Larger Product, Low Volume Prototyping and Manufacturing

I’ve been working on products smaller than a breadbox for pretty much my whole career. I have recently been working on a product that falls into the category of “large cabinet”, or vending machine in stature. It is a product that the client seeks to create an iconic brand vision through design, so my work is cut out for me.

Where I lack in this process knowledge is WHERE to manufacture these kinds of products, maintain visual design interest (more than just a 2D graphic application of imagery a la a vending machine). I see this project akin to medical product design.

The image below is a good comparable for the type of design my client is seeking. I acquired this image from Behance, I did not ask permission, but I suspect it should be fine for this discussion. It is not my design, nor is it representative of the final product. It is simply an image that brings some context to what we’re talking about.

What I see below that stands out…

  1. Form beyond bent sheet metal. Larger pieces of plastic, or urethane (Reaction Injection Molded?).
  2. Sheet Metal parts that would require a level of quality and precision to ensure repeatability in manufacturing (hinged doors, etc.)

This is a low volume 200 - 500 per year. If it goes over that, I will be more than happy to deal with that problem.

My ask is to the designers on this forum who have done design more in this realm where you have gotten early prototypes as well as production done for products like this. I am working with a very junior engineering group that I need to provide guidance. Early communication with a manufacturer would be very helpful


I’ve worked on a few large medical products that used compression molded plastics, since injecting something that big is difficult and expensive. Depending on the product I’ve done a bent sheet metal cabinet with compression molded fascia (like an ATM machine). A preheated sheet or pellets are put into a mold and then pressed. The wall thicknesses tend to be a bit on the thick side (good for making strong panels) and the features can be very crisp (because you have both sides of a mold and are pressing that plastic in). These parts also tend to be pretty heavily textured. I’m not exactly sure why on that. I always assumed to help get them out of the mold or hide mold imperfections.

Some links:

I figured something like vacuum or pressure forming could work. I haven’t worked with either in 25 years. Like riding a bike, right :wink:

Thanks for the pressure forming direction.


I did some work on a vending machine where we wanted to have something beside sharp square corners. We actually kept it mostly sheet metal, but they used custom dies (cost in the hundreds, not thousands) to create large radii (I think we did 3 inch). Depending on the shop you may luck out with them already having the radii you’re looking for. Still doesn’t allow super complex forms, but may allow you to create most of a form similar to what you showed.

To prototype before they committed to the die they approximated the bend with a series of slight bends close together. The term they used is “bumping” the bend. I think it some circumstances this may actually be a preferable way to create a bend if the radius or sheet thickness is too large.

A place I worked in college ( made large doors for some special low volume copiers using urethane casting. I think the run was around 100-200. They had a pretty slick setup with an injection machine and quick setting urethane, but I’m guessing it was still pretty expensive per part (though tooling was certainly way less than an injection tool). A recent client of ours was using urethane casting for their product with quantities in the dozens and I was surprised at how high the piece price was (different urethane vendor).

  • We did a robotics enclosure once. It needed to be modular so we designed custom aluminum extrusions for the corners in order to connect the flat sheet metal panels. The corners became the design element.
  • We also did a front fascia for an electric vehicle. Our client was shipping the whole cab from italy with a fiberglass fascia and they wanted to make it in house. They made the whole cab from sheet metal fabrication and we ended up designing the front and bumper with vacuum forming and a roto-molded bumper. With something this big, a “rapid prototype” would cost as much or more than the tooling to make a production part. This is were a good designer that knows about shrink rates and material thickness/thinning comes into play as well as working closely with the Vacuum Forming vendor. The parts we designed came out right on the first shot.
  • Recently we helped a medical company go from urethane castings to injection molded parts. The parts were heavier (thick walls) with some variances and the shipping costs were horrible. If you find the right manufacturer in Asia you can pay less …but it opens a larger can of worms. Quality control, skilled Injection Molding design for large parts, etc. For larger Injection Molded parts we have used Asian RP houses were they CNC the parts in smaller sections, bond them and paint them. At the end you can’t tell.

At the end is a matter of knowing which processes to use and for which parts. Getting cleaver on how to combine them without making it obvious. Good luck.

There’s Reaction Injection Molding (RIM), which yields decent results and can use ‘soft’ tools. Rather than pressure, it’s like a 2-part epoxy that cures and hardens. There are shops in WA state that do this, both in Seattle and the other side (Spokane area).
We use this place for some parts - not RIM though:
I think most of the time however medical products will cleverly ‘disguise’ sheet metal sides and backs with ruled-surface forms, and have them blend nicely into a ‘money-maker’ front fascia where the interface and branding will live. Fun with 2D shapes and color blocking. See: Biodesy — Anvil Studios and Precision NanoSystems — Anvil Studios

I have used RIM (can actually use Renform for the molds but aluminum is more typical), vacuum forming and pressure forming for floor-standing medical devices. But I always liked the challenge of bent metal.