Gas station without pumps

2023 May 19

Tripod table

Filed under: Uncategorized — gasstationwithoutpumps @ 19:09
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I wanted to use my document camera and USB microphone for recording a standing video (instead of seated in front of a green screen, the way I’ve mostly made videos).  Unfortunately, both are designed for desk-top usage with no way to mount them on a tripod.  I tried stacking up books and other klugey ways to get the camera to the right height, but the results were very unstable. The pan-tilt head on my tripod was too small to safely support the camera (I dropped it at least once while trying to adjust the camera).

What I needed was a solid tabletop that I could mount on top of the tripod.

It took me longer than it should have to realize that I could make one, just by 3D printing a copy of the foot that fits into the shoe on my tripod, then gluing a piece of MDF markerboard to the foot.

Here is a picture of the STL design file I made (using OpenSCAD with the BOSL2 library).

Here is the foot glued with contact cement to the center of a piece of MDF. The glue surface was the top surface when printing, so it did not need to be roughened for adhesion.

Here are the camera and mic on the table on top of the tripod.

The first print (printed with 15% gyroid infill, 3-layer walls, and no brim in silk gold PLA at 0.2mm) worked fine, though I had to sand the bottom edges a little, as the first layer tends to spread a bit, and I had not allowed extra clearance for that spread. Sanding was probably needed anyway, to eliminate the sharp edge.

The table is not particularly stiff (the MDF is a bit flexible), but it works well to hold the document camera and mic, and I can easily adjust the height of the camera.  I used a bubble level to make sure that the table was level before putting the camera and mic on it.

Update 2023 May 20: The contact cement is not strong enough—I overloaded the table with an unbalanced load and the glue joint failed slowly, breaking 5 minutes after I left the room, crashing everything to the floor.  The mount for the head of the camera snapped, which made this a rather expensive failure.  I’ll probably try gluing the camera mount back together, but I’m not confident of the high-stress glue joint holding when the camera is adjusted.

Update 2023 May21: I glued the camera housing back together with a cyanoacrylate glue—it seems to have worked ok, and I didn’t glue my fingers together, nor get glue on the rotating part of the joint, so the camera is one again usable.

2023 April 6

3D-printed test pot

Filed under: Uncategorized — gasstationwithoutpumps @ 18:40
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I’m looking ahead to this Fall, when I hope to take the pottery class again.  I was thinking of designing a form for making small sauce dishes.  We have one vintage one (which my wife inherited from her grandmother) that I thought would be fun to make more of. The dish is small—about 80mm across and 23mm high and has a somewhat complex pattern on the inside.

I plan to make a two-part press mold that I can squeeze a slab between to make the pot, but to check whether the design is any good, I first did the design to make a positive model of the pot. I expected the interior design to be difficult, but it turned out to be really easy, while getting the right profile on the outside with roughly constant wall thickness took me much longer.

I made an SVG file of half the cross-section of the bowl, then used “rotate_extrude” in OpenSCAD to get the basic shape.  To get the raised pattern on the inside, I intersected a slightly raised bowl with a set of twisted linear extrusions.

The outside has a number of steps that should become more visible as glaze flows a bit.

The inside has a raised network of curves that I had originally thought would be hard to create, but turned out to be really easy.

My main remaining concern is determining how difficult it will be to get the clay out of the mold intact. Will I need to switch to a 3-part mold (to push the clay out from the bottom of the slump mold)? Will I need to mold it with a flat bottom and trim the pots when they are leather-hard to make the foot? Should I use a mold-release spray (like Should I use a powder mold release (like cornstarch)? Or a light coating of oil? How dry does the clay have to get before I can remove it from the mold (most of the advice I’ve seen calls for letting the clay dry to leather hard on mold, but that could take quite a while with a plastic mold)? Should I let the slabs dry a bit before using the molds like stamps?

I can see that I’ll have to do a fair amount of experimenting to get something that works.  I may play around with polymer clay to see what I can get to work there (though it tends to be less sticky than real clay).

