Stacking Chess Pieces Printed via SLA

Stacking Chess Pieces Printed via SLA

A few months ago I designed a display stand for cabochons (aka cabs, gem rocks cut and polished, generally for pendants) to let you display a cab on a shelf. I printed a few with my FDM printer (fused deposition modeling -a thermoplastic filament is fed into a hot nozzle and layered onto the print, I use 1/4 mm layers). The print is functional but low resolution and not visually appealing. SLA (stereolithography - a liquid resin is cured in layers by UV laser, with 1/10 mm or thinner layers) is readily available as a service, so I tried printing the stands at ArtLab ( www.artlab3dprinting.com ). The results were beautiful - far better than my FDM prints, well suited to displaying cabs.

I tried an inexpensive LCD resin printer (similar to SLA but uses an LCD to mask UV light which cures the resin). The results were good - not quite as good as ArtLab's SLA prints. But the procedure is a nightmare. You need to wear gloves and a mask when handling the resin, after the print is finished it must be transferred to an alcohol wash and then needs additional UV curing. You need a lab with a hood to use these printers. So back to ArtLab.

Next, I tried a project for fun. I designed a set of chess pieces that stack for compact storage. This has been done before, but to me, they haven't captured the essence of traditional chess pieces. The initial design took a couple of days. But it became interesting enough to spend some time detailing the pieces. I made some changes to better reflect the traditional shapes and I modified them so that the rook, bishop, knight, pawns could be stacked in any order. Due to the height of the king and queen, they can only stack on top of the other pieces and not on each other.

The results are shown here, travel size (6 cm king), but easily printed at any reasonable size.    

The stacking of pieces suggests an interesting chess variation - a piece that takes another can stack on top of it and assume its movement options. This would likely need some limitations - let's say rook, bishop, and knight can assume movement options from a rook, bishop, or knight (only from the top piece of a stacked piece). So if a rook captures a bishop, optionally, it becomes a queen. If that same piece then captures a knight, it may become a super-queen. This has some interesting implications for trades.

The problem with SLA via service is the price. The complete set with 6 cm king costs over $100. Growing it by 25% (3 inch king), over $150;

If you are interested in getting a set, contact me (see www.ravitz.us for my phone, email). I am going to work on reducing the cost. See www.chess.ravitz.us for an STL file for printing these pieces.

Ubuntu Linux 20.04 and LXQt Desktop

Ubuntu Linux 20.04 and LXQt Desktop

I updated from Ubuntu Linux 16.04 (.04 is a stable release) to 20.04 recently. 20.04 has been available for over a year. I assumed it would be a good release. I also switched from LXDE desktop to LXQt desktop. LXQt is an updated version of LXDE, using the Qt library instead of the GTK library. I have no idea what these libraries do or why I should prefer one over the other.

The update required updating to 18.04 first, then on to 20.04. This took a couple of hours.

When finished, it worked. Running my 3D printer from Cura, printing to my Ethernet laser printer, running Wine programs (Windows environment), browser, old apps (except when they played music) all worked.

But there were some problems.

The system hangs during shutdown, depending on how you shutdown. This is my original write-up of the problem - I don't know if it is correct. Shutdown and reboot took a long time, I didn't time it, but a few minutes. Finding the problem took a long web search. Finally "sudo apt-get remove --auto-remove iio-sensor-proxy" fixed it. Why? Because it was looking for the light sensor. When it didn't find it, it just kept waiting and retrying, and refused to be interrupted. Why was it looking for a light sensor? Something about notebooks and laptops needing to know if the cover is open. My desktop apparently doesn't have a light sensor.

Next, every time I clicked on a shortcut icon, it told me that it is an executable (it is) and asked me what to do. Another web search - PCManFM-Qt (file manager) has an option that defaults to this behavior. I just needed to tell it to execute executables.

Next, no sound. Another web search - "sudo apt purge timidity-daemon". Timidity is a Midi player/converter. Apparently it keeps a background presence (daemon) which prevents the system from recognizing the sound output devices. Daemon purged, sound works. Well, the sound from the headphone output. The internal sound on my notebook still doesn't work.

The mouse arrow switches between large and small, depending on the current window. Another web search - run lxqt-config - Session Settings - Environment and create a new variable, XCURSOR_SIZE with a specific size.

Chrome keeps giving an annoying message that it is not the default browser. Clicking the button to make it the default does not get the job done. Web search - run lxqt-config - Session Settings - Environment and change the BROWSER variable to chromium. This does not work. Find the shortcut that is used to start Chrome, it was named google-chrome.desktop. Set the BROWSER variable to google-chrome - problem fixed.

An executable preload message was constantly appearing. And shortcuts to apps were taking several seconds to start the app. Web search - set the LD_PRELOAD path. This didn't fix it. When I removed it, both problems were fixed. I have no idea what caused the issue to be fixed.

I updated Wine (Windows environment). But the new version wouldn't start. Web search - a Wine program was already running at version 5, so version 6 wouldn't start. This shouldn't have taken me so long to find.

Wine 6 kept pouring out warnings about font page 20. Like ten at a time. Web search - no fix, but I found out how to suppress the warnings. In .bashrc (the terminal initializer script) - "export WINEDEBUG=fixme-font".

While removing "obsolete" software (a long part of the Ubuntu update), I lost OpenSCAD. Easy to replace. Thankfully, I didn't lose EasyABC (truly obsolete, but it does what I need and has not been replaced) or a down-level version of Cura that works much better than later versions.

One more detail. If the border of a window is off of the screen, you can't grab it to adjust the size. Use alt/left_mouse_button, anywhere in the window, to grab the window and move it until a border is visible.

And I switched from LXDE desktop to LXQt desktop. There is not a whole lot of difference. LXQt has an integrated preference app - a big improvement. The CPU monitor is inferior to the LXDE monitor and you can't choose what icons are in the system tray. I will stick with LXQt because LXDE will not be updated (as I understand it).

LXQt lets you choose from several different windowing packages. But Openbox (the one used by LXDE) is the only one that has a "minimize" button on the title bar. I can't find any way to get a minimize button with the other windowing packages.

This all took about 12 hours. That's ridiculous. I don't know about other Linux distributions. Any suggestions?