3D printers with two print heads: This is how dual extruders differ

Even with modern 3D printers, perfect overhangs, bridges and filigree structures are difficult to implement. A support structure under the actual print model is helpful, but peeling it off leaves unsightly damage. A water-soluble support structure can help. To print them, however, you need a 3D printer with two extruders. The same applies to anyone who wants to print in two colors.

3D printing is the pioneering technology when it comes to complex components or filigree constructions. This is possible because 3D printers work additively, in contrast to conventional mold making systems. While CNC milling machines remove material and their shape is tied to 5-axis systems and the length of the drill bits, 3D printers are freer in their options. You apply the bottom layer first and work your way up layer by layer. 3D printers can easily build complex structures with undercuts and openings. But if a part of the model only starts from the middle, has strong overhangs or long bridging, a workaround must also be used in 3D printing.

The little helpers are called support structures. They are support structures, roughly comparable to trade fair stands or scaffolding. They hold, support and stabilize where the construction of the model lacks support. These structures are printed on a standard 3D printer using the same filament as the actual 3D model. Once the print is complete, the support structures can be detached thanks to the minimal distance between the support and the model – at least in theory. Depending on the angle, distance and filament type, this sometimes works very easily with just a strong jerk or it is hardly possible. If the distance is too small, the support structures can only be detached from the model with difficulty or not at all. This means that easy detachment can quickly turn into hours of unwinding, nibbling and filing. With a bit of bad luck, the actual print will be damaged or unsightly traces of the support will remain on it. If the distance is too large, the bottom layer of filament sags too much. The undersides of support structures are generally printed less cleanly than the rest. Even when it comes to working with two different colors, you won’t get any further with the standard extruder.

This is where dual extruders come into play, they have two independent processing units that can be equipped with different filaments. The two print heads each consist of an extruder and hotend. There are now countless different construction variants for dual printing or multi-printing. Techstage presents the three most prominent variants here.

With the dual extruder, both filament processing units are coupled. The two print heads form one unit and move together. The merged double print head is controlled by the same movement mechanics. So that the nozzles do not get in the way, the print head that is not currently required is pushed up a few millimeters and the temperature of the stand-by nozzle is lowered. By default, 150° Celsius is enough here so that no filament can seep out. In addition to the switching time when changing the filament, this dripping is the big sticking point in double filament processing. We’ll go into more detail on that later.

Examples of a dual extruder are the Qidi Tech i-fast (test report) and the Qidi X-Pro (test report). Incidentally, most dual extruders switch mechanically between the print heads. To do this, the entire print head moves to the left or right as far as it will go and pushes in a lever on the print head. This lever then raises or lowers the print head.

IDEX, stands for Independent Dual Extruder. Independent dual extruders also share most of the motion mechanics except for the × axis. However, each of the two separate print heads has its own × motor and toothed belt. Two independent systems run on the ×-axis, which only share the y-axis and the print bed. In contrast to the simple dual extruder, an IDEX 3D printer can print the same model twice at the same time or additionally mirror it.

Another underestimated advantage of these printers is the shorter waiting time when changing printheads. In addition, the printed image is more precise overall in practice, since the stand-by extruder moves to the edge of the print area in word order, thus avoiding contamination from filament seeping out.

Multi-print systems are either tailor-made for a specific printer model or open-source for all models. Examples of this are the AMS for Bambu Lab printers or the MCU for Prusa 3D printers. The Mosaic company, for example, offers an open multi-printing system. Before the actual printing process, it cuts the required filaments into pieces and then welds them together into a strand. With this solution, a single extruder can also print in multiple colors. However, this is a do-it-yourself solution, which we will not go into further.

If you want to buy your first dual extruder, you should know about the special features of dual extruders or IDEX 3D printers. Since the devices are not exactly cheap, we offer a short guide to which system is better suited for whom. In our opinion, an IDEX 3D printer has clear advantages over the dual extruder, which is why the additional price is worth it:

But now to the printers with dual extruders that we have already tested or that we are currently testing. In the overview of the technical data and the price table, we have also included devices that we have at least requested.

The Snapmaker J1 is currently the non plus ultra among the IDEX 3D printers. The manufacturer is known in the 3D printing scene for high-quality components and precise workmanship. The printer can record a maximum print area of ​​300 × 200 × 200 mm. Maximum nozzle temperature of both nozzles is 300 degrees. The PEI-coated print bed makes it to 100 degrees. Due to the closed pressure chamber, the IDEX printer is the first choice for functional parts with high mechanical loads. The model can handle all filaments from PLA to ABS-PC and Nylon.

The manufacturer Sovol, for example, produces a pleasingly inexpensive IDEX printer. Sovol obtains most of its components from the Creality conglomerate, but also has its own production facilities. The Sovol SV04 has a very good price-performance ratio. The Cartesian structure with the moving print bed does not allow for movements that are too fast compared to an xy core printer. But the S04 offers a very large print space of 300 × 300 × 400 mm. In addition to the Snapmaker J1, it is the only model that has an automatic measurement system for the print bed. The printer is equipped with everything that a normal 3D printer offers. These include silent mainboard, filament runout sensor, flexible PEI printing plate and dual Z-axis guide. With the temperatures, the print nozzles manage up to 260 degrees and the print bed 100 degrees.

The Flashforge Creator Pro 2 is also an IDEX printer. At 200 x 148 x 150 mm, the printer has the smallest installation space of the 3D printers presented here. The nozzles can be heated up to 240 degrees and the print bed up to 120 degrees. The model has just arrived at the editorial office and will be examined more closely in a practical test over the coming weeks. However, the approximately 21 kg dead weight already promises a decent counterweight to the fast print head movements.

The Qidi i-fast is the giant among the dual extruder printers. The two extruders share a print head here. The printer scores primarily with the large print volume and the maximum print temperatures. The installation space measures a whopping 330 × 250 × 320 mm. The nozzles create up to 350 degrees and the print bed 120 degrees. In addition, the i-fast has an additional installation space heater. This is how he brings it to a temperature of up to 65 degrees inside the pressure chamber. The closed pressure chamber and the high upper temperature limits allow a variety of filaments from PLA to demanding nylon PA6/P12 and ABS-PC.

The Qidi X-Pro (test report), which we tested in 2021, is significantly cheaper, but also smaller and less well equipped. Unfortunately, the device can currently only be found with luck, as it is no longer produced.

As is so often the case, the acquisition costs are related to user-friendliness, the variety of materials and the size of the installation space. At around 500 euros, even the cheapest IDEX printer is more than twice as expensive as a conventional FDM printer with a single extruder. In the best-budget category, the preference for XY core or the classic Cartesian structure in relation to the printing speed is the primary deciding factor. If you don’t care, you get with the Sovol SV04 a printer with many extras and a large installation space. The S04 works great with filaments like PLA, TPU and PETG.

In the higher price range, the purchase decision is more difficult, Snapmaker J1 and Qidi i-fast both reach very high temperatures and the i-fast also offers pressure chamber heating. Here you have to decide between print quality/ease of use and the size of the build space – the i-fast offers a much larger print space. In contrast, the J1 has a whole repertoire of automatic calibration tools and offers faster and higher print quality in dual printing. And even without pressure chamber heating, the J1 achieves an interior temperature of almost 50 degrees. So the J1 is our first choice when it comes to processing high-temperature filaments for dual operation. It offers the highest ease of use and works more precisely than classic dual extruders thanks to the independent print heads.