Longer’s new, self-designated flagship printer has a lot going for it, not least of which the close-to-$200 price tag and a rich touchscreen UI. But, an easily upended bed level, need for a pass over to tighten belts and whatnot, and underwhelming out-of-the-box print quality, make it a bit of a lame duck.

The Pro is for ‘Probably not the printer for you’

Probably is the operative word in the subtitle above, because, despite our grumbling, there are some redeeming features of the Longer LK 4 Pro.

Starting with the design, the Longer LK 4 Pro apes Creality’s Ender 3, in that you have a boxy-looking frame of aluminum extrusions, with belt and lead screw-driven axes running on V-slot wheels in the extrusions’ grooves.

A 220 x 220 x 250 mm build volume puts the LK4 Pro on par with similar printers in its price range, matching the likes of Creality’s Ender 3 V2. Setting up is a quick build constituting a handful of parts that must be bolted together using the provided tools. It’s a leisurely 20-minute build, stopping for a drink now and then. Such is a sophistication of “cheap” 3D printers in 2020 – the core experience of putting one together is largely the same, straightforward process.

As a piece of printing hardware, the LK4 Pro is relatively well equipped, with a Bowden extruder pushing filament to a hot end that heats to 250 degrees Celsius. An optical filament sensor sits shotgun to the extruder, which appears to be of the MK8 (or similar) old MakerBot-spinoff variety. The heated bed can reach 100 degrees Celsius.

Both bed and hotend are 24V, which means they heat quickly.

You’ll be able to print up to PETG in terms of temperature, but even then, we’d caution against prolonged use at the upper end of this range. The LK4 Pro likely has a length of PTFE inside the hot end, which could degrade at such temperatures, giving off dangerous fumes.

Firing the Longer LK4 Pro up for the first time greets you with one of the printer’s nicest assets – its UI. Clean and without clutter, you have a row of icons at the bottom of its 4.3-inch touchscreen display, serving as tabs housing the essential functions of the printer. The buttons are clear and easy to hit, and, speaking as a leftie, this writer found the positioning of the display on the left of the machine the most comfortable thing about it. It is easy to wrap a hand around and tap away as if it were a smartphone. And the responsiveness certainly contributes to that feeling, with menus and settings changes registering immediately.

In terms of usefulness, the menu structure of the LK4 Pro has the necessary functions on hand. Still, power users may find the simplification and a lack of access to granular settings frustrating.

Longer differentiates the LK4 Pro (and the LK-2 and LK4 before it) with a stilted design that raises the print volume off the benchtop, suspending the power supply and control box beneath, but in such a way that you have unfettered access to the underside of the print bed. It looks a little awkward, but the reality is that this makes it extraordinarily easy to reach the bed leveling wheels, which is fortunate, because you’re going to need them a lot.

It’s difficult to pinpoint what exactly is the issue, but something about the bed and its setup just does not like to stay level. The bed is a glass panel backed on one side with a rather unforgiving grip sheet, of the type that has an impossibly narrow ‘golden zone’ of distance from the nozzle where the filament will properly stick. We found greater success in flipping the bed and printing directly onto the bare glass. Keep it clean with IPA, and give it a spritz of hairspray as an adhesive if necessary.

There are telltale signs of the bed not being completely flat, which is a pain to counter with only manual bed-leveling at your disposal. You could print with a raft and sacrifice a lot of material, but that’s a pretty lame solution for a “Pro” desktop printer with a heated bed in 2020.

Needs a Little Longer

As is commonplace with budget 3D printers, the Longer LK 4 Pro ships with a faintly customized and rebadged version of Ultimaker Cura (why is it always Cura 15.04.6? If anyone knows, sound out in the comments). It’s a reasonable expectation that the provided software will offer the superior slicing experience for your machine, but this is invariably not the case. The purchase of a cheap printer is often accompanied by the swift install of the latest Cura, PrusaSlicer, or another contemporary slicer.

We’re happy to report though that Longer’s effort with Longer 3D Slicer isn’t bad. The basic profile is enough to run with PLA prints with little effort. But as with the UI on the printer itself, a lot of the granular settings are omitted, meaning more demanding prints are better served by newer slicers – we used the profile of an Alfawise U30 (a rebadged Longer LK4) in Cura 4.6.1 as a starting point.

Fervently firing up a print after assembly resulted in layer shifts and all-round messiness that we quickly pinpointed to both a loose belt and loose grub screws in the extruder pulley. Not the greatest out-of-the-box start ever, but at least the issues were quick to diagnose and move on from.

Another minor irritant of the LK4 Pro is the obnoxiously large print cooling fan duct. On our unit, this printed part (which, incidentally, has support structures still attached to it – hopefully not a sign of things to come) lies precariously close to the print bed and absolutely will entangle stray extrusions that other printers might skip by. You could roll your sleeves up and bend the metal bracket the fan and duct are attached to, but a safer option would be to print a different duct.