Inconsistent Tool Pickup

This issue is a summary of notes taken on Github under Issue #43.

This issue can be tricky to diagnose, but the main symptoms are:

monochrome prints look good.
multicolor prints appear to have small layer shifts that affect one or more tools.
if printing with a purge tower, the layer shifts will also be present there.

Here’s an example.

What’s Happening?

In the image above, the silky gold filament looks fine, but the marble filament is displaying what looks like inconsistent extrusion. Assuming the above symptoms hold, this issue is likely to inconsistent tool pickup.

In principle, the tool should only seat into the coupling in exactly one way where the twist lock applies only a downward nesting force through the wedge plate that pulls the tool into the carriage. In practice, however, the tool may twist on pickup, causing the twist lock and wedge plate to form a reference feature. In this case, the tool will wiggle, since it is not contacting the coupling correctly.

Cause: Wedge Plate Smoothness

Some tool plate designs are more susceptible to this issue than others. The original printed wedge plates are especially susceptible to this issue since the print layers are a source of added friction that can cause the tool to twist on pickup. E3D tool plates are less susceptible to this issue as their wedge plates features are smoother. The current revision of Jubilee uses wedge plates made from injection molded Delrin. Delrin has an extremely low coefficient of friction, making this issue almost entirely non-existent on the latest design.

Cause: Misaligned Tool Pickup/Parking Location

If the tool pickup location is severely misaligned, it can lock a tool without properly locating it into the coupling.

Fixing

If you are using 3D printed wedge plates, switch to Delrin wedge plates or an E3D tool plate. Next, adjust the parking post location. The key idea is to ensure that the tool neither twists nor shifts while it is being picked up by the carriage.

Checking the Fix

After adjusting the parking post location, do the following:

Perform a tool pickup to load the tool on the carriage.
With your hand physically try to wiggle it. Did it wiggle? Did it click or make any audible noise?

A properly engaged tool should not wiggle at all, nor should it make any audible noises. If the tool still wiggles, readjust the parking post location. Ideally, when tools are picked up and put down, they should not show any signs of play.

Other Notes

Every time you disassemble/reassemble the machine’s xy moving components, you should check to ensure that tools are being picked up consistently.

This issue has been discussed in and is related to Github issues #43 and #44