Do I have to settle down in the mold shop for three or four years and be familiar with the materials before I can design?

I am a technical secondary school student, now facing an internship employment, I am very confused about the employment prospects of the mold industry. I heard from the teacher who has worked in the factory for more than 20 years, in this industry I must be spent in the workshop for three or four years then I can only design if I’m familiar with the materials. What if I learn mold design by myself in the later stage, but I may not be familiar with the materials. What will happen? Do I have to stay in the workshop for several years to have a certain foundation?  
supplementary question:
Do you have any good suggestions or opinions?

No best answer

It is not necessary, because many college students do this and do not have such experience. You first learn the design software, then learn the theoretical knowledge of molds, understand the structure of the mold, and then practice case design and learn the design process. Slowly you will be exposed to many related things. If you want to learn mold design well, it is best to find some good training institutions, so that you will have a systematic learning plan.