You did understand it right. I made some changes in the drawing according to your suggestions. Lets call it "constant-effective-radius-spool". Biggest problem I see is the variable spring force of the compensation idler. What kind of mechanism could solve this problem? Is there a way to do it without electronics? If we would have a simulation we could predict the force on the strings and revon Dahah - Hangprinter
PS: Is constant-k really the right name?von Dahah - Hangprinter
No, I do not know the weight. The printed parts and bearings should be quite light weight. But I do not know if the forces/weights on the spools increase if you pull with three spools (and the additional spool bearings and springs) and not just with one spool. As it pulls the same end-effector (mover) I guess it is not too much for the nema17 stepper motors. But I do not know it by calculation..von Dahah - Hangprinter
So silent out here...... In my hometown it is very hot these days........ I made a concept for a constant-k-spool. I attached an image.... I found the idea in the fb group. It was said it comes from historical weaving techniques. By the way: The jaquardt loom was the first machine using binary code on a changable medium -> punch cards! It produces programmed digital imagery without electrvon Dahah - Hangprinter
Yes, it is a good idea to solve the problems step by step instaed of designing the best case scenario.von Dahah - Hangprinter
ROS Additive Manufacturing (RAM) The ROS Additive Manufacturing (RAM) project is a set of ROS packages that enables automatic generation of trajectories for additive manufacturingvon Dahah - Hangprinter
Maybe it is enough to see it as a rigid joint and a rigid cable that expands/decreases=flexes in length?von Dahah - Hangprinter
In the existing Gazebo/ROS simulation there are no flexible lines. They use ridgid joints and cables. How to formulate not just the line flex in a Hookes law sense but to simulate as well the way the lines bend on the spools, line rollers and anchors? I need to understand more of ROS. Tobben, do you have experience in ROS? Do you think you could hack the existing sim to the hangprinters needs?von Dahah - Hangprinter
rotary encoders If I would have an exact k-value, would it be possible to calculate/simulate the values for the line being stretched when rolling in, and slack when rolling out? How to measure the flexibility in the system (except lines)? How big are the flex movements in the mechanical parts?von Dahah - Hangprinter
Finding k Seems easy! One just uses good and precise hardware and gets precise calculations. Closed loop I would prefer o-drives over mechaduinos. It opens up the possibilities to use any dc motor, so in the whole there could be more individual iterations of the hangprinter depending what kind of dc motor is available. One could go without belts or gears using a hoverboard motor and o-drives. Avon Dahah - Hangprinter
Modulus It is a starting point! And a quick one Formula for flexible lines and tension What sensors on the hangprinter could measure k or could measure data to calculate k? High-res cameras? (Just quick thoughts: Line tension could be measured with a load cell - easy and cheap - and three v groove bearings, line length with a rotary encoder.) Other flex than line flex. We should try to getvon Dahah - Hangprinter
PS: Using a complex simulation - which can run on computers at home - would be an update - auto callibration of the hangprinter did it allready - of the RepRap technology (2008) from 1980s tech eg. home computers, cheap microcontrollers, stereolithography (1983), FDM (1988) and the broad use of the internet (1990s) to a more contemporary approach using complex software to solve problems in normvon Dahah - Hangprinter
Some thoughts on moving anchors and frames: Thinking of anchors that move in z-hight I do not see it as a frame. It's just three axis coming up vertically from the floor. I guess if the anchors can move 70 cm to 1m in Z, it would be very useful for a lot of printable objects. Seeing how slow the hangprinter moves due to layer hight and flow rate of the extrusion, I dought there will be a lot ofvon Dahah - Hangprinter
Is there a visual 3D simulation of the hangprinter? I know there is the simulation for the calibration points. But I am looking for a visual simulation like Webbots or MS Robotics Studio. I found some papers about cable driven parallel robots using XDE and Matlab/Simulink or Gazebo and ROS to build simulations. Matlab: Gazebo: I am thinking of a visual model (in the best case with physics) ovon Dahah - Hangprinter
