Stratasys FDM in the Bambu Age

It’s beyond doubt that Bambu produces incredible 3D printers. They make absolutely beautiful parts right out of the box, with an ease of use that is practically unparalleled across hobbyist and even professional 3D printers. But how do they stack up against Stratasys FDM?

The Bambu can handle a wide variety of filaments and is open to 3rd party materials, too.  Its enclosed chamber helps to minimize warp and enables the successful printing of bulky ABS parts that would otherwise fail on similar hobby printers.  Its positional control is lightning fast, and also of very high accuracy -- a tough combination to achieve. ​

Bambu Labs X1C printer

In several ways, the Bambu arguably outdoes our workhorse Stratasys FDM machines – machines that are current in today’s industrial marketplace and cost hundreds of times more than a Bambu printer.  The Bambu can achieve layer resolutions and cosmetic appearances that approach that of PolyJet or SLA, handily trouncing the relatively coarse finish of even a well-tuned Stratasys FDM machine.  

The speed of the Bambu is also impressive.  While Stratasys FDM machines (especially when set to their larger tip diameters) can keep up or even outpace the Bambu with bulkier builds, it’s wild to see that a machine as inexpensive and easy to use as the Bambu can even come close, and in many scenarios speed past the Stratasys offerings.
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While the Bambu has several advantages over Stratasys FDM, it also has a few obvious setbacks.  For starters, the size (or lack thereof) of the Bambu means that larger parts must be broken up into smaller pieces in order to print.  Doing so creates extra work, introduces more room for dimensional inaccuracies, and can often result in a weaker final part depending on how the individual pieces are joined together.  

Our Bambu X1C, with its AMS, tucked inside of our Stratasys F770 FDM printer.

Another advantage that Stratasys FDM machines have over the Bambu is their dedicated support material extruder.  Although the Bambu’s AMS system is amazing in its own right and can make for simple changes between a large number of materials, it has some limitations borne of the unavoidable fact that the Bambu has only one extruder, so any changes require purging (time and material waste) and even then will never be perfectly clean.  

Stratasys FDM machines, on the other hand, have 2 extruders: one dedicated solely to model material, and one to support.  This arrangement enables quick transitions between the two materials (each remains loaded at all times) without the need for additional purging, which can save large amounts of time and material in the context of jobs with significant support requirements (a lot of the work we do at POP requires extensive support).​

Stratasys units like our 400mc machines have dedicated extruders for model (left) and support (right) materials. Image courtesy of University of Maryland.

We bought a Bambu machine of our own, to make small parts around the shop for internal use, and also to keep up to speed with the ever-changing world of 3D printing.  With the machine at our disposal, we wanted to do some more in depth testing to clarify the utility (or lack thereof) of a couple seemingly significant Stratasys features that are missing in the Bambu, to see whether or not they are important to part functionality.

HIGH-TEMPERATURE HEATED BUILD CHAMBER

Stratasys machines are known for their oven-like build chambers, which can exceed temperatures of 200C depending on the material being printed (Ultem, for example, prints in a chamber that’s around 200C).  We can’t print Ultem on the Bambu but we can print ABS on both machines, so we started there.

Stratasys machines print ABS in a chamber that's held around 95C (depending on the exact profile being used).  The Bambu heats its bed to about the same temperature, and with the doors closed can approach chamber temperatures of ~40C while printing ABS.  Clearly, this is a big difference.  But does it matter?  We designed and printed some simple test parts (solid infill) to find out: one on our Stratasys 400mc, and the other on our Bambu X1C.  Both samples used the same material, with recommended (default) solid infill settings.    

Both sets of parts looked good out of the machine, but the Bambu’s looked crisper.  This is partly attributable to the slight difference in layer resolution (we opted to use the “strength” profile on the Bambu slicer at 0.2mm, set to 100% infill) vs the Stratasys default layer resolution of 0.010” (~0.25mm).  But, even accounting for the slight difference in z-height, the Bambu parts looked nicer, with better seams and a slightly more refined appearance overall.  

The differences in appearance between the Stratasys sample (left) and the Bambu sample (right) are most subtle, but the Bambu unit is clearly the more attractive of the two.

We wondered, though, if the heated build chamber does more than prevent warp with XL builds.  In order to determine the interlayer strength of the test samples, we devised and printed a simple hook fixture that allowed us to hang a bucket off the end of each sample, which we would slowly fill with water until the beam broke in bending (shearing along layer lines).  Videos are below.   

The Bambu part failed under a weight of ~4,750g while the Stratasys unit made it all the way to ~7,900g at failure.  While we can’t say for sure, I attribute this large z-strength difference to the heated build chamber – the Stratasys, when depositing fresh plastic onto a hot part, can ensure more substantial fusion between layers.  The Bambu, on the other hand, is depositing hot plastic onto a cooler part, which likely makes full fusion more difficult (setting the extrusion temperature extra hot might help slightly but could introduce other issues).  

Bambu

Stratasys

The Bambu part broke more cleanly, suggesting that interlayer adhesion was weaker

The Stratasys break was messier, and spanned more layers, suggesting better interlayer adhesion

TRACE SUPPORT AND ITS EFFECT ON LAYER ADHESION

The other question that we wanted to answer was whether or not the Bambu’s single extrusion head would introduce problems related to material contamination after switchovers between support and model.  While this is of course mitigated by the generous purge volume and purge towers recommended by Bambu (which we followed – and even increased slightly), it is an issue that is impossible to fully resolve (one can only asymptote to a pure material in the context of purging).  Moreover, the solution (ever more purging) involves more wasted material and time.

To test whether or not this is an actual issue, we built another test bar, this time with a sister part that had a single layer of breakaway support embedded in it.  The resulting part again looked nearly flawless.

This model has no support in it itself, but was printed in a pack with another model that had a support break at the circled Z height.

While the part doesn't look tainted at all, a stark difference was noted in strength.  While the original Bambu sample could hold a bucket of water weighing ~4,750g at failure, the new model could only support ~1,650g – almost a 5x decrease compared to the Stratasys sample.  As the sample broke precisely at the layer during which the material changeover occurred, it is very likely that contamination had an impact in strength, as anticipated. This was confirmed by our observation that it was relatively easy to peel back layers of ABS around the break, compared to the more solid interlayer adhesion throughout the rest of the part.​

Conclusion

Getting this out the way -- we love our Stratasys FDM machines, but we also remain very impressed with our Bambu X1C.  Neither solution is perfect, with each offering unique advantages and disadvantages.  The Bambu offering is easy to use, inexpensive to operate, and is capable of making prints that are nearly flawless in their aesthetics.  I would quickly recommend it for fit-check prototyping (assuming that dedicated support material isn't a hard requirement), and for anyone who wants to get into 3D printing without a major investment or very specific needs.  

Stratasys FDM machines, especially the very large format units, are on another level in terms of cost -- these are typically not practical for an individual or even a company (that's not focused on 3D printing) to own and operate.  With that being said, they do make decent looking parts that are truly functional.  Their reliability, lack of warpage concerns, and dedicated support materials set them apart from other FDM solutions.  We aren't ready to replace them!