Reprap Forum - Polar Machines, SCARA, Robot Arms

MPScara G92 and machine coordinate issues (49 replies)

Chip Bark — Wed, 18 Mar 2026 06:52:49 -0400

Hello all,

I have been working on a custom scara with a funky drive train, but it functions like a standard MPScara with a belt driven distal arm.

After trying a lot to make Marlin work and it vehemently refusing to do so, I switched to RRF and DWC with the SKR 3 EZ. The motion works fine when commanding moves, but after trying to fine tune the M669 code in the config to be correct per the days of forum searching, now the machine absolutely refuses to use a XY of 0 or move due to it.

Adding G92 in the homeall file or commanding it in console does nothing. Z works perfect, Y does weird arbitrary non-zero numbers, and X never changes below 1100mm.

The attached files show the SolidWorks math to derive the M669 values for min/max angles at home (highlighted blue. Max distal angle is also the 130.9~ since it is mirrored). Other files show the position at boot up which is the same if I home it. And then images of G92 Y0 done twice with an M114 to show the lack of changing X, with the Y changing with each use of the command with one case being ~0.032 or similar.

Of note, if I run a G10 L20 command, it correctly sets the tool position to 0,0,0, but with the machine position still wrong, no motion is allowed.

I'm at my wits end at this point. Because it won't set 0,0 correctly, I can't command any G0/G1 moves since it calls an out of machine limits error, but it will home correctly every time physically. Per the config.g, the volume is 0:635 x 0:635 with the home and 0,0 at the bottom left corner. I will never understand why both Marlin and RRF can make scara so complex, such as Marlin requiring the bed 0 at center and the homing to somewhere far away from said center, but I digress.

With the config.g, the steps/degree are all calculated from the 3d model as is all else. Please let me know what is either wrong with the config or wrong with something because it is currently impossible to even try and make it draw a line. If any files or images need to be provided, I certainly can.

I hope to do a Morgan Scara after this, but the nightmare of just getting the firmware side working is a large put off due to the severe lack of documentation on both sides of the major firmwares.

Scara robot with Marlin Y axis Transition makes unnecessary rotation (no replies)

texe07 — Fri, 24 Jan 2025 09:30:37 -0500

Scara Arm(2 link) on Marlin firmware making revolution when x <=0 and coordinates changes on y axis mean after passing 0 makes one more rotation. Note both arm can move 360 no obstacle inbetween in hardware.
SEE LOGS
Recv:19:57:07.686: X:0.00 Y:220.00 Z:0.00 Count A:150B:155 Z:0
Recv:19:57:07.688: SCARA Theta:90.00 Psi:90.12
Recv:19:57:15.210: X:0.00 Y:220.00 Z:0.00 Count A:150B:155 Z:0 (3)
Recv:19:57:15.210: SCARA Theta:90.00 Psi:90.12
Recv:19:57:28.232: X:0.00 Y:20.00 Z:0.00 Count A:290B:11 Z:0
Recv:19:57:28.232: SCARA Theta:174.00 Psi:6.40
Recv:19:57:33.356: X:-10.00 Y:20.00 Z:0.00 Count A:335B:56 Z:0
Recv:19:57:33.356: SCARA Theta:201.00 Psi:32.56
Recv:19:57:43.649: X:-10.00 Y:0.00 Z:0.00 Count A:446B:159 Z:0
Recv:19:57:43.649: SCARA Theta:267.59 Psi:92.44
Till here the theta is +ve and when it goes y passes axis it take one more rotation as per kinematics to -49 degree
Recv:19:57:49.740: X:-10.00 Y:-10.00 Z:0.00 Count A:-83B:-383 Z:0
Recv:19:57:49.743: SCARA Theta:-49.80 Psi:-222.67
Recv:19:57:54.751: X:-10.00 Y:-20.00 Z:0.00 Count A:-57B:-350 Z:0
Recv:19:57:54.751: SCARA Theta:-34.20 Psi:-203.49
Thank You : )

SCARA Plasma Marlin-ArcDroid (5 replies)

vfear — Fri, 24 Apr 2026 17:17:57 -0400

I came across an interesting repository on GitHub — a project for a CNC plasma cutter with SCARA kinematics, called Marlin-ArcDroid.
After studying the open-source code and doing some research online, I put together an initial specification:
• Display: BigtreeTech TFT70
• Controller: Custom-built (though the code mentions compatibility with BigtreeTech and MKS)
• Motors: NEMA 23 with separate encoder boards
• Drive system: Belt-driven
• Probe: For generating CNC control programs
• Mechanics: SCARA kinematics
• Plasma cutting relay: For triggering the cutting process
• Calibration: Supports machine calibration with offset storage on an external drive
• And much more.

