Worx Mulcher Paper Bag Adapter

I use a leaf mulcher to help me compress an entire yards worth of leaves into as few bags as possible because I need to drive my yard waste to the county dropoff point myself. Unfortunately, the county only accepts brown paper style yard bags and not the cheaper more common black plastic bags that are meant to fit my mulcher. This year I decided to make an adapter so I could use the paper bags with my mulcher and it worked out great!

Design files and a full bill of materials are available on the Github repository.

Files are also available on Thingiverse and MakerWorld.

Problem

I use a WG430 leaf mulcher from Worx. it is powerful and robust, although I wish the strings would last for a full yard’s clean-up. The giant orange motor/trimmer/funnel assembly sits on top of an aluminum tripod which can also be used to hold a plastic leaf bag. The plastic bags sometimes need to stretch a little bit to wrap around the top lip (inside diameter of 18, outside diameter of 19 inches) but they feel secure once in place. The top lip is 28″ off the ground, which lets most of the weight of the mulch rest on the ground.

Standard brown paper yard bags are a 12×16 inch rectangle, 35 inches high. When you compress them full of leaves they basically turn into a cylinder with a diameter just under 18 inches. Unfortunately, the ring at the top is too large, and if you try to wrap the paper bag around it then you will eventually rip the bag. Additionally, a significant amount of the height of the paper bag goes unused.

My goal was to create a simple adapter to the mulcher that would:

  • Secure and seal the top lip of the brown paper bags quickly and easily
  • Utilize the full height of the brown paper bags
  • Stand up to the damp, sunny outdoor environment along with the dust and vibration from the mulcher
  • Pack away efficiently when not in use

Design

The main mulching/motor unit rests on top of and inside of the circular metal tube at the top of the leg weldment. My adapter needed to replicate the top and inside face of the weldment to properly constrain the mulcher. This is a simple revolve feature and not too hard to design.

Capturing the bag is a bit tricker. A well stuffed bag has a circular profile, but an empty bag being attached to the adapter has a rectangular profile, so I had a hard time deciding what shape to make the lead-in features and mounting features. In the end I decided that a full bag is much stiffer than an empty bag, so I should baseline a circular profile for both the lead in and the mounting feature.

I considered making the adapter sit between the existing legs and the mulcher to add the extra 6-7 inches of height required, but the diameter of the existing leg weldment is so similar to the diameter of the paper bag that the existing leg weldment would interfere with any reasonable flare or lead-in feature for the paper bag. Instead I opted to design some cartridges to accept cheap EMT conduit as legs and ditch the original legs completely.

The adapter ring is necessarily about 20″ x 20″ because of the size of the mulcher, which is much larger than any 3D printer I have access to! Splitting the ring into identical segments and bolting them together was a safe choice for reducing the printer size required, although with more testing I might have been able to convince myself that a glued and doweled connection would be sufficient.

I had hoped to only split the ring into three sections so I could have exactly three legs for better stability (one on each section). Unfortunately the resulting size was still too larger for my printer (Bambu P1S). Quadrants would just barely fit on the print bed but meant that there would be four legs. I considered breaking the part into 6 pieces, but decided that the cost and complexity of extra bolted joints wouldn’t be worth the benefit of fewer legs.

The final feature that I added was a toggle clamp to secure the bag within the adapter. I considered some other options, like a bulldog clip or even a binder clip, but I had trouble packaging the standard spring-clip options within the printed part in a way that was comfortable for the operator to use.

To prepare for 3D printing there were a few small details to add. Things like hexagonal capturing features for all of the nuts (0.005″ clearance), and weird cutouts and slopes to limit overhangs and bridges.

Build

Acquiring the parts for this build was not hard. I happened to have a lot of the hardware just laying around in the garage already, but everything (including the EMT conduit) is readily available at the hardware store for under $30. A full bill of materials with links is shown in the github repository readme.

The adapter quadrant is designed to be printable from its top face or bottom face without supports (I chose the top face). Most of the bridges are under 1/2″ and the total footprint is just under 250mm x 250mm, so it could fit in my Bambu P1S. i used standard print settings (2 layer walls) with a 0.4mm nozzle and consumed about 370g of PLA filament.

The result was nearly perfect, with just a few hairs peeling away from some of the larger bridges.

Each quadrant was fairly easy to assemble, especially because of all the captured hex nut features.

The quadrants screwed together very snugly. The alignment feature on the interface flange, along with a flat table, made it easy to form a perfect circle for the mulcher to rest on.

I cut the legs to length with a reciprocating saw. The legs dropped in with a little more play than the hardware. I used 0.010″ of radial clearance in the leg hole because I did not trust the repeatability of cheap conduit, although maybe it would be safe to bet on conduit not coming in oversized.

Usage

The first thing I wanted to test was the lead-ins for mounting a bag. It wasn’t completely painless, but it was fairly easy to work the bag into the slot while going around the circle once one clamp was attached. Adding some extra long thin lead-ins on the bottom and resigning myself to upside-down printing would probably improve the experience. The fit within the channel was very snug, and the height of the legs had the bottom of the bag resting solidly on the ground.

I took the assembly outside and put the mulcher on. The fit was very snug, more than with the OEM legs. When placing the assembly over grass the bottom of the bag is scrunched up a bit more, so maybe increasing the leg size from the 37″ shown here would be good in the future.

I took it for a test spin using a small pile of leaves at the bottom of my hill. It worked great! It felt super stable despite the crazy vibrations from the motor. The air pressure from the mulcher (which usually inflates the black plastic bags) didn’t seem to impact the bag or my two clamps at all.

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