"For low-volume production (approximately 10-100 parts), 3D-printed molds save time and money. They also enable a more agile manufacturing approach, allowing engineers and designers to easily modify molds and continue to iterate on their designs with low lead times and cost."

Lightweight construction has now become one of the most sustainable trends in the automotive industry and global demand for polycarbonate (PC) components for roof systems is on the rise according to system supplier Webasto (Stockdorf, Germany).

Webasto CEO Holger Engelmann is convinced that, "in the future, roof components made of polycarbonate will gain an important share in the largest automobile market in the world." Webasto experts predict that the share of polycarbonate in vehicle roof systems will rise to about 20 percent over the next five years. Polycarbonate has half the density of glass but extremely high impact strength. Elements made of polycarbonate can therefore achieve weight savings of up to 50 percent. The entire roof in this instance weighs approximately 1.2 kg, with length of approximately 98 cm and width of slightly over 1 m at the front.

It's worth noting that the LDPE didn't stick to the molds, i.e. they didn't require any release agents. They did, however, get a little flash. And they report that the cycle time was three minutes per shot.

Technically, manufacturing components for roof systems to Class A standard is a highly complex undertaking. To achieve this, Webasto makes the components exclusively at its Plastics Competence Center in Schierling.

RainIs this the White Paper you referred to?https://archive-media.formlabs.com/upload/injection-molding-from-3d-printed-molds.pdf

Another factor is that sliding and panorama roofs are very popular in China, topping the specified equipment statistics worldwide. About every third car made in China is delivered with a sliding or panorama roof. The ratio rises to every second car for high-end luxury cars from global OEMs.

With a stereolithography (SLA) 3D printer, you can produce molds that are smooth and strong enough--at least with a little help--to use for injection-molding small runs (10 to 100 parts, Formlabs reckons). What they've done in their testing is placed the molds--which have cavities, gates and sprues, they're the real deal--into aluminum frames, which prevent the mold from warping. You can work with standardized aluminum frames from injection molder manufacturers, or spend the bread to have something custom fabricated at a machine shop.

Due to several new projects, Webasto continues to invest in lightweight construction technology. "We have invested 45 million euros [$61 million] to expand our technology leadership in polycarbonate components for car roof systems even further," says Engelmann. First, a new production hall (about 4500 m²/48,438 ft²) was built at the Schierling site near Regensburg. This facility was then outfitted with three new injection-molding machines and a new paint shop to guarantee that production of polycarbonate components remains state-of-the-art. As a result, these plant extensions assure a production capacity of one million components annually.

For the mold material they used both clear and high-temperature resin. Obviously you need something that can withstand a higher temperature than the plastic that's going to be squirted into it.

The leading roof system supplier is molding PC panels at its plant in Schierling, Germany for supply to China. The PC panel is used at the company's Guangzhou plant to make the panorama roof for the Golf A7. The roofs are then shipped to FAW VW in Foshan and assembled in cars for the Chinese market.

Next they used a desktop (okay, benchtop) Galomb Model B-100 Injection Molder, which is relatively affordable at about four grand. They squirted low-density polyethylene into the mold--LDPE was specifically chosen for its low-melt temperature--and were successfully able to produce these parts:

Lightweight construction has now become one of the most sustainable trends in the automotive industry and global demand for polycarbonate (PC) components for roof systems is on the rise according to system supplier Webasto (Stockdorf, Germany).

Besides fixed roof elements for the Smart, Webasto also produces panels in Schierling for various car manufacturers. These low-weight panels surround the front and sides of sliding and panorama roofs, producing a high-quality solid glass-like appearance for the entire roof area.

While it's free to download, there is a catch--you need to enter your e-mail address, and they openly state "We will also opt you into other relevant marketing communication," so you can presumably expect some spam.

Now that desktop 3D printing has become widespread, there's another production method crossing over into the DIY realm: Desktop injection molding. It's now possible "to create molds in-house to produce small, functional parts in production plastics," writes Formlabs.