Reducing prototype costs?

Having two of the above posts prototyped would cost me 1400€ (and then I don’t even include the adaptor-case on the right) and while this might be a fair price, it is still a lot for a personal project.
So I was wondering whether there are cheaper ways to do this, other than bending four laser-cut stainless steel sheets?

The post’s height is 900mm.
The hole and kink in the front are designed in function of a spray nozzle, the big hole on the side accommodates a hose and the perforations allow sound to enter.
I prefer not to explain the overall concept in order to avoid time-consuming discussions of this matter,
but please ask if there’s any other type of obscurity that needs to be clarified!

Thanks in advance!

Hey dansercoer
I’m not sure if you are going to be able to get decent responses without telling us more. I have no idea what this things purpose is therefore it is hard for me to recommend materials or process. Right now all I see are two enclosures.

1400€ = $2,050US
900mm = 35.43"

It would be interesting to see your complete drawing set for details. You did not state what the material thickness is, or the width (I’m guessing 200mm +/- ). It is difficult to see if the “kink” details are hard creases, or radii.

As a prototype part:

The large radius at the top not withstanding, it is a simple enough form. Judging by the hole pattern running down the exterior face of the panel I will assume that the “end panels” will have a return flange to accommodate fastening them to the exterior. The detail at the top radius of the end panel, where this flange is - will the flange stop (to accommodate the end radius), or do you require it to be continuous around the radius (to be water tight)? If continuous, add forming time. Without the benefit of laser cutting capability, the “grill” pattern would take a quite a bit of time; either drilling (preferred for this closely spaced pattern) or punching (lots of deformation and work hardening by the punching operation); is this detail on both ends? If so double the effort. If this end panel was a stamped piece in production the return flange would not be as troublesome. But as a fabricated piece there would be some fitting of material and welding required to form a continuous flange. More time.

Two (2) units required; six (6) pieces total (two shrouds, four end panels); you mentioned that your quote did not include the adapter case(s).

For talking purposes, based on the size of the piece, I am guessing that you will be specing at least a thickness of .093" [2+mm]. Using that figure your stainless is going to cost roughly 165€ ($240USD); remember the length of the stock is twice the height and then some. That leaves 1,235€ for labor.

Using an average US shop rate of $80 (55€) per hour - if you divide the 1235 by the 55 shop rate that gives you roughly 22+ hours of fab time. Granted this is a very simplified analysis, but it sounds like a reasonable quote given the detail work required.

So, where did you get this quote? A model shop? How about going to a craftsman that does stainless sinks and counter work. Or an HVAC company; heating, ventilation & air conditioning.

Laser cutting the parts (especially the grill patterns) would definitely be the course to take. Forming the large top radius of the exterior, and the flanges of the end panel(s), without benefit of a sheet metal break would be difficult to do accurately; and if you don’t get the angles spot on nothing is going to fit. If this were a “mock up” the fabrication requirements would obviously be much less critical.

If it were me, I’d pay the 1400€. You are not going to become a precision sheet metal boffin overnight, and the amount of wasted time, material, and effort should be another project consideration.

Thanks for the replies!

Choto: Simply put, it’s a version of these which starts watering when conversations are taking place.

Lmo: The sheet thickness is 5mm, this makes it reasonably vandal-proof and allows for snake eye M3-bolts to be screwed in sideways, which means there’s no need for flanges. I discussed both this and the large top radius with “my” metal constructor and he said there’s no problem in doing this. The top part can spring a bit and it doesn’t need to be 100% water tight, there would always be the grill anyway.
Everything but the top radius has a minimal 5mm radius, the width is 236mm.

I guess I should sell some of my redundant audio equipment and spend those 1400€.
22 hours fabrication time seems a lot though…

These are the drawings of the separate parts;

dansercoer: What are you going to use the prototypes for? Selling the idea, working prototype, aesthetic prototype, everything?

One thing I see that you might want to change is split the bottom on sides into seperate sheets. It will take special tooling to create the second bend seeing as the die won’t be able to reach into the piece. They will probably use a brake press like in this video (watch about 30 seconds in, with the sound cranked to 11):

your problem is the 5mm… that’s crazy thick and nothing in material that thick is going to come cheap, let alone the material itself.

accepting your statement “this is a personal project”, meaning it’s for you and you are willing and able to put in your labour:

eliminate all bends.
delete the side pieces edge drilled (and tapped?) holes.
move side piece holes to their flat face, i.e. laser cut.
find proper sized commercial brackets
bolt all the laser cut flat pieces together with decorative or anti-vandal hardware via the brackets.

