I can see why you might think that having a sewing machine in house would be good for quick mockups, but i think Skinny really touched on it -
not only are the machines very specific, and the skills required to use one as well, but you dont want to limit your design based on what you can stitch.
i’m a big fan of getting to know the manufacturing processes involved in design to make you a better designer, but i have also seen many times designers limit their design because of a some limit in knowledge. designing only what you can 3d model…designing only what you can make in the shop… etc.
this is a dangerous habit to form.
better yet, i’d suggest that you try to take some trips out to the manufacturer (or local sample shop if thats not possible). find out how they do things, ask a lot of questions, and when they say they can’t do something, ask “why?”. this is to get in more in touch with how the things you design are made.
once you learn how/why they work (or don’t- it may not always be a limitation in technology, but sometimes cost, time, etc.), you will be in a better position to explain what you want in terms they can understand.
guaranteed, that once you know how to communicate (drawings, text, etc.) in a language they can understand, you can do so quicker than trying to stitch up your own wonky sample. in the end, you will find that also leaving something for your supplier to work out can be advantageous, as no matter how much you learn, they will have more experience. you’ll learn to explain the minimum in design intent, and suggest a process, expecting their experience to add even more.
R