Why the Form 4L is the Obvious Choice
A close look at the Formlabs Form 4L, the large-format resin 3D printer that scales the Form 4's Low Force Display print engine up to a build volume of more than 24 liters.
The Formlabs Form 4L is the large-format resin 3D printer in the Formlabs Form 4 series. It runs the same Low Force Display print engine as the standard Form 4, scaled up to a build volume of 353 × 196 × 350 mm. That works out to 24.2 L.
The Form 3L held this position for years. It produced the surface finish and material range that stereolithography is known for, at a size no desktop machine could match. The tradeoff was time. Large jobs ran overnight, and reliability at that scale was the most common complaint from owners. The Form 4L was designed against those two problems specifically.
How Masked SLA Changes Print Time
Unlike previous generations of Formlabs machines, the Form 4L is a masked SLA printer. This change explains most of how it behaves.
A laser-based printer draws each layer point by point. A wider cross section takes longer to trace. Masked SLA works differently. A backlight unit shines up through a Light Processing Unit, and the LPU masks that light into the exact shape of the layer. The whole layer cures in one exposure.
The consequence matters more than the mechanism. Print time is set by how tall the parts are, not by how many of them sit on the platform. Adding parts to a job costs almost no additional time, as long as they are not taller than what is already there.
This is why the machine rewards a full platform. A half-empty build takes nearly as long as a full one.
Inside the Print Engine
The backlight unit uses 145 LEDs behind collimating lenses. Together they deliver 16 mW/cm² at the print plane, at a wavelength of 405 nm. Collimated light holds its shape as it travels through the LPU. That keeps features sharp across the entire platform instead of only near the center.
The Light Processing Unit 4L does the masking. It stacks polarizers, optical coatings, and a custom LCD. Formlabs rates it for 600,000 to 1,900,000 layers, depending on the material and the layer height being printed. It is a serviceable part, replaceable in the field once it reaches the end of that range.
Two other components work to reduce the force on each part as it separates. A release texture on the LPU introduces airflow during the peel, which prevents suction from building under the layer. The resin tank uses a flexible film that releases gradually from the edges of the cured area rather than all at once. Lower peel forces protect fine features, and they extend the working life of the tank.
What the Onboard Sensors Do
6 sensors monitor the print while it runs.
To hold the resin at working temperature, conduction heaters warm the tank from below while an infrared sensor reads the temperature throughout the job. Warm resin flows and cures more predictably, and the heating system is what makes thicker, filled materials viable.
To adapt to part geometry, the Z axis measures how each layer separates from the film. It then adjusts the peel movement as the print goes on. A tall thin part and a wide flat one need different handling, and the printer works that out on its own.
To keep resin coverage consistent, the mixer sweeps across the tank between layers. It stirs fresh resin into the pool and checks for debris in the same pass. On a long build, catching a dropped support early is the difference between a finished plate and a wasted one.
Resin level is tracked separately, so the printer knows when to dispense more before the tank runs low.
Resin Handling and Material Options
Resin loads on its own. The Form 4L takes 2 cartridges, which lets a long job draw from more than one container without anyone standing by. Shops running higher volume can connect a Formlabs Resin Pump with a 5 L container instead. Formlabs rates the pump for roughly 600 hours of pumping time and recommends changing the tubing every 6 months, which is what the Resin Pump Maintenance Kit covers.
The machine is not limited to first-party materials. An Open Material Mode license unlocks printing with any 405 nm photopolymer resin. Custom profiles are built in the PreForm Print Settings Editor, which exposes exposure, layer height, heating, wiping, scaling, and interlayer motion. Profiles can be saved and shared across a fleet.
Two limits come with that. Third-party resin has to be poured into the tank by hand, so the Resin Pump is not available for it. And Formlabs does not support tuning or troubleshooting custom profiles, which makes this a feature for experienced users rather than a casual setting to switch on.
Upgrading From a Form 3L
Owners coming from a Formlabs Form 3L will notice the speed first. The Form 3L traced every layer with a pair of moving lasers aimed by mirrors, and that time compounded quickly on large parts. Formlabs puts the Form 4L at 2 to 4 times faster across its material range.
Real parts show a wider gap than that range suggests. A Radio Flyer scooter seat that took 21 hours on a Form 3L prints in 2 hours 37 minutes on a Form 4L.
Accuracy improved alongside speed. Parts that use the full build volume now fit together properly, which was inconsistent on the Form 3L. For anyone printing enclosures, housings, or anything with a mating surface, that change is as valuable as the time saved.
