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Flsun QQ-s Pro 3D printer in review: Hardware top, firmware flop

The Flsun QQ-S Pro is one of the stark examples of the 3D printing community's strengths. This is because the large delta 3D printer comes with strong hardware, but firmware that does not meet the minimum requirements. Only a firmware from GitHub eliminates almost all problems of the QQ-S Pro in one fell swoop.

Flsun is one of the few manufacturers to offer 3D printers with a different motion system than the classic Cartesian one. The large and small delta printers from the Chinese company are primarily designed to offer high speeds. To this end, they are equipped with robust frames and powerful computing hardware. The Flsun QQ-s Pro, which costs around 300 Euros (~$329), comes with a titanium extruder, automatic mesh bed leveling, a 32-bit microcontroller and a print bed with a diameter of 26 cm (~10.2 in).

With the delta motion system, the print head is mounted on three equal horizontal axes around the circular print bed via three arms. For each movement of the printer, all three axes, here usually called A, B and C, must be moved. Behind this is relatively simple mathematics based on the Pythagorean theorem (a²+b²=c²), which is translated into fast and interesting to observe movements. Nevertheless, for the computing hardware in 3D printers, the equations of motion are not easy to solve, because several square roots must be drawn for each motion. Thus, for linear delta robots, primarily the firmware should be well adapted to the hardware.

Technical data

The Flsun QQ-s Pro has been available for quite some time. There are no big surprises here in terms of hardware; the limit switches, hotend and extruder are standard parts, as they are also used in many other printers. Nevertheless, the hardware can deliver convincing performance.

Flsun QQ-S Pro
Technology used FDM, FFF
Maximum print volume ∅ 260 mm × 360 mm (circular print bed) ≈ 19.113 L ≈ 19,113 cc
Installation size (without cable) 400 × 360 × 950 mm (~15.8 x 14.2 x 37.4 in)
Motion system Linear-Delta
Extruder 1 Bowden extruder with gearbox (titanium style)
Control board
Microcontroller
Flsun Highspeed based on MKS Robin Mini Board
STM32F103T6 (32-bit ARM)
ESP8266 Wi-Fi board
Firmware of the test device Delivery state: MKS Robin_Mini_V2.0.7
changed to: Marlin 2.0.9.3
Stepper motor driver 4 × A9488 (Pololu compatible)
Connectors microSD, USB type-B
Control touch screen, serial interface via USB, Wi-Fi
Power supply internal 110 V - 240 V to 24 V power supply unit
Features magnetically attached print bed sensor
Manufacturer page Flsun
Provided by Geekmaxi



Structure and setup

Scope of delivery Flsun QQ-S Pro
Scope of delivery Flsun QQ-S Pro
Packing
Packing

The Flsun QQ-S Pro is amazingly quick to set up. After the six silver steel axles are inserted into the print head arms and the base, the upper end plate is put on. Here, everything fits, and the assembly is easy. The subsequent cable connections are also described in the instructions in an easy-to-understand manner. It is noticeable that the assembly of the 3D printer is simple, but good. After less than half an hour, all components are in place and the last screw is in place. The fact that you only need one type of screw throughout the entire assembly eliminates the need for searching. All the necessary screws are in a zip bag and in another are spare screws, should one go missing.

As for tools, everything necessary and more is included, and Flsun is also generous with other spare parts. In addition to an additional heating block with nozzle and heatbreak, the package also includes another nozzle, heating cartridge and thermistor, limit switches and grease.

Since the 3D printer is almost one meter (~3.3 feet) high when assembled, it is recommended to place the printer on a low table from the beginning, depending on your height. Otherwise, no difficulties are encountered during assembly. The instructions are good, although a bit small. However, there is also help in the form of videos on the included microSD card.

Cable management

The triangular base of the QQ-S Pro looks tidy. Only the ribbon cable to the screen looks lost here. The cable harness to the top cover is well packed, it is not moved much anyway. The aviation connector with a lock nut is particularly pleasing here. Thus, the connection should be secure for a long time. From the cover to the hotend, the wiring harness is coupled with the PTFE tube for filament supply. Again, there is no criticism here. A 3D-printed plastic part protects the cable harness from kinks.

Only the cables of the three limit stop switches are unsuitable. Due to their length, the cables could get in the way of the axle slides and be damaged by friction or pinching. Here, there is a simple solution with tape or a somewhat more elegant solution with a few printed parts. The template of the cable clamps, which ensure a secure fit of the cables, can be found on Thingiverse.