My questions are:
1. Is it possible to use this firmware on a custom-built SCARA robot?
2. Which controller would be the best choice for this project?
3. How should the firmware be compiled?

This project is compact and well-designed. It would be great to see more enthusiasts develop and expand on this idea.

[github.com]

SCARA MORGAN SCARA, MP SCARA Configuration Endstop error possible fix (no replies)

phearl3ss1a — Sat, 03 Aug 2024 18:42:43 -0400

In attempting to get my Scara working with the newer firmware Bugfix 2.1x, I was having nothing but problems with the MP Scara config and could not make it work until I found a youtube video that changed some configuration settings that did make it work. ,[www.youtube.com] but could not home and when trying to home both arms were moving together. I have noticed many people have posted about the Scara arms moving the wrong direction and not stopping when endstop triggered but I could not find a solution. But I beleive this might be the problem. That video makes changes in Scara.ccp. It instructs to change ln 75 from #if ENABLED(MORGAN_SCARA) to #if ENABLED(MP_SCARA) and that did make it work. However, the Morgan Scara has two arms and the homing process is a dance to prevent the arms from hitting each other while homing. So they both move in one direction then the other and the Morgan_scara uses a Cartesian XY home position. So I think this is why many people are posting the problem. The solution I found is to copy the homing procedures from the MP_Scara below and comment out the Morgan_Scara procedures. ie. (starting at SCARA.CPP ln 75)
#if ENABLED(MP_SCARA) //instead of MORGAN_SCARA
// the following pasted from MP_SCARA BELOW)
void scara_set_axis_is_at_home(const AxisEnum axis) {
if (axis == Z_AXIS)
current_position.z = Z_HOME_POS;
else {
// MP_SCARA uses arm angles for AB home position
#ifndef SCARA_OFFSET_THETA1
#define SCARA_OFFSET_THETA1 12 // degrees
#endif
#ifndef SCARA_OFFSET_THETA2
#define SCARA_OFFSET_THETA2 131 // degrees
#endif
ab_float_t homeposition = { SCARA_OFFSET_THETA1, SCARA_OFFSET_THETA2 };
//DEBUG_ECHOLNPGM("homeposition A:", homeposition.a, " B:", homeposition.b);

inverse_kinematics(homeposition);
forward_kinematics(delta.a, delta.b);
current_position[axis] = cartes[axis];

//DEBUG_ECHOLNPGM_P(PSTR("Cartesian X"), current_position.x, SP_Y_LBL, current_position.y);
update_software_endstops(axis);
}
}

// Comment out the MORGAN Homing.......

// void scara_set_axis_is_at_home(const AxisEnum axis) {
// if (axis == Z_AXIS)
// current_position.z = Z_HOME_POS;
// else {
// MORGAN_SCARA uses a Cartesian XY home position
// xyz_pos_t homeposition = { X_HOME_POS, Y_HOME_POS, Z_HOME_POS };
//DEBUG_ECHOLNPGM_P(PSTR("homeposition X"), homeposition.x, SP_Y_LBL, homeposition.y);

// delta = homeposition;
// forward_kinematics(delta.a, delta.b);
// current_position[axis] = cartes[axis];

//DEBUG_ECHOLNPGM_P(PSTR("Cartesian X"), current_position.x, SP_Y_LBL, current_position.y);
// update_software_endstops(axis);
// }
// }

/**
* Morgan SCARA Inverse Kinematics. Results are stored in 'delta'.
*
* See [reprap.org]
*
* Maths and first version by QHARLEY.
* Integrated into Marlin and slightly restructured by Joachim Cerny.
*/
void inverse_kinematics(const xyz_pos_t &raw) {
float C2, S2, SK1, SK2, THETA, PSI;
After I made these changes, it works and the homing works. So I think I am using the Morgan_Scara for the inverse Kinematics and the MP Scara for homing. But I am far from an expert.

