In the 3D-printing world, bridging is when your 3D printer prints a flat, horizontal part of the model mid-air to connect two raised points. Compared to FDM printers, resin printing seems to have almost no tolerance for overhangs. If you’re here, you’re probably wondering whether your Resin 3D printer can bridge in the first place.
Resin 3D printers can bridge well using supports. Large, unsupported bridges and overhangs are more prone to breaking, sagging, and cracking, contaminating your resin vat and interfering with the print. When bridging, reduce printing speed and tilt your model for better strength and adhesion.
This article will discuss how to optimize your resin 3D models for bridging and why you almost always need support in your resin prints. So, let’s get into it and print better bridges on your resin 3D printer.
How To Optimize Your Resin 3D Printer Bridging Quality
Although it can be tough to create sturdy, straight bridges in 3D printing, it’s not impossible. You can create very stable overhangs in your resin 3D models if you design your print correctly.
However, you don’t necessarily need to use any support material with bridges less than 5 mm (0.20 in) long. These bridges are usually close enough to the objects you want to bridge together, so they typically won’t sag or warp.
For bridges longer than 5mm (0.20 in), you will need to find a way to support the structure. To optimize your resin 3D overhangs, you can follow the tips below.
Support Overhangs of Less Than 19 Degrees
Although not all overhangs in resin 3D printing require support, you must support those with a larger surface at an angle of 19 degrees or less from the horizontal base. So, if your bridge rises a bit from the build plate, you’ll need to create a support structure.
Printing an overhang or bridge at more than 19 degrees from the build plate will make the overhang break off owing to its weight. Large surfaces get heavy with their weight, and as the printing continues, it grows over the limit and gets separated from the base.
Support Overhangs Longer Than 1 mm
The same principle applies to overhangs longer than 1 mm (0.04 in).
I recommend keeping your unsupported overhangs at a maximum length of 1 mm (0.04 in). The printing process will slightly deform anything more than that, and the deformation will become more pronounced as the length increases.
Overhangs up to 1 mm (0.04 in) are sufficient to hold themselves together by their intermolecular force of attraction. However, as the length increases, gravitational forces will cause sags and resin disintegration.
Decrease the Print Speed
When bridging using a resin 3D printer, you want to take your time.
With a lower print speed, the resin layers will have time to adhere to each other better, and your bridge will be better attached to the other ends. The final look will also appear smoother and neater.
Finding the right balance between print speed and quality can be difficult, especially because each part of your 3D model is unique. What works for one object might not work for another.
However, a lower print speed will ensure a higher UV exposure time for each layer, resulting in an adequate cure. Anytime a layer of the resin 3D print isn’t fully cured, the subsequent layers won’t have a solid foundation to form a solid model, nor will your bridges properly adhere to the other ends. It’s also essential to avoid over-curing your prints.
Follow the Under 45-Degree Rule
When creating 3D models, it’s essential to follow the 45-degree restrictions for any unsupported angles on your 3D print. This rule also includes bridging angles.
The 45-degree rule is a method to ensure that your bridges don’t float away or stick to the bottom of your vat. It requires you to reorient your 3D model to make steep overhangs rise from the build plate, creating an angle that your 3D printer can print in many layers instead of just one layer.
For example, when you create a 3D model without supports at a 45-degree angle, the 3D printer builds layer after layer, with each successive one offset by no more than 50%. That means that at least 50% of the new layer’s surface area remains in contact with the previous one, and it’ll stay in place since there’s sufficient groundwork for it to stick to.
If you did not follow this rule, your overhang or bridge would likely require fewer layers to print, reducing structural integrity and increasing the chances that the piece will break off in your resin vat.
As the degree angle goes higher and closer to the horizontal, the offset amount gets more extreme, which means less sufficient foundation.
Using supports is one way to cheat the 45-degree angle rule if you must.
Why You Need Supports in Your Resin 3D Models
Resin printing uses a light source like a laser, LED, or projector to cure liquid resin, causing a chemical reaction that solidifies it. Like other 3D printing methods, this happens layer by layer, but the model is inverted compared to FDM printing, and the printing platform is upside-down.
The print model shifts a bit upwards to give room for the next layer, peeling off the bottom of the container. Without proper support structures to attach delicate parts of the model to the printing platform, the newly cured layer may adhere to the bottom of the container and break off from the model.
Resin printing typically uses tree-type supports. These supports are ideal for printing bridges since they are easy to snip off, leave minimal scarring, don’t require too much resin and lattice to create a durable scaffolding. Once the print job is over, you can remove your model from the supports and rinse it in isopropyl alcohol to remove the excess resin.
It’s crucial to use support when bridging your 3D prints. Incorporating structural elements will help you achieve firmer layers to support the bridges.
If you don’t want to use supports, consider reducing the speed and rapidly cooling your bridges to solidify your resin faster or sticking to the 45-degree angle rule.
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I started 3D printing since 2013 and have learned a lot since then. Because of this I want to share my knowledge of what I have learned in the past years with the community. Currently I own 2 Bambulab X1 Carbon, Prusa SL1S and a Prusa MK3S+. Hope you learn something from my blog after my years of experience in 3D printing.