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Project:Cupcake-o-Matic: Difference between revisions
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→Adding a Cantilever Z Axis
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===Adding a Cantilever Z Axis=== | ===Adding a Cantilever Z Axis=== | ||
[[File:cupcake_cantilever_z_axis.jpg|thumb| | [[File:cupcake_cantilever_z_axis.jpg|thumb|350px|A cantilever Z-axis in laser cut acrylic.]] | ||
In order to move the extruder up and down in the Z-axis the Cupcake CNC used a platform suspended on 4 M8 nuts on threaded rods. These threaded rods were linked together with a timing belt such that if the motor moved one step (1.8degrees) then all the threaded rods would rotate by the same amount. This meant you could get an accuracy of 0.00625mm per step. Unfortunately this was very slow and relied on the threaded rod being exactly straight which it rarely was. What would happen is as the Z platform rose during a build one or more of the threaded rods would move in the x or y axes there by throwing off any precise accuracy in these axes. Another serious problem with this arrangement was the assumption that the 4 M8 nuts would always remain level and wouldn't jam. As a result the Z axis platform would be wonky which didn't help when printing. | In order to move the extruder up and down in the Z-axis the Cupcake CNC used a platform suspended on 4 M8 nuts on threaded rods. These threaded rods were linked together with a timing belt such that if the motor moved one step (1.8degrees) then all the threaded rods would rotate by the same amount. This meant you could get an accuracy of 0.00625mm per step. Unfortunately this was very slow and relied on the threaded rod being exactly straight which it rarely was. What would happen is as the Z platform rose during a build one or more of the threaded rods would move in the x or y axes there by throwing off any precise accuracy in these axes. Another serious problem with this arrangement was the assumption that the 4 M8 nuts would always remain level and wouldn't jam. As a result the Z axis platform would be wonky which didn't help when printing. | ||
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The first solution I found was a middle point solution, the [http://www.thingiverse.com/thing:18849 ACME rod upgrade for Makerbot Cupcake]. You needed to replace the bent M8 threaded rods and nuts with an ACME screw thread on CNC machined rods, this would be both smooth and straight. This seems like a great idea but it requires purchasing $85 worth of ACME threaded rod from the USA, which would cost a ridiculous amount with overseas shipping. So I had to shelve this idea with some regret. | The first solution I found was a middle point solution, the [http://www.thingiverse.com/thing:18849 ACME rod upgrade for Makerbot Cupcake]. You needed to replace the bent M8 threaded rods and nuts with an ACME screw thread on CNC machined rods, this would be both smooth and straight. This seems like a great idea but it requires purchasing $85 worth of ACME threaded rod from the USA, which would cost a ridiculous amount with overseas shipping. So I had to shelve this idea with some regret. | ||
The Thing-o-Matic had come out for some time ago at this point and I was rather interested in the Z axis which was made up of a cantilevered platform which had 2 smooth rods for stability and a linear stepper motor for positioning. | The Thing-o-Matic had come out for some time ago at this point and I was rather interested in the Z axis which was made up of a cantilevered platform which had 2 smooth rods for stability and a linear stepper motor for positioning. What with the Thing-o-Matic being rather similar to the Cupcake CNC I looked around for a way to add this cantilever in. The first examples I found require the back plate be removed and then the fitting of some large plastic parts to be fitted to accommodate the rods and motors. These struck me as being a little too focused on the need to be 3D printable to actually be usable. However I also found the [http://www.thingiverse.com/thing:14492 Cantilevered Z-Stage for Cupcake] which is a laser cut design in 5mm plywood. Unfortunately I've not been able to find anywhere in the UK that supplies, let alone cuts 5mm plywood, it seems to be a uniquely US thing. With that in mind I had to settle for acrylic which is available in a range of colours with a 5mm thickness. | ||
[http://www.thingiverse.com/thing:14492 Cantilevered Z-Stage for Cupcake] | |||
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