Feasibility of using prebuilt support structures

Question

I'm new to 3D printing so I'm not sure if I'm missing something glaringly obvious. It seems to me ideally you'd design models for 3D printing in ways that use joints and whatnot to avoid the need for supports entirely. Or you would model small specific supports for that model where and as needed. This way you reduce cost, print time, blemishes, etc. Which is all very well and good if you're designing for print runs. But if you're just making a one-off or you need a handful having support makes sense. My question then, would be rather than dealing with the problems of traditionally generated supports or having to deal with print time and added costs for each print, what if we could use prepared blocks to support bridging, etc? Perhaps with screws to adjust the height and angles of some wedges, and printing a thin outline at the start and pausing after the first couple of layers to place blocks within the outline. Would this be precise enough to avoid most issues and support bridging? In my mind, it seems like it would work but as I say I've only had my first printer for a few days.

I presume that the biggest issue would be the print head colliding with the support structure but that could be adjusted in the software I reckon. There is already the print one object at a time thing going on (although I've only tried that once and the head did collide with the first object...) Perhaps pausing and adding support blocks when approaching the required layers would be better than having it on from the start to reduce travel times. It still seems feasible to me.

Answer 1

You're correct the head colliding is the biggest problem. What you underestimate is the geometry of the print head, where the blower ducts, fans etc mean a lot of dead zone around the nozzle where there's only several millimeters of clearance. You'd need to print roughly 30-40mm away from the support block to fit the print head, meaning at least that much of unsupported bridge between the part and the support block. This one is right off until we get printers with long, thin needle-like print heads (which isn't something being developed).

Pausing and adding blocks might be doable, but comes with a lot of headaches:

• place the block by hand
• the print is paused hours into the process; someone must be there to place the block then.
• pausing and resuming print mid-print is risky, often resulting in a flaw in the print, sometimes in total print failure
• attaching the block firmly to the print bed is going to be tricky. It going loose during print would be disastrous, and it must be easily detached.
• finding the location for the block would be quite tricky. Maybe some 'help' print on 1st layer height?
• You would still need to project it into the print process, adding a lot of hassle.
• filament is cheap. Supports are mostly hollow. They rarely add a lot of time, and in cases they do, you want to be 100% sure they work right and the print comes out well, not try to save up on the filament.
• a failed print is far more of a time and money loss than supports on a successful print. This kind of fiddly manipulation mid-print is asking for trouble.

In short, the headaches outweigh the benefits by so much no-one is even trying that.

The one exception you see occasionally is desperate attempts at rescuing long prints where supports failed. I occasionally see posts on r/3Dprinting where people noticed the print failed within a support but the main part of the print goes correctly, and the supported section hasn't been reached yet, so they use assorted clutter to provide a "block" for the printer to continue printing the support on top of it. Examples: 1 2 3. I wouldn't recommend doing this on regular basis.