scara arm grbl, cant go to all coordinates (2 replies)

scott_12345 — Sun, 24 Jul 2022 20:15:16 -0400

I've made a scara arm (attached image) and im trying to use this version of grbl that supports a scara arm, it works as intended but has a slight problem, it seems to stop me from going to specific coordinates, for example, I can go to (x100 y100) but can't go to (x10 y100) or any negative coordinates, which should be possible, is there something in the code preventing it from going here, as both my arms can rotate 360 degrees so I don't need limits. also if I enter some coordinates it doesn't like it seems to crash and become unresponsive. does anyone know how I would go around fixing this? thanks

grbl version: [github.com]

SCARA arm plotter / printer using Nema 23 stepper motors (3 replies)

CptBlueberry — Mon, 24 Jan 2022 07:12:05 -0500

Dear RepRap'ers,

Currently I am working on a project where I am trying to get a SCARA arm robot to function as a printer. Having browsed google up and down I have found a lot of information but I am stuck on the software part.

So far I have managed to get the SCARA arm to print using UGS Platform (GRBL basis). However I am dissatisfied by the result, low quality print (stepsize / gear ratio related) and the plotted image (text in this case) being plotted at an arc [see image] (image used as visual reference for the acquired end result).

FOB50Q4KIFZTU5E.jpg

After some more looking around I have found this laser engraver project which equals the end result I would like to achieve. However this project makes use of the following components:
- Arduino Mega (controller)
- Ramps 1.4 board (motor drivers)
- Nema 17 stepper motors
[howtomechatronics.com]

The problem with this is that with my current stepper motors I am unable to use the ramps 1.4 board as I am using different driver (see components list for controller, driver and motors). Now I am wondering, is there some way to find the arduino mega outputs used in the marlin software, as used in the above mentoined project, so that I may be able to connect my drivers and homing switches directly to the megaboard?

Components list:
- 2x Nema 23: 103h7123-5740 (required for torque)
- 1x Arduino Mega 2560
- 2x TB6600 Stepper motor drivers
- 2x limit switches (not really important for this question I guess)

Software source:
- [marlinfw.org] (basic marlin software)
- [github.com] (SCARA arm configuration files)

Hopefully you will be able to point me in a certain direction.

TL : DR
Can I somehow find the output pins used in the SCARA arm marlin software in order to directly driver 2 tb6600 stepper drivers in combination with an arduino mega instead of having to use a ramps 1.4 board?

Tripteron patent deadline (17 replies)

alegiaco — Wed, 18 Jan 2023 00:28:49 -0500

Hi, i'm interested in Tripteron robot, but I know there is a patent (US 6,729,202) on the machine, but I don't understand if the patent has an end-of-life in April, 2022. Someone understand something about patents? Can the university renovate the patent or the patent will be finally dead in 2022? So starting from april can we build some tripteron robot?

Dual-Polar Printer (2 replies)

heinz — Tue, 10 Sep 2024 20:16:52 -0400

I recently built a Dual Polar Printer and since most info came from here I should post the results.

It fit my purpose of a fun and compact printer that can also be used as a toolchanger,
since the bed can be rotated 360deg around the Z axis and move to a difference tool. [www.youtube.com]
The almost static printhead (only slow movement in Z) allows for some heavy toolheads.
I mounted a 5er diamond hotend with directdrives (2kg) on it, no problem.

It is not my design originally, more of remix of different designs I found here
on the forums and on youtube. See Brenon K's Bi-Polar printer [www.youtube.com]
Beaglyfurys RepOlaRap and unlimitedbacons Theta printer were especially helpful. Check [reprap.org] and [hackaday.io]
Conversion forumlars are arrived form unlimitedbacons Marlin version,
I had to add additional compensation for distortion introduced by the middle gear to route the Z-axis through.
With a small gear in the middle I didn't notice the distortion at the beginning.

It prints on a cold bed made from perfboard. With a hot enough first layer PLA works fine.
Some pointed out its more an inverted SCARA than polar printer, not sure about correct definition.

