MultiBot

More work done

2011-03-17T22:54:00.000-07:00

It's getting there...

I got the motors mounted, the coolant tank done, radiator mounts made and the PID mounted into the front faceplate. I also mounted the circuit boards but I really don't like it- I'm going to figure something else out so it's just temporary.

Hot end done

2011-02-12T14:07:00.000-08:00

I was able to finish up the extruder hot end. I had to remake part of the heater section as I had previously made the hole for the resistor too big- now it's a perfect fit. The water fittings are .375" OD since that's the most common size tubing used on PC water cooling pumps, which is what I'll be using. I also felt using .25" tubing would have restricted the coolant flow too much given the estimated length of tubing necessary.

Extruder construction

2011-02-04T21:00:00.000-08:00

I started building the extruder and it's definitely a bit of work to build it this way as it's entirely welded from stainless steel. I still need to weld in the inlet/outlet fittings to the water jacket. The nozzle is made from two brass pieces silver brazed together and you can see the hole for the enamel resistor. The nozzle size is .4mm and it attaches to the stainless tube with a set screw so I can easily swap/replace the nozzle/heater assembly. There are also two small holes in the bottom near the water jacket so I can push out the liner if need be. I sure hope this thing works...

Since the extruder will be driven using a stepper motor I'm going to attempt to make my own worm drive gear using some spare ACME rod I have. The worm gear will be cut from a Delrin blank- should be fun and at the very least a good learning experience. :)

I also had a whole bunch of parts show up and the drive belts should be here early next week- woohoo!

Now that's what I call a heat sink

2011-01-25T21:46:00.000-08:00

I finally got the Linistepper driver boards and the parallel port breakout board soldered. The Linisteppers require a large heat sink and this one should hopefully fit the bill- it measures about 7" square by 3" thick. I'm using the Linisteppers to handle the CNC machining using EMC. Eventually I hope to add another driver board for a four axis milling setup.

Got a radiator

2011-01-06T11:25:00.000-08:00

I obtained a small heater core for use as a radiator for the cooling system for the extruder and the high speed milling spindle. It measures about 9.5" x 6.375" x 2". I modified the heater core by cutting the ends off the tubes and fitting hose barbs to the inlet and outlet. I'm going to run coolant lines to the extruder and spindle using quick disconnect fittings so I can easily swap them.

After reading multiple discussions on the CNC forum it looks like cooling fans probably will not be necessary since I really do not plan on using anything more than a 1.3kW maximum spindle. I still need to find an inexpensive pump...

Liquid cooled extruder revisited

2011-01-02T22:15:00.000-08:00

I'm finally getting back to working on this- seems like it's been forever! I realized there were some problems with my previous liquid cooled extruder design so I designed a new version. The new extruder has a delrin liner and a removable nozzle similar to my original concept. The heater element is a simple power resistor but I'm going to try a vitreous enamel resistor in a small aluminum block as well.


power resistor version

enamel resistor version

Building the chassis

2010-05-16T22:55:00.000-07:00

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.

Liquid cooled extruder

2010-05-14T22:31:00.000-07:00

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 tubing. The 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...

Heating element and relay arrived

2010-02-19T21:46:00.000-08:00

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.

Extruder nozzle design

2010-02-18T22:19:00.000-08:00

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....

And so it begins...

2010-01-30T13:37:00.000-08:00

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....