LDO Positron v3.2 3D Printer Kit Review: Build Your Own Portable, Foldable, Adorable, Upside Down 3D Printer

The Positron is not your average 3D printer. It’s a flex, both from the designer who figured out how to fold a working printer into an empty filament box, and for those who decide to build one. Do you really need a tiny, portable, upside-down printer? No. Do you want one? Yes. Yes, you do.

I’ve been following the development of the Positron for years, and when I learned that LDO Motors was backing this project, I got excited. After all, LDO is well known for its high quality stepper motors and printer kits. We previously reviewed an LDO Voron 01 kit, and that printer is still in use today. The Positron is something different. It’s not exactly an everyday workhorse, but it’s easily a show-stopping travel printer.

Like a Voron, the Positron is for advanced makers. To build one, you need a 3D printer that can produce high-quality ABS or ASA parts. You also need to be more than a little handy with hex keys and have a basic understanding of electronics. Once it’s assembled, you’ll need to install Klipper, tune the printer, and set up sensorless homing, following directions online.

The LDO Positron 3.2 kit is $674 from Matterhackers. The complete printed parts kit is available for an additional $35.

Specifications: LDO Positron 3.2 Kit

LDO Positron 3.2 Kit: Included in the Box

This is a DIY printer kit that arrives as several boxes of parts. You will need to print a significant portion of the printer yourself, or you can purchase a complete kit with all the necessary parts from Matterhackers. It includes a travel case with room for the finished printer, LCD screen, detachable bed with its support, the 24V 200 Watt external power supply, power cord, and the spool holder. The printer is well-designed and folds easily without tools or much trouble at all.

We printed the Positron out of Polymaker Galaxy ASA for this review.

Design of the LDO Positron 3.2

The Positron has several features that make it stand out: it's truly portable and prints upside down. The printer was designed to fit into an empty 1KG filament box, though thankfully LDO upgraded the kit with a hard case that is suitable to use as an airline carry on bag. This makes it the only 3D printer that can easily travel with you by plane.

Its ability to print upside down may seem like a gimmick, but it’s actually part of the portability solution. The print head and motion system are on the base of the machine, with a folding gantry that suspends the print bed over the tool head.

It uses a glass bed, which seems incredibly old school, but is absolutely necessary. Because the nozzle is on the bottom of the build plate, the only way to see your first layer is if the bed is transparent. This poses a unique problem, with a unique solution: how do you heat a glass bed and still see through it? The bed is made of high temperature borosilicate glass, coated with a thin layer of Indium Tin Oxide on the non-printing side, which conducts electricity. The leads on the edges of the glass heat the bed, much like how an airplane windshield is defrosted.

While watching the Positron do its upside-down printing is endlessly fascinating, it does have one drawback. Any oozing filament – or worse, a failed print – will usually find its messy home attached to the nozzle. If you are a neat freak, this leads to a lot of cleaning time.

The motion system of the Positron is complicated, with one belt driving both the X and Y axis on linear rails. The Z axis is belted and runs on a linear rail as well, and all are driven by high quality LDO motors. The frame is made of machined aluminum parts with carbon fiber covers. The fit and finish of the manufactured parts is first-rate. The hotend is custom-made by Phaetus with a 90 degree bend at the V6 Style nozzle. The mainboard is custom-made by LDO and has a CM4 to do the heavy lifting for Klipper.

To get the Positron into its case, it has to be folded. There is a lever to remove tension from the Z belt, and one thumbscrew to release the Z column and another to remove the bed holder, and that is it. To be fair, the printer fits in a filament box but the bed, screen, power brick, and spool holder do not. They do fit brilliantly in the included custom case.

Assembling the LDO Positron 3.2

Like a Voron, the Positron is a DIY project. You can source your parts from a bill of materials provided by the designers or buy a kit from several different manufacturers, like Matterhackers. Our kit came directly from LDO, which is the wholesaler. LDO is considered a superior kit for its high quality parts. All the wires are pre-crimped and marked, which is something you won’t find in cheaper kits. This can save you hours, if not days, of work.

The multitudes of metric hardware and heat set inserts are in labeled bags and in sufficient numbers for spares.

Building the Positron V3.2 can take days of printing and a solid weekend of assembly time, especially if you’re taking your time to make good-looking, functional parts. We used Polymaker ASA in Galaxy Blue and Galaxy Black, printed with 4 walls and 40% infill.

