Thanks guys! Got another one for you... This time we’ll go into file setup and the production processes used.
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3D to 2D to Metal
Even though I designed ‘Splash with SketchUp, most shops want solid digital models generated by SolidWorks or Inventor (unfortunately not possible with free SketchUp). With a solid model, the shop can check parts for accuracy & interference, separate individual parts from one another and ultimately produce files that their specialists can use on the various machines. For a small fee* (*not actually that small), the production vendor converted my SKP and DXF file into something they can use:
Along the way they adjusted a few things – bend radii, simplifying parts where possible, making design tweaks to correct things we wanted to improve, etc. Once the solid model was finished, mechanical drawings were printed out & reviewed for accuracy:
Where before a single model depicted our case, now each part is detailed on a different page. Each part is made separately depending on what material it is and what needs to be done to it. For instance, the sidepanels only need to be punched (cut out)… done! Whereas the main chassis needs to be punched, bent, tapped, and the numbers need to be laser cut. I won’t go into how each individual part is made, but these are the general processes used on various parts of each case:
Cutting – Originally Splash was designed to be laser cut, but it turns out punching is a much faster process if you deal with a big enough shop that has punches (tooling) of enough different shapes & sizes, and is also dependent on the shapes that need to be cut out. Think of it this way: a laser always goes the same speed - and goes slower the thicker & denser your material is - and has to travel the distance of ALL the cuts on a part… the more cuts, the more distance needs to be covered. With a punch, you can knock out a big chunk of metal in an instant. It’s also CAD controlled so several similar shapes can be knocked out in rapid succession in a pre-defined pattern. For instance, the air vents on ‘Splash are all cut with a 2-inch oblong bit... the basic punch pattern for each slot is shown below. One downside to this is that sometimes places where the punch hits multiple times can be seen after the punching is done (small points are seen on an edge that should be seamless & straight). Most of that will be invisible once parts are powdercoated.
Other things that would normally be a time-consuming process (like tapping and countersinking holes) are also done on the punch which saves a lot of time, hassle and risk of f-ups. The finished part looks very similar to a laser-cut part, but in some ways a punched part is stronger. Tapped holes aren’t cut… the metal is actually twisted into threads which makes them stronger. Also since our material is EG (electro-galvanized) steel, the punching process actually pulls the corrosion-resistant coating over the cut edges to make them less susceptible to rust. And all countersunk holes are exactly the same and are accurate to .005” (.1mm).
Bending – which is done on a press brake, is actually more difficult than you’d think. Thick steel takes a LOT of force to bend, so huge hydraulic presses are used. But despite their size, precision can be built in with jigs to make sure bends end up in exactly the right place. ‘Splash is tricky too because of the four 90-degree bends in the main chassis. The below illustration shows the basic shape of a press with a cutaway view of ‘Splash overlaid on top. Like with the punch, different tooling can be fit into the press to allow this type of bend, where normally with more basic equipment the interference shown would be a problem. Another benefit of the shop we ended up going with is that they’ve been in business for years and have a pretty large inventory of existing tooling that they were able to use on the project. That saved a lot of money, as custom tooling starts at $200 and can easily be over $1,000 for larger bits.
And the rest – Finally there are a lot of little things that are unique to Splash that made fab…. interesting. Typically a production run enables each part to be inexpensively made by batching hundreds (or thousands or more) identical parts into a single production run. That’s because the man-hours involved in setting up the machinery can be spread over a larger number of units. While we built 85 units on the latest production run to help bring per-unit costs down as opposed to only making 20 or 30, not all 85 of those are identical. In fact, each one is 100% unique due to the individual numbering & customized name plates. Even though most of ‘Splash is cut out with a punch, numbers and nameplates were laser-cut due to the uniqueness of each part. There’s just no efficient way to do that on a punch, since each letterform (0-9 and A-Z) is different and each individual part needed to be set up as a one-off. So the nameplates and back panels were punched out, bent on a press brake and finally laser-cut before we could call em done.
Oh, and I almost forgot to mention the delete options. My account rep almost shot me when I mentioned 15 of our 85 cases needed to be different than the others because of the fillport and IO delete options that were initially presold. He flipped because that changed (from a fabrication perspective) one run of 85 parts into four runs of four unique parts, like so:
- 65 cases with BOTH fillport and front IO
- 5 cases with fillport but NO front IO
- 5 cases with front IO but NO fillport
- 5 cases without BOTH fillport and front IO
That obviously is a much more expensive operation than just knocking out 85 identical parts, but to my vendor’s credit once they found out it was important to all of us keep these options they made it happen.
So that pretty much brings us to where we are now… once I got all the parts back from fab, they were sorted into color batches and sent out for powdercoating. And I’ll have parts back from powder by the end of the week! When I do I’ll post an update about that & see if I can make updates happen as close to live as possible… there’s still quite a bit left to do including assembly and finally packing & shipping.
Thanks for reading!!