improvement please email me.