The BCN3D Sigma is not just a fantastic 3D printer for dual extrusion; it’s a fantastic 3D printer, full stop. Read our BCN3D Sigma review.
Dual extrusion 3D printers have an absolutely terrible reputation. While the option of printing with different materials and colors is mighty tempting, newbies are regularly deterred by the difficulties involved.
“It’s too complicated”, people say. “Too much hassle”, bays the mob. “Call your mother”, advises the life coach.
So when a dual extrusion 3D printer comes along that just works, it’s a pleasant surprise. And when that same dual extrusion 3D printer leaps to the top of the charts on the 3D Hubs quality rankings, and sits there uncontested for three months (and counting)…
Well, you can bet we’re gonna sit up and take notice.
Designed and manufactured in Barcelona, Spain, the BCN3D Sigma is a truly impressive machine. It’s not perfect by any means, but compared to other desktop 3D printers we’ve used, it’s very nearly the complete package.
And we haven’t even told you the best bit. The BCN3D Sigma is 100% open source, so all the software, hardware and supporting documentation is tweakable, hackable, and modifiable under the terms of a General Public License. Pretty impressive, huh? Read on for our full BCN3D Sigma review, test and verdict.
Dual extrusion doesn’t have to be a pain in the ass. That’s the starting proposition with the BCN3D Sigma, and with an intelligent approach it has completely changed the conversation. The possibilities for dual extrusion are exciting once again, and it’s all thanks to the open source community.
But the BCN3D Sigma also works exceedingly well as a single extrusion fused filament fabrication (FFF) machine, providing quality prints that are frankly spectacular. The build space is generous, the operation is simple, and the industrial design is unique.
Minor niggles are that it doesn’t have wireless connectivity; the firmware has a few teething troubles; and frugal makers may be troubled by the waste product generated by dual extrusion. But these are trivial in comparison to the versatility and performance of the BCN3D Sigma. Highly recommended.
The story of the BCN3D Sigma is an interesting one. Parent company BCN3D Technologies is not actually a company, it’s a special division of Fundació CIM, a not-for-profit educational foundation attached to the University Polytechnic of Catalonia.
As such, the group has deep roots in the RepRap movement. For nearly two decades they’ve been researching and exploring the possibilities of additive manufacturing, and then sharing their knowledge with the wider community in the spirit of open source.
Their earliest forays into desktop 3D printing were DIY kits like the BCN3D+, which are designed to be assembled at home. From there, they experimented with dual extrusion, and through a process of trial and error developed a new approach — Independent Dual Extrusion (IDEX).
Where previous dual extrusion machines attempted to mount two extruders and hotends onto a single carriage — which makes them heavy, bulky, and prone to error — the IDEX system splits them into two, so that each print-head operates separately from the other. This also makes it efficient for single extrusion jobs as required.
It’s a genius solution. In our tests with the IDEX, we were repeatedly surprised by the quality of the prints and the reliability of the machine. In several cases, complicated two-tone models were printed correctly at the very first attempt.
But that’s not all that we found impressive about the BCN3D Sigma. There’s a whole suite of clever features that make this printer an all-round pleasure to use.
The powder-coated, aluminum-framed BCN3D Sigma is an absolute beast of a machine, measuring 465 mm wide by 440 mm deep by 680 mm tall. Part of its size is attributable to the unusual design, with sharp angles and sweeping curves on a semi-open frame; the top and front are open, whereas the two sides have plastic transparent inserts.
The build area of 210 mm x 297 mm x 210 mm is one of the biggest of any 3D printer we’ve tested, after the E3D BigBox and the Ultimaker 2 Extended. Resolution ranges from 300 microns down to 50 microns, where a micron is .001mm.
The print bed is a glass surface overlaid on a PCB heatbed, and the glass is held in position using magnets. This makes it stupidly easy to remove for cleaning and maintenance, but you’d imagine that the magnets would weaken over time from exposure to heat, right? This is avoided by providing cut-outs where they sit flush with the heatbed.
