PushPullFeeder alpha release

[Toby Dickenson]

Hi all,

I continue to use a PushPullFeeder in production based on Mark's
design on my lumenpnp machine, and have been gradually improving it
over the last year. This alpha release is a significant improvement
since I last mentioned it here. It is smoother, parts are less likely
to jump, and the mechanism is less likely to jam and break. It has
much improved printability on modern 3d printers. I dont think it is
faster than the previous release, but it is a significant quality of
life improvement.

This is an alpha release that I am testing in production over the next
few weeks:

https://github.com/tobydickenson/PushPullFeeder/tree/test

[Satya Gupta]

Sorry if i am asking this question in the wrong post. 

But why not add a simple spring for pull action? Use header only for pushing not pulling. 

[Toby Dickenson]

On Fri, 6 Mar 2026 at 03:41, Satya Gupta <3.s...@gmail.com> wrote:
>
> Sorry if i am asking this question in the wrong post.

This is a good place to ask.

> But why not add a simple spring for pull action? Use header only for pushing not pulling.

I guess the PushPullFeeder would be better named a PullPushFeeder. The
first action is the Pull, so a spring return action would leave the
feeder in the wrong idle position.

But maybe you can spot a mechanical solution that I have overlooked.
Feel free to share a sketch of any ideas and I might just test it.

Toby

[Satya Gupta]

True that, this is first time i am using this. Did a test print to understand how it works and yes indeed it is a PULL and PUSH action.

The CAD is in OPEN SCAD which is not my cup of tea, i will try to modify or add some automation in it. 

[andrew...@gmail.com]

Toby, What are the cut strip feeders in your videos on the machine (F23 to F31)

[Toby Dickenson]

Hi Andrew,

A common problem with strip feeders is that you have to peel back the film to expose multiple parts, but then you have the risk of them jumping out of the pockets. BlindsFeeder was one solution but that did not really work for us. This design actively clamps the tape edges to prevent vibration and is quite effective. We made lots of boards using just those feeders before adopting PushPull, and still use them for short ends of tapes.

We had always intended to publish the design, but the menlu feeder published their design first with a very similar clamping principle and better DFM (on a modern 3d printer) so I  recommend looking at that.

Our old design has some advantages over the menlu feeders; higher density, and less wasted Z space, so maybe I will do a best-of-both remix at some point.

--
You received this message because you are subscribed to the Google Groups "OpenPnP" group.
To unsubscribe from this group and stop receiving emails from it, send an email to openpnp+u...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/openpnp/4eeb1cfc-8e99-476c-a1a5-a64473b76774n%40googlegroups.com.

[andrew...@gmail.com]

Thanks - i'll try some menlu ones for my short strips.

I am just printing some of your push/pull design to replace a couple of problematic original Mark design ones

Marks original has been fantastic for many tapes I have tried, but a couple of tapes I have just not getting great results. 

[Toby Dickenson]

Thanks,

I would be grateful for any feedback.

If you have some of Marks original design and like his machine mounting scheme then I believe my current version of the model still supports it - just disabled by default.

To view this discussion visit https://groups.google.com/d/msgid/openpnp/a6db0a75-0646-4c1c-b636-7c72a766fca9n%40googlegroups.com.

[andrew...@gmail.com]

Still have to print a few more to use them in anger - but playing with them so far

Things I like.

1, I love the spiral groove to catch the printing seams.  My original prints needed so much reworking from seam pimples.

2, The friction springs are much better.  Original ones I needed to heat and bend them to get the friction just right.

3, Spring under the paper tape is great.

Problems I have

Sometimes the lever gets into a funk where the spike/peg on the front won't engage the tape holes on thicker paper tape.

I am going to try drill a hole and put a brass peg in there like the original dining philosopher ones.

Unless of course that is a problem you have encountered and you can just tell me I am printing something wrong.

For there lever I am using no-name PETg in a Bambu P1S.  0.12mm layer height , Inner and Outer wall set to 0.3mm as recommended.

[andrew...@gmail.com]

I increased the "Thorn Length" to 1.1 and "Pointedness" to 0.72 and the pointier peg is working much better

[andrew...@gmail.com]

"Thorn Sideways Tension" had to be set to -0.4 to move the peg sideways enough to have it always drop into the hole on the thicker paper tapes I have.

[Toby Dickenson]

One of the changes in this release is the "bumper cam": this lump.

The idea behind this feature is that it is a 3d cam. When the pusher dog moves backward, it takes the blue path over the top of the cam which quickly withdraws the thorn from the tape hole to avoid having it drag along the top surface of the tape. When it pushes forward it takes the green path to the right of the cam which lowers the thorn into the hole before pushing forward. 

That means the pusher dog (and its thorn) are reciprocating slightly in X and Z direction, while making their large movement in Y direction.

If you benefit from adjusting the thorn position, then maybe this bumper cam mechanism is not working quite right for you. But I cant imagine exactly what is going wrong. Another parameter that might be useful is "Dog Bumper Tension". The big hole for the lever axle is not quite perpendicular, to add a small force on the dog to return it from the green path onto the blue.

To view this discussion visit https://groups.google.com/d/msgid/openpnp/58cf6866-b1cd-43bb-8cbf-8d276025befen%40googlegroups.com.

[andrew...@gmail.com]

All the thin paper tapes and plastic tapes worked fine.  The dual-path-cam mechanism worked as expected.  Back to the left/up forward to the right/down.

However with some thicker paper tapes the thorn/peg was preventing the dog-spring from pushing to the right/down path along the cam.

I didn't realise the axel hole was not perpendicular.  That might be another parameter for me to play with later.

I have now printed 24 of them and am about to make a few hundred small boards - I already have some feedback - but will wait a week or two till I have finished getting a good feel for them.

Thanks again - keep up the good work :)