This is a very simple balance beam scale. It uses a tray on each side. Each tray includes round indentations that match the sizes of US dimes, pennies and nickels because my purpose was to compare the weight of coins.
Each tray is suspended from the beam by hangers. The tray snaps into the hanger. I was able to snap the tray into the hanger in most cases, but I did have a one little nib snap off. YMMV. If the fit seems too tight then file down the nib on the hanger a little. If the nib does snap off, simply superglue the tray onto the hanger.
The beam includes four separate detents that accept the hangers. If you want to hang one tray at notch 2 and the other at notch four on the opposite side then the tray at notch 2 will require twice the weight to balance with the object at notch four. However, the tray itself is part of the weight, so there is a separately printable object I called a tray topper. It is intended to be placed in the tray at notch 2 and there are keys to hold it in place. Its mass is equal to the combined mass of a hanger and a tray, which allows the scale to be balanced.
Whether the mass of the tray topper is equal to the mass of the hanger/tray depends on the infill settings of the print. The key is to create a sliced file of one hanger/tray with the desired print settings. Note the amount of filament used. Then create a separate sliced file with the same setting and only the tray topper. In the slicer software, slice off the bottom of the tray topper until the filament used is the same as the hanger/tray. You can then add all of the needed parts to that file or keep the files separate.
There is an adjuster for each side of the scale beam. They can be slid left or right to level the beam before putting items in the trays.
Note that you need to print two feet, two adjusters, two hangers and two trays. You only need one copy of the other parts.
No support required. The stand, feet and trays were all printed upright. The beam and fulcrum were printed upside down. The hangers were printed on their backs. The adjusters were printed flat on their sided.
There is some assembly required.
1) The fulcrum should be glued to the beam. I use superglue (CA). The fulcrum is very small and has a tiny rectangular tenon that fits into a mortise on top of the center of the beam. The tenon is tiny and is intended as a locator pin. Make sure to clean off any plastic bits with a file or sandpaper so that the pin does not get stuck or it will surely snap off while test fitting it. Note that it also isn't a bad idea to file the two points of the fulcrum to sharpen the points. Be sure not to change their shape or dimensions, just file away any layer lines.
2) Two feet are added to the bottom of the stand. I was able to press fit the stand down into the top of the feet, but a little superglue can be added if the fit is loose.
3) The beam with the fulcrum attached simply sits on top of the stand in the corresponding notch.
The adjustors are slightly left to balance the empty trays.
One penny on each side.
The topper on the right at half the distance required a little more adjustment to level.
Two pennies on the right, one on the left.