Monthly Archives: February 2019

Printer build update: electronics

Doing some electronics testing now…have the Arduino Due, RAMPS-FD v2.2 (the one I built a while back), a 128×64 LCD module (the usual ReprapDiscount design), and a Raspberry Pi 3 B+ all hooked together, with OctoPrint running on 64-bit Gentoo on the Raspberry Pi.

Some issues:

  1. At some point, something changed in Marlin such that it now doesn’t want to write to the EEPROM. M500 throws an error: “field esteppers mismatch” [sic].
  2. The SD-card slot in the display works well enough to get a listing, but not to read or write files, which makes it kinda useless. I reworked the display adapter a little to use a different chip (a 74HCT244 instead of a 74HC07) that was more readily available, but could this substitution affect SD-card performance? Should I try whacking in a 74HC244, or should I go back to the original design and hope I can find 74HC07s somewhere?

On the other hand, I did get OctoPrint to talk to the Due/RAMPS stack over the Due’s native USB port, which is much faster than the “programming” port that uses the same ATMEGA16U2 as in the 8-bit Arduinos. (Marlin images are burned through the native port in about 4 seconds, vs. 32 seconds when going through the AVR.) I had to patch OctoPrint’s firmware updater plugin to talk to the native port; those changes have been put in a pull request. Maybe faster communication between the Raspberry Pi and the Arduino Due’s native USB port will mitigate the need for the SD-card slot when running complex print jobs.

CoreXY First Run

First run for my printer, anyway: :)

Just got the CoreXY mechanism working. This is just the right motor, but I also checked the left motor and it moved the carriage the other way. I think I’ll need to put endstops on the rods to constrain motion so that (for instance) the hotend doesn’t slam into the motors; that should be a fairly simple design. (I’m thinking printed rings clamped to the rods with screws, as I plan on using stall detection in the TMC2130 drivers in place of endstop switches on X and Y.)

Right now, I’m driving one motor at a time with a DRV8825 stepstick and a Teensy 2.0 on a breadboard. Maybe it’s time to finish wiring the electronics. 

Exhibit #∞ in how SJWs Always Project

Vox Day proven right again:

He’s staying on as governor because Virginia, he says, needs a “healer,” and what better healer that a guy who can supernaturally transfer his own corruption into the bodies and minds of others?

In the Post interview, Northam spoke as if the citizens of his state had done something terrible, and needed to make amends:

“It’s obvious from what happened this week that we still have a lot of work to do. There are still some very deep wounds in Virginia, and especially in the area of equity,” he said. “There are ongoing inequities to access to things like education, health care, mortgages, capital, entrepreneurship. And so this has been a real, I think, an awakening for Virginia. It has really raised the level of awareness for racial issues in Virginia. And so we’re ready to learn from our mistakes.”

What’s this “we” stuff?

Dialed in

For the first time, I printed this tolerance test and got all of the inserts to spin. 0.1 mm took a little bit of persuasion, but I was able to break it loose with my fingers. Previously, I was lucky if I could break 0.2 mm loose at all, and I’d frequently need tools to break gaps smaller than 0.3 mm loose.

What changed? I’m calculating flow percentages for my filament, according to this page I ran across recently:

I also usually set the first-layer horizontal expansion to something like -0.1 mm to combat elephant foot. That and overextrusion from the default 100% flow rate (I’d sometimes punch in 95% for PLA if I remembered, but the rolls I’ve tested so far have come back at 90-92%) were the likely culprits of previous tolerance tests that got stuck.

Bottom line: high precision (by 3D-printer standards, anyway) is achievable, even with the A8. :)

(This is the tolerance test I’m using::