2023 March 27

Yet another monogram stamp

Filed under: Uncategorized — gasstationwithoutpumps @ 20:38
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In Monogram stamps again, I showed some clay stamps I’d 3D-printed with handles.  I was not really happy with the design of the one I did for Liz, though she had approved the design before I printed it.

LIZ (in Apple Chancery font). The separate letters result in some stringing and blobbing as the nozzle moves from one letter to the next. I tried to clean it up with a riffler, but there was only so much I could do.

Today I designed a new monogram for Liz, based on the Cinzel Decorative font, but moving the individual letters in Inkscape to overlap, then converting them to paths and unioning the paths. The resulting design is a little more elegant:

This is the design of the monogram that I sent to Liz for her approval.

And here is the resulting stamp:

The stamp is 18mm wide at the top and 17.5mm high. There is a bit of blobbing on the end of the curl on the I, and a little on the serifs of the L (which look intentional in the final impression). A better quality 3D printer (or even better adjustment of mine) might make a print that doesn’t need cleaning up with a riffler.

Designing the clay stamps is fun, and the printing is fairly fast (about an hour to print a stamp).  The amount of plastic used is miniscule: about 4g or 10¢ worth of PLA filament.

2023 March 23

Trilobe planters

Filed under: Uncategorized — gasstationwithoutpumps @ 18:12
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In Incense holders as glaze tests, I showed my first attempt at a die for a hollow extrusion, and why it failed. Here I’ll introduce my second attempt at a die for the same hollow shape.

I showed this cookie cutter for cutting the shape of the outside of the extrusion out of a slab.

Here are the two parts of die. The inner part is intended to be held by a bolt. The notches in the inner circle of the outer die are intended to hold the ends of the spider that support the bolt. Both dies are tapered so that the clay will be wedged together as the clay passes through.

Here is the inner die mounted on the spider, viewed from the side that would be on the bottom of the extruder.

Here is the die in the extruder. You might notice that the spider is not resting in the notches intended for it. That is because the spider tapers in a bit at the end that sits on the die, and I did not measure it accurately, so the notches were too far from the center. The extruder is not very clean, because the high school students always forget to remove the excess clay when they are done. It also helps to put a rag between the clay and the piston, so that the sides are wiped down as the clay is extruded.

I made 5 small planters out of the trilobe extrusion, with the hollow tube drying overnight before being sliced.  The tube dried very fast and slumped a bit on the board it was drying on, losing the 6-fold symmetry. By the time I was shaping the 5th planter, the tube was getting a bit too dry to work with easily. I think that in future I would try slicing the clay while still fairly wet, and letting it dry to leather hard as vertical tubes, rather than as a horizontal tube.

For the glazing, the bottom of every planter had the stamps painted with black, then the excess wiped off, before any other glazing was done. Two of the pots were dipped (the brown one in temoku gold and the candy-red one in candy red)—the other three were hand-painted with commercial glazes.  All the glazes are cone-6 glazes.

All the pots are about 60mm–65mm across (measuring the highest point when lying the planter on its side).  They have two tubes (a long one for the planter body and a short one for the planter foot) joined by a slab that has a couple of holes punched in it. The slab was fresh-rolled while the tube had dried overnight, so there was some difference in the size—this resulted in a bump rather like a joint in bamboo, so I decided that it was a feature, not a bug. I carved notches in the feet, so that each planter has three separate feet.

The planters did vary in height, depending on the lengths of the tubes.  Here they are from shortest to tallest:

Yellow planter

The yelllow planter is 66mm–69mm high. The glaze is a commercial “China yellow” glaze applied with a brush in two layers. Getting a uniform coat was difficult, and some bubbles formed in the glaze.

The bottom was painted with 1 layer of commercial “marigold” glaze. The black glaze in the stamps is clearly visible.

Brown planter

The brown planter is 68mm–72mm high. The surface was brushed with steel brush before the bisque firing, making a rough surface that held the glaze well. Some of the roughness can still be felt after the glazing.