The build volume grew as well, from 21.4 L to 24.2 L.
Running costs moved in the right direction too. General Purpose resins for the Form 4 generation are priced below their Form 3 equivalents. Tank lifetime is now uniform at 75,000 or more layers regardless of material, which replaces the old system of per-material lifetime restrictions that owners had to track.
One thing to plan for: consumables do not carry over. Tanks, build platforms, and cartridges are all specific to the Form 4 generation. A first-generation Form Wash L needs the Universal Build Platform Adapter to hold a Form 4L platform, and the current Form Wash L V2 and Form Cure L V2 are sized for the Form 4L platform out of the box.
How the Form 4L Compares to the Form 4
The build platform on the Form 4L is nearly 3 times the area of the one on a standard Formlabs Form 4. Because print time scales with height rather than quantity, that extra area converts almost directly into throughput.
In internal testing with the same part, the same resin, and the same layer height, the Form 4L cleared a queue up to 3 times faster than a Form 4. The Form 4 needed a second print job to finish what the Form 4L completed in one.
The reason is straightforward. A layer takes roughly the same time to expose whether the platform holds 6 parts or 18, because the whole layer cures in a single flash. More XY area means more parts per bed at nearly the same cost in time. Longer wipe moves add some overhead on the larger machine, and individual print profiles vary in how well they are optimized, but the underlying relationship holds across materials.
That saving carries past the printer. Everything on a single platform comes off together and moves through the wash and the cure as one batch. Three separate jobs mean three rounds of file preparation, part removal, and post-processing labor.
Cost per part follows the same logic. The Form 4L uses a larger tank and a larger LPU, but it spreads those consumables across far more parts per job. Resin consumption is identical either way, since a given part uses the same volume on either machine. What changes is how much labor and how many machine hours sit behind each finished part.
When the Form 4 Is the Better Choice
A larger printer is not automatically the right one.
Printing a single part at a time, the Form 4 finishes sooner. Its smaller platform means less resin sitting in the tank, so a machine that runs occasionally costs less to keep loaded and ready.
Running several materials at once favors two Form 4s over one Form 4L. Two machines with two tanks avoid the swapping a single large printer would require.
Physical footprint can be a limiting factor in some spaces. The Form 4 weighs 18.3 kg (40 lbs) and fits on a standard storage shelf. The Form 4L weighs 58.5 kg (129 lbs) and needs a large shelf or deep workbench with clearance around it for loading and service.
The value and performance of the Form 4L show up when production requires more than a few parts, or when that part simply will not fit on a smaller platform. When space is at a higher premium than capability, the Form 4 is a practical solution to that problem.
| Specification | Form 4L | Form 4 | Form 3L |
|---|---|---|---|
| Technology | Masked SLA | Masked SLA | Laser SLA |
| Print engine | Low Force Display | Low Force Display | Low Force Stereolithography |
| Build volume | 353 × 196 × 350 mm | 200 × 125 × 210 mm | 335 × 200 × 320 mm |
| Build capacity | 24.2 L | 5.25 L | 21.4 L |
| Build area | 692 cm² | 250 cm² | 670 cm² |
| Pixel size | 46 microns | 50 microns | 25 micron XY, 85 micron laser spot |
| Layer thickness | 25 to 200 microns | 25 to 300 microns | 25 to 300 microns |
| Light source | 145 LEDs, 405 nm | LED array, 405 nm | Dual 405 nm laser |
| Optical power | 16 mW/cm² | 16 mW/cm² | 250 mW per laser |
| Resin cartridges | 2 | 1 | 2 |
| Printer dimensions | 664 × 528 × 794 mm | 398 × 367 × 554 mm | 770 × 520 × 740 mm |
| Weight | 58.5 kg (129 lbs) | 18.3 kg (40 lbs) | 54.4 kg (120 lbs) |
| Tank lifetime | 75,000+ layers | 75,000+ layers | Varies by material |
| Biocompatible materials | Form 4BL only | Form 4B only | Form 3BL only |
The Form 4L closes the gap that has always separated large-format resin printing from desktop resin printing. Parts that used to be split into sections and glued back together now print whole. A full platform finishes in a working day instead of overnight. The workflow is the same one anyone can learn in an afternoon.
Choosing between the Form 4 and the Form 4L comes down to what runs through the shop. For questions about which machine fits a specific application, or about how the Form 4L would fit into an existing production workflow, our expert team at MatterHackers can help you find the perfect solution to your 3D printing needs.