That is interesting… maybe it does actually have some kind of sensor fitted because they knew we would try to do exactly what you are attempting to do… would definitely be interesting to find out the response from MarkForged… keep us updated.
Perhaps you really should try surreptitiously switching the labels on the filament spools
Carbon Fiber is too stiff to make the sharp turns that the machine can make with either fiber glass or Kevlar. Hence the reduced options in the Carbon Fiber menu.
I was a bit disappointed by this as well with my Mark One. Pretty sure the limitation is due to the brittle nature of carbon fiber. Dig into you composites text books. You will find that there is a minimum radius of curvature that you can bend a brittle fiber around before it breaks. It is a function of the individual fiber diameter, modulus, and strain capability of the fiber. Markforged does not really tell you what the exact fiber they use. So exact fiber modulus, fiber diameter, strain capability are hard to come by. Isotropic Fiber mode has to bend the fiber around a very sharp radii after each pass. The fibers would likely break at every pass and jam up the extruder. Looks like the Mark Two can run in Isotropic Fiber mode to put down discrete fiber orientations. I think the Mark Two keeps the chamber hotter which might help keep the tow bundle from breaking. They also put the fiber cutter much closer to the extruder so the minimum cut area is 15x smaller per their literature. The cutter location distance to the extruder on the Mark One dictates the minimum filament length that has to be put down. The Mark Two might be able to cut the fiber at each pass before it changes direction eliminating the need to bend the filament. Haven’t seen the Mark Two in action yet, so I am only hypothesizing.
These are the main improvements on the MarkOne and its interesting to note that firstly they have upgraded the spec to be “15 times smaller” regarding adding reinforced fibres and also “additional sensors in the print head”… implying that there were already some there other than just for heat perhaps?
Looks like the MarkOne was a bit of DODO?
Carbon, Glass & Kevlar fibre melted down to 260-290C can hardly be too ‘stiff’ can it?.. the concept of 3D printing with something like carbon fibre generally speaking is an anathema… carbon fibre products get their strength from the weave & layering of the fibres bonded by/within resin which in turn gives the beautiful patterns on traditional carbon fibre products… hence the term ‘carbon fibre’.
However if carbon 3D filament is laid down correctly within the confines of another strong 3D printing material rather than using traditional resins it does indeed act like a reinforcing and rigid fibre style alternative… encased by nylon regarding the MarkForged printers. This 3D printing concept relies therefore on printing in long bonded lines to achieve something close/near to what/how traditional raw carbon fibre is woven/made/produced/prepared to function as a super strong engineering type material which in turn is then manufactured into a multitude of shapes and sizes.
The MarkForged printers have therefore been designed to deliver this conceptual dual 3D printing/Carbon Fibre production/preparation which necessarily limits/governs how these printers actually produce finished 3D prints… damn clever but is it really a ‘carbon fibre’ 3D print or just a smart ‘smoke n mirrors’ alternative using both carbon and nylon printing filaments which look, feel and function well when printed together?
Buy one and you’ll find out… just don’t bother with the MarkOne though cos it looks like it wasn’t very useful. (oops… he has bought one… no offence intended
Last couple of points… I always wondered why they didn’t have the carbon filament layer in a weave type pattern on the MarkOne… would have at least looked more convincing… and why no black nylon filament alternative?
P.S. I’ve just ordered a reel of 3DXMax™ CFR Carbon Fiber Reinforced Nylon 3D Filament 4 to test on my UM2 so printing with carbon & nylon definitely interests me.
They are all pretty much carbon fibre dust… including the Markforged filament… by the time the filament has been heated up and forced out through the nozzle its just a ‘mush’ anyway so not actually sure what your point is here?
…I do have to add that you can always rely on you Yanks to try and knock us Brits off our Limey ‘high horses’… always makes me chuckle… bless you… you rarely succeed of course but don’t stop trying cos we love you ‘lot’ and always have done… trouble is in general we always seem to be a couple of years behind you though… :):)
Not sure what you mean by a “me too company” but I came away from working at Airbus thinking what a bunch of scumbags and liars from top to bottom… horrible conglomerate with some of the most repugnant people I have ever had the misfortune to work with/for. Loved the industry/technology though… especially working on the A400M… no problems with semantics here then.
I currently use Colorfabb’s XT-CF20 (XT being a type of PETG - polyester based co-polymer) which is pretty good for my needs… however post-print work can be extensive… including sealing and sanding down.
