2020 DrawRobot pen holder mod

thingiverse

Description: This thing allows using a pen on my the Prusa i3 style Frickel Maschine called "Fraesli". It has the parts taken and modified from https://www.thingiverse.com/thing:2374238 Update: (08.September 2019) -All the hints found on the internet pointing at sending the A1- and E1-commands are related with grbl 0.9xx. Later versions DO NOT WORK this way at all. ----- -Read from this website. http://wvs-k.weebly.com/laser.html It is a little bit hard to read and understand. It has mixed the laser- and the servo-stuff many times. But the author did some research and shows how the Mana does generating the PWM signal. On the youtube site he responded: "The laser runs with 7.7khz, the pwm signal for the pen is ( annotation:has to be) much lower" ---- -Some background information on servo PWM: https://forum.arduino.cc/index.php?topic=14146.0 -It is up to you to find something that transformes the Mana-PWM to a properly timed servosignal. From my understanding the Mana PWM output could be set to 255 (full level). This should spit out, when activated, a continously signal, similar to TTL (ON/OFF) Put on a adjustable circuit (a servo tester?) that generates on "ON" a signal that makes the desired rotation eventually. ------ -Some simple servo testers (not tested by me) - https://trandi.wordpress.com/2013/06/18/servotester/ - https://quadmeup.com/simple-servo-tester-with-arduino/ - http://www.speedy-bl.com/servo-e.htm (1xNE556 or 2xNE555) - https://www.hackster.io/gatoninja236/0-45-servo-tester-board-3ad552 -Programming an ATTiny45/85 chip using Arduino IDE 1.6 http://highlowtech.org/?p=1695 ------ -After a long journey youtuber "Atomic shrimp" got it working somehow. The story dates back to 2017, but nothing has changed. -Watch this and the 3 other videos of the series on youtube.com /watch?v=q2fi7PuR3nE -He has modified the actuator in way i wanted to do, let the sevo lever bring the pen holder down when needed only. ----- After a plot of 30 minutes and during the fiddling with the requiered settings for minimum/maximum Laser power (misused PWM cycles ) for bringing the servo up and down I have lost two servos. Burned. Conlcusion: I will go back to where I succeeded with selenoids. The stl-files: -sliderbase plate -slider with pen clamp -intermediate mountplate On the baseplate stl-file are some artifacts/residues of developing still. Can be ignored safely. It does no harm. Changes made: Reduced the rod holes diameter to 3mm.
 With my setup there is not much space behind the baseplate.
 Have brought up the rods by increasing the hight of the posts.
 Put the servo on top of the base plate.
 It required some cut off of the slider where the servo arm grips to allow it passing the servo body.
 Even with the modified baseplate the body of the servo goes 9mm below the sliderbase plate. In order to mount the slider assembly on my cnc mill or other tools I have made an intermediate mountplate.
 The mountholes distance on the x-drive face plate is 30mm.
 Have used two screws M5.
 The sliderbase has 4 M3 screws.
 They connect to 4 hidden nuts M3 sitting at the back of the intermediate plate. TODO: The 2020DrawBot has the spring pushing the pen always down toward the bed. But if not lifting up by driving the servo it will draw unwantedly on the paper. Silly. Better reverse the order. like this: When doing a plot, activate the servo, bring down the pen then. Otherwise even if there is no power on the machine hold the pen at a safe distance above the bed.