Mini Arbor Press

A small arbor press intended for the kind of light-duty pressing tasks that often crop up when assembling 3D prints.  Designed so that forces are primarily in the layer plane or are supported by screws when oriented to split layers.  STL files are oriented for optimal printing.  Prints entirely without support.

The only press-fit parts are the bearings, which are not a tight fit.  (If you already had a good way to press things together, you probably wouldn't need this arbor press.)

The entire axle-gear-handle assembly can be flipped if you want the handle on the left side.

A model for a fully-printed, plastic-only ram is provided, as well as several ram models that accept hardware to provide a metal pressing tip: a 10mm diameter 100mm long metal rod or fully-threaded bolts up to 4" long with 5/16"-18 or 3/8"-16 threads.

You can also use any module-1 gear rack that is up to 15mm wide (left-to-right) and up to 17.25mm thick (front-to-back, including the teeth; 15mm excluding the teeth).  If you want to use a gear rack that is thinner than the included models, you can print cylindrical spacers to go around the horizontal posts at the front and keep your gear rack pressed against the spur gear.

Parts

• 3D printed parts (generally fine with standard settings, such as 15% adaptive cubic infill)
  • Left Axle
  • Right Axle
  • Spur Gear
  • Left Upright
  • Right Upright
  • Handle (consider 5 wall loops, 5 top and bottom layers, and 50% infill for strength)
  • Base
  • Ram (only need one)
• 10x M3x30 socket head cap screws
• 10x M3 nuts
• 2x 6003 bearings or 2x 3D printed “Bearing Blank”

Strength

I printed the arbor press with default settings (e.g., 15% adaptive cubic infill) on my Elegoo Centauri Carbon and Elegoo Neptune 4 Pro with Sunlu PETG and used the ram with the 10mm diameter steel rod.

Through all the testing, the C shape of the uprights flexed open significantly before anything else happened.

When applying force, the first thing to break was that the tip of the ram punctured the base.  After putting a more solid piece between the puncture and the steel ram tip and applying more force, the point in the handle where the screws attach it to the axle came apart and the screws were slightly bent.  Removing the screws tore out a chunk around one of the holes.

With a new handle printed with 5 wall loops, 5 top and bottom layers, and 50% adaptive cubic infill, the 18-8 stainless steel M3 screws that I used to hold the handle to the rest of the gear-axle assembly started to bend before anything else broke.

Assembly Instructions

Overview:

1. Begin by taking the Left Axle piece (cylindrical piece with two holes) and putting two M3x30 screws through the holes so that their heads sink into the part.
   
2. Take the Spur Gear piece and place two M3 nuts into its hexagonal recesses, then slide it onto the two screws sticking out of the Left Axle piece through the other two holes in the Spur Gear, trapping the nuts between the pieces.
   
3. Take the Right Axle piece (cylindrical piece with four holes), place two M3 nuts into its hexagonal recesses, slide it onto the two screws sticking out of the Left Axle and Spur Gear assembly through the two holes with the nuts, and tighten the screws into the nuts.
   
4. Take the Left Upright, the Right Upright, and the two 6003 bearings (or two Bearing Blank pieces) and press a bearing into each upright.
   
5. Place the Axle and Spur Gear assembly into the bearings and between the two uprights.  Put M3 nuts into each of the 6 hexagonal recesses in the Left Upright and connect the two uprights with 4 M3x30 screws through the upper 4 holes.  Do not put screws into the bottom two holes yet.
   
6. Slide the Base onto the uprights and secure it with 2 M3x30 screws.
   
7. Secure the handle with 2 M3x30 screws.  Depending on printer tolerances, you may need to hold the arbor press with the handle side facing downward so that gravity will pull the nuts down closer to the screws that attach the handle.
   
8. Slide the Ram in from the top, with its teeth facing the teeth of the Spur Gear.  If you're using the version of the Ram with a metal rod, you can put the Ram into the arbor press without the metal rod and use the force of the press to insert and seat the rod.