It has some nice timelapse capabilities as well :) [www.youtube.com]

Scara Firmware Setup Confusion (11 replies)

Phearl3ss1 — Sun, 03 Nov 2024 07:02:48 -0500

https://youtu.be/24I21K-Frxk

I am trying to setup a single arm scara. In the configuration.h example I have started with the Mp_Scara. It states:

// SCARA tower offset (position of Tower relative to bed zero position)
// This needs to be reasonably accurate as it defines the printbed position in the SCARA space.

#define SCARA_OFFSET_X 100 //mm
#define SCARA_OFFSET_Y -56 //mm

I assume that zero position means X 0 Y O. If so and if we are measuring from the tower relative to bed zero position why would there be a different offset for the X and Y when both are at the zero position?

FiveAxisRobotic Kinematics for ReprapFirmware 3 (3 replies)

JoergS5 — Wed, 12 Aug 2020 02:37:05 -0400

I am currently developing the kinematics for a 5 axis robot for ReprapFirmware 3 (Duet 2, Duet 3, maybe Duet Maestro, possibly for LPC1768/1769 port). The reason why I am unsure whether Maestro and LPC are working, is that the kinematics uses trigonometric functions a lot, so a MCU with floiting point is advantageous for enough performance.

Documenation of the parameters, axis and arm explanation, example prototype and config are in [duet3d.dozuki.com]

Yesterday I could finish kinematics and inverse kinematics for P4 mode (and test it), so I can implement firmware now in my github fork and build a prototype next.

If you are interested in building a prototype or robot 3D printer also, you can start now ;-)

In this case it would be useful to tell me the construction (where are the axes, arm lengths, which direction the arms are), so I can test the code with your setup to make sure the kinematics are correct for your setup.
Your prototype should follow the described restrictions, however: arm 4 vertical, the directions of the axes like described.

My prototype is like the two images at the beginning of the documentation. I will try to build hinges with gears with low backlash and stable arms, as I expect those two points as important for precision.

Polar 3D printer design (1 reply)

Shadi — Wed, 29 Jul 2020 11:04:49 -0400

Hi All
i need a help as i build a Polar 3D printer which in the concept seems like R-360 that works on Marline R-360, however my design is a bit different as you see in the attached picture however i have face difficulties configuring the Marlin R-360 although i have experience of Marlin configuration.
I need help and some guidance on what is required to get it configured just make it work as principle and will look for the other possible issues.

I think Marlin R-360 has an issue in case of 360 degree rotation command, and the other point I have used Arduino Ramps 1.3 and ATEMGA 2560 board however the commands never completed and the machine somewhere was stopping on 4th line, i think Arduino is not able to process the commands even they are same of normal Marlin firmware if i am not mistaken, i do not have programming experience.

Z axis planned to be gas or oil cylinder however i did not finalize that as once they are complete will be fixed at the outer circle of the aluminium frame.
I appreciate the reply on my message.

Marlin R-360 link on github:[github.com]

Regards;

Problems config SCARA ARM marlin (1 reply)

AndreeaAchitei — Thu, 12 Dec 2024 08:09:24 -0500

Hello!
I'm working on a project Robotic SCARA arm and I encountered difficulties with calibration. I use firmeware Marlin and I control it with Pronterface. I use ARDUINO MEGA, RAMPS 1.4 and driver DRV8825.
In this Drive you have the code and a picture with the dimensions:
[drive.google.com]

I modified the following lines of code:
#define Linkage_1 248
#define Linkage_2 180
#define SCARA_offset_x 210 // mm
#define SCARA_offset_y -110
#define SCARA_offset_z 0
#define SCARA_RAD2DEG 57.2957795
#define X_MAX_POS 420
#define X_MIN_POS 0
#define Y_MAX_POS 260
#define Y_MIN_POS 0
#define Z_MAX_POS MANUAL_Z_HOME_POS
#define Z_MIN_POS 0
#define MANUAL_X_HOME_POS 630
#define MANUAL_Y_HOME_POS -190
#define MANUAL_Z_HOME_POS 100
#define HOMING_FEEDRATE {2060, 2060, 20*60, 0}
#define DEFAULT_AXIS_STEPS_PER_UNIT {71.11,17.77,1600,2}
#define DEFAULT_MAX_FEEDRATE {200, 200, 30, 25}
#define DEFAULT_MAX_ACCELERATION {1000,1000,1000,1000}