I saw a video from Richrap about your workshop at E3D. He shows a smaller Version of the Hangprinter. Seems like it uses the same parts for the top plate and just a smaller triangle (D-Linerollers/mover). I would like to experiment with mover size. Do I have to change the firmware if I use a bigger or smaller triangle (D-Linerollers/mover)?von Dahah - Hangprinter
How about printing 3mm filament? You would get much more material to the nozzle. This could increase the flow rate? Do you have experience with 3 mm filament? How does the stiffness of the filament influences the movements? The extruder motor pulls on the filament and there will be a force generated by this on the system, too? How does 1.75 differs from 3mm?von Dahah - Hangprinter
After manual calibration my printer runs dry. No extrusion, yet. I need to buy a new extruder. All the scrap ones I had lying around are crap. It is a very beautyful machine and moves elegant! Well done Torbjørn! My gears are printed on a Markforged industrial FDM 3D Printer. These gears run relativley silent. Maybe bigger gears would fit the DIY printing resolutions better. As I can not get alvon Dahah - Hangprinter
Ok, I found the answer to the data points question in this video at 04:05 random but different exept the middle point/zerovon Dahah - Hangprinter
Torque mode was save But one motor doesnt switch to torque mode but works well in position mode. I have to flash the mechaduino again I guess. That will be a difficult task under the sealing. Z-hight is about 4.2 m. Here's how Win10 (should work for Mac and Linux as well ) users, who like GUIs can use the python simulation for auto calibration: Download and install Anaconda for Python 2.7 :von Dahah - Hangprinter
All the fire line is in place. I marked the triangle on the surface/bed. The mover is up in the air. All motors turn in the right direction. Is it save to apply torque mode, now?von Dahah - Hangprinter
So finally I solved the problem. It was something between stupid faults and maybe a lot of different Arduino IDEs on different systems and maybe some magic *** No PID or other difficulities. It was my fault and I do not know exactly what it was. I just repeated a lot of steps very concentrated and in the end it worked. My printer is up the sealing and I try to figure out how to callibrate Marlinvon Dahah - Hangprinter
Anyway, I made a video with one motor plugged and vibration. Maybe the sound tells the problem. If I start a print from pronterface with all motors plugged it works, but the vibration is still there and with four motors the resonance is stronger. One knows that frequency from other machines. Where does that frequency come from? I am reading now into PID Tuning. Does anyone has an idea whavon Dahah - Hangprinter
It is a rather abstract form of music. Just a sinus vibration resonating in the wooden top plate.....a video would be worth it. No need to be scared. It's just my lack of knowledgevon Dahah - Hangprinter
I tried some things to find the error. I changed the 12V/5V level shifter. The motors still vibrate. If I disconnect the 5V VIN on the Mechaduino with the 12V connected the vibration stops. I tested another wire for 5V Vin connection. The motors still vibrate. So it seems the vibration comes from the Mechaduino board. What could be the problem?von Dahah - Hangprinter
I posted to early.....thinkingvon Dahah - General
There's a need to change the vibration. It is very strong and everything on the platform vibrates heavily. I am afraid it will loosen the screws over time. And it is very annoying..... I set the PID like you adviced. But even with pKd=0 and pKp=0.1 the motor vibrates. No change during the step down tuning of the pKp value. What could be the problem?von Dahah - Hangprinter
@ atmark I thought abot the same. That would be a great feature! But it does not fully support the design principles of the actual design, because you will need electronics on the ground and a connection to the mainboard (RAMPS/Arduino) for those vertical anchor axis. Maybe as an add on for people who dont mind having electronics on the anchors? I guess one could build it at low cost using fire lvon Dahah - Hangprinter
Do I have to tune each motor seperatly or do I have to use the same PID values at each motor. Does the D-axis need another PID than A-, B- & C- axis?von Dahah - Hangprinter
In the end the wooden frame wont be used for now. After understanding more about the cables (fire line) and the geometry of the printer I decided to hang it to the sealing as soon as the electronics/software run. It will be more practical on the sealing if the printer is not in use. Of course I am planning to use it intense but my space is kind of limited......von Dahah - Hangprinter