Menlu Strip Feeder 8mm/12mm for LumenPnP

Even though I liked the minimalistic design of the original LumenPnP strip feeders, they had some difficulties with both thicker paper tape (like 1.2mm thick with more bulky capacitors) being hard to push all the way through as well as thin plastic tape being not so well guided and supported and hence very sensitive against touching the tape and the parts jumping upside down or off the tape. That's why I tried to come up with a flexible strip feeder design which can cope with different tape thickness and supports the tape more tight over the full length.

The Menlu feeders are mainly composed of two parts. An outer guide rail which clamps the tape on top (pretty much like the original feeders) plus an inner slider which is spring loaded and moves on two slightly tilted ramps resulting in an up movement when released and hence firmly pushing the tape to the top and decoupling the parts from touching the overhanging tape accidentally or working on adjacent feeders.

It fully supports the ~3mm tape section with the holes from underneath and when printed in a color different from what type of tape is being loaded, it also helps with hole detection in the vision pipeline of OpenPnP.

At the end of the slider a 1.5mm alignment pin can be added, which help with locating the pockets at the same position when forwarding the tape and hence no re-teaching of the hole position in OpenPnP is necessary. Note: The 1.5mm hole in the print comes out slightly too small (even though I made it a bit larger) and might require finishing with a 1.5mm drill bit.

To help with both guiding the peeled-off cover tape as well as covering/securing remaining parts when not in use or during forwarding the tape, a clip can be slid over the top with the peeled-off tape inserted into it.

For mounting the feeders to the LumenPnP I made dovetail plates in various sizes into which the feeders can be inserted. Both 8mm and 12mm feeders can be inserted side-by-side in any order without wasting space on the staging plates. The dovetail plates come in multiples of 15mm which is the hole spacing of the LumenPnP. The dovetail plates have holes for standard M3 countersunk screws, which are flush with the top surface.

Printing

I printed everything in PLA (Overture PLA+/Professional actually) on a Prusa Mini+ and Prusa MK3S+, but should work on any decent 3D printer. No supports are needed.

The sliders have to printed upside-down i.e., with the top side to the print bed. They have a recess on both sides and hence require some bridging. Make sure to check the bridge orientation before printing, bridges should cross the gap over the shorter distance obviously. Note: In Prusa Slicer a bridging angle of 0° means rather “automatic” and sometimes the slicer gets this wrong. Set to 180° if necessary.

The outer guide rail also requires some bridging over the dovetails but just about 3mm, so should be no issue. See above on bridging angle.

Since the slider runs on slightly tilted ramps in the outer guide rail to results in an up/down motion, those ramps should be as smooth as possible - which is challenging on top surfaces with FDM printing. I got decent results with “Variable Layer Height” in Prusa Slicer, which does recognize sections with slight angles and reduce layer height in those layers. I set Quality/Speed parameter to 0.3 and selected “Adaptive”. This led to 0.07mm layer height in the ramp sections of both the outer guide rail and the slider. Printing everything in e.g., 0.1mm layer height made bridging poor so Variable Layer Height would be beneficial.

The clip for the peeled-off cover tape also needs to be printed upside-down.

I added three .3mf files for the 8mm feeder, 12mm feeder and dovetail plates for the Prusa Mini+ which include above settings. Also added ready-to-print .bgcode files for printing with generic PLA.

Finishing

To give best support of the tape over the full width, the clearance of the slider inside the outer guide rail should be minimal. By design the gap is 0.15mm, which works fine on a good 3D printer. On some prints I had to sand the sides of the slider a bit on sandpaper (mainly due to a bit of x/y corner overshoot rather than the actual dimensional accuracy) but better that than a too big gap inside.

Assembly

Only required assembly is mounting the spring. Put the outer guide rail to the desk and insert the spring with one ring over the pin and the spring laying inside the bottom opening slot. Then insert the slider up to the spring, make sure the spring is centered so the bottom recess of the slider can slide over the spring and fully insert the slider. Next step is a bit fiddly. When flipping the feeder the spring can slip off the pin and above steps would need to be repeated. Better is to hold the feeder upright with the bottom opening facing to you. Now grab the other ring of the spring with a pliers or tweezer and slide it over the second pin which should be accessible through the bottom opening slot.

Mounting

The dovetail plates can be mounted anywhere on the LumenPnP with standard M3 countersunk screws of proper length. Make sure the screw is flush with the top surface.

The feeders have slots on the bottom which go over the mounting plate dovetails and when pushed down the feeder slides over the dovetails. It should be a firm fit, depending on your printing tolerances a bit more or less.

Additional Parts

The feeders requires one tension spring to pull the slider into the up-position. The spring's free length is 25mm and diameter 5mm. The alignment pin for the tape holes is 1.5mm diameter. Below are some links of the parts I used.

• Tension Spring 25mm/5mm: https://www.amazon.de/dp/B07PLBJPQG (EU link), https://www.amazon.com/uxcell-Extended-Compressed-Diameter-Stainless/dp/B07NRJY862/?th=1 (US link)
• Alignment Pin 1.5mm/6mm: https://www.amazon.de/dp/B07NVFRZTT (EU link), https://www.amazon.com/uxcell-100Pcs-Stainless-Support-Elements/dp/B07MNP4N5K/?th=1 (US link)

Comments

The pick height of these feeders are a bit higher than the original LumenPnP reference strip feeders (about 1mm) but this height is still in focus of the top camera.

Questions

Feel free to reach out and looking forward for feedback, suggestions and ideas for improvement!