Sunday, May 16, 2010

Building the chassis

It's finally starting to take shape! The footprint is roughly 11" x 11". It's still missing the rear reinforcing plates. The lower rear plate will serve as the stepper motor mount for the Y axis and the base plate that holds the Y axis (which is not yet bolted down) is Delrin for now- I'll eventually replace it with a 3/8" thick Mic6 cast aluminum tooling plate.

The Igus linear slides are so nice- just bolt them in place and you're good to go. No need to worry about rails not being in alignment or binding in the system.

 

Friday, May 14, 2010

Liquid cooled extruder

I've been thinking about extruders and their problems concerning the nozzle/barrel design. Nophead had mentioned the idea of a water jacket for an extruder and I thought that was an idea worth considering. The goal is to have a short melt zone for the filament without having a large heat sink mounted to the extruder/Z axis to remove heat from the upper barrel. 

I welded this extruder from stainless steel tubingThe diagram (not to scale) shows how it's constructed- the inner barrel is tapered at the tip and then has a short thin wall transition section to the upper barrel section to minimize heat transfer to the upper barrel. The upper barrel has a water jacket around it for cooling. This assembly will be mounted to the Z axis by a block that clamps around the water jacket.

This particular extruder has a one piece barrel/nozzle. The next version will probably have a removable nozzle/heater so I can easily change nozzle size without removing the entire extruder or having to take apart the entire assembly. The machined groove at the top of the barrel is for a plastic guide for the filament to reduce friction as it enters the barrel.

I'll use a small aquarium pump with a PC radiator and cooling fan to complete the system.

I still have to make the heating element- more than likely it will be an aluminum or brass piece with a resistor mounted to it. No idea how well the water cooling will work but it'll be a fun experiment! I can easily modify the shape/size of the water jacket if needed.

I've been out in the garage cutting aluminum extrusion for the chassis so I should have another good update before the weekend is over...