Gear Wear Rig Calculations

Forget calculations. Plating a gear radically changes any characteristics of the plastic beneath it. That's a waste of time. You'll be testing the metal and NOT the plastic and the metal is much harder. Your conclusion, no matter the load, will be that the plastic wears out sooner.

Just make the size and pitch match and get on with it.

KISS!

Choose a motor big enough to drive the apparatus under any load and make your apparatus adjustable to apply different friction loads.

You must first determine the load and environmental conditions together with design life to select the material of the gears and the material properties needed to meet the goal....Once you determine the load, operating conditions, and length of service expected, then you can determine which materials will fit this criteria...another critical factor can be lubrication, what type of lubrication, what delivery method and maintenance interval works for this application...needless to say you need people who specialize in each of these fields for efficient results....Your test rig needs a way to accurately measure torque...

https://www.rtpcompany.com/products/product-guide/nylon-6-pa-polyamide-6/

https://www.machinedesign.com/mechanical-drives/plastic-gears-more-durable-ever-plastics-get-gear

https://www.hindawi.com/journals/at/2015/926918/

I suppose you're right and that's what I am expecting, however for the project I'll still need to back it up with some calculations for the rig. Unfortunately...

Thank you for the links, I am getting on top of getting info from them now.

What kind of equation should I be looking at to determine torque of a motor / required based off the friction created by the load?

https://www.orientalmotor.com/technology/motor-sizing-calculations.html

I think I would use a spring balance...

oh, that's a great idea actually. Thank you

Connect a spring scale between the fixed point (on the right) and the belt. If you subtract the weight of the mass counterweight from the scale reading, you get the force supplied by the friction. Multiply this force by the radius of the pulley to get the load torque.

Perfect thank you, I will probably use the spring load then, makes it much easier to do any calculations.

Thank you for the book suggestion will be looking for it now and doing further research.

You can also measure motor voltage and amperage to calculate watts. It will more likely be accurate than the spring scale method since you will have a range for belt/pulley friction coefficients and those coefficients vary quite a bit depending on surface conditions and temperature. You can get further accuracy by putting a permanent magnet motor and variable load instead of the belt and pulley brake and measure watts out as well. Given watts in and watts out you can measure losses and estimate normal forces. You will also be able to measure at which loads the wear mechanism begins to ramp up.

Before I leave, you said "overall wear of plastic & 3D printed gears however the 3D prints will be electroplated.

3D printed gears ARE plastic." 3D printed gears DO NOT have the same mechanical properties as machined or injection molded gears of the same material.

As I said before plating 3D printed gears renders your entire project invalid! You have NO IDEA what the mechanical properties of the plated gears are, until it is tested.

Finally, Relativity PL is an expert in the field of plastics and processing, but be sure to recognize the fact that his data was for a specific type of Nylon material Zytel - Wikipedia derived before 3D printing was invented. It my still be valid for molded or machined gears, but 3D printed gears? I don't know, maybe he does.
You did not specify the material type. This may help: Online Materials Information Resource - MatWeb

You still have a LOT of work to do.

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Great, someone with an idea for a project engaging in a sensible discussion.
I've rated this 5 star .
Ive measured toque to turn peristaltic pumps by mounting a long bar to the pump head (or gear in your case) and hanging weights on it until it turns (or shears a tooth in your case?) That would give a max static torque/load maybe, which is prob a good place to start.
Interesting project
Del

You may want to go to a plain bearing manufacturers site and look into CV values for plastic bearings. CV is load times velocity and various materials and plastics types are rated for CV values.Since the gears will experience sliding wear at the contact point, use the CV data.

The electroplated 3d printed gears will have an additional failure mode, specifically low cycle fatigue of the metal film followed by spalling of metal flakes, largely driven by elasic/plastic deformation of the plastic under the metal film. You also do not mention gear lubricants which will have more effect on the wear than any other component in the system.

CV is usually a valve term (coefficient of volume). For bearings, the more usual designation is PV (pressure x velocity).

You're right.

I've the gears now selected and will be sourcing the pulley and belt now. After having a look at an appropriate motor so I've made progress. Still open for any suggestions and discussion. Thank you all.