Mainboard

Flsun Highspeed V1.0
Flsun Highspeed V1.0

The Flsun Highspeed V1.0 is a slight modification of the MKS Robin Mini and also runs natively on the same MKS firmware 2.0.7.0. The innovation here are Pololu-compatible, i.e. pluggable, stepper motor drivers. This makes it possible to replace the relatively noisy A4988 drivers with quieter TMC drivers. On the mainboard, an STM32F103T6 controls all functions of the printer and the touch screen. In addition, there is an ESP8266 module for a WLAN connection, via which GCodes can be transmitted to the printer via Cura plugin. The MKS Cloud is also available if you want to control the 3D printer via app. However, the WLAN connection was partly difficult in the test, since the small ESP8266 is well shielded by the metal casing.

The MKS firmware or an adapted Marlin 2.0 version is available for the mainboard. In our eyes, the latter is clearly the better choice.

Firmware

Since Marlin 2.0 has been available for the Robin Mini, MKS has not updated the MKS firmware for the board. It is surprising that Flsun also still uses the two-year-old 2.0.7.0 version of the MKS firmware because the MKS firmware has several rough edges. In principle, the use of this version is not recommended because the firmware lacks important features.

Test temperature protection
Test temperature protection

The temperature runaway protection is most clearly affected by errors. If a temperature sensor slips or is torn off, the 3D printer may not be able to detect it. In an emergency, the corresponding heating elements are on full power until they burst into flames or melt the surrounding plastic. There is a fire hazard! We tested this by plugging a thermistor into the corresponding port on the mainboard instead of the original one and then starting a print. During the heat-up process, the Flsun QQ-S Pro with the original firmware was unable to detect that there was a (deliberate) error here. The good news here, however, is that the printer does at least detect defects or shorted sensor cables. This should be the much more common error case.

The other firmware issues limit print quality and speed. At higher speeds, the print head experiences stuttering. But short dropouts can also occur during inputs on the touch screen. Neither faster memory cards nor the choice of other slicers solved these problems.

The easiest solution for us here is to fall back on the 3D printing community and install an alternative firmware on the device. Installing the firmware is quite simple. From the releases folder of Foxies Marlin 2.0 Repository you can download the current Marlin2.0.9.x-FirmwaresV2.zip archive. The archive contains firmware versions for many different configurations of Flsun 3D printers. For our test device the file named "SCWTPULR-Robin_mini.bin" fits. Copy this file to the SD card of the printer and rename it to "Robin_mini.bin". Once the SD card is inserted into the printer, restart it. The update should now run automatically.

Frame

In the middle of building the 3D printer, when the long sheets of the three sides are not yet installed, the device seams to be unstable. However, once every component is in place, the Flsun QQ-S Pro feels very stable. Nothing wobbles here.

The axis slides and ball joints are also free of play. The bronze bearings of the slides are self-lubricating. Only the six silver steel axles and the six arms could be a bit stiffer. Due to the length of the axles, every bit of flexibility results in ghosting on the printouts.

There is also a small point of criticism with the filament spool holder. The arm is so short that wide spools don't stay on it. The spool must not be wider than 7 cm (~2.8 in). Here, too, there is a simple solution - to print out an extension.

Control

The Flsun QQ-S Pro is controlled via touchscreen, USB cable or WLAN. The MKS firmware offers a very easy-to-understand interface here, which features pictograms and large touch buttons. You do have to master a few English words here, but once again the video instructions explain how to operate the printer.

The Marlin can also be operated via touchscreen. The individual operating points are rather text-based, but Marlin offers the option of setting German and many other languages in addition to English. The initial setup of delta 3D printers with Marlin is a bit more complicated than with the MKS firmware, but after PID tuning, delta calibration and UBL, i.e. mesh bed leveling, have been run through, the printer is ready for use.

In principle, both operating concepts are appealing, even if some functions are somewhat hidden in Marlin, since it is not always clear whether a screen element is also an operating element.

Main menu MKS firmware
Main menu MKS firmware
Tools Menu MKS Firmware
Tools Menu MKS Firmware
Marlin main menu
Marlin main menu
Marlin language selection
Marlin language selection

Power

Print bed with the first layer of the print speed test
Print bed with the first layer of the print speed test
Thermal image heated print bed
Thermal image heated print bed

Print bed

The round print bed of the Flsun QQ-S Pro consists of a multi-layer construction. Insulation, heating element, a heat-distributing aluminum plate and a ceramic-coated glass plate form the print bed. It takes just under 2:30 minutes to heat up the print bed from 22 °C to 60 °C (71.6 °F to 140 °F). The heating power is around 200 watts. The approximately 200 watts of heating power seem almost too little here, even though the insulation and heatspreader ensure very even heating.

The thermal image hardly shows any clearly colder points. Not much heat is lost even at the three mounting points.

The print bed adhesion shows the typical picture of ceramic glass. As soon as the distance from nozzle to print bed is correct, there are hardly any problems with PLA adhesion. ABS and ASA, on the other hand, require some preparation and PETG should not be printed on glass.

