Part Supply Issues

[JaredBaileyDuke]

The parts are largely unavailable, link to different parts than listed, or have major discrepancies in price. Updates are needed. Preferably more McMaster options.

[tjacobs]

Let's add the BOM parts list here to order and they can make a tab in the doc with them:

https://www.amazon.com/dp/B0CW8VGBGT <- I hope correct

[JaredBaileyDuke]

I've sourced different parts from McMaster. I'm happy to provide if needed.

[tjacobs]

yes please

i'm trying these

https://www.amazon.com/Feelers-Stainless-Threaded-Threads-Length%E3%80%90Pack/dp/B092QC2RD6

https://www.amazon.com/ZDingTech-Support-Shelves-Rod-304-Stainless/dp/B0F28XKTMW

https://www.amazon.com/uxcell-Cylindrical-Mechanical-Manufacturing-Installation/dp/B0DRSKF61F

https://www.amazon.com/uxcell-Bearings-Wrapped-Oil-Less-Bushings/dp/B07SHSN6NP
https://www.amazon.com/uxcell-Flanged-Bearings-Plastic-Bushings/dp/B0DNMK1PMD/

https://www.amazon.com/uxcell-Stainless-Phillips-Tapping-Screws/dp/B01KXTTSCI/

https://www.amazon.com/uxcell-Stainless-Phillips-Tapping-Screws/dp/B01KXTU2WS/

https://www.amazon.com/VictorsHome-M2-5-Washer-Stainless-Washers/dp/B0DZVTT1VH/

[JaredBaileyDuke]

I tend to prefer a site like McMaster because I know they will consistently have the parts. I don't have to rely on individual Amazon and Ali sellers, who can come and go.

Feetech SCS0009 Servos

I'm going to try subbing out for a different brand of 9g servos (1kg and 2kg), as these are much cheaper and won't take forever to arrive. This is untested. Right now they fit fine in the hand.

Ball joint M2

amazon, although McMaster has ball joints. I just wasn't 100% confident that I could get the right one.

M2 threaded rod L300mm

or 25mm and 16mm

Axis D2x10

Axis D2x16

Bushing Dinterior 6mm / Dexterior 8mm (GFM 0608-04)

Screws 2.5x6

Screws 2.5x8

Washer M2.5 Dexterior 8mm (large serie)

[JaredBaileyDuke]

These servos won't work with the current code. I'm going to work on new code this month.

[SteveNguyen]

Thanks for your help, we will check all of this and update the BOM for different countries.

[DominikLe]

I tend to prefer a site like McMaster because I know they will consistently have the parts. I don't have to rely on individual Amazon and Ali sellers, who can come and go.

Feetech SCS0009 Servos

I'm going to try subbing out for a different brand of 9g servos (1kg and 2kg), as these are much cheaper and won't take forever to arrive. This is untested. Right now they fit fine in the hand.

Ball joint M2

amazon, although McMaster has ball joints. I just wasn't 100% confident that I could get the right one.

M2 threaded rod L300mm

or 25mm and 16mm

Axis D2x10

Axis D2x16

Bushing Dinterior 6mm / Dexterior 8mm (GFM 0608-04)

Screws 2.5x6

Screws 2.5x8

Washer M2.5 Dexterior 8mm (large serie)

To be honest, I would not buy these servos, because they cannot return their current positions, current and other informations. Yeah, they are cheap, but you "pay" with missing features.

[JaredBaileyDuke]

I installed the cheaper servos and they work like a charm. I also didn't have to wait for delivery from China. I made one hand with 1kg servos with plastic gears and a second with 2kg servos with metal gears. I just needed new code to get moving. I wrote my own script to find min and max servo angle limits, and converted those limits to 0% - 100% for servo movements in the final code.

Torque feedback would be useful, which I'm missing out on. But I'm not sure how useful it is this far down the finger. I think I would rather have force information at the fingertips.

I think the closed loop control may be overkill on this hand. I could see this being more useful on a high end hand.

All this said, I think using the cheaper servos may be a great option for many. I'm happy to provide information on my process and the code. I also understand if you're not interested.

[crabarca]

@JaredBaileyDuke I also got the cheaper servos, basically PWM controlled servos. Do you have more insights on how to operate them?

[JaredBaileyDuke]

@JaredBaileyDuke I also got the cheaper servos, basically PWM controlled servos. Do you have more insights on how to operate them?

Both sets of motors (high and low torque, plastic and metal gears) work like a charm. I don't think the more expensive servos from China are needed. I really didn't want to wait on the servos to be delivered either. The extra feedback on position from the Chinese motors isn't perfect since you can wiggle the fingers a bit while they are stationary, and the hands aren't robust manipulators.

I would get a PCA9685 driver board, and give the servos more power. I wrote two pieces of code:

1. calibrate each finger to find its degree ranges (say 35-160 degrees)
2. operate the fingers from 0% (closed) to 100% (open) based on constants of the degree ranges. this code currently has set hand positions such as pointer finger open and the rest of the fingers closed.

Everything is operated from an Arduino. I'm hoping to add Google's Media Pipe next, as I've been playing with it on a Pi 5.