Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing Hi everyone, my apologies for the weird headline... Digital_Dentist introduced me ( us ) to a cool machine he wants to DIY CoreXY-style. Sisyphus Kickstarter campaign I thought of building a smaller, cheaper and easier to build desktop version. It is based on bipolar-modded 28BYJ stepper, because it fit's the bill and has plenty of steps/turn ( ~4096). That's important, because I want to build a 2D polar-Delta mechanic, which guides the magnet. The motor shaft will only turn 120° at most. [attachment 105709 polar_delta_2d.jpg] I hope the picture tells it all, but feel free to ask details. I want to use Arduino UNO and CNC shield, because it has a small footprint and is cheap. Problem is, I have no idea how to implement this kinematic into GRBL or any other FW that fits a 328P MCU. Anyone having better controller in mind or is willing to cooperate in any way? We could call it: RepRap-Christmas project *wink* I also have intentions to replace the sand with some transparent fluid ( honey-like consistence ) and just let the steelball carve some, slowly disappearing, traces while we could also watch the hypnotic moves of the mechanic. https://reprap.org/forum/read.php?4,826670,826670#msg-826670 Thu, 15 Oct 2026 22:22:43 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?4,826670,858807#msg-858807 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,858807#msg-858807
Best regards,
Liam]]> LiamBlack Reprappers Mon, 02 Sep 2019 01:01:04 -0400 https://reprap.org/forum/read.php?4,826670,828121#msg-828121 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,828121#msg-828121 I made some tests with 2mm thick glass and the magnet holds the ball pretty good.
But I'm afraid, the sound of sand grinding on glass could be pretty disturbing.
Another option would be a thin sheet of aluminum. When the magnet moves slow, the 'Eddy-currents' won't have an effect I guess.

Is there any sheet material, that could dampen the sound instead of amplifying it?]]> o_lampe Reprappers Mon, 09 Jul 2018 01:56:33 -0400 https://reprap.org/forum/read.php?4,826670,828119#msg-828119 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,828119#msg-828119 I chose two different sized v-groove bearings ( V603 and V624 ), but V624 would work for both jobs.
The carbon rods are nested in the V-groove, but don't touch it.
The 3rd. roller might be useless. The cable tension will hold the X-gantry together.

[attachment 106021 basic_frame.jpg][attachment 106022 X-corner_mag.jpg][attachment 106024 X-base.JPG]]]> o_lampe Reprappers Mon, 09 Jul 2018 01:42:38 -0400 https://reprap.org/forum/read.php?4,826670,827831#msg-827831 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827831#msg-827831 Trakyan Reprappers Thu, 05 Jul 2018 02:59:46 -0400 https://reprap.org/forum/read.php?4,826670,827699#msg-827699 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827699#msg-827699
Quote
myself
I thought of building a smaller, cheaper and easier to build desktop version.

With desktop version I meant a small one that fits on a desktop :) The 100mm levers were already lifesize if I'd go that route.]]> o_lampe Reprappers Wed, 04 Jul 2018 02:20:42 -0400 https://reprap.org/forum/read.php?4,826670,827684#msg-827684 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827684#msg-827684
I don't think backlash will be an issue, you're not going to need high precision and there will be a lot of slop/lag between the magnet on the effector and the steel ball it drags around. I think your bigger issue is the lack of torque, have a look at the speeds 3d printers that use these motors run at. This machine will be table sized if I understand correctly (bigger, heavier than the 3d printers that use these motors), and the drag from the magnet dragging the ball through sand is more force on the effector than what a 3d printer sees. If it moves at all, it will be very slow. Why not use nema 17s? Buying two nemas instead of two byjs wont make a big difference to the overall cost.]]> Trakyan Reprappers Tue, 03 Jul 2018 23:32:09 -0400 https://reprap.org/forum/read.php?4,826670,827624#msg-827624 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827624#msg-827624 weight lifting test with a 100mm long lever, pressfit on the 28BYJ. Although the driver-current was set pretty low ( Vref 125mV@A4988 ), the motor didn't stop at all, but the output gear slipped. IDK if that's a bad batch I got, or a 'safety feature', but the force required to make the lever slip is pretty low.
Don't get me wrong, the lever is tight around the flat sides of the output shaft. It's something inside the gearbox slipping.

As a sidenote, I noticed that the gears have significant backlash. The idea to use a spring to replace the third motor makes even more sense now. It would eliminate this backlash, too.

I've ordered a few V-grooved bearings and a PTFE tube. We'll see soon if the slip is a problem or not.]]> o_lampe Reprappers Tue, 03 Jul 2018 09:29:57 -0400 https://reprap.org/forum/read.php?4,826670,827589#msg-827589 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827589#msg-827589 Trakyan Reprappers Tue, 03 Jul 2018 03:16:34 -0400 https://reprap.org/forum/read.php?4,826670,827390#msg-827390 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827390#msg-827390 It seems to me DD was right by using a CoreXY kinematic for his project. I want to make one, where the idler wheels also act as linear guides, stay tuned...

Oh, my.. it's almost as time consuming to paint a '3D' drawing as it would be using a CAD tool...

