How to Make the Open-Source Leg

Update (5/10/2021): 3 parts have been redesigned to facilitate assembly / servicing. The new parts are also updated in the STEP files provided by the website in case users are in the process of build a new leg. For questions please contact us.

The OSL is assembled from both machined and stock components. In selecting components used throughout the OSL, the design attempted to minimize the following criteria:

  1. Price
  2. Lead times for machined parts
  3. Number of vendors from which stock parts need to be purchased

The vendors employed along with the cost associated with each vendor are enumerated below.

  • Star Prototype (machined parts) ……………….. ~$15.6 k
  • Dephy (actuators and encoders) ……………….. ~$8.7 k
  • SDPSI (belts) ……………………………………… ~$0.2 k
  • McMaster-Carr (bearings, fasteners, etc.) …….. ~$1.6 k
  • Misumi (shafts) …………………………………… ~$0.1 k
  • Motion Industries (angular bearings) ………….. ~$0.8 k
  • Amazon (batteries and case) …………………… ~$0.5 k
  • K&J (magnets) …………………………………… ~$0.0 k
  • Shipping charges ……………………………….. ~$0.9 k
  • Total Cost ……………………………………….. ~$28.5 k

Detailed quotes can be downloaded below. You can download all drawings and STEP files by clicking on the links provided.

All parts bought from suppliers are organized into an Excel sheet, which can be downloaded at the “Purchased Parts Required” section. For help with navigating the sheet, a description is detailed further down on this page.

Because the OSL is a high power device, it is recommended the E-Stop, an emergency stop button, be used with the OSL. See the linked page for instructions for assembly, manufacturing, and use.

1) Files Required for Manufacturing

The following drawings and STEP files need to be downloaded and sent to Star Prototype for manufacturing. The drawings highlight only special features (hole placements, counterbores, etc.) and are not fully dimensioned. Click on any of the links to download the STEP files and drawings for the given joint. You may also view previously made quotes from Star Prototype.

Drawings/STEP Files for Knee With Series Elasticity

Drawings/STEP Files for Knee Without Series Elasticity

Quote for Knee Prosthesis

In addition, we also have provided a quote for two knee prostheses to demonstrate how order quantity affects price: Quote for Two Knee Prostheses

Drawings/STEP Files for Ankle Prosthesis

Quote for Ankle Prosthesis

In addition, we also have provided a quote for two ankle prostheses to demonstrate how order quantity affects price: Quote for Two Ankle Prostheses

For your convenience, you can find the STEP file of the entire OSL assembly here.

2) How to Contact the Manufacturer

Sample Email

The page linked above displays a sample email that can be sent to Star Prototype. To order from Star Prototype, compose a message similar to the sample email (or copy and paste sample email), attach the drawings and STEP files, and send the message to Dara Shabnam (dara.shabnam@starrapid.com) for manufacturing.

NOTE: The current quotes specify part finish color to be either natural or black. If you would like a different color, please communicate this to the manufacturer in the email.

3) Purchased Parts Required

Purchased Parts – Excel Sheet – note that this bill of materials does not contain parts to build the E-stop, which is described separately.

Under the “Parts to Order”, parts are organized into the different subsystems, as can be seen in column A. Solidworks part numbers are located in column B, manufacturer part numbers are in column C, a quantity is listed in column D, and a link is embedded in column E. You may order all parts for the desired system.

Once all parts have been received, proceed to the “How to Assemble” page.