Thursday, May 10, 2012

Z-Axis Wobble Fix Update

It's been some time since I created some fixtures for my RapMan intended to reduce or eliminate Z-Axis Wobble.  Before posting I wanted to make sure that the fix stood up to day-to-day printing.

Here is the fix as I now have it installed on the printer.

The fix involves isolating the print bed from the source of the Z-Axis wobble, the Z-Axis threaded rods.

It involves using two separate new pieces to guide and  hold the bed.

The bed is detached from the Z-Axis holding plates and the bottom printed block is attached in its stead.  There are four of these.  One for each corner.  These blocks are held rigid at all four corners by connecting rods. 

The bed is attached to the new top printed block.  This block attaches the bed to the outside rods of the RapMan using 3 small bearings.  This piece is completely isolated from the Z-Axis threads once the Plexiglas supports on two corners that connect both the outside rods and the threaded rods are cut.

A short piece of spring steel is inserted into the blocks.  These pieces of spring steel will be used to hold the bed up.  The fact that the spring bends is what provides the isolation from any wobble for the bed.  It is strong enough to support the table; but, still flexible enough to not pass the wobble to the top bed holders.

Here are the drawings for the bottom fixture that is fixed to the original bed mount. 

Bottom Z-Axis Wobble Fix Fixture

Note the post in which the flexible wire is attached. 

The top unit is a bit more complex. 

Top Z-Axis Wobble Fix Fixture.
The top fixture is designed to accommodate 3 bearings that attach the fixture to the smooth corner rods of the RapMan.  "Piano Wire" commonly available in hobby stores is used to link the bottom and top fixtures and provides the isolation between the printing bed and the Z-Axis threaded rods.

The wire is strong enough to raise and lower the bed without being strong enough to break the hold that the bearings have on the smooth rod.

I have one or two more extended tests to perform before declaring that this system is a complete success.  If it passes those tests the items and a more full explanation will be uploaded to free download sites.

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