[attachment 105856 sissy_cxy2.jpg]

As you might guess, the idler pulleys for the CoreXY mechanic also act as guide rollers. The X-axis has to be stiff enough to deal with the cable tension, otherwise the guide rollers will loose contact to the smooth rods. I'm glad it doesn't have to be precise like a 3D printer...

WOW, what a brain fart!! 8-)
The rollers can't be idlers, except the cable would slide on the rollers. Or the idlers would have a bearing inside the rollers....Hmmm]]> o_lampe Reprappers Sun, 01 Jul 2018 02:47:29 -0400 https://reprap.org/forum/read.php?4,826670,827317#msg-827317 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827317#msg-827317
If you want a square working area just replace one of the springs in the dual spring diagram with a third motor.

if you want a round work envelope then really only your original solution will work out of whats suggested so far. You could also have a gantry spanning the diameter as a linear axis, and then have that gantry rotate about the circle center. Like how some polar printers work but with the x gantry revolving around the bed instead of the bed turning.]]> Trakyan Reprappers Sat, 30 Jun 2018 07:12:55 -0400 https://reprap.org/forum/read.php?4,826670,827289#msg-827289 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827289#msg-827289 Reminds me off deepsea jellyfish.]]> o_lampe Reprappers Fri, 29 Jun 2018 12:24:30 -0400 https://reprap.org/forum/read.php?4,826670,827273#msg-827273 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827273#msg-827273 www.instagram.com]]]> VDX Reprappers Fri, 29 Jun 2018 05:03:29 -0400 https://reprap.org/forum/read.php?4,826670,827255#msg-827255 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827255#msg-827255
[attachment 105828 Sisy_cartesian_spring.png]

Hmmm, just noticed it's not Cartesian, because of the anchor points on the mover.

So here's an alternative.

[attachment 105829 Sisy_delta_spring.png]

Both cable driven versions reduce the playground area to a triangle shape. Or the motors/spring anchor point would have to move further outside.
Me not like...

I still think a smooth rod/teflon bearing gantry would be better. Can be cable driven and spring loaded, too.
Running out of time to make a third sketch
CU later]]> o_lampe Reprappers Fri, 29 Jun 2018 00:22:37 -0400 https://reprap.org/forum/read.php?4,826670,827253#msg-827253 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827253#msg-827253 My concern about the strings_only approach is: the toolhead might tilt too much. We had to build the 'mover' pretty large which would reduce the playground.]]> o_lampe Reprappers Thu, 28 Jun 2018 23:57:54 -0400 https://reprap.org/forum/read.php?4,826670,827249#msg-827249 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827249#msg-827249 Trakyan Reprappers Thu, 28 Jun 2018 22:25:43 -0400 https://reprap.org/forum/read.php?4,826670,827184#msg-827184 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827184#msg-827184 VDX Reprappers Thu, 28 Jun 2018 06:28:52 -0400 https://reprap.org/forum/read.php?4,826670,827163#msg-827163 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827163#msg-827163
I would draw a picture but I'm afraid I'm no good at drawing pretty things, it's why I use openscad :P. Essentially it looks the same as your picture but with strings coming off the motors and to the effector instead of the guides.

One reason I particularly like the string idea is I think the sound of ball bearings on a smooth rod will ruin the intended effect of a zen garden table. The string would be quiet in comparison. That being said, you can in theory build a rail-less cartesian system that just relies on the belt/string tension between the carriages to guide the motion. Motion will be relatively sloppy but it will also be cheap and quiet.]]> Trakyan Reprappers Thu, 28 Jun 2018 03:13:34 -0400 https://reprap.org/forum/read.php?4,826670,827158#msg-827158 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827158#msg-827158 The gantry will be made from small smooth rods ( 4mm dia? ) and run on Teflon bushings.]]> o_lampe Reprappers Thu, 28 Jun 2018 01:44:08 -0400 https://reprap.org/forum/read.php?4,826670,827059#msg-827059 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,827059#msg-827059 Can you draw a pic of the 2D string driven system? I have no idea how I'd route the lines.
In the back of my head I think, there's a fourth motor on the hangprinter to tighten the three lines?
I'm also afraid, the output bearing of the BYJ motor won't like high side loads from string tension. That would require a second gear with propper bearing.]]> o_lampe Reprappers Wed, 27 Jun 2018 02:54:34 -0400 https://reprap.org/forum/read.php?4,826670,826956#msg-826956 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826956#msg-826956 The two equations you'll want to solve are more or less atan((x-x0)/(y-y0)) for your polar version, where x-x0 and y-y0 are the difference between your desired x/y position and the x/y position of your motor.
r^2=(x-x0)^2+(y-y0)^2 is what you'll need for the string driven version I suggested. It's a 2D version of the inverse kinematics delta printers use. r is the length of the string that needs to be off the spool for that motor.]]> Trakyan Reprappers Tue, 26 Jun 2018 05:32:08 -0400 https://reprap.org/forum/read.php?4,826670,826952#msg-826952 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826952#msg-826952 I'd like to figure out the math for the polar Delta and compare it to normal Delta algorhythms. Maybe it's easy to rewrite Marlin]]> o_lampe Reprappers Tue, 26 Jun 2018 05:14:51 -0400 https://reprap.org/forum/read.php?4,826670,826949#msg-826949 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826949#msg-826949
EDIT: I'm not sure if its about the clock speed, but from what I've heard trig is more computationally intensive then squares/squareroots.]]> Trakyan Reprappers Tue, 26 Jun 2018 05:05:42 -0400 https://reprap.org/forum/read.php?4,826670,826924#msg-826924 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826924#msg-826924 I tried to envision the mechanic with only two steppers in the first place, but I saw problems with accuracy and torque at certain areas. Then I thought: a third motor would compensate that, since the three motors will bundle their torque and result in even forces and accuracy.

