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Re: Projet s2a (Single Arm Articulated) - 6 years ago

Bonjour and Good Job on this bot. I've come here via Hackaday, which you mention in the previous post so again congrats for that too I don't suppose you guys are willing to switch to english just for the sake of getting international but you would get a hella lot more involvement and advice from people around the world and this could get bigger still.

by realthor - RepRap Groupe d'Utilisateurs Francophone

Re: Best Z-axis configuration? - 6 years ago

I contemplated the same idea to have a stationary extruder motor by using a belt that would turn the extruder gear but never got time or enough will to try it. I don't really get it in your sketch how the motor will -at the same time- move the selected axis with the speed/accelleration/jerk/etc and push/pull filament through the extruder. I believe that can't be done with only one stepper. But wi

by realthor - CoreXY Machines

Re: Kappa 3D printer - The next generation 3D printer - 7 years ago

I believe the most difficulty -precision-wise- is when the arm is fully extended and the two sliding arms (a and b on your drawing above) are closest to each other. To avoid this a and b should be fairly long so that when fully extended (printing at the opposite extreme to the Z tower), there is a comfortable distance between the a and b arms' sliding ends. Have you measured or noticed anything w

by realthor - General New Machines Topics

Re: MiniM's Core XY project - 7 years ago

This joint relies on presumably flat faces of the extrusion and might be easy to to/adjust: But I see you already have the corrected parts coming anytime so maybe a too late of an option

by realthor - CoreXY Machines

Re: Kappa 3D printer - The next generation 3D printer - 7 years ago

No other responses from July ... strane. I find the design very interesting as you basically save one axis worth of linear guides/rails and also pretty compact. Personally I would have better liked a rotating X axis like the Polar3D so that the bed wouldn't stick too much out of the footprint but nevertheless this design is very welcomed. By not receiving a response I assume the design is not ope

by realthor - General New Machines Topics

Re: Can stall detection at stepper driver level be used to account for backlash in a geared system? - 7 years ago

Hmm, that's a pity. But it would be nice to have that feature in the motor drivers, so that they can let the firmware know when resistance was detected (tooth-on-tooth contact), so that the firmware only calculates distances based on that point onwards, basically neglecting the backlash. Otherwise backlash-free operation is difficult to achieve and only some sort of real position of the effector

by realthor - General

Can stall detection at stepper driver level be used to account for backlash in a geared system? - 7 years ago

Hi there, quick question here. The cheap way to provide precise movements via imprecise mechanical components is to leverage software and/or in-chip features like the StallGuard of the Trinamic stepper drivers (and others with similar features). I believe it is feasible to record in software the backlash of a geared system by measuring the rotation of the motor without any load until it hits the

by realthor - General

Re: I have designed an application-specific, zero-backlash gears system. RFC ... - 7 years ago

I know about these scissors or split spring-loaded gears but I need the cable to be inline and the whole application of this is to have that cable to move the payload. So employing such a split spring-loaded gear will be redundant at least. The spring loaded split gears, as far as I know, are not very precise either as they settle at half backlash whereas I need predictable movement, which I beli

by realthor - Mechanics

Re: Can you guys confirm if this is zero-backlash? - 7 years ago

@dd: Yes I rely on the tension in the cable to grant the backlash-free operation. That is the main idea because otherwise any gears will have backlash by operating the way you describe it. I even imagine a metal ribbon used to lock the loop so that at all times the driven gears contact the motor gear the way I shown in the picture. I don't see it not being able to take large loads ... unless it g

by realthor - Mechanics

Re: Can you guys confirm if this is zero-backlash? - 7 years ago

@DC: Ideally the tooth engagement is to have contact with both larger gear's adjacent tooth flanks or with several teeth but in practice the gears are not perfect and there is always a gap besides the tooth (pls excuse me if this looks like lecturing you, it's not): However, because I am tensioning the cable (steel?) so that both driven gears press on opposing flanks on the motor gear's teeth (

by realthor - Mechanics

Re: Can you guys confirm if this is zero-backlash? - 7 years ago

Thanks DC for chiming in, I find myself from time to time in search of a very low or no backlash solution and this might be the closest I got so far. But I fear there is something I am missing and this might have backlash after all. I say this because it is somehow mandatory that there is a gap for any tooth to be able to engage so that gap will translate in a disconnect when reversing direction.

by realthor - Mechanics

I have designed an application-specific, zero-backlash gears system. RFC ... - 7 years ago

Hello guys, I am quite unsure if this application I have will be zero backlash using the solution in the attached image. I don't really have any means to test this so asking around sounds like a good feedback chance. Edit: the preload can take the form of a tensioned cable like in the pic below: I believe that the tension in the cable will create a "closed loop" where at no time the motor ge

by realthor - Mechanics

Re: Polar coordinate programming - 7 years ago

I have been toying at some point with a similar concept but have left scara&polar aside for a while. It's an interesting concept I would like to re-consider at some point. I still have the CAD, here attached is my design I explored back a year or so... The linear part of the XY gantry should only be able to move half way of the diameter to cover the whole print surface. You should look into

by realthor - Polar Machines, SCARA, Robot Arms

Re: Are the two different masses of the XCarriage and whole Y+X gantries for the other mass a real issue? - 8 years ago

One thought, with corexy would it be possible somehow to balance the two axes by assigning different accellerations, etc so that the performance of the Y gets closer to the one of X? Just a thought...

