Suite Redux: Greg's Wade Extruder & Herringbone 9/47 Gears

I wanted openSCAD source for the Greg's Wade extruder so I could tweak how well components fit. Unfortunately, the available source didn't seem very user friendly as far as understanding the design and tweaking it. I also realized that adjusting the motor mounting holes was going to require an understanding of the herringbone gear designs, and the source I found for those also seemed lacking as far as useability.

Design files provided here reflect a pretty substantial overhaul of the openSCAD source scripts for both, with a focus towards people being able to tailor the designs to their liking. Want to tailor the Wade block for the nature of the cut in your hobbed bolt or to reflect the use of 1.75mm filament in a PTFE feed tube? Want to improve the fit of the bearings? Want to adjust the motor mount location, perhaps experimenting with a belt drive instead of gears? Want to eliminate recessing the heads for the motor mount screws? These and other changes should be a lot easier to do with these files.

I scrubbed through all the modules and algorithms, replacing hard coded constants with labeled parameters. I've tried to apply a consistent approach to parameter labels. Parameters that users would normally have a reason to adjust are separated from those that should be left alone. Files have been extensively commented. The openSCAD MCAD polyhole method is now used where possible in order to provide improved dimensional control of small holes.

The featured gallery image shows the extruder and gear components installed on a MakerFarm 8-inch i3v printer, with an e3dv6 hot end, e3d hobbed bolt, and custom (unpublished) e3dv6 cooling shroud and print cooler duct. While driven by a desire for improved designs to use on the Printbus MakerFarm 8-inch i3v printer, the enhancements should have applicability to a range of printer applications. Detailed revision and usage information is included in each openSCAD file; the following is only a summary.

GREG'S ACCESSIBLE WADE EXTRUDER
The revised files leverage the Greg's Wade reloaded by jonaskuehling, http://www.thingiverse.com/thing:18379.

To allow for a thicker motor mount plate, a more robust design and lighter M3 hardware, the ability to flip out the M4 spring bolts has been eliminated. Since they tend to not print well and most users don't seem to use them, the "internal" nut traps for use on the guidler hinge bolt have also been eliminated - simply use a locknut on the exposed far side of the hinge bolt.

Various new options, however, have been added. Hot end support options have been expanded to include the hexagon and e3dv6 hot ends. A u-channel mounting plate tailored to exactly match the extruder base is available. A 8mm x 20mm hinge pin for the guidler can be printed. A small spacer block is available for installation on the exposed guidler spring bolt; the block can be used as a mount for an LED that lights up the recessed hobbed bolt and filament feed area. A spacer plate can be added between the motor and the motor mount; it can be used as a tie-point for extruder wiring. Finally, a hole test plate has been added that can be printed first for the purpose of testing/refining the fitment of hardware in all the holes used in the extruder design. The base has the option for mounting holes to be used with MakerFarm's type of hot end shroud that mounts to the base.

The extruder base is formed by the roundCornersCube method available at http://www.thingiverse.com/thing:8812. An option to add an open source hardware logo to the Wade block is provided through use of the oshw method available at http://www.thingiverse.com/thing:27097. An option to label the Wade block with the design filament size is available.

The gregs-wade e3dv6 1r75 univ.STL file is provided mainly to show the different component options now available. It is optimized around use of a universal e3dv6 hot end for 1.75 filament, with the filament fed into the extruder base with 4mm nominal OD PTFE tube. Rather than use the STL file directly, the user parameters in the gregs-wade openSCAD file should be reviewed and adjusted for any particular printer application.

HERRINGBONE 9/47 GEARS
The revised files leverage the Parametric Herringbone Gear Set by triffid_hunter, http://www.thingiverse.com/thing:10707. The improvements continue to leverage the Greg Frost involute_gears method now included in the openSCAD MCAD library. The user is now isolated from the puzzling need for certain involute_gear parameters to be factored by 180/pi - that adjustment is taken care of behind the scenes as the involute_gear module is used.

The open cavity side of the large gear has been swapped so the printed face is now to the outside of the extruder. This has an advantage in that the open cavity can now clear the motor mounting bolts without recessing them into the Wade motor mount, and the cavity can also clear a locknut installed on the far side of the guidler hinge bolt in lieu of trying to use hidden nuts on the hinge bolt. More importantly, swapping the open cavity allows the hub of the large gear to be extended as necessary to properly space the large gear on the bearing in the Wade block without the use of any shims or washers.

The amount of chamfer applied to the gear teeth seemed excessive and has been reduced. Reflecting the occasional debate on which herringbone direction is preferred, a top level geometry option is now available to define the tooth direction. Arguments have been made that reversing the tooth pattern on the gears causes the small gear to better dig into the teeth of the large gear.

The top level geometry area of the file has been revamped to allow each gear to be generated individually or as a printed pair. Note that the involute_gear results are not perfect and require repair in netfabb or similar before slicing.

GEARS UPDATE May 9, 2015. I've made some adjustments to improve the nut trap on the small gear and added RevA files for the herringbone gear openSCAD and STL files. Refer to my comment dated May 9 2015 for more info.