The whole calculation should be done in integer. The UNO has 16MHz clock, like the Mega. Maybe we run short in terms of RAM, but the machine wouldn't need all the fancy stuff like a 3dPrinter. And we can go slow, so no risk to see stuttering.

edit/ Mega/Ramps wouldn't be much longer than the CNC shield. We could use it as a starting point and shrink it down later.]]> o_lampe Reprappers Tue, 26 Jun 2018 00:45:08 -0400 https://reprap.org/forum/read.php?4,826670,826849#msg-826849 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826849#msg-826849 Those are some big levers on the motors, when the ball is further away from the motor I imagine the tiny steppers you plan to use will struggle. Having used them before, I actually have trouble believing they can handle the lever/guide things if they are even remotely "big". That being said, happy to be proved wrong.
Secondly, the system is over constrained, you have three constraints in a 2D plane. Aside from redundancy issues you'll probably end up with the motors fighting each other at some point and they will strip their gears, this I can say from experience.

I suggest something like the hang printer with three cables/wires attached to the magnet that get spooled onto the three motors. Aside from lowering the cost of the build, it also simplifies the kinematics a little from the microcontroller's point of view since it uses squares/square roots instead of trig functions. This is especially important since you plan to use an Uno which has even less grunt than a mega. I'd be happy to help you with the inverse/forward kinematics. Another little bonus is it puts a constant load on the motors rather than having a variable lever length changing the load on the motors.]]> Trakyan Reprappers Mon, 25 Jun 2018 09:07:35 -0400 https://reprap.org/forum/read.php?4,826670,826742#msg-826742 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826742#msg-826742 It doesn't matter which printer kinematics you have, just like a slicer it doesn't care. I haven't found a way to set bed center to 0,0, but that's a minor issue.]]> o_lampe Reprappers Sun, 24 Jun 2018 13:32:23 -0400 https://reprap.org/forum/read.php?4,826670,826712#msg-826712 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826712#msg-826712 the_digital_dentist Reprappers Sun, 24 Jun 2018 09:09:12 -0400 https://reprap.org/forum/read.php?4,826670,826706#msg-826706 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826706#msg-826706 I thought of writing some basic routines and add random numbers in firmware to generate various patterns.
I didn't know there's a Spirograph-plugin. That would make things much easier. I wonder if there's one for Inkscape, too?

I'm not sure if the delta kinematic math fits here. The steppers move left/right and work with polar coordinates.
Generally I agree about Marlin. At least we could take a look how they implemented different kinematics. Then try to sqeeze that into a UNO.]]> o_lampe Reprappers Sun, 24 Jun 2018 08:23:07 -0400 https://reprap.org/forum/read.php?4,826670,826681#msg-826681 Re: Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826681#msg-826681
Bcnc also has a Spirograph generator built in.

Perhaps you can convert the xy coordinates to delta style with the same maths as marlin uses to convert.

edit,

Thinking about it GRBL is only XYZ, might be easier to hack marlin and a ramps board at least it has delta built in]]> adambrum Reprappers Sun, 24 Jun 2018 04:36:55 -0400 https://reprap.org/forum/read.php?4,826670,826670#msg-826670 Sisyphus mini: The polar-Delta_Ultimaker-gantry Thing https://reprap.org/forum/read.php?4,826670,826670#msg-826670
Digital_Dentist introduced me ( us ) to a cool machine he wants to DIY CoreXY-style.
Sisyphus Kickstarter campaign

I thought of building a smaller, cheaper and easier to build desktop version.
It is based on bipolar-modded 28BYJ stepper, because it fit's the bill and has plenty of steps/turn ( ~4096).
That's important, because I want to build a 2D polar-Delta mechanic, which guides the magnet. The motor shaft will only turn 120° at most.

[attachment 105709 polar_delta_2d.jpg]

I hope the picture tells it all, but feel free to ask details.
I want to use Arduino UNO and CNC shield, because it has a small footprint and is cheap.

Problem is, I have no idea how to implement this kinematic into GRBL or any other FW that fits a 328P MCU.
Anyone having better controller in mind or is willing to cooperate in any way? We could call it: RepRap-Christmas project *wink*

I also have intentions to replace the sand with some transparent fluid ( honey-like consistence ) and just let the steelball carve some, slowly disappearing, traces while we could also watch the hypnotic moves of the mechanic.]]> o_lampe Reprappers Sun, 24 Jun 2018 02:28:48 -0400