He moves chaotically, it has no linear motion. Can someone help me with this problem?
I don't know where is the start position for the X and Y axis
I follow this project [reprap.org]
Sorry for my english, I use google translate :)

Seeking V-plotter firmware options (7 replies)

Ohmarinus — Sat, 26 Mar 2022 14:09:39 -0400

Hi, so as the title implies, I'm looking for firmware to run my v-plotter on. I've just built a quick and dirty model right now to get familiar with how it works. Eventually I'm willing to make a machine that the ability to create bigger than A0 drawings but let's start with something smaller. The firmware side however, is a bit difficult, I haven't been able to find a suitable solution.

First stage, setting up the frame:

YupqiHZ.jpg

The specs are as follows:
- Ramps 1.4
- Reprapdiscount Smart Controller
- 2x A4988 (since I have like 20 left over, also soldered ROSC pin to ground)
- No endstops
- 1x Servo
- 2x weights on the outside 100 grams per piece
- 1x support weight under carriage of 50 grams
- All parts are reused from salvaged machines or other trash or second hand, but basically the only thing I paid for were the belts
- Paper and ink should also be environmentally friendly
- Expected draw area ~550x750mm
- Aluminium frame can be placed on top of any piece of wood so it's basically a module with an aluminium U-profile that can be placed over any desired plate
- Easily upscalable, still working on a version 2.0 that is more lightweight and has suction cups as an option.

And now, the problem I'm running into, I have found multiple firmwares but they all have quirks causing it not to work with my set of ingredients:

Makelangelo firmware
Website http://www.makelangelo.com/
Link to Firmware https://github.com/MarginallyClever/Makelangelo-firmware/releases

Nicely designed open source firmware and software for their own v plotter model. Can also be used for personal projects.

Pros
Works well with Ramps, RRD LCD. Also they have their own software that works together with their own firmware.

Cons
Sadly the versions of this firmware I've found need endstops to work, now I can of course add endstops, but I like the simplicity of the system without using endstops. I have not been able to figure out of I can use the latest firmware without endstops since their forum is really quiet.
Rotary encoder doesn't respond well to movement, in Marlin it works flawlessly and I haven't been able to find out where to tune this.

Polargraph Controller
Website http://www.polargraph.co.uk/
Link to Firmware https://github.com/euphy/polargraphcontroller/releases

Personal open source/semi commercial project by Sandy with it's own software suite as well.

Pros
Easy to setup, supports ramps: [github.com], no need for endstops, big plus

Cons
RRD LCD is not supported and I don't know what LCD to use to make this work. I am not going to run the v plotter from my laptop as I want it to be standalone printing from an SD card

Repetier firmware Polargraph version
Website http://www.polargraph.co.uk/forum/polargraphs-group2/code-software-forum2/repetier-version-of-polar-graph-thread444.0/
Link to Firmware https://github.com/RickMcConney/PenPlotter

Awesome piece of firmware based on Repetier firmware adding very smooth and precise movement to your v plotter

Pros
Smooth lines, precision, flexibility, supports Ramps, LCD, etc.

Cons
It doesn't compile!!! I'm pulling out my hair. I used four versions of Arduino IDE, from 1.6.2 - 1.6.9 - 1.8.4 and 1.8.9 And different versions give me different errors. So I'm hoping for a solution some day but it's very quiet over at their Github.

If anyone has another piece of firmware for me that works with Ramps, LCD and is suitable for a v plotter without endstops. Let me know. I would really like to progress in this project :)

... sourcing parts for a parallel SCARA (7 replies)

VDX — Sat, 21 Dec 2019 17:49:34 -0500

Hi all,

... got some interesting parts from a friend, perfectly suited for building a parallel SCARA B)

This are Z+A axes from industrial dispensers, so two of them with synchronized moving in Z and rotating the "arm-shoulders" are the "core" of the parallel SCARA:

[attachment 113607 Parallel-SCARA-Basis.jpg] [attachment 113608 Parallel-SCARA-Basis2.jpg] [attachment 113609 Parallel-SCARA-Hinten.jpg]

The steppers are Vexta 5-phase types, so will replace them wit 2-pase-steppers, for lack of 5-ph-drivers ...

