How tight to make the Wades hobbed bolt

When putting the washers and nuts on the Wades big gear hobbed bolt, it is free-wheeling, but wobbly, if the nuts are not tight. And the inside of the bearings are not turning (the bolt is just spinning inside the bearing). If you tighten the nuts more, the wobble goes away, but the gear no longer free-wheels (it will stop itself as soon as you let go). But the bearing is turning this time.

Which way is correct?

The hobbelt bolt is held in place by a pair of M8 nuts. Just tighten the first M8 nut until there is no more play in the bolt. Now loosen it by 1/10th of a turn. Finally tighten the 2nd M8 nut against the 1st M8 nut so that both are locked in place.

The resulting assembly should have no play along the axis of the hobbed bolt, yet it should turn freely.

If in doubt, there are a number of videos on YouTube on how to properly assemble a Greg`s Wade's Geared Extruder, a quick search should get you there.

The worst design error on my wade´s is:
The number and thickness of washers between bearing and big gear have to be a perfect match.

Otherwise, after tightening the nuts like Andrew described, the hobbed part isn´t in line with the filament guide, causing low feed force.
So I decided not to tighten the bolt but leave some air for it to center itself by pressure from the filament-guide. Then align the small gear on the stepper and the herringbone gears keep the hobbed bolt at the right place. ( More or less )
-Olaf

Quote
o_lampe
The worst design error on my wade´s is:
The number and thickness of washers between bearing and big gear have to be a perfect match.

Otherwise, after tightening the nuts like Andrew described, the hobbed part isn´t in line with the filament guide, causing low feed force.
So I decided not to tighten the bolt but leave some air for it to center itself by pressure from the filament-guide. Then align the small gear on the stepper and the herringbone gears keep the hobbed bolt at the right place. ( More or less )
-Olaf

Actually this is not a case of "design error" at all, the simple fact is that different hobbed bolts have a different distance between the head and the hobbed part. The Greg's Wade's Geared Extruder OpenSCAD source code takes this into account by using this distance which you measure with a caliper (before rendering and printing the gears and the extruder body) as a parameter that automatically adjusts the geometry of the parts.

As you will notice if you read the OpenSCAD source code, no design error here, just the opposite in fact: the design is very flexible.

I stand corrected,
it´s not a design fault. But I only had the .stl files from the i3 rework and thought, the hobbed bolts were all the same.

How would you proceed in my case, Andrew?
-Olaf

The problem with the i3 Rework version of Greg's Wade's Geared Extruder is that it is a derivative of the original extruder "reworked" using SolidWorks, consequently all the parametric qualities were lost. Unfortunately this is what happens when you don't comply with the GPL and break the source code development chain. See this page for details: Genealogy / Archeology of the Greg's Wade's Geared Extruder.

I am working right now on "reverse engineering" the changes of the i3 Rework extruder back into the OpenSCAD source code of the Ultimate Greg's Wade's Geared Extruder, to solve this long-standing problem. So you can either wait until I am done or change your X-carriage into this one, which will accept both standard and 90-degrees rotated extruders.

Edit:

Or you can use a hobbed bolt without head, with threads on both sides. This allows you to adjust the position of the "hobbed" part in relation to the gears. This kind of hobbed bolt is harder to find but it does solve the problem in a simple way.

Edited 1 time(s). Last edit at 08/14/2015 01:17PM by AndrewBCN.