Relationship Database design question

Ok, so this might be a little confusing to explain but I will try my best.

We manufacture a product which takes in 4 categories of raw materials. Say Raw Material A, Raw Material B, Raw Material C, Raw Material D. Each category of raw material has different variants available such as 100, 101, 102…and so on. Most products will use multiple variants of multiple categories of raw materials. So a typical product will be made such as:

Raw Material A 25% - {subdivision of this – > } ( 101 - 20%, 102 - 80%)
Raw Material B 50% - {subdivision of this – > } ( 101 - 50%, 102 - 50%)
Raw Material C 25% - {subdivision of this – > } ( 101 - 33%, 102 - 33%, 103 - 33%)

I have 4 Tables - one for each raw material category.

Now when the product is being built, I have a page which shows the ideal consumption for each variant of each category. During production, raw materials are not issued at one go. They are typically issued between 3 to 5 times.

Now I have managed to build appropriate pages and tables for everything above but I am confused about best practice aspect for one particular thing and that is where I am hoping for some input. When we issue raw material, I am storing them in Raw_Material_Issue and Raw_Material_Issue_Line_Item tables. In Raw_Material_Issue tables all I am doing is saving the product_batch_Number , date and reference Raw_material_Issue_line_item.

In Raw_material_Issue_line_item I am confused how to link them to the tables for the raw materials. Because if I have 4 relations with each of the raw material table then in every line item entry 3 columns will remain empty and I am sure this will cause problems in lookups later on. Shall I just put in column called Category which stores the Category of raw material as a text and a colum called ID which stores the record id as Text which I can later use to find from the relevant table or is there a better way to do this?

Please let me know if my problem is not clear and I will try to rephrase it. Thanks for your help

I really don´t know what the question is , but from I can deduce, this is a dBase design issue, not really to do with Appgyver.