Any inexpensive robot arm kits using stepper motors? (6 replies)

dc42 — Sat, 18 Jul 2020 05:12:44 -0400

I plan to add robot arm kinematics to RepRapFirmware as a standard feature, so I need a 5- or 6-DOF kit to work with. Can anyone recommend one? It must use stepper motors, and obviously I don't need a controller.

Electronics for SCARA (1 reply)

monkmartinez — Mon, 02 Dec 2019 06:37:08 -0500

Hello all,

I have all the parts printed and ordered for this scara: [www.thingiverse.com] I am going to start building this after I order electronics...and when I return from a two week hitch on an oil rig.

I have printed a ton of stuff but used an off the shelf printer (Craftbot plus). I have very little experience with Marlin or firmware in general. I see that Duet and the newest Marlin support SCARA arms.

I don't mind buying the Duet if its going to be leagues easier to use... However, I have plans to play with this robot for a few months and then move on. I really want a to build a BIG OLE 6DOF ARM bot next year sometime.

I am looking at MKS Gen L V1.0 boards with TMC drivers as a comparison...

With all that in mind...What would you all recommend?

Robotic Arm turned into a 3D Printer (Inverse Kinematics) (8 replies)

3DJLed — Sat, 13 Mar 2021 09:44:38 -0500

Hello,

I use Arduino Mega 2560 with Ramps 1.4 & Marlin Firmware with Inverse Kinematics (I.K.) included.

[www.youtube.com]

3DJLed

Help Identifying Surplus Scara Electronics (3 replies)

Phearl3ss1 — Tue, 24 Sep 2019 03:56:52 -0400

I purchased a Scara Robot frame from a University Surplus Auction I am trying to figure out what I have and have been unable to locate any information on it. It was made by US Robotics from Japan in the 90’s. I needs some help with identifying a couple wires. First It has Sanyo Denki 350w 75v 6.4a 1750 rpm motor C-200t-2553e08 with Tacho 7v/krpm and an Optcoder that has 6 wires 5v, 0v S1,s2 and M and stranded wire I assume is ground. I am unsure what the M wire does. The motors are connected to shafts that each have two sensors installed offset by 90 deg. I think these are hard stops but am unsure what they actually are or how they work. They are in a tube that points at the shaft but nothing is noticeable on the shaft. The end of the tub has three wires coming out one side, I believe are + s -. the other side of the tube looks like wax or plastic covering up the end of the tube. There are four of these sensors two on both the x and y . The robot didn’t come with anything on the z. Can someone tell me what these four sensors are and how they work or if two work together is some way. Also what is the M wire? . Below are a couple pictures. Thanks in advance, Scott.
I bought this just for fun and to learn.

Rotary Printer (again and again) (2 replies)

plasticmonk — Tue, 25 Jun 2019 17:49:49 -0400

Hey there,
I´m just the next nerd whos trying to build a rotary 3d-Printer like a record player. A rotating buildplate and a arm, who also describes a circle wich crosses exactly threw the center of the buildplate.
I created some basic hardware wich is good enough to get the most importat part on track: the Firmware.
I realized there has bee several projects talking about printers like this but no one came up with a public version of Marlin. Ok there is R-360 but he has olny one circle and one linear axis. I had a look into this Marlin version but I don´t think it is suitable for me and my limited knowledge about coding.

So I came up with the idea to exploid some up to date marlin´s scara code for my project. After all there are two axis wich are already using polar coordinates and I was hoping just to adapt it somehow. Examining the Marlin_main.cpp I realized that I am not quite able whats happening there.

Appart form some other things I found this:

float a_sin = sin(RADIANS(a)) * L1,
a_cos = cos(RADIANS(a)) * L1,
b_sin = sin(RADIANS(b)) * L2,
b_cos = cos(RADIANS(b)) * L2;

but I coudn´t find out what ore were the definition fo (a) and (b) takes place L1 and L2 are the arms so much I was able to find out. Thats just an example... it goes on and on and I just cannot get a hang of it.

