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...  

Friday, February 19, 2010

Heating element and relay arrived



The heating element from Omega arrived today. It's a thin silicone encased element that measures 6in by 6in and produces 10W per square in. The element maxes out at 450 degrees Farenheit but I goofed when I ordered it- I ordered it with the adhesive backing which limits the output to 250 degrees so that means using it for a surface mount soldering hotplate is out.....a bummer but not a deal breaker as it's still good for the heated bed build platform for 3D printing.

More info on the heaters here:
http://www.omega.com/ppt/pptsc.asp?ref=SRFR_SRFG&ttID=SRFR_SRFG&Nav=

Since the element uses 115v input it'll be connected to the PID controller via a solid state relay. 

 

Thursday, February 18, 2010

Extruder nozzle design



So here's the basic nozzle design- the drawing isn't exact but you get the idea. It's a stainless tube with a stainless stop washer welded to it and a machined brass nozzle. The O ring should help seal the nozzle to the stainless tube. I plan on using a load resistor to heat the nozzle and this is held in place using a small circlip (if this doesn't work I'll probably go the nichrome wire route.) The nozzle is held onto the stainless tube using small set screws that sit in a machined groove. Time will tell if this all works out....

Saturday, January 30, 2010

And so it begins...

I originally wanted to build a nice desktop 3 axis CNC machine for milling circuit boards but after following the RepRap project and seeing a MakerBot in action I knew I just had to build a 3D printer. The trick was to build it with enough rigidity for accurate CNC machining in order to get the best of both worlds. I also wanted to use as many off the shelf parts as possible to reduce the amount of custom machining/fabrication.

The build area measures 150mm x 150mm x 75mm but since it is a modular design I will be able to increase the travel of any one axis without completely rebuilding the machine.

I quickly made a list of requirements:

3D printing
accurate CNC machining
swappable toolheads
modular construction
heated build platform
small footprint
low cost

When I'm finished building it I'll post an entire build tutorial on Instructables.


So here's the parts I've gathered so far-


 
These two 80/20 Aluminum extrusions will form the main chassis components- they're quite heavy.


















 
 

The electronics (stepper driver boards, motherboard, end stops, extruder controller) all come together as a package from the nice folks at Makerbot, as does the power supply. Eager helper not included....

















 
For motors I'm using some surplus NEMA23 stepper motors. These will drive the linear slides using timing belts and pulleys.

 
The linear slides are manufactured by Igus- they're very high quality and can handle high loads.
 
 


The machining spindle will consist of a Foredom handpiece driven by a DC motor. Motor control is provided by an old R/C speed control that will get a PWM input from an Arduino microcontroller. Electrical power comes from a salvaged PC power supply. Eventually I'll make a better quality spindle using an ER11 collet system and a more powerful brushless DC motor.

The extruder toolhead will be built using some parts from Makerbot combined with my own design nozzle assembly.

 

Control for the heated build platform will be done using a PID controller w/thermocouple. The build platform will also double as a surface mount soldering hotplate.

I still need to get the drive belts, some bearings for the belt tensioners and the aluminum for the build platform.

Stay tuned....