Japanese to English Tech/Engineering Manufacturing

I'm translation a presentation for a manufacturing consulting company. Here is the phrase where the term appears, talking about one specific type of standard work (Toyota Terminology) "各代表型式に層別し、タクトタイムに対してそれぞれの工数を山積みした作業"

Please note, that I don't need a dictionary answer, but some help understanding how to translate this term in this specific context. Thanks in advance for your help.