For me the most important factor is the almost complete lack of warp and extremely good printing accuracy of this 20% carbon reinforced material which provides an 0.2mm precision from CAD to 3D print on my UM2. I can also print with it down to 0.06 layer height which produces some fantastic looking prints.
The Markforged ‘printing continuous fibre’ tosh would only make any sense/authenticity if the carbon filament was a high percentage continuous single carbon fibre and it clearly is not by any stretch of the imagination… you probably wouldn’t be able to print with it if it was… they don’t even tell you what % carbon the filament contains on their data sheets so I’m afraid that’s just more marketing waffle and what’s commonly known as a ‘Red Herring’. As I said earlier there’s just a bit too much ‘smoke n mirrors’ surrounding this printer and they really should be more open regarding its actual capabilities and technical specifications… and in particular regarding their proprietary filaments.
If the MarkOne/Two printed like the 3D printer in your aircraft wing video then that really would be a whole new ball game… at least the UM2 does actually print in diagonal layers offering some kind of weave appearance/enhanced lamination.
That’s not to say that MarkForged can’t come up with something good if they keep going the way they are… it is far and away the best looking 3D printer ever and a marketing department to match… so why they don’t just also ‘pump out’ a less expensive, non-proprietary, dual hot end version is way beyond me… they’d sell a ton.
Thanks for the link to the paper. I don’t see in the paper where it drives you to the conclusion that the fibers are not continuous. There was one specimen where they happen to catch the beginning/ending of the fiber path in the test area. Makes sense that they would see lower results with that discontinuity in the test gauge area. They did measure the fiber volume % at 34.7%. For sure that is low for an optimal carbon composite which would be more in the Vf%=55-65% range. 34.7% is still respectable. And their modulus and strength correlated to T300 which is a very common standard modulus aerospace fiber…think fairings and control surfaces Not a bad paper for what was clearly put together by undergraduates. Not quite the level of testing necessary to be able to actually develop a statistical allowables database to be able to design with a reasonable margin of safety.
You are correct… they did observe some microscopic continuity but hardly the point when all the ‘voids’ they found are also noted and even if this research was for their first degrees (which it isn’t) you would still have to concede that this very informative and thorough scientific research report does not support ANY of the Markforged marketing hype… particularly regarding structural integrity… the concluding 6 carbon layer tensile results were actually appalling when compared to traditional carbon fibre products… and to claim that MarkOne prints are comparable to metal in any way at all is clearly reprehensible after reading this report… but hey if you want to believe otherwise… why not… you paid more than $5000 for the privilege of self delusion so its clearly your prerogative? Personally… I’ll be steering well clear of ANY MarkForged products… once bitten twice shy!
One last question… if you print and sell a load bearing product through your hub… whether you knew what it was going to be used for or not… using your much hyped Mark One and it failed catastrophically… do you think MarkForged or even 3D Hubs will be held responsible… or do you think it will be you who will suffer the consequences?
The voids did not surprise me. I think you would find significant porosity in most any FDM part under the microscope. Would have been interesting to also see a more zoomed out view. Guessing there would be significantly more porosity between the courses for each fiber bundle. That level of porosity wouldn’t impact the performance all that much parallel to the fiber direction. 2-3% porosity is usually kind of a magic number where the matrix dominated properties (shear and transverse strength). Eyeballing those photos look to be less than 5% not bad for a process without an autoclave or press.
Failure at tabbed areas of the thicker coupons probably has more to do with how they chose and prepped the tab material. Coupon alignment in the load frame and the stress discontinuities where the tabs terminate will also cause low failures. Add to that grip damage and their higher variability in the 6 ply coupon probably has more to do with the test than with the material. Even on the low end the ply modulus and strength were significantly higher than say 6061-T651 (aluminium to you). Average modulus was about double 6061. The strength ranged from 370 to 520MPa. That is much higher than the yield strength of 6061 at 276MPa. You could still probably match the stiffness in laminate form with multiple ply angles. Strength might be a bit less in the laminate but that would really depend on the ply orientation stacking sequence. So their marketing material stating you can get stiffness similar to aluminum is still accurate. I am still holding out hope that Markforged can update the settings on the Mark One to allow multiple ply orientations with Carbon. I hope you were not under the illusion that printing with the Mark One/Two would give you isotropic performance like a metal. No composite can do that. The properties are always planar and highly tailorable.
As to structural guarantees for parts that I print on 3D HUBS, I make none. I do not offer structural analysis service. It’s up to the customer to proof test their own design. I just give advice on whether their design will be printable or not. 3D HUBS is a nice way to help offset the cost of a very expensive hobby.
