A cheap DIY conveyor for moving small loads with precision, all made from common hardware shop parts.
I was doing a pick n place type machine, but became tired of the time needed in a xyz style of machine to travel back and forth. It seemed to make more sense for the part to move close to the dispenser.
Conveyors are a basic element of many production systems, and needed a simple open source hardware design. Commercially available conveyors of similar size (with much higher quality engineering) seem to cost around $1000 onto which you need to add $200+ for a variable speed controller! It seemed possible to make a sufficiently good one for less than about 80$ and control it properly from a stepper motor.
This is a small contribution toward a low-cost Open Conveyor.
Similar designs have been used in the context of T-shirt dryers e.g.
These tend to use rotisserie motors for continuous motion, whereas I needed the precise control of a stepper motor.
Design your conveyor
The strength, length and width of your conveyor needs to be determined. I cut the steel bar down to 180cm so it would fit on my desk, and chose a width of 40 cm with rollers every 15 cm which required 12 rollers. If it needs to be stronger you could triple the density of rollers.
Total cost without electronics ~ 70 euros
Some of these parts have special qualities that make the project possible.
Cheap electrical tubing (IRL 25 mm) is used to make the rollers. Buy the cheapest quality with the 1.5 mm walls. Wise to take a bearing with you when buying this to make sure that it fits. It should push in with a gentle to medium push. You should not have to force.
This is what is going to give most of the rigidity and allow you to attach it to a table or attach other tools to the conveyor. You need it to have a dimension that will allow a roller plus the belt to move freely. You'll also be attaching lots of 8 mm bolts, so it will help enormously if it has 8 mm slots in it.
The classic 608 bearing has an outer diameter of 22 mm that corresponds with the inner diameter of the PVC tube. It also has an inner diameter of 8 mm which allows strong 8 mm bolts to be used. These can be picked up from sporty discount shops or ebay in packs of 8-10 for about 0.5 euros each.
22 mm Rubber Bung / washer
Somewhat rare but available in decent hardware shops, these allow you to grip to the inside of the plastic tube. They act as a coupler between a drive shaft and the tube. You probably can't find them with ~7 mm inner diameter, so you'll have to drill out the middle a little
Anti-slip sticky tape
This is an expensive luxury but works very well. It is like sandpaper on one side and very sticky on the other side. This is what grips the underneath of the table cloth. You may be able to just stick sandpaper onto one of your rollers, or use paint/varnish/glue and some sand.
'Waxed' Table cloth
These days they are made of a soft plastic coating with a fabric underside. They are generally sold in 1.5m widths which is far too large. The fabric side helps grip the grippy roller. The plastic top is flexible and relatively durable. This was the cheapest material I could find that had the right properties.
Stepper motor and controller
Typically this might be a NEMA 17 motor + Arduino + Motor shield. I won't go into this side of things.