[Geek Detour] had a mystery to solve. A round part he was printing had a distinct pattern of blobs. If you’ve been 3D printing for any length of time, you know that pauses in printing can cause blobs like this. He also showed a perfectly-printed version of the same part and claimed it was from the same printer with the same material and even slicer settings. So what was causing the blobs? You can find the answer in the video below.
As you might guess from the title, however, the issue was the power loss recovery feature built into the printer. While there’s a lot going on in the video, you can break it down to a few items, all of which you can fix in one way or another including the simple fix: turn off power loss recovery.
If you have never used a printer with power loss recovery, the intent is to make it so that you can pick up a print job where it left off if the power dies. To do this, the printer periodically writes some state information to the SD card. If your SD card is slow or you are trying to print from the same SD card, you can trigger this problem. But there is more to it than that.
The first problem is that smooth, round objects like this tend to generate a lot of gcode. You can control this in several ways, including at design time and by setting the resolution of the slicing. What’s more, you can ensure you have support for arcs in your firmware and instruct your slicer to emit arcs or use a plugin for Octoprint called arc welder. This can significantly reduce the amount of gcode involved in these arcs.
Another possibility is to increase the buffers in your firmware. If you can rebuild Marlin, this is not very hard to do. The problem is that using the power loss feature is also tying up the SD card, so the more you can read ahead, the more time it has to write to the card for power loss. There is an Octoprint plugin called Buffer Buddy, by the way, that can give you some insight into your printing issues, although it can also hang your printer, especially — we’ve found — if you have Meatpack enabled to compress gcode over serial, too. Even if you don’t want to install it, the discussion of why curved lines sometimes cause blobs even over USB is well-explained in the README file, not to mention the associated blog post.
We also were impressed with [Geek Detour]’s time-lapse videos which are quite cinematic and use a motion-control camera. If you want to know more about arc welding (the 3D printer kind, not the spark-and-metal kind), we’ve talked about it before. If you want to know more about making time lapses of your 3D prints, we’ve covered that, too.