Hotend and extruder

There is no criticism of the strong titanium extruder. However, it is located far away from the hotend. The PTFE hose for the filament supply is almost 80 cm (~31.5 in) long. This is partly noticeable in the print quality, as the plastic pressure in the nozzle cannot react as quickly as it should.

The hotend is an E3Dv6 clone, where the filament hose extends into the heating zone. It is better not to expose the hotend to temperatures above 260 °C (500 °F), since PTFE loses its strength beyond this temperature. Due to the lack of thermal insulation of the heating block, some heat is lost, since the air from the coldend's fan can only escape downwards. As a result, the temperatures of the hotend fluctuate more significantly than in other 3D printers.

Two radial fans are installed to the left and right of the nozzle for object cooling. These generate a strong airflow that covers the area around the nozzle well. The print bed sensor is magnetically attached to the print head as long as it is needed. Since the mesh bed leveling values are stored in EEPROM, the sensor is only needed after the QQ-S Pro has been set up for the first time, or if changes have been made to the unit. When the sensor is not in use, it can be attached anywhere on the printer thanks to the strong magnets.

The extrusion quantities in the extrusion test are not necessarily stable, but our measurements here can also only reflect the real behavior of the extruder to a limited extent. Due to the long PTFE hose from the extruder to the hotend, it takes time for the filament to build up a corresponding pressure in the nozzle. Thus, especially at the beginning and at the end of the individual extrusions of the Anycubic PLA filament, you can see that it takes some time until a stable filament flow is achieved. Based on the results, we can estimate that with an extrusion width of 0.44 mm and a layer height of 0.2 mm, a printing speed of 120 mm/s should be possible without making any adjustments.

However, the practical test with the original MKS firmware reveals considerable weaknesses here at higher printing speeds. Already from 80 mm/s onwards, the firmware apparently no longer keeps up with the calculation of the movements. This manifests itself in jerks and later also in large holes in the walls, since the filament flow is not stable when the firmware repeatedly stops the movements of all motors briefly.

Marlin, on the other hand, has fewer problems and somewhat exceeds expectations in the practical test of printing speeds. The movements remain smooth throughout the test. Problems only arise at higher speeds from 130 to 140 mm/s onwards. Here, however, only after the directional changes at the speed indicators. Adjusting the retraction, acceleration and jerk settings should help here. It can also be helpful to increase the stability of the printer somewhat, since the problems are probably caused more by vibrations than by a lack of material flow. Finally, Linear-Advance in Marlin also manages to make an improvement. During printing, you can adjust the Linear Advance setting in the printer's menu.

Extrusion test
Extrusion test
Extrusion test results
Extrusion test results
Practical test print speed MKS firmware
Practical test print speed MKS firmware
Practical test print speed Marlin
Practical test print speed Marlin

Print quality

The firmware has a big influence on the print speed and quality. At low speeds, as set in the practical test, the Flsun QQ-S Pro always shows a decent quality regardless of the firmware. The test printout with Marlin in gray shows slightly less stringing and blobs than the one with the MKS firmware in white, but it should also be noted here that the temperatures from the hotend are apparently calculated differently by Marlin and the MKS Firmware. Thus, the difference can be justified here.

Otherwise, both test prints are relatively true to size. Thin walls get a bit wider to the edges, because here the effects of the long Bowden extruder come into full play. But the consequences of the somewhat too flexible vertical axes also become clear. The small rectangles at the front left look so distorted, the smallest even twisted. The only thing that helps here is to reduce jerk and acceleration. Overhangs are created up to 60° without problems. In general, a slight under-extrusion is noticeable in various places. The individual layers are neatly layered here. Overall, the result is sufficiently good to produce many interesting things with the 3D printer, if you are aware of the device's weaknesses.

In practice, the difference between Marlin and MKS firmware is much more noticeable in some models. Especially when many rounded surfaces are to be created, Marlin has a clear advantage. The firmware calculates the movements better and so the nozzle does not get bogged down. Often, however, this is the only major difference between the Marlin and the MKS Firmware. Objects with many straight lines are created equally well.

In terms of print quality, the lack of stiffness and the high distance between the extruder and nozzle are the biggest causes of problems with the Flsun QQ-S Pro. Ghosting caused by vibrations of the print head is very obvious on many prints. However, if the print speeds are adjusted accordingly, this disappears.

A real advantage of the Delta printer is that you can create many higher objects one after the other. Because the arms of the extruder come from above, they do not get in the way of models that have already been made. This saves heating and cooling times between individual prints.

