Prusa MK4S: New 3D printer prints even faster - even extreme overhangs

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Unexpectedly, 3D printer manufacturer Prusa has unveiled an upgrade to its Prusa MK4 model, the Prusa MK4S. It comes with some long-awaited changes, but not necessarily those predicted by leading glass ball users. We have already been able to get our hands on the device and get a first impression.

According to the manufacturer, the MK4S is available immediately and effectively replaces the MK4, as it costs the same as its predecessor: the finished device is available for 1199 euros and the kit for 889 euros. The upgrade kit from the MK4 to the MK4S costs 109 euros and will be available from the end of August, according to Prusa.

Steeper and faster printing

The most striking element is the new cooling system. It makes it possible to print even extreme overhangs of up to 75 degrees. Until now, with many 3D printers, support structures had to be planned for much smaller overhangs and added by the slicer to prevent the overhanging parts from sinking. This significantly increases the printing time. After printing, the supports also have to be laboriously removed and disposed of - often resulting in a lot of filament waste.

During our stress test, the ventilation was audible, but the fan runs at a lower speed on less demanding models and then fans the filament much more quietly. The all-round fan is noticeable because the air duct runs almost completely around the filament nozzle so that it is barely visible. The cooling air is therefore blown onto the model from all sides. Cooling on one side only could cause parts of the model to warp because they are even warmer than neighboring parts of the print.

In the editorial office, the MK4S printed a plate with large overhangs as a test model. The result was very even, without the overhangs sagging differently depending on the direction: The upper edge was absolutely plane-parallel to the underside, nothing wobbled.

A new fan in the upgrade would have been advisable in any case, as it has more filament to cool in terms of volume. In the MK4+, a high-flow nozzle liquefies the filament from the roll. This means that more build material reaches the print bed in the same amount of time: this is not always the case, but it is beneficial when printing infills, for example, which have a high filament hunger. According to the data sheet, the output of PLA with a standard nozzle diameter of 0.4 mm is increased from 16 to up to 24 cubic millimetres, and even up to 30 cubic millimetres with a nozzle with a 0.6 millimetre bore. The new nozzle was developed together with the manufacturer Bondtech. Bondtech has gained a reputation in the 3D printing scene because it has been selling extruder conversion kits of all kinds for other printers for a long time. The increased flow rate has the practical effect of shortening printing times.

We also printed some other models, which allows a comparison with the MK4. A fidget cube, i.e. a finger toy made of movable cubes connected by hinges and printed as a single part, requires a fairly high degree of precision to ensure that all parts can move. Here, the MK4S saved only 6 minutes compared to the MK4 in fast printing with an input shaper profile and standard nozzle with a printing time of 1 hour and 14 minutes. The better quality, especially of the hinge elements, was also noticeable.

Cosmetics and all the trimmings

Prusa kills two birds with one stone with the fact that some parts of the MK4S are not 3D-printed from PETG material, as was the case with its predecessor, but are produced using injection molding. To do this, the manufacturer uses a mixture of polycarbonate and carbon fibers. This should not only be more temperature-resistant and stable, but also reduce the workload on the Prusa printer farm in Prague itself. The housing of the control panel and the cover for the nextruder, i.e. the print head, have been modified in particular.

The predecessor was also easy to put into operation, and the MK4S was up and running within ten minutes, including unpacking and self-testing. The MK4S automatically searches for Wi-Fi networks to connect to the Prusa Connect print management system. You can also choose between configuration using a QR code or transferring access data from the slicer. In practical terms, this means that there is no need to transfer print data to a USB stick (or even an SD card on older devices) and print jobs can be sent directly from the slicer to the printer via Wi-Fi and Prusa Connect. Most of this was already possible with the predecessor, but the interaction between Prusa Connect and the printer has improved with the changes and is easier to access.

There is also a new native app for Android and iOS smartphones. We have not yet been able to take a look at it, but it has been announced for the sales launch. This more or less brings Prusa Connect to your smartphone and allows you to monitor your printers on the go. According to Prusa, this allows you to start, pause and resume prints and - more importantly - trigger a print job directly from the Printables model database. Time-consuming prints in particular are then already on the printing plate when you return, provided you have loaded the printer with filament before leaving the house.

With an NFC-enabled smartphone, the app also shortens the setup time, as the Wi-Fi connection to the home network can be established with a tap.

More for hobbyists and people who want to add functions to the printer: A small GPIO board for the main board is available as an accessory for the MK4S. It can be programmed with G-code commands to switch a camera pointing at the print bed on and off or to switch on lighting, control servo motors or do any other things that can be controlled via G-code.

Accelerometer only as an option

An important and very time-saving new feature of the MK4 is the suppression of resonance vibrations that affect the print image due to ghosting. The "Input Shaper" analyzes the printer's own movement and adjusts the print head movements accordingly. As a result, you can print at higher speeds with good quality. The MK4S also has this feature. However, neither the MK4 nor the MK4S have an accelerometer built into the device that measures the printer's own movements and then spits out correction values. Instead, Prusa uses values that have been empirically calculated by the manufacturer with the help of numerous printers.

There has been much speculation that the next generation of bed pusher from Prusa will enhance the two technologies "Input Shaper" and "Pressure Advance" with a sensor. Its job would be to calculate new compensation values if, for example, the extruder or other acceleration-relevant parts of the printer have been modified and the resonance ratios have changed as a result.

This expectation has not been fulfilled. However, the MK4S now at least supports accelerometer components that are procured from elsewhere and offers a workflow in the printer that includes a complete calibration.

Purchase pressure

At first glance, the MK4S appears to have few changes, but for an upgrade price of 109 euros you get two major innovations that primarily affect the speed of printing. The now significantly steeper possible overhangs save time and filament during printing by eliminating many of the support structures that would otherwise be necessary. The nozzle with a higher flow rate also represents a step towards even greater speed.

The manufacturer's latest summer promotion, which offers a voucher for 100 euros for kits ordered with free shipping during the promotion period, makes sense in retrospect, as you can redeem it for the upgrade right away. Anyone who has bought a ready-made printer does not have this advantage, but instead only has a one-year extended warranty.

(mil)