The top full round piece is the most problematic:
In stainless steel, cutting off the ~900mm flat faces, the full round can somewhat easily be roll formed on a hand operated roller. Copy the hole pattern and use flat bracket - tie straps behind with same decorative hardware.
Change the top round to alternate material that you can find and/or modify yourself, i.e. large SS soup pot?

Small enclosure, same details. Or, there are lots of stock electronic enclosure companies, some actually with nice designs, many specifically target the high end audio DIY crowd.

like mr. 914 said, the purpose of the protoype will determine a lot of things. If it’s only a personal project and you just need a visual model, you might even be able to do it in wood or cardboard. if it needs to be as per the actual product in terms of materials and production, you will likely have to shell out a bunch more $ to get what you want.

most cities usually have model shops and proto shops that could easily do something like this. as has also been suggested looking at alternate suppliers might also be a way to go. autobody shops, hvac, sheetmetal artists, etc. maybe even give a local school that has a shop a call and see if you could get some students to make it for you for cheap (and maybe an extra bonus mark)?

R

That seems like something you could easily do at home with a sheet of aluminum, a drill and a jigsaw.
Use a fat dowel rod for the big curved bend.

5mm is crazy-thick even for aluminum! No-way for steel! I’d say 1.5-2mm aluminum will give you the workability + rigidity you want. I would also reconsider your fastener strategy. Start with: how can I build this with no fasteners at all?

Other cheap/fast ways to make this if appearance isn’t important:

  • Foamcor, (or gator-foam for a more durable option)
  • Plywood structure with bent styrene sheet top
  • Acrylic sheets, bent with jigs and a heat-gun

“One-off with small edition-potential” might be a better description, so it needs to be both aesthetic ánd working.

This was my reasoning:
I’m not sure I can built this without fasteners (welding, snap fits, etc.) as it should be possible to be disassembled by an installer, not a vandal.
Concerning those brackets; how would you hold the nuts from the outside, or is there something like cheap threaded brackets?
I also thought about the die not being able to reach into the piece, but I though it was worth trying as it would simplify things a little. So far I didn’t get a remark from my fabricator, but I’ll specifically ask him about it just to make sure.
Concerning the material: isn’t aluminium too soft to resist vandalism?
I could also make the top part a bit thinner, but isn’t it cheaper to make it out of the same sheet?
I’ll have a better look at some stock electronic enclosures, this is the adaptor, it needs 15mm all around and some grid.

I agree with Lmo when it comes to DIYing it:

In that case, I think you need to bite the bullet and pay $3250 US or redesign your product with this new knowledge in hand. I’d stick with metal as my material, it will look and feel more high end. Like cg said, go aluminium. I’d add a lead weight in the bottom to give it some heft, aluminium might feel a little cheap/light, even at this size. You can go a lot thinner than 5mm though. 1.5-2.0mm seems reasonable.

Even though you won’t become a sheet metal boffin (what does that mean Lew?), I would suggest buying a sheet of thin sheet metal, and/or some cardboard and working through the assembly yourself before committing to a final design.

I want to know what a sheet metal boffin is too… hilarious!

One idea is that if you want to assembly and dis-assemble in a low profile way, you could use Pem nuts with your tamper-proof screws or even just go with nice rivets. Done in carefully, it could have a cool look like a Ron Arad chair or an old metal skin prop plane. Pems basically attach the nut to the metal, making nuts in hard to reach places easier to work with. Rivots are super easy to use and can be drilled out for disassembly. I’m sure there’s other ways to attach the parts

One other idea, if that top round is so difficult/expensive to bend…why not cut all the sheets flat with the laser cutter or water jet as mentioned before, and that construct those pieces with the screw/nut/back-bracket.

For the top round, maybe you could either buy a standard large diameter metal rod or tube (after modifying the design to accommodate the standard size) and cut it to length. For the Pipe, you could carefully cut down the length on each size, then attach with the same screw/nut/back-bracket. If you used a thick metal rod, maybe recess could be CNC-ed out?

