How We Make Our BMW E30 Door Panels December 31 2015, 3 Comments

There is a lot of love and attention to detail that goes into making our BMW E30 aluminum door panels. Here is an inside look at what goes into making our aluminum door panels. There are a lot of little details that go into making a product with proper design and fitment.

We start with a raw sheets of aluminum and cut them on a waterjet machine. It cuts by shooting a 60,000 psi stream of water and garnet sand. Both the door skin and the pull strap bracket are cut on this machine. We deburr the edges by hand afterwards to ensure there are no sharp edges. From there, we bend up the flanges of the aluminum sheets using a finger brake.

The pull strap then gets sewn to the bracket by hand, using an extra strong polyester thread and a back stitch for a secure seam. 

The bracket is finished off by riveting on some custom nutplates that we modify in house. Why did we have to make custom nutplates? We could not find any metric nutplates that would meet our needs. We refused to use English fasteners, because it is just asinine to require our customers to use English tools when everything else on the car uses metric fasteners. It might even force you to go buy some English tools just for that job. We've seen other companies do this, and we absolutely hate it! We resorted to drilling satellite holes in plain carbon steel metric weld nuts and then chrome plating them to provide corrosion resistance.

We also prefer nutplates over rivnuts, because most rivnuts require our customers to buy an expensive rivnut installation tool, but more importantly, nutplates are more secure. If a rivnut starts spinning, it can cause a lot of problems and can very difficult to extract, especially when there is a panel covering it. One might even have to cut the panel to get to the failed rivnut.

One of the other details was to make tapered shims for the screws that mount the pull strap bracket to the door. Since the factory screws go through the factory arm rest and into the door at an angle, using those same holes requires a tapered shim for proper fitment. 


Next, the door handle bezel is cut on a CNC mill from aluminum billet. A spinning carbide bit carves away the billet until it becomes a door handle bezel. A stream of coolant keeps the bit cool and prolongs tool life as well as improving surface finish.

When done, we flip it over and use a radius bit to round off the edges. We then deburr the piece by hand with a file. We had used a welded piece in prototyping, but the tolerances and the final aesthetic did not meet our standards. This door handle bezel is touched so often, that quality is especially important here. The final piece is an improvement over the stock plastic piece that BMW uses.

Lastly, all the pieces that are exposed get powder coated satin black. The process involves bead blasting the surfaces to be covered, thoroughly degreasing the part, spraying powder over the part and then baking in an oven to cure the powder. This produces a finish much more durable than paint, which is important on a part that is touched so frequently. Our bare aluminum prototype quickly showed corrosion where the driver's arm touched the door. The smudges quickly became permanent.


From there, the various pieces are assembled together using stainless internal hex head fasteners. We could have cut cost and used a hex head fastener or a phillips head fastener, but those other fasteners can have sharp edges that can scrape bare skin or snag clothing.

The completed panels are then boxed up and shipped out. We take pride in making things properly, and we hope that our customers notice the extra touches we put into making our products.