Spring Break Report

I've noticed the double vend issue is persistent occasionally, particularly with very thin packaged condoms and even more so when a section of the inventory is all thin condoms. I think that further reducing the height of the aforementioned face slot by another increment will clean this up more. I've redesigned the inventory chute with thicker plywood and the inventory height adjustment, and a few other minor details.

I've also redesigned the case to reflect a coin mechanism location, and reduced overall dimensions -- (190mm W, 475mm H, 155mm D)  compared to (275mm W, 500mm H, 120mm D) for the current model -- 50.8% volumetric.

This also has reduced the amount of sheet metal required from 8 sqft. to just over 3.5 sqft. This of course isn't free, the new model incorporates 3 sqft of plywood which was not included in the previous design. However, this version 0.3 is also weld- and machine-screw free, incredibly. This eliminates welding equipment from the assembly requirements, as well as specialized hardware. These joints have been replaced or redesigned to incorporate tapered thread screws -- think wood screws, or drywall screws -- that's the thing, they're very interchangeable and far more common.

I've uploaded a copy of my working folder for this project, in the spirit of open source. The folder will be maintained at Google Drive, accessed (read- and download- only) at the following link. The data is provided under GNU FDL.

Current CAD models are in proprietary Solidworks format. I'm looking into options for exporting the data to a more friendly format, such as STL or another polygonal format. This does, however, preclude the end-user from practically modifying the design. There are open-source CAD formats available, I'll have to look further into those possibilities.

Perspective view, note new shield design, coin tray, braces, removable inventory chute (slides out front), secure vend slot.

Partial cutaway view of mechanism

Side view, cutaway

Side view, gear orientation

New Inventory Chute, Goodbye double-vends.

Over the last few days, I've put together a new inventory chute assembly, to attempt to correct the issues with double vends (~10% of the time) and non-vends (~3% of the time). I hypothesized that the gap on the front of the inventory chute through which condoms are dispensed was too tall, and thus allowed multiple thin condoms to slip through easily.

New (L) vs Old (R). Note the reduced size of the (L) interface plate.

I made some other modifications to the geometry of the interface plate and system, reducing the depth by .500", the width by 2.00", and increasing the usable height to the full 12" height of the chute.

New and Old, side by side. You can see the reduced width, and the elimination of the brown "liner" components. The width and depth of the access slot has also been increased, allowing much easier stocking.

Installed. Note the reduced width, the right cam has been slid left about 2.5"

 I ran about 150 condoms through the device. The current capacity is about 100 condoms, at 50 per chute per 12". The chutes could be extended vertically to an arbitrary height and capacity at this rate.

Although the overall success rate is still right at 97%, I've basically eliminated the double vend issue. I believe that by adjusting the z-position (depth) of the chute vs. the axle, I can improve on this further.

Further bulletins as events warrant! Things are looking nice.