Just some ideas, maybe they would be cheaper. Have you gone down to a local sheet metal factory yet? They might be able to suggest other ideas. I’d quote a couple places too, just to make sure you’re getting the best price

I’ll add a few things to consider here:

What is your finish? Mill finish stainless? If you’ve asked for it brushed, that adds cost but does improve the quality.

Just looking at it, without getting too out of whack with your aesthetics, here’s how I’d put it together.
First use, 16GA stainless steel for the top “skin”, that is more than adequate for vandal resistance. Keep your hole placement since you want to use mechanical fasteners. Cut the sides in 2 pieces, and create a bottom plate (this is where you’ll have the 5mm Stainless) that you can bolt down to a floor. Afterall, what’s the point of making something tamper proof if you can just run off with it? You’ll need some holes drilled and access for wiring, etc. Weld (or glue!) the sides to the plate, and have some u-shaped straps brake formed and epoxied in place (something like LORD adhesive is perfect). Make those straps out of 16GA as well, and drill and tap holes for your fasteners. While we’re on the topic of fasteners, avoid the “snake-eye” headed bolts, especially an M3. Go bigger and use Torx or “Pin-in Torx” The problem with stainless fasteners is that they can be brittle when they’re small, and you can rip the heads off them pretty easily. Not to mention the tool for that fastener also has a tendency to break.

Doing all this should save you a considerable amount of money.

Is there a reason behind your unusual profile shape?

If not, why not just make this out of a standard extrusion with a cap on the top, and a baseplate? A tube would probably be your best bet. You’d need only one or two screws to hold it to a baseplate, where you could slide in the internals…

good point.

If the cost is too much, maybe it’s time for on of those slight design changes that happens mid-steam in a project so often. Design it for more affordable manufacturability… don’t worry about the design integrity. As a portfolio piece, it might show more maturity that you successfully refined the original design for manufacturing anyway

I want to know what a sheet metal boffin is too… hilarious!

During World War II, “boffin” was applied with some affection to scientists and engineers working on new military technologies. It was particularly associated with the members of the team that worked on radar at Bawdsey Research Station under Sir Robert Watson-Watt, but also with computer scientists like Alan Turing, aeronautical engineers like Barnes Wallis, and their associates. Widespread usage may have been encouraged by the common wartime practice of using substitutes for critical words in war-related conversation, in order to confuse eavesdroppers or spies.

Boffins were also skilled craftsmen. My personal experience with sheet metal “boffins” is my British sailing buddy’s dad who was an airframe field mechanic in the Royal Air Force during the war. He used to tell stories (when plied with an appropriate quantity of Guinness) about fabricating components needed to patch up combat damage in a hurry, with limited tools and materials. In his later years he built incredibly detailed scale model R/C aircraft; the man was a master with his hands, and a piece of aluminum.

Actually I thought about using profiles before I designed the current shape.
There’s a kink in the front panel because the spray nozzle needs to be under an angle of 30° to be efficient. Installing this nozzle in a (vertical) rectangular profile would result in a large hole to allow for the 90° spray cone, a lot of water would enter the enclosure this way. I’m sure this can be solved with a simple cut-out, in case I could find such a profile that is. But I’m not sure whether this would compensate for the extra manual labour and aesthetics? This is even more so for round tubes.

I also did a test with an M3-bolt and two pliers at full force; the head didn’t come of, Pin-in Torx might be an option though.

If you have a closer look you will detect those holes. :wink:

Concerning the type of metal: aluminium is cheaper, but difficult to laser cut, apparently it wouldn’t compensate for the extra manual work either. I didn’t ask for any finish, but if necessary I will sand it by hand.
I discussed the other options with my fabricator (who in return discussed this with ánother fabricator) and in the end the best way to reduce costs is by using a standard adaptor-enclosure. Thanks again for pointing that out! Apart from that he can make everything according to my drawings for 1134€ ($1672US).

I even got a $1400US quote (including adaptor-case and shipping) from a Chinese company called Creat who visited this board, has anybody been contacted by them before?



To conclude: this is the best adaptor-enclosure I found so far (black plastic, perforations), but it’s 50mm wider than what I need (190 x 130 x 50mm). Maybe somebody remembers having seen something smaller?