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The old question: which joints for my Delta build

Posted by Protoprinter 
The old question: which joints for my Delta build
August 08, 2019 03:41AM
Hi,
after some experience with my Hexagon Delta Printer, I decided to build my own.

If you are interested:
The Main-Frame is free of printed parts, Motors/elektronics on top to Keep the belts short, I shrinked the z-hight to 240mm as I never Need more higth (again, keeps belts short). Hanging Extruder with a self designed big bearing to prevent small bowden radius when the Effector is homed. 0,9° Stepper with Support bearings for more belt tension, 9mm Gates HTD belts, OLED Display, Rpi3 with Octoprint, 220V heated Bed 500W


It is not finished yet, I am waiting for Lasered parts to close the Frame etc. Well it already prints nice with a good Quality. The geometrical Errors seems to be very small (if there are any). Have a look at the build thread for Pics and further Information (german)

Now my question. I am still using my old rods from the Hexagon. The IGUS rodends are quite old and have play and are getting noisy while printing quick infill. I don´t want to use magnetic Rods. I am looking for some steel or better aluminium Rod-Ends with a minimum of play and good reliability. Something like this. Futher suggestions/experience?

Nice fact: even with this old rods, the print quaility of the Printer is so much better than my old Hexagon. Frames and belts seems to be more important for print quality

Edited 2 time(s). Last edit at 08/08/2019 05:34AM by Protoprinter.


Deltadrucker, Tantillus Reborn by Toolson/Protoprinter, Ashray - (445nm Lasercutter), die Delta-Kalibrieranleitung
Re: The old question: which joints for my Delta build
August 08, 2019 09:24AM
Quote
Protoprinter
I don´t want to use magnetic Rods. I am looking for some steel or better aluminium Rod-Ends with a minimum of play and good reliability.

I used to feel the same way about magnetic rods, I found that my fears/reasoning for not wanting to use them was unfounded. Plus nothing beats the play free movement and ease of use if you want to work on the effector.

I'd reconsider magnetic rods.


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Re: The old question: which joints for my Delta build
August 09, 2019 03:44AM
@Protoprinter:
You can consider these too: [mpjet.com]
I do not use them myself. I use plastic MP-Jet joints.

@blt3dp:
It all depends what kind of accelerations you want your printer to handle and whether you mind the extruder disconnecting in the case of a crash.
What accelerations and print speeds do you use?

Edited 2 time(s). Last edit at 08/09/2019 03:47AM by hercek.
Re: The old question: which joints for my Delta build
August 09, 2019 04:49AM
@hercek
Nice. I already ordered some plastic MP Joints, but I can bent the black part of the Joint easily...not sure if they are stiff enough. Usually my print speed is 100mm/s with Acceleration 4000mm/s^2. But maybe I can increase these values. I think the bottleneck in my build are the ball links...the linked Joints don´t have a Version with a 3mm bore but 2mm - that means I do have to Exchange Effector/Carriages to fit a smaller nut...but ist changed quickly...

@blt3dp
Thanks for your answer. Well, I am not afraid of magnetic Joints, but it makes everything more komplex. I do have to redraw my effector and carriages, the wight of moving parts will increase. Ball links are simple and light. My effector usually stays in place for years, no need to change it. Two screws and I have got the hotend out - instead of a nozzle change, I usually change the entire hotend within 2 minutes.


Deltadrucker, Tantillus Reborn by Toolson/Protoprinter, Ashray - (445nm Lasercutter), die Delta-Kalibrieranleitung
Re: The old question: which joints for my Delta build
August 09, 2019 06:27AM
Plastic joints are probably stiff enough. Notice that the forces on the diagonal rod are almost entirely in the direction of the long diagonal rod axe. The only forces trying to bend a ball joint to a side are coming from the friction between the ball and its sleeve and the inertia (acceleration/deceleration) forces from the diagonal rod itself (its weight). These are very small.

Magnetic joints are good enough for 100 mm/s and 4000 mm/s². Well if your platform is not too heavy. Many people here use them with these settings. I do not use magnetic joints. They are too heavy for the holding force they can provide. My accelerations are typically around 10000 mm/s². Printing speed varies from 80 - 120 mm/s. Non-printing speed is always 240 mm/s. I doubt magnetic joints would withstand this. And even if they would they would unnecessarily increase the weight and the ringing on the prints.
Re: The old question: which joints for my Delta build
August 09, 2019 12:02PM
@Protoprinter
I can understand that. If your effector is plastic, then everything you said about the weight would be true and there would be no benefit to changing just the rods to magnetic rods. In my case, because I changed the effector too, my whole setup got lighter than it was previously. Probably not as light as yours though. Ease of use stayed about the same, I can see there not being much benefit.

@hercek
I'm using 3000 mm/s² accelerations, non travel moves at 120 mm/s. I routinely print at 90 mm/s
I suppose I don't understand the need for such accelerations. If I graph a move of my entire bed diameter (300 mm) @ 120 mm/s with both 9000, 6000, and 3000 mm/s² acceleration, the distance it takes to accelerate to 120 mm/sec is something like 2 mm, 4 mm, 6 mm respectively. I suppose I don't understand the practical difference. You're probably right about them coming detached at speeds and accelerations as high as yours. If my use case were different, I would consider different options.


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Re: The old question: which joints for my Delta build
August 09, 2019 02:35PM
@glt3dp:
Notice that the print head must decelerate to s stop and accelerate to the target speed at every direction change. Imagine you are printing hexagonal infill or you are printing an infil between two wall which are only 6 mm apart. Your print head has 3 mm to accelerate and 3 mm to decelerate when printing infill. With your acceleration of 3000 mm/s² it will be able to accelerate to the max speed in the middle of the infil and then it must immediately start to decelerate. The result is that the infill is printed with an effective speed of 60 mm/s and not the speed of 120 mm/s. In other words, accelerations are important when you use hexagonal infill or you often print models with a lot of holes. Like e.g. this one: [deskthority.net] .
Re: The old question: which joints for my Delta build
August 10, 2019 03:25AM
For me it has to be magnetic joints and Smart Effector (but I'm biased, because I designed the Smart Effector). Total effector mass is 150g. I've tested it raising and lowering an additional 1.5kg mass slung below the effector, and had no problems with joint disconnections.

On another topic: as you have a hexagonal frame, have you considered mounting the extruder drive on an additional carriage riding on one of the spare towers, driven by another stepper motor? That would allow you to use a shorter Bowden tube. Like this [www.youtube.com].



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
Re: The old question: which joints for my Delta build
August 10, 2019 04:47AM
Thanks for the discussion. No, I don´t have a hexagonal frame...three towers, see the picture in my 1st Post. I have had one (Hexagon). The hanging extruder works really nice, the Bowden ist quite short. As it may rotate around ohne Axis, the bowden isn't bowed in sharp angles..


Deltadrucker, Tantillus Reborn by Toolson/Protoprinter, Ashray - (445nm Lasercutter), die Delta-Kalibrieranleitung
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