The brown planter was dipped in temoku gold glaze, using a piece of wire through the hole in the center to hold the pot. This side of the pot came out somewhat lighter and more speckled than the side shown in the previous picture.

The black in the stamped portions is not really visible with the darkness of the temoku gold.

Candy red planter

The candy-red planter (dipped once in candy red glaze) was the one that deviated most from being vertical, with the top varying from 78mm–88mm high. I haven’t decided yet whether this is a problem or a feature. Most of the variation is in the tube that makes up the foot of the planter, but there is some curvature to the top tube also.

This view of the planter on its side shows some of the curvature.

The inside of the pot is fully coated, but the candy-red glaze is nearly clear in places. This seems to be a common problem with this glaze.

The foot shows considerable distortion of the trilobe extrusion, because of the tube getting a little too dry while lying on its side. Again, I’m not sure whether I prefer a more regular “machine-made” extrusion look or this rather funky “handmade by incompetents” look. Perhaps there is some middle ground to look for.

Cherry red planter

The cherry red glaze came out as a really bold red—much better than the almost transparent candy red. The planter is 86mm–89mm talll, but rocks a little on its base.

The inside of the planter is glazed 2cm–3cm down, so that the bare clay will not show (much) when the planter is filled with soil.

The bottom of the cherry-red pot was painted with “cinnamon gloss”, which seems to make a more uniform brown than the temoku gold glaze. (I like the speckling of the temoku gold for this application, but it is nice to know that a more uniform brown is available.)

Mist blue planter

The mist-blue planter varies from 92mm to 97mm tall, but has less lean or curvature that the candy-red one. The glaze flowed terribly on this one, so I will not use it again, even though I like the color.

The bottom right foot here shows where the glaze bubbled and flowed onto the kiln shelf—something you really don’t want to have happen with a glaze!

Looking down from the top, you can see a little cracking between the slab and the sides—it was difficult to apply pressure for the joining that deep into a narrow tube. I think that there is sufficient strength, because the slab and the tubes are well joined on the outer surfaces, but I’ll have to think of a technique for making smoother joins on the inside.

The foot of the mist-blue planter was painted with purple crystal, which seems to result in a rather unpleasant mix of purple and green colors—so this pot has two glazes that I don’t want to use again. You can also see two places on the foot where the outer mist-blue glaze flowed onto the kiln shelf, even though I had left at least 3mm unglazed as specified.

So my first real attempt at using hollow extrusions was not a total disaster, though I clearly have to improve my technique a lot. If I get into the pottery class in the fall, I’ll play with this extruder die some more, as well as practicing throwing.  At least with the extruder my wall thicknesses are a fairly uniform 6mm–7mm, unlike the very thick walls of my thrown pots.

I’ll probably plant some small succulents in these pots, then give them all away.

2023 March 19

Stage jewelry

Filed under: Uncategorized — gasstationwithoutpumps @ 14:33
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As a social outlet during retirement, I’ve started acting with the “Readers’ Theater” group of Nextstage, where I have been cast in two roles: John in Ferris Wheel by Mary Miller and Rollo in Emotional Baggage by Nina Shengold. In Cigarette propsI posted about a prop I made for Ferris Wheel. Here I’m posting about a costume piece for Emotional Baggage—not for my character but for Phyllis, a carry-on bag who has a line about her monogram.  I made a necklace for the actor to wear as the monogram:

The monogram is printed in Silk Gold PLA about 2.5mm thick and 130mm wide. The chain was a cheap gold-plated brass one (75¢ a foot) that I bought downtown.

I actually made two pendants, but I thought the first one was too small—we want the letters to be visible from 20′ (6m) away.

I made the monogram by placing large Cinzel Decorative Heavy letters with Inkscape, converting to a path and importing the resulting svg file with OpenSCAD. I could have done the whole thing in OpenSCAD, but I thought it might be easier to adjust the placement in Inkscape. In retrospect, it would probably have been quicker to use OpenSCAD exclusively, though I would have had to adjust the positioning by editing numbers, rather than with a mouse.

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