Both the print bed and the IDEX assembly are positioned on moveable, motorized carriages. The print bed moves on the x axis (vertical), while the two extruders move on the y and z (horizontal) axes. The BCN3D Sigma has a slot for an SD card but unfortunately no wireless connectivity, and you manage the machine using a color touchscreen display. It’s responsive enough, albeit a little squishy to the touch.
The filament is situated inside the body of the Sigma, which is another reason for the large bulk. Each spool sits on its side in a lower recess of the machine, whilst the filament is fed through the bottom, under, and then behind the machine, until it emerges above in a sweeping curve through the guiding tube into one of two print-heads. Faced front on, it looks like a glasshopper on steroids. We were worried about what to do in the event of broken filament, but it hasn’t happened yet.
Read more about the design evolution of the BCN3D Sigma here.
The list price for the BCN3D Sigma is €2,295, which positions it somewhere between the enthusiast and prosumer bracket. But that’s not to say it’s a complicated machine with an elaborate setup.
Using the illustrated quick-start guide, which is readable in both English and Spanish, the time it takes from unboxing to commencing the first print is about 15 minutes. Further documentation and support material is available online.
There is no assembly stage. Just carefully lift the Sigma out of the box, remove some packing foam and security tapes, and you’re ready for setup. A box of tools, cables and instructions is also provided, so nothing is lacking at the outset, plus a can of adhesive spray for the print bed.
For the setup, there are about 6 steps; pop in the glass bed; add the two filament spools and insert ends to the feeding unit; attach the guidance tubes for each filament and clip them to the hotend cables; insert “cleaning rubbers” for the hotends; and then slot in the SD card and the power cable.
The next stage is loading filament and calibration — for which users are guided step by step on the touchscreen interface — and then prepping a model for printing using slicing software on your computer. BCN3D offers a bespoke version of Cura, but you can also bring your own application to the party.
To reiterate — the time it takes from unboxing to commencing the print is about 15 minutes.
The BCN3D Sigma takes 2.85 mm filament, the thicker of the two common sizes used in FFF 3D printing (the other being 1.75mm). The machine works with a wide range of material, so you’re not limited to just acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA).
For our test run we printed with Colorfila black and white PLA, but the Sigma also supports ABS, HIPS, polyvinyl alcohol (PVA), TPE, and ColorFabb co-polyesters and specials.
The important thing to note here is that dual extrusion becomes a powerful technique when using the right filament. You can go ahead and make two-tone prints for aesthetic purposes, but if you were to pair PLA with PVA (pictured below), or ABS with HIPS, then you’re looking at using a primary material for building the object, and a dissolvable secondary material for supporting your object.
Suddenly, you don’t have to contend with things like overhang and bridging that physically limit the scope of your designs. Be as wild and crazy as you like, and the Sigma can print it.
The BCN3D Sigma is compatible with a wide range of 3D printing slicer software. That includes Cura and Slic3r (which are free), and Simplify3D (which is paid). Whichever programme you end up using, the point of a slicer is to convert an STL file into layers based on your preferred resolution and supports, and spit it out into G-Code format for printing. For our testing, our preferred application was Simplify3D.
Simplify3D is very easy to use, but rich in features. Open it on your computer, and a virtual print bed appears on the screen. At the left side of the window is the menu where you import your model and your process settings, which lets you tinker with the resolution: High Quality Print, Medium Quality Print, or Fast Low Quality Print. There’s also an option for a Strong Print.
You can specify the type of filament you’re using, which brings in a range of presets to optimize the printing process. You can choose between several styles of infill, whether for stability or lightness, or to be economical with filament. You can also add custom supports on any area of the model, to hold overhanging parts of the object in place during printing. Other options include adding a brim, a thin extension of plastic around the base to help secure it, or a raft, if you’re having problems with the first layer of the print sticking to the bed.
For dual extrusion, the thing to remember is that you actually have two STL files that intersect with each other. In Simplify3D, there’s a nifty wizard that guides you through the setup process, by grouping the models together and aligning them correctly. You can also see a preview of how it will print in a fast-forward animation.
Once you’re ready to print, simply export the file to the included SD card, slot it into the Sigma, and then select it from the print menu.
