It seems like the way to do it is have a recipe something like either:
- (1 tool + X ingredients -> Y% tool + Z products). This is how it works for Angels Bio wood: 1 saw blade + 1 tree -> 6-8 wood + 90% saw blade. IMO that's balanced a bit towards over-use of iron (1 blade worn to nothing for 60-80 wood is some hard wood), but iron is cheap (we all have enough iron, right? right?), so whatever.
- (1 tool + X ingredients -> 1 damaged tool + Z products). This is like slag slurry -> mineral sludge in Angels, which needs the filters to be reconditioned, but the filter frames are infinitely reuseable. You could have the reconditioning process occasionally swallow a broken tool in addition to whatever material is consumed by the reconditioning process (e.g. coal in the coal filter example).
My problem: I want to have very expensive tools, that take a lot of ingredients, complexity and time to produce. Orders of magnitude more than what they are used to produce.
If the recipes aren't heavily skewed like (1 tool + 1000 ingredients -> 1 damaged tool + 1000 products), you might need a lot of tools in circulation between these machines and wherever the tools are fixed to keep the machines tooled up. For example for Angel's trees, you need to have a saw blade available for every single tree that comes along. That's not so bad when the blade is not damaged, as you might be able to cleverly filter insert. If the resulting tool is damaged, however, it has to head off somewhere to be fixed, so you need a new one on hand while that happens. If your fixing station is far away (maybe a train ride), you need a lot of very expensive tools in the system. Not only is this a lot of resources, but you need to oversize the tool production lines to build out the factory that uses the tools, but then the flow to keep the system "topped up" by replacing broken tools is hugely smaller.
However, skewing the recipes this way is a bit ugly as it multiplies both the input buffer size of the machine as well as the crafting time by N, and then dumps N products all at once. For any kind of "realistic" tool life (thousands of products), it makes a huge mess.
I have considered "burning" tools as special fuel, very slowly, but then there's no tool fixing mechanic. And it's a hack and is inflexible. I have no idea if Prototype/Tool can be used somehow, but in the end, unless there's some extra magic somewhere to return a damaged tool when exhausted, it's basically like burning as fuel.
Are there any other ways to balance this out a bit? What I'd ideally see is a relatively slow, but pretty consistent flow, perhaps bidirectional, of expensive tools alongside a much higher, but still consistent throughput of much cheaper products. Ideally it would not tend to produce static solid belts of tools representing wasted resources and tool manufacture capacity.