Josef Prusa’s designs have always been trustworthy. He has a talent for scouring the body of work out there in the RepRap community, finding the most valuable innovations, and then blending them together along with some innovations of his own into something greater than the sum of its parts. So, it’s not hard to say, that once a feature shows up in one of his printers, it is the direction that printers are going. With the latest version of the often imitated Prusa i3 design, we can see what’s next.

The printers from Prusa research are my recommendation for anyone getting started in 3D printing who wishes to understand the magic box on their desk, humming away into the night. The Wanhao duplicator is okay, but it’s a cost optimized version of the work done by Prusa, E3D, Ultimachine, and others. You’ll only learn when it breaks, and it will break. Prusa puts top of the line parts into every printer, the design is accessible, and the documentation is the best out there. It’s the Old Heathkit quality of 3D printing.

As Prusa tells us in the video interview below (we caught up with him at the Microsoft booth at Maker Faire — a RepRap at the Microsoft booth!), The MK2 is packed with new features.

Auto Bed Leveling and Its Many Benefits

Le glass et mort.
Le verre est mort. Prusa recently posted a trashcan full of borosilicate glass plates on his twitter. 

There’s been a big push for auto bed leveling in the industry. It’s my absolute favorite upgrade for my printer. In my mind, it transformed the printer. I didn’t realize that being forced to level the bed on my printer was keeping me from using it until I did away with the chore.

Starting with servo motors moving limit switches into place, and ending with non-contact inductance sensors, the reprap community has been moving towards auto bed leveling for a while. At MRRF this year SeeMeCNC was showing off their tiny Eris delta printer which uses accelerometers under the build plate to accomplish this task. The MK2 uses another trick, with a non-contact inductance sensor for its own auto bed leveling.

This along with a cold-corner compensating heated bed let Prusa ditch the glass or aluminum build surface common to 3D printers. This is a feature that has been making it into the industry for some time now; E3D launched the VariPower bed in their Big Box printer before the MK2. A cold-corner compensating heated bed is a bed that has different trace densities at different parts of the board. This allows the heated build platform to put more energy into typically colder parts of the bed; which results in a more evenly heated area.

A thermal image showing the effect of the new heated bed.
A thermal image showing the effect of the new heated bed.

A circuit board does not traditionally have a significant flatness tolerance on it, especially once constrained, vibrated, and heated past normal design requirements. It is, however, the cheapest and most reliable way to get a heated surface without using alternating current in a 3D printer. Glass plates were either placed on-top of the circuit board or aluminum under to make a flat surface for heated beds.

When auto bed leveling a glass plate, the easiest way  is to have the software measure in three places. This gives the firmware enough information to define a plane and a vector normal to it. It uses this to transform gcode; keeping the nozzle perpendicular to the bed at all times. However, if you don’t have a perfectly flat surface like glass, another option is to use a feature called mesh bed leveling. In this method the printer measures a grid of points, produces a nonplanar surface, and then compensates for the variation in the bed over the whole surface.

The inductive sensor above the pre-arranged spots on the i3 MK2's new heatbed.
The inductive sensor above the pre-arranged spots on the i3 MK2’s new heatbed.

Since the flatness provided by glass is no longer necessary, the MK2 uses a PEI film directly on the heated bed circuit board. PEI is a plastic material known as a long-lasting film that has excellent adhesion properties. Most 3D printer materials stick to it flawlessly when it’s slightly warm and come right off when its cooler. Lulzbot and others have been using it in their printers for a few versions now.

Along with this, they heavily improved the Marlin firmware to benefit the leveling process. As expected from a man with the Open Source Hardware logo tattooed on his arm, you can find all the code changes on their fork of the Marlin firmware.

The Increased Buying Power of 3D Printer Ecosystem

When home 3D printing was just starting, things like cheap stepper motors and linear bearing were not as easily found. However, people have kept buying and building 3D printers. This has created a demand, and now there is a pretty good market for 3D printer components.

This shows up in the components used in the printer kit. The circuit board used is the Rambo Mini from Ultimachine. This is a bullet proof board made just outside of Chattanooga, TN USA.  Rambo was designed by the same man who made the Ramps board that everyone copies.

The extruder is another example. The MK1 used an E3D v6 Lite, which could do PLA and ABS. The MK2 has been upgraded to the full E3D v6. This UK made extruderer opens the printer up to any desired filament. The close partnership between these companies is yet another indicator that both are commitment to a community that puts users and quality first.

Prusa found a motor manufacturer and now gets whitelabled motors made for the printers to the exact specs required. Including a faster and lighter extruder motor.
Prusa found a motor manufacturer and now gets whitelabled motors made for the printers to the exact specs required. Including a faster and lighter extruder motor.

Another trend that’s showing up more and more at events like MRRF is the ability for manufacturers to purchase custom parts. Since Prusa Research is doing very well with its printer sales it can purchase its own branded stepper motors. The aforementioned E3D gets custom heater cartridges made to their specifications as well.

Price and Polish

The Included QC report. Prusa is known for shipping parts that fail his tests back to manufacturers
The Included QC report. Prusa is known for shipping parts that fail his tests back to manufacturers

Along with the improved supply chain, printers everywhere are seeing better and better hardware as they start to compete on Z-axis resolution and ringing in prints. Lulzbot has begun to use larger smooth rods with properly loaded igus bushings, for example. In the MK2, Prusa has switched the Z from the problematic threaded rod, to real lead screws integrated with the motors. The printer also has a larger build volume, is quieter, and is easier to assemble.

One thing Prusa does very well, is the quality control of his printers. I was helping my friend put his together and was amazed to find a full QC test report inside the box. This is not typically done in the 3D printing world.

Throughout the assembly I was impressed with the amount of polish. The flat black threaded rod with matching nuts looks great. The wire harnesses are all pre-soldered and pre-crimped. Just follow the manual and plug them in. It should work, it’s all been tested. I think this is a trend in 3D printing as well. The people who compete in the premium tier such as Prusa, SeeMeCNC, E3D, Lulzbot, etc. (As opposed to the import tier, Wanhao, Hobby King, etc.) have to compete on reliability, precision, sound, performance, and support cost. They have to get the most performance possible out of the 600-3000 US dollar range while still being able to make money.

Conclusion

Prusa delivers again. If you want to get started in 3D printing or you want a kit printer that will just work; there are few choices as good as the MK2. Once you build an i3, it’s hard not to get hooked and move on to a more complex build like the deltas from SeeMeCNC. It exemplifies everything a 3D printer kit should be. Community designed, polished, tested, and stuffed full of good components. Just buying the E3D and Rambo Mini for a custom build  printer would make up nearly half of the cost of the Prusa i3 MK2, and you wouldn’t get the motors, HBP, frame materials, or most importantly, the extremely thorough testing.  The documentation is fantastic too. It shows a promising future still for home 3D printing.



Source link