Cons to UV printing

Question

I've been curious about the various UV/Laser printers in (or coming into) market that use liquid resin. I've seen the samples of the Pegasus Touch, Form1, and the Carbon3D as examples. I like the specifications of the quality that machines can put out. However, in my experience with FDM printing, there almost always seems to be something not quite right about the print.

So, what are some major maintenance considerations for these types of 3D printing? Also, specifically, are supports and overhangs as much an issue in these types of printers as with FDM/FFF?

Here are some things I consider major maintenance considerations in FDM:

• Extruder Clogging
• Build platform conditions (i.e. levelness, clean, type of tape, bubbles in tape)
• Variances in material quality (i.e. diameter, purity, physical conditions)
• Mechanics of the machine (i.e. belts, rods, gear teeth, etc.)
• Build environment (i.e. ensuring steady temperature in the build environment, minimize draft)

_{I'm not necessarily looking for printer recommendations, more so technical insight on the technology.}

Answer 1

Taken in order your questions:

Maintenance for a resin printer means keeping the vat or tray clean, using appropriate methods to remove the unused resin (or leaving it in the vat per manufacturer's directions). Cleaning the tray should be done also per manufacturer's spec, although each printer's user forum may provide better or more effective options.

The Pegasus Touch has a caution regarding dripping resin on the mirrors, so there's operational care considerations for these types of printers.

There is a build platform for these printers. The flatness and level are as critical or more so for resin printers, as the resolution can be astonishingly high. If any portion of a print does not bond to the platform, that entire print will have a failed section, creating an entirely failed print. Gravity is not particularly helpful in that respect, at least with the Pegasus Touch.

The release medium varies from device to device. The Pegasus Touch originally used PDMS (silicon release compound) and now uses what's called a SuperVat. The plastic material in the SuperVat is purported to provide better release and fewer failures, along with increased lifespan. PDMS becomes cloudy from repeated printing in the same location and can be torn away from the vat if the print does not properly release.

I've become aware of a product from Australia that has had good reports from use in a B9 Creator resin printer. The report indicates that it releases the model quite easily and barely turns cloudy. I have an order pending for this material, as I am hopeful it will perform as described.

The mechanics are also varied. One expects a system to raise and lower the build platform and to direct the laser or illumination system (DLP), but generally, this type of printer is somewhat simpler mechanically.

Because I live in a hot humid climate, my Pegasus Touch remains in the box, and my brain is about to explode with what I've learned of using it. Environmental conditions are likely to vary with different machines. I've seen references that 70 degrees F is too cold, others that say 70-75 degrees F is just fine, anything higher is too hot. Another user says that 65 degrees is good. The type of resin also becomes an important factor for environmental conditions.

The laser will create heat in the resin, so I'm inclined to believe that cooler is better. Different colors require different durations of laser light, somewhat akin to various plastics having different temperatures.

supports and overhangs are important considerations in an SLA or DLP printer, just as they are in FDM.

Expect also that many of the resin printers require that the user purchase only the product provided by the manufacturer. This isn't necessarily a negative as most of the resin sources are priced similarly.

If I've missed any part of your question, let me know.

Answer 2

Despite how many vendors make it appear, resin-curing SLA/DLP printers are industrial or commercial tools that are really not suitable for home desktop use. Here are the major downsides:

• Significantly more expensive to operate than FDM printers, in most cases.
• The resin is seriously toxic until fully cured. Fumes can be an issue for users handling raw resin, and you should NEVER put a photopolymer print into a chemically-sensitive environment like an aquarium or children's toy.
• Prints require messy post-processing to rinse off excess resin (usually with rubbing alcohol) and additional UV light exposure to finish hardening the photopolymer. The used alcohol/resin rinse mix is basically hazmat waste.
• In bottom-up printers, the window in the print vat is typically a consumable. Some printers require replacing the vat ($$) after every liter or two of cured resin. (Technology is advancing rapidly here though.)
• The peel mechanism in bottom-up printers is often a major source of print flaws, due to the need to rock/tilt/slide the print to free it from the vat window.
• In top-down printers, you have to pay a large up-front consumables cost to initially fill the resin tank. (There are workarounds here like floating a layer of resin on brine, but these have their own technical issues.)
• If you leave the resin in the printer for an extended period, you'll probably find a hardened layer on the surface from stray light exposure and have to clean out or replace the vat.
• Resin vats/tanks need to be kept clean and free of cured resin debris from failed prints or stray light.
• Every combination of resin chemistry, printer light source, and printer optics requires specific tuning to dial in the photopolymer curing behavior. This means it's somewhat difficult to change resin brands, and you may effectively be locked into the printer manufacturer's resin. Many light sources will change in intensity or develop dim regions over time as they age, which will either harm print quality, require period recalibration, or require frequent light source replacement.
• There is a limited number of options for print materials. Technology here is advancing rapidly, but for the most part, SLA/DLP prints are non-load-bearing models with a limited range of color options.

These are some pretty significant "user experience" downsides compared to a consumer desktop FDM printer. It's more hazard, more work, and more cost than FDM. SLA/DLP is primarily advantageous where high resolution or high print speeds are required.