Certainly, angling larger models can help them fit inside the workspace of smaller printers but that is not the only reason to angle a model.

Long story follows, please bear with me, if interested.

Bottom line up front: angling a model can improve print quality. Here's how that works.

There are a number of factors that affect print quality during printing, including:
- gravity, which can result in resin sag between supports
- resin type and strength
- printer configuration
- build platform peeling forces in the Z-axis
- layer height (thinner layers are weaker during printing and thus more susceptible to warping)
- aliasing (pixelated light causing rough surfaces - think Minecraft)
- etc.

These factors play off each other, amplifying their impact, and generally affect smaller models like a 20 mm Oerlikon less than they do larger models like a hull. Larger models can be badly affected by these factors spoiling the model.

Printing a model flat increases the impact of these factors. Flat printing can lead to print failures (e.g. models missing parts), warping, models breaking up during printing, resin sag between supports, dimensional inaccuracy, and other problems.

Peeling forces. One of the most important reasons to angle a model during printing is reduce peeling forces on the model. Peeling forces are a big deal. Here's why.

When a model is being printed in resin, the model is printed inverted. The model is suspended from a metal plate called a "build platform". The printer raises and lowers the platform at first in, and later above, a vat of liquid resin to produce each layer. The model is created at the bottom of the resin tank. The bottom of the tank is typically just a thin, clear sheet of plastic film. Each layer of the model is created directly on that clear plastic sheet of film on the bottom of the tank. The sides of the tank itself may be metal, but the bottom is nothing more than a clear plastic sheet. When the resin tank is properly fitted to the printer, that sheets lies on top of the ultraviolet (UV) light source. The UV light shining up through the clear plastic sheet is what hardens the liquid resin creating the layer.

At the time the layer is created, the model is literally attached to that clear film. To print the next layer, the printer lifts the platform, exerting strong peeling forces on the model to break the model free from the film and create space to print the next layer. Some printers lower the resin tank rather than lifting the platform but peeling forces occur the same way. Other printers do both, raise the platform and lower the tank. But no matter which way it's done, it is done to break the model free by peeling it off of the clear plastic sheet.

Those peeling forces are enormous. They can literally tear a model apart or badly warp a poorly oriented model. Printing a model flat maximizes peeling forces. Angling the model minimizes peeling forces. Thus, angling the model in turn reduces warping and resin sagging between supports. If peeling forces get too large, the printer can pull the model apart leaving debris in the resin tank which can potentially damage a printer. So not only do you lose the model, you lose the printer, too.

Aliasing. The other major factor angling a model helps address is aliasing. Most resin printers today use an LCD light screen much like the one in your smart phone. Some use a laser but this is less common. Unlike your smart phone, a 3D printer's LCD screen normally emits only one color, a specific band of Ultra Violet, the color required to harden the light sensitive resin. The LCD screen, made up of millions of light-emitting rectangular pixels, hardens the resin in the shape of all those rectangles, which is called "aliasing". In other words, the printer is incapable of printing smooth surfaces and rounded shapes without applying some tricks, both physical and through the use of software. A 3D printer naturally wants to create objects that look like Aztec stairs or Minecraft buildings.

The software and the physical tricks work together to produce smooth and rounded surfaces. The software trick is called "anti-aliasing" and it is a function of the slicer program used to control printing. The physical trick involves angling the model in 2 dimensions. Doing so helps the anti-aliasing software work best. Printing a model flat defeats anti-aliasing.

Often, when I see a model printed flat, my first reaction is to think "that's a rookie mistake". But there are some rational reasons that the person who set up the model printed it flat. Among those reasons, printing flat speeds up print time and reduces the amount of resin needed to produce the supports saving money. So flat printing is often done for economic reasons.

Other times, it is truly a rookie mistake.

But in most cases, the model will look a lot better if the model is printed at an angle.

Food for thought.