So my questions are:
1st. ist there by any chance a Malin firmware present for download wich works with this kind of setup? I coud not find any but it took me ages to find R-360. So maybe there is something out there and I just don´t know.
2nd. ist there any recource wich kind of logicly explains how the scara setup in marlin is implemented? Essencially I have to change some stuff of the calculation and movie the ankle points somehow to the location were they are. And the speeds inclination has to be reversed. I cannot understand the marlin_main.cpp its a bit to high for me...

any help or hint would be appreaciated. I just wanna get this thing to work. Then I will continue on the hardware.

best,
Florian

X and Y homing not working on Morgan (1 reply)

Mayankgogia97 — Thu, 09 Jan 2025 01:59:37 -0500

I tried building a RepRap Morgan. After some time trying to build it with spare parts i had laying around, the arms are moving fine if I input increments using printrun but the printer halts when I try to home X or Y or all axis. Z axis works fine in both movement and homing. I am using hall effect modules as endstops. I have no idea what I am doing wrong because this is my first printer and I am not able to find the source of the problem.

When i either home X or Y or home all, the arms don't even budge a bit and the printer stops giving the printer halted error in printrun. If I individually home the Z axis, it is done succesfully. I have rechecked the connections multiple times. I have used m119 to see if the endstop logic is wrong but they are open when not near the magnets.

Polar 3D Printer (6 replies)

nirus1208 — Thu, 30 May 2019 00:52:26 -0400

I have designed and manufactured a 3d printer. It resembles R-360 3D printer. I use the firmware of the R360. But it always has errors. Can anyone help me a firmware to run this 3D printer? Thank you very much

Parallel SCARA Robot (1 reply)

anhanyoung — Thu, 02 May 2019 11:57:56 -0400

Hello everyone!

Yes, I am new to the forum.

I came across a few parallel SCARA robots as I was looking for a new project to work on, as I just finished with my 3-D printed robotic arm.

My inspiration was drawn from this youtube video
[www.youtube.com]

From my understanding, 2 servos will be needed (which I have recently ordered, I went with teknic). I was planning on using an Arduino uno but realized that I could only control one servo at a time using an Arduino. I am leaning towards a raspberry pi now as I have read some people having success with this. If someone has had success with possibly a Arduino Mega, please let me know!

I have been teaching myself reverse kinematics since it seems to be necessary in order to move the two arms with an end effector to a specific point. Though, I am kind of thinking of using Solidworks and finding my angles from there. (Please let me know if there is a better way to go about it).

I noticed that one servo is lifted above another. I am assuming this is because it helps one of the arms clear the other in order to create a 360 work envelope? Is there a specific distance that the motors should be placed and lifted? I am having a difficult time finding any information about this. From my previous knowledge, I am assuming that the length of the arms would dictate how far the servos would need to be in order to create a 360 work envelope? I suppose what I am here for is to ask for advice in building one from scratch.

Thank you so much in advance! I appreciate any advice!

Marlin Armlevel issues with the z-axis (on a Morgan) (2 replies)

jdargot — Sat, 06 Apr 2019 04:10:39 -0400

Greetings!

I am building a wacky little Morgan 3D printer out of spare parts I have and am running into an issue with the z-axis (a little unexpected seeing as the x & y axes calibrated just fine).

When I tell the axis to home, it only travels about ten mm before stopping if not manually triggered on the endstop already (I'm using regular switch endstops). And if I give a motion command to the z, it only ever moves in one direction regardless of the direction I told it to go. And it continues moving until the machine is restarted. Has anyone seen a problem like this before? I looked it up under general Marlin issues but most of those dealt with auto bed leveling, a feature that isn't even in this firmware version.

Attached are my mechanical settings although not a huge amount has been changed in the z-axis yet. I changed some things in eeprom as well if any of that is needed.

Any advice is greatly appreciated.

