v1.1.0 - DFA Improvements

Summary
The LumenPnP 8mm Feeder v1.1.0 was released to address design for assembly (DFA) improvements. The design switches away from machine screws w/press-fit hex nuts and moves to use DIN 7500 trilobular self-threading plastic screws.

BOM Corrections
The feeder-compression-spring was entirely missing from this repo previously. This has been corrected in v1.1.0 - we have since provided a 3D model for this item and added it to the BOM.

Issues Closed
This release address the following issues:

• Fixes #30
• Fixes #28

v1.0.1 - Printability Improvements, Improved Drive Wheel

This is a small bugfix update that mainly improves the manufacturability of the feeder. This includes:

• Removing a chamfer on the nose of the feeder that is likely to warp during printing, preventing the fiducial PCB from fitting
• Opening up the fiducial PCB void to make fitting easier
• Decreasing the gap between the buttons and the frame to prevent warping
• Widening the slot bracket slightly to make mounting feeders easier
• Updating the spool arm to contain two parts instead of just one. The spool arm now has a thimble that is inserted and rotated 90 degrees, tightening into place. The ability to print these parts separately allows for a more optimal print orientation and better print quality.
• Drive wheel teeth were extended slightly to provide a more secure interface with very thin plastic tape, and allowing the peel sequence in firmware to overshoot a bit more, ensuring proper film removal.
• Two drive wheel holes that were originally added for a potential bolt-on shaft collar were removed.

Full Changelog: v1.0.0...v1.0.1

v1.0.0 - First Official Release

Summary

This is the first official release of the 8mm LumenPnP Feeders! A ton of wonderful and intelligent people have put in tremendous effort to get us to this point. Thanks to the incredible LumenPnP Dev Team, DVT beta testers, Opulo employees, and everyone in the STR Discord server. It truly takes a village to make good hardware.

As of this release, feeders are also available for sale at opulo.io.

For more information about feeder usage, check out the feeder docs page.

Being the first release, there's a lot to say about what's in here:

System Overview

The LumenPnP feeders are a mostly 3D printed 8mm tape feeder capable of reliably feeding 0402 components. They are designed to easily mount to a 20mm x 20mm v-slot aluminum extrusion. There are two motors in the system: a drive motor and a peel motor. The drive motor is a right-angle N20 motor with an encoder, giving us incredibly high resolution control of the motor's position. The peel motor is a standard N20 motor that peels film using a few 3D printed gears. The feeder has two buttons for tape loading and manual control. A third button puts the feeder into bootloader mode, allowing anyone to flash new firmware using a common FTDI USB to UART converter.

Feeders connect to power and communication when mounted to a rail through what we're calling a slot. Slots all connect back to a LumenPnP motherboard using an IDC cable. Each slot has a 1-Wire EEPROM onboard which holds the slot's address. This address is used to tell OpenPnP where a certain feeder has been mounted. All communication back to the motherboard happens over RS-485 using the Photon Protocol.

Drive Subsystem

The right-angle N20 motors used for driving tape have a 1:1030 ratio gearbox, providing a high torque output. The encoder on the back shaft of the motor has 14 ticks per revolution, which results in a theoretical 8.8 micron tape movement resolution. Of course, there are many other factors at play that reduce how precise the feeder is actually able to position tape, but the encoder is plenty precise enough for our application.

Peel Subsystem

The straight shaft N20 used for peeling is much less complex. It's a standard N20 with a 1:210 gear ratio, with a printed worm gear attached to the output shaft. This worm gear interfaces with a gearbox used for peeling the film. The two straight gears that perform the peeling are mounted with a positive interface, ensuring the frame holding them in place is constantly applying pressure between them. This interface is what grips the film and pulls it away from the tape.

Software and Communication

There are three components to the software stack with feeder communication. At the bottom of the stack is the feeder, running Photon Firmware.

Above the feeders is Marlin. Feeders and Marlin send data along an RS-485 bus that connects to every slot. They send data using the Photon Protocol. A new M command for Marlin's gcode interface, M485, allows a host to send data down the RS-485 bus using Photon, and thereby communicating with feeders.

At the top of the stack is OpenPnP, who acts as the host in this scenario. OpenPnP sends M485 commands to Marlin, and gets data from feeders back as a result. A custom OpenPnP feeder type PhotonFeeder supports common Photon commands such as feed, self-identify, initialize, or check for feed status.