by realthor - CoreXY Machines

Re: Are the two different masses of the XCarriage and whole Y+X gantries for the other mass a real issue? - 8 years ago

Thanks D_D, this is one aspect of corexy design that I haven't considered until now and it is quite a surprise to me that it wasn't obvious from the start.

by realthor - CoreXY Machines

Are the two different masses of the XCarriage and whole Y+X gantries for the other mass a real issue? - 8 years ago

Hi guys, i've heard that with corexy the two different masses that have to be moved, XCarriage in X direction and whole Y+X gantries for Y direction could be an issue. Is that true? I can't seem to be able to wrap my head around it. Each motor in corexy, when moving, will move both masses so there is no differentiation in torque needed or anything else. I could be wrong though so I want some feed

by realthor - CoreXY Machines

Re: Cycloidal Extruder Drive: A lightweight direct extruder drive unit - 8 years ago

Wow, that looks fantastic :-o

by realthor - General

Re: Cycloidal Extruder Drive: A lightweight direct extruder drive unit - 8 years ago

Please share the results with Acetal, I am too interested in a 3D printed version of this nice development. Great work guys!

by realthor - General

Re: This engineer claims 100 grams direct extruder. I want one - 8 years ago

I have followed with great interest the whole thread and this is exactly what I was after: a concept that would crystallize into something real. I am a big fan of the cycloidal drive so this is so much more interesting to me. While I hope this thread will continue to have folks show off their lightweight extruders concepts and prototypes, I am glad that your design got a well deserved new home.

by realthor - General

Re: Bowden PTFE tube with micro perforations. - 8 years ago

Too long tube and you're in the bowden-syndrome area, where the little difference between ID of the PFTE tube and filament OD will add up to a point where what the firmware knows of the filament is no longer true and you get lower quality prints. Ideally bowden will be shortest possible, that's why some deltas use the flying extruder to shorten the PFTE tube.

by realthor - General

Re: Scara 3d Printer - 8 years ago

Imi place, foarte compacta. Felicitari. Nu prea am ce comenta. Poate roata de jos puteai sa o faci herringbone-style si sa scapi de curea. Imi place ca Z e pe curea, fara surub trapezoidal sau bara filetata (sper ca nu am visat). Ce firmware folosesti?

by realthor - Progres, imbunatatiri. Alte proiecte si idei

Re: Z bed cantilever - 8 years ago

Wood "works" and changes with themp and humidity. Wood is also pretty heavy if you are talking about hard woods like oak. It is also more expensive than ALU most of the times. In my view you could get away with a wooden bed if you have a bed leveling probe and do the calibration routine before every print. I would suggest to take some inspiration from wooden ultimakers and makerbots for a bed su

by realthor - CoreXY Machines

Re: Inverted FFF printer - 8 years ago

Yeah, mea culpa, i've jumped to the last page and didn't see any (updated) photos/sketches. Quite impressive, I agree this deserves applause.

by realthor - General

Re: Inverted FFF printer - 8 years ago

Any actual build based on these ideas? I have been and still am interested in bringing all the heavy components down for a low center of gravity printer... Also the idea of an inverted open box style bed is something I've been thinking about, to keep the hottest at the first layers of the print, with no hot air escaping that area.

by realthor - General

Re: Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/stretch when tensioned? - 8 years ago

I know very few designs that use the kind of spring that d_d reffered at the top of the thread and those are pretty much known to be wrong designs. I am talking about designing a lock-in-place tensioner, either at the steppers mounting plate or at the printhead. Because there is no easy way to tension a belt to the proper value by the thumb-test cozmicray was talking about, I thought that there

by realthor - CoreXY Machines

Re: This engineer claims 100 grams direct extruder. I want one - 8 years ago

The 12:1 you use now would be more than enough for the 1.75mm filament, what changes are necessary to make it 1.75mm compatible?

by realthor - General

Is there any "rule of thumb" to know how much would a 6mm GT2 belt creep/stretch when tensioned? - 8 years ago

Hi guys, I hope this is not a very stupid question but I would like to know what difference in length one could expect after crocheting the GT2 belt through the corexy XY stage and tensioning it via whatever mechanism? Say I can manage to have 1500mm of belt per motor. I will pull one end and insert it in a toothed printed part. How much would the belt elongate during this procedure? I don't have

by realthor - CoreXY Machines

Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one - 8 years ago

Nah, linear rail is still too expensive for justifying the price. My latest design is using 10mm with SF-1 or sintered bronze bushings (will probably go for SF-1 for now) some 60-70mm apart for good stability, so the bearings' weight is saved here (they're incredibly heavy compared to the LM8UUs). The hotend to move is to make a Renishaw-probe arrangement where the hotend itself is the probe. E

by realthor - General

Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one - 8 years ago

QuoteDjDemonD They might bend if you are fortunate enough to have your head crash in the centre of their travel, but near the supports at the ends of the travel - probably not a great deal at all. Sorry to be a little puzzled at this topic but head crashes are occasional unfortunate events, which generally don't cause much harm as they usually only happen when calibrating/modifying the machine a

by realthor - General

Re: Bed Stability: 3-point leveling should be in fact 2-point leveling and a fixed one - 8 years ago

QuoteMechaBits Lol...Just put X arm on a hinge...then you might only need to level bed in one direction. I don't get it... what X arm? And really, I don't know if 10mm rods will flex before heatbrake gives away ...

by realthor - General