Cable clamps
Cable clamps
Small parts boxes
Filament roll holder - left MKS firmware - right Marlin
3DBenchy - left MKS firmware - right Marlin
Test files from Flsun
Infinity Cube - left MKS firmware - right Marlin

Security

With the MKS firmware, the biggest criticism of the Flsun QQ-S Pro is the partial lack of temperature runaway detection. Even though the 3D printer detects short circuits and missing thermistors, it does not shut down when there is no temperature change despite heating up. Ultimately, this behavior cannot be glossed over or accepted.

The firmware from Foxies on Github remedies this, but at least in our eyes, this safety feature should not be missing in the delivery state. We retested all temperature errors with the Marlin 2.0.9.3 version and did not find any problems with the protective shutdowns.

Emissions

Stepper motor with vibration damper
Stepper motor with vibration damper

Due to the A9488 stepper motor drivers, the QQ-S Pro is relatively loud, even though the dampers on the motors in the base swallow quite a bit of noise. But the fans of the large 3D printer are not exactly quiet either. The Voltcraft SL-10 sound level meter still shows a maximum volume of around 60 dBA even at a distance of one meter (~3.3 feet). Due to the constantly changing frequencies, one also only gets used to this sound level to a limited extent. An upgrade to TMC stepper motor driver is probably worthwhile here.

Energy consumption

During the printing process, the Flsun QQ-S Pro needs around 135 watts on average, independent of the firmware. MKS firmware and Marlin control the print bed differently here. While the MKS firmware relies on a bang-bang control, Marlin uses a PID control with PWM. Thus, although the energy measurement with the Voltcraft SEM 6000 results in quite similar curves on average for the 3DBenchy test print, the individual measured values of the MKS firmware fluctuate strongly. With bang-bang control, the heating element of the print bed is turned on at regular intervals to maintain temperatures. Thus, the energy consumption measurement shows that the mainboard, motors and heating element of the hotend require about 55 watts in operation, and the heating element of the print bed requires another 220 watts.

Energy measurement - Flsun QQ-S Pro MKS Firmware - 3D-Benchy (moving average and measured values)
Energy measurement - Flsun QQ-S Pro MKS Firmware - 3D-Benchy (moving average and measured values)
Energy measurement - Flsun QQ-S Pro Marlin - 3D-Benchy (moving average and measured values)
Energy measurement - Flsun QQ-S Pro Marlin - 3D-Benchy (moving average and measured values)

During the heating phase, the print bed heats up with a maximum of 250 watts, and the hotend then reaches 40 to 50 watts. During the printing process, it becomes clear that less energy is needed to maintain the temperatures with increasing object height, since the fans remove less heat from the print bed for cooling. Marlin and MKS firmware also appear to be preconfigured with different values for acceleration and jerk. The same GCode is thus produced around seven minutes faster by Marlin. However, this has a negative impact on the quality of the 3DBenchy. While the layers and extrusions are created more accurately by Marlin, ghosting also increases here.

Conclusion

The Flsun QQ-S Pro provided by Geekmaxi
The Flsun QQ-S Pro provided by Geekmaxi

Those looking for a perfectly functioning 3D printer from the factory will probably be disappointed by the Flsun QQ-S Pro. But hobbyists who like to put some work into their 3D printers can quickly achieve good results. Thus, many other upgrades of the 3D printer are conceivable besides an improved firmware. You can find suggestions on Thingiverse and in various Facebook groups. The strongest criticism of the printer is the only insufficiently functioning temperature runaway protection in the delivery state. Apart from that, the 3D printer can do a good job. After all, the mainboard, frame, extruder and hotend provide a more than sufficient basis here. High printing speeds of sufficient quality are possible. But if you adjust the many setting options of 3D printers correctly, very clean prints are also possible. Especially the small parts boxes printed in vase mode showed a good-looking overall picture.

The Flsun QQ-S Pro is not perfect, but it invites upgrades and improvements thanks to a good base. The 3D printer can also achieve acceptable results ex-factory.

Energy consumption and noise emissions are at an acceptable level ex-factory, but at least in terms of volume, strong improvements could be achieved with better stepper motor drivers and quieter fans. Considering the low purchase price of under 300 Euros (~$329) for the size of the device, it is clear that the savings Flsun has made are justified.

The limitations of linear-delta printers do become apparent with the Flsun QQ-S Pro, but they are manageable. Overall, you will probably have to invest a bit more time until the 3D printer meets all requirements.

Prices and availability

The Flsun QQ-S Pro is available at Geekmaxi for 289 Euro (~$317) plus shipping from EU warehouse. Customers can cut the shipping costs with the coupon codeFSQQSPRO .

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> Notebook / Laptop Reviews and News > Reviews > Flsun QQ-s Pro 3D printer in review: Hardware top, firmware flop
Marc Herter, 2022-03-29 (Update: 2022-03-29)