Is the SCARA algorithm used in marlin correct? (no replies)

dongxuzhou — Mon, 25 Mar 2019 05:06:09 -0400

I noticed that the firmware called the kinematic inverse solution of the SCARA robot before calling the plan_buffer_line function, and then assigns the calculated three joint angle values to the plan_buffer_line function.After reading the plan_buffer_line function in detail, I feel that this is wrong.
This is because all the computational algorithmic processes in the function are directed to Cartesian Cartesian coordinate space, for example:

block->millimeters = sqrt(square(delta_mm[X_HEAD]) + square(delta_mm[Y_HEAD]) + square(delta_mm[Z_AXIS]));

This is to calculate the spatial moving distance through the three target coordinates of Cartesian space. If it is replaced by three joint angle values, is this wrong?
The latter algorithm has similar problems, especially the Breasham algorithm in ISR, which is completely an algorithm of Cartesian space. If the value passed to the algorithm is three joint angle values, I think it should be incorrect.
I looked at the code for the marlin 1.1 version and there are similar issues.
I hope that my doubts can be answered, thank you!:)
My email address: dongxvzhou@gmail.com

SCARA 3D PRINTER- PROBLEM AFTER HOMING ARMS and Printing Model to Scale (no replies)

ScaraMan — Sat, 09 Feb 2019 06:42:40 -0500

Hi Guys,
I have built a SCARA 3D printer, it is completed. I have an aluminum frame structure, heatbed raises up and down like the Ultimaker.
The arms have there motors fixed on the top mounting plate. I have attached a top view of my printer with the critical dimensions.
I have been trying for a long time now on and off to make it functional, have used many firmwares from different users
Invent 2main, vitaminrad, and others as well. I edit the settings to match my setup.
The issue I am having is that I have no problem homing the arms to the end stops, the problem starts when they try to go to the 0,0 position
of where I would like my nozzle probe to start. Each firmware I have tested gives a different result, but never correct.
I have even switched positions of the end stops from left to right and back again , thinking that maybe that would be the problem
In other words a left or right handed Scara. but it isn't.
And just to be clear I never actually print with filament, don't want to until I know that the printer is setup correctly.
I test run a print through pronterface just to see the arms move, and see if they are printing the part accordingly.
what I have realized that if I was too attach a pen to simulate the print, it would be skewed based off the real print.
I am using motor pulleys with 20 teeth that drive the larger pulleys with 120 teeth, so that's a gear ratio 0f 6
microstepping is 16 , I come out with 53.33 steps for the X and Y motors.
From what I understand and have experienced, is that Marlin firmware is not suitable for Scara printers, unless someone
know the secret magic formula to make my printer functional the way I want it to run, I have given up hope.
So at the moment, I am using a code translator from cartesian to scara ( MPSCARA from Thingverse ) and then run it
through pronterface. I let the arms just move but not actually print, it seems to be ok, but the printing region is out of the heatbed area,
so that causes another issue- seems that there is no control from the homing end tops position afterwards.
I just cannot believe that this is so complicated , when it shouldn't be.
I enter the parameters in the configuration.h file correctly-there is no secret here, and theoretically it should give me the correct results
but it doesn't. do the kinematics need to be modified in the main marlin.cpp ?? what gives ??

Donut shaped polar printer? (4 replies)

disneytoy — Thu, 16 Jun 2022 05:24:08 -0400

Hello!

I'm working on I guess a polar printer. But the build area is a donut. The z axis is in the center of the circle. And the X arm rotates 360 degrees. I see most Polar printers have the Z axis outside of the circle.

But I'm thinking the same commands would apply. You still have a radius and distance.

Is there any firmware for my style Polar printer?

Thanks

Max

i need help with my scara build (no replies)

papo — Mon, 07 Jan 2019 12:55:43 -0500

[www.youtube.com]

The Educated Monkey (2 replies)

MechaBits — Thu, 03 Jan 2019 09:45:32 -0500

4_20_1.jpg

This thing looks pre etch'a'sketch, so even Scara was descended from apes.

1d4a9afcf0501f4a0e04e4391a5dc2df_preview_featured.jpg

[www.thingiverse.com]

SCARA with marlin (1 reply)

AimHigh — Sat, 15 Sep 2018 05:57:56 -0400

Scara robot, currently can take any space in the line, to achieve writing and drawing, fixed hole punching, handling, etc.
but the accuracy of writing and drawing is not very high

Abl Info (no replies)

Mauxx — Sun, 02 Sep 2018 18:22:48 -0400

Hello

Where i can find Auto Bed Leveling settings for Scara?
I'm using Marlin for ArmOni but it doesn't work