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Wednesday, October 14, 2015

First impressions on bq's Hephestos 2

I was asked to be a beta-tester of this new machine sold in kit form by Spanish firm bq.  It's a bit hard to keep the experience to myself while the testing was taking place. I won't say it is great and rosy but their approach was a bold one and I think it stands out of the crowd.

So what is it?

Hephestos 2 is a 3D printer kit to be assembled by the user. While it might find its routes in Josef Prusa iteration 3 model, this time it is just a faded image. That was entirely the case with the former Hephestos that shared most of Prusa i3 features with a few of exceptions: no heated bed, a couple of cable chains and a very well engineered extruder/hotend combo.

But the Hephestos 2 breaks with the Reprap tradition and includes no printed parts and a body made of powder colored folded metal parts. Only Y-axis uses 8mm diameter smooth rods and linear bearings but Z and X-axis use miniature Hiwin linear rails for extra accuracy. A new electronics board integrates an ATmega 2560 plus five DRV8825 drivers with electronic current control (no potentiometers to fiddle with) and a large LCD monochrome graphic display that enables autonomous printing off an SD card.

Not having a heated bed keeps the power supply requirements low so a brick type power supply comes with the kit. By the way, the bed is A4 size (297x210mm) and max print height is said to be 220mm (I haven't printed parts that tall).

Firmware is based on Marlin and source code should be available and it uses a custom-developed inductive bed sensor for automatic bed calibration (tramming).

How it works?

The machine prints PLA very nicely at 40mm/s and Filaflex at 25mm/s. Both speeds can be increased by a fair amount and still get decent prints. The machine insists on doing things its own way so those of you with another printer may wonder why homing requires heating up the nozzle, but these are minor details (that are in fact done for a reason). 

Printing quality has been great in my opinion but what captured my attention mostly was the extruder/hotend combo that is even better than the former Hephestos, now with a dual hobbed gear (a la Bondtech, but direct drive). 

Printer is not noisy but at  a point extruder fans are.

There are some quirks in the beta firmware that made the time between prints not not very reliable, but once a part started printing it always finished ok. I have been using hairspray on the glass bed with great results, but I have not attempted parts with are really large base. I would prefer to have a choice of heating up the bed but I have got excellent results with the cold bed.

What about the build process?

Let me start by saying that my build was a bit of a mess because it started before the manual was available, so I made a few wrong guesses that I needed to undo later in the build. I have been told a trained person can do it in less than two hours (and this has been shown in the product presentation) but I would say it can be done in a morning or evening by one person, though it is always better if you get some help (I was lucky my friend Ruben helped me out and despite all my mistakes the printer was finished in less than four hours). 

I cannot elaborate on the final user manual but the document I used was very detailed so I guess people would have no trouble building the printer. 

The electronics is well thought out and using a combination of color coded calbles and different types of sockets we got a working printer at the first attempt (almost, I messed up the z-probe, but that was again my mistake). 

I just loved the fact all the wires were already inserted into the cable chains. The bed is held by two quick-fit levers (getting them into the threads was most likely the more difficult part of the build).

Conclusion

I will not doubt for a second to name the Hephestos 2 a quantum leap from its predecessor. It feels solid, it looks good and, specially, it prints beautifully. 

Bed is large and that allows large objects to be printed but it means more mass is moving too, and it is not light, so the machine will not be a speed demon. The printer looks good and has a clean design, electronics uses no fan and it can print from SD or from USB. 

Unfortunately I have not been able to use it with Pronterface or Slic3r but used Cura instead that was the manufacturer's software of choice. I tried not to create more noise during the beta testing of the firmware but I hope the final version will play nicely with these fine programs too. 

Did I say it prints Filaflex great, let me say it again. If you are for printing flexible parts mostly, look no further, this is your printer!



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