Complete assembly instructions are beyond the scope of this review, but LDO has an excellent assembly guide at https://ldomotion.com/p/assembly/Positron-V32. There are also social media channels run by the Positron team, which are very helpful should any questions or problems arise.

Leveling the LDO Positron 3.2

The Positron 3.2 has an IR sensor on the tool head, but leveling is still challenging. It was inconsistent due to a wiggle in the socket that secures the bed to the carriage block – this was eventually solved by carefully adding more CA glue to the socket. The bed has a 3-point system that requires manual adjustment with a slip of paper. Two adjustment screws are in the front, while the third point in the back is adjusted in the software. Klipper makes finding the Z height fairly easy.

The bed should be re-leveled every time it is taken off the printer. Since the bed is glass, you may find yourself leveling it after every print.

Klipper makes finding the Z height fairly easy.

Loading Filament on the LDO Positron 3.2

The Positron uses a table-top spool holder positioned just behind the machine, and material is loaded into an awkward port attached to the base of the machine. Loading and unloading can be done from the touch screen or from the Fluidd interface on a network PC. The load and unload routines work fine, but be aware that if you already have filament partially loaded, hitting load will make a mess on your nozzle as the filament is extruded.

Preparing Files / Software for LDO Positron 3.2

The Positron 3.2 doesn’t come with slicing software, but OrcaSlicer has a profile for it. Files are sliced in the normal manner, saved, then loaded into the printer over your network or with a USB stick.

Printing upside down can affect overhangs a little bit differently, but not enough to really be a concern.

Printing on the LDO Positron 3.2

The Positron doesn’t come with test filament, so you’ll definitely want to check out our guide to the best filaments for 3D printing for suggestions. It does a great job with PLA, PETG and TPU. We printed quite a lot with the Positron, but here’s a few of my favorite prints.

The first print on a newly built kit printer can be an adventure, so I started off with a trusty ol’ Benchy. I used OrcaSlicer’s default speeds and standard Speed Benchy parameters: 2 walls, 3 top and bottom layers, 10 % grid infill, a .25 layer height and .5 layer width. I also turned off minimum layer times to give it a bit more pep. It took 34 minutes and 45 seconds.

This boat is a little bit rough, but its shape is well-defined, and no signs of ringing. This was printed in Polymaker gray Polyterra PLA, so none of the defects are hidden.

The next print was a vase mode rose that printed just perfectly at a .2 layer height at 25 mm/s in 1 hour 33 minutes in Polymaker Dual Shadow Red Matte PLA. The layers are even and there’s just a bit of goobers on the last layer that were easily brushed off.

This Articulated Shrimp highlights the strangeness of printing upside down. This printed with the back and antenna of the shrimp on the glass, with the legs hanging downward. It said it could print without supports, but upside down the legs are a rough looking. The sides are very nice and the antenna came off the glass without any trouble at all.

For PETG, I printed a vase in a smoky grey translucent from Bambu Lab at a .2 layer height and average of 35mm/s speed. It only took 2 hours 29 min and maxed out the Z height of the printer. The lines are somewhat noticeable, but the print is strong and flexible.

TPU is always a challenge with Bowden extruders, but the Positron gave it an excellent try. Unfortunately, I gave it a print that needed supports, so the bottom (top?) top of this massage ball is rough. The rest of it is really good, with smooth layer lines because it ran much slower than the PLA prints – an average of 40mm/s. It took 2 hours and 20 minutes to print in Bambu Lab’s red TPU for AMS.

Bottom Line

The Positron is probably the only 3D printer you can carry on a flight as hand luggage, and if you put it on a table at a craft fair, you will not be able to stop talking about it with passers-by. After securing the bed mount, this printer has run successfully and leveled consistently, even after being folded up for storage multiple times.

It looks like a novelty…and heck, it is…but it's a fun machine for makers looking for a tinkering project. The $674 price tag is steep, but you don’t buy this machine just because you need a printer.

Its build size is similar to other “mini” printers, which are easy to throw in the car, but not quite as portable as the Positron. If you want the experience of building a printer without having to print it out first, the Prusa Mini kit can scratch that itch for a couple of hundred dollars cheaper, with a price of $429. The Bambu Lab Mini is an even better deal with a $249 price tag for a single-color machine.

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