We printed over a dozen test objects with the BCN3D Sigma. Several were at a high quality print resolution of 50 microns, one at a fast low quality setting of 250 microns, and the rest at a strong setting of 200 microns. Because resolution is a measure of layer height, the lower the value, the higher (or finer) the resolution.
The BCN3D Sigma printed out the majority of our test objects without a hitch. We had to do some initial tweaking on the extrusion multiplier and temperature, to ensure the first layer was pushed out smoothly, but once this was dialled in we were happy with the results.
Print quality in single extrusion is exceptional. We have a 3D Hubs Marvin mascot, a 3DBenchy and a Rook chess piece printed at high quality, and the detail is so fine as to be comparable to a selectively laser sintered (SLS) object. Placed side by side and viewed in low light, at a funny angle, after a few drinks, you may not be able to tell them apart.
Moving on to dual extrusion, the results were equally impressive. Using strong settings we made a striped frog by nervoussystem, a puzzle draudi by BCN3D, and a traffic cone by R3ND3R; they all printed correctly the first time.
Some post-processing is required to remove threads of stringing from the models, because of the constant hopping between the two print-heads, but they were otherwise fine. Due to this particular setting, however, the surface layering was clearly visible. If we step up to a different quality setting, the resolution would be finer… but then the job would take longer.
The only real disappointment was a two-tone 3DBenchy. It printed successfully using the fast low quality setting, but the finished product was a lot scrappier than its monochrome counterpart.
Watching the printer in operation during dual extrusion, we made a few other observations. The auto-calibration probe is really cool, where a sensor checks on the level of the print bed before commencing operation, and adjusts the height of the IDEX accordingly.
Some issues we noticed were that each extruder is still pushing out a small amount of filament when it’s not in use. Presumably this is to maintain temperature and constant flow when it’s “resting”, but the cleaning rubber container soon fills up with waste when you’re doing a medium sized print. Another waste factor is the color calibration column that the IDEX creates to maintain consistency while printing.
Also, the time it takes to complete a print job is not displayed on the touchscreen. Instead, you’re given a percentage estimate. This is not particularly useful, and we’d rather know how long we can expect to leave the printer running.
This relates to another problem, where the time estimate given for a dual extrusion object in Simplify3D didn’t tally with the time it actually took to fabricate. We had an estimate of 12 hours for one model, and we were surprised to find it actually took 16 hours. This may have something to do with the slicer software we used, so we’ll give the BCN3D Sigma the benefit of the doubt here.
Finally, we found the touchscreen interface was occasionally buggy when navigating menus. When tweaking the settings in the middle of a print for the dual 3DBenchy, the menu just froze, so we had to sit back and wait for the job to complete. We would like to see this problem fixed in a firmware update.
Noise levels and fume emissions on the BCN3D Sigma are pretty much the same as with any desktop 3D printer. 56 decibels are within the permissible range, but it’s still pretty loud. The standard advice is to work in a well-ventilated area, where the noise is not going to disturb your colleagues or neighbors.
The BCN3D Sigma is a large, semi open-frame 3D printer that’s geared for use primarily by hobbyists and professionals. It has an easy setup that’s comparable to the Ultimaker 2 series, which makes it a good fit for a general audience.
The Sigma can print large objects with reasonable detail, and small objects with intricate detail, and in both cases proved reliable in our testing. The switch between single and dual extrusion is seamless, and the IDEX system is a fantastic innovation by the open source community. Expect to see it adopted by other manufacturers in the near future.
However, the print time was difficult to reliably estimate, based on confusion between the slicer software and the percent completion indicator on the machine. This problem is multiplied the bigger or more intricate the print job, but this should be easily addressed in a future software update.
It’s a dependable and versatile machine. While dual extrusion might be considered overkill for an absolute beginner, for folks looking to graduate to the next level in fused filament fabrication, the BCN3D Sigma is the ultimate desktop 3D printer.
That’s the end of our BCN3D Sigma review. Any questions? Are you a proud owner? Tell us about your experiences with the BCN3D Sigma in the comments.
License: The text of "BCN3D Sigma Review: A Fantastic 3D Printer" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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