Assembly and printing issues

[a357450371-cmyk]

Dear Author,

I would like to ask you two questions.

How is the tendon routing configured? I’m not quite sure whether the tendon should wrap around the guide pulley completely, or if it should pass over one half of the pulley on one side, go through the joint hole, and then pass over the other half of the pulley on the opposite side to drive the joint.

Did you use 3D printing for fabrication? I used an FDM printer in our lab, but the printed parts turned out to have poor dimensional accuracy, making assembly quite difficult. I’d like to ask how you fabricated your components.

[wengmister]

Hi - apologies for the late replies - tendon pulley goes through the hole, but also remember to tie a knot that can be shoved through the hole and apply adhesives. The tendon is then terminated on the pulleys on the servo end.

I 3d printed all the linkages with Formlabs SLA printers. The tendon grooves on the linkage parts are difficult to print with FDM unless you have really good resolution. I'd recommend SLA (albeit more fragile) or SLS if you have access to them for the finer details.

[a357450371-cmyk]

Thank you very much for your reply. I will try your guidance. Thanks again. Zhengyang Kris Weng ***@***.***> 于2025年11月3日周一 02:13写道：

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*wengmister* left a comment (wengmister/BiDexHand#6) <#6 (comment)> Hi - apologies for the late replies - tendon pulley goes through the hole, but also remember to tie a knot that can be shoved through the hole and apply adhesives. The tendon is then terminated on the pulleys on the servo end. I 3d printed all the linkages with Formlabs SLA printers. The tendon grooves on the linkage parts are difficult to print with FDM unless you have really good resolution. I'd recommend SLA (albeit more fragile) or SLS if you have access to them for the finer details. — Reply to this email directly, view it on GitHub <#6 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BX5VHX7H4Z7LFEGZZZDJZNT32Y3T7AVCNFSM6AAAAACJ4FXPLSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTINZYGE2TQMJXGU> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[HJT-Droid]

Dear author;
I have a question I want to ask you
How is the left and right swing of the metacarpophalangeal joint, is, the MCP joint, arranged with lines, are the tendons just wrapped around the pulley? Is there any connection with the pulley fixed, if just wrapped around pulley, then how does friction drive the entire finger to swing left and right?

[wengmister]

Dear author;
I have a question I want to ask you
How is the left and right swing of the metacarpophalangeal joint, is, the MCP joint, arranged with lines, are the tendons just wrapped around the pulley? Is there any connection with the pulley fixed, if just wrapped around pulley, then how does friction drive the entire finger to swing left and right?

Hello!

Apologies that I don't have a better picture with me at this moment, there's a screw clearance for an m1.6 SCHS on the knuckle part for MCP splay. You can either do a bowline knot or a simple knot and crush it with the screw head to keep it fixed with the linkage.