Sunday, September 29, 2013

Active cooling of J-Head insulator...

Construction of my self-build Mendel90 continues. Recently my new J-Head hot-end arrived, the final part of the jigsaw! Experience from my other printer has taught me that active cooling beneath the x-carriage has a number of positive benefits. Placement of a small fan that directs cooler air horizontally beneath the x-carriage causes a disruption to convected heat rising from the hot-end, preventing a temperature rise in the x-carriage that might cause deformation if overheated. It also cools the PEEK insulator on the J-Head which then maintains a short thermal transition zone, essential to prevent jamming. (There is a good illustration and explanation of thermal transition zone here on Nophead's blog.)

The current (at time of posting) Mendel90 x-carriage design didn't have a mounting point for such a fan. I had been designing a clip-on fan bracket when I saw Goopy's x-carriage modification to take a direct drive 1.75mm extruder, which included an under-carriage 40mm fan mount. Goopy's x-carriage wasn't suitable for me as he had also altered the carriage opening and extruder mounting-hole positions. So I imported the original x-carriage stl into Sketchup and modified it to meet my fan mounting needs. I also included M3 nut-traps into the design, which makes fitting the fan much easier, especially after the carriage is fitted to the printer. Goopy's lower shroud (half ducting) was of use as it directed the air flow above the stock cooling duct.
Illustrated above is the design change to the M90 x-carriage. 40mm fan mount. Design shared on Thingiverse.
Photo above/below shows first fit of 40mm fan and half-ducting.

Photo below shows new J-Head V in position. 

Below is a view from beneath the x-carriage, showing the new fan in position (right of pict) and the existing larger fan ducting for cooling the work. The half ducting on the new fan redirects air nicely up and over the larger ducting.
Finally below, a side view of the new fan mounted in position. It sits flush under the x-carriage resulting in no change in the length of the the carriage.

Controlling the fan:
The fan takes it's power via the ribbon cable to the x-carriage. The Mendel90 design has spare capacity on the 20 strands of ribbon cable that run to the x-carriage. I have the fan turning on/off automatically from the the Marlin firmware. A pin on the Azteeg X3 controller board becomes active when the temperature of the hot-end rises above 50deg C. This is all set is the ConfigurationAdv.h tab of Marlin (Section shown below.)

// Extruder cooling fans
// Configure fan pin outputs to automatically turn on/off when the associated
// extruder temperature is above/below EXTRUDER_AUTO_FAN_TEMPERATURE.
// Multiple extruders can be assigned to the same pin in which case 
// the fan will turn on when any selected extruder is above the threshold.
#define EXTRUDER_0_AUTO_FAN_PIN   5 //IOS 20130914 //-1
#define EXTRUDER_1_AUTO_FAN_PIN   -1
#define EXTRUDER_2_AUTO_FAN_PIN   -1
#define EXTRUDER_AUTO_FAN_SPEED   255  // == full speed 

The benefit of this is the fan operates automatically under firmware control, and I don't need to add any start/end g-code to drive it. It remains on after the job has finished, but automatically shuts off once the nozzle temperature has dropped below 50, or some other temperature specified in firmware section above.

Thanks for viewing!
Comments and questions welcome.

Wednesday, September 11, 2013

Cooling Fan speed control via Azteeg PWM Fan Pin Output

The Azteeg X3 Controller has four low powered outputs which can be used to drive fans or even LEDs. These outputs can be controlled by the host-software or called on when printing by gcode commands inserted by the slicing software. Marlin firmware is configured to call on the Azteeg pin D4 when the M106/M107 (Fan On/Off) gcode commands are used. (Azteeg full wiring diagram here.)

I'm currently experimenting with the Azteeg board controlled by Reperier-Host software and Marlin firmware onboard. That combination enabled immediate testing of the newly wired (two-wire) cooling fan on my 'scratch build' Mendel 90. But I soon found that despite the suggestion of possible speed control by Repetier-Host, with it's 0% - 100% Fan Output slider, the fan would only run when the slider control was near or at 100%. A little more research revealed that the simple two-wire fan could utilise the PWM (Pulse Width Modulation) Fan Pin Output of the Azteeg board if two simple common components, a capacitor and diode, were added to the fan circuit. I had to try it! (There was an article on the Bukobot site which gave full details on this hack: Credit and thanks!)

I first bread-boarded the two components to test that it would work... and it did! This basic set-up, the 10uF capacitor in parallel with the fan wires, and the common diode (1N4148 / 1N914 diode) in series on the negative wire provided the speed management of the fan.

I then placed the components on my stepper mounted connector board and wired them in. Pict below:

The following short video best shows fan speed control being tested.

The true benefit will come when I enable Auto Cooling within Slicer and the commands to switch on/off, and change cooling percentages are applied to the sliced gcode and called on during the print job. Slic3r now contains such settings... see screenshot below:

Other controller boards may also provide PWM Pin Output, and this simple two component addition to the  fan wiring gives great control of print cooling when combined with the Slic3r Auto-Cooling features.

Hope you found it of interest.

Thanks for viewing!

Saturday, September 7, 2013

Azteeg X3 controller wired up (Mendel90)

Did I mention I'm building a Mendel90? :-)

I've chosen the Azteeg X3 3D Printer Controller from Panucutt as the motherboard. It's a full featured controller. I've wired it up and downloaded Marlin firmware to it. With some tuning it's performing basic movements. It's coming together nicely. There's lots more to say on the topic, the experience of installing this controller on the Mendel90 and combining it with Nophead's Marlin, but for now just a photo. Most of the day was spent wiring things up and doing some basic movement tests. It is coming together nicely.

The ribbon cable arrangement to the x-assembly give a neat wiring solution (Nophead's design). Via a 20 strand ribbon it's possible to drive the x-motor, extruder motor, hot-end (taking up 6 wires), control two fans (one for cooling the PEEK on the J-head, one for focused cooling of printed plastic), the hotend thermistor and x-endstop. It took some head scratching but I got it all wired up today.
This shows the wiring to the x-motor (on the right) and the x-endstop being readied for soldering to the ribbon cable strands. The joints are then neatly concealed in the x-motor housing.
A side view of the Mendel90. The electronics and powersupply are hidden in this corner.
That's it for now. More on the construction and set-up experience to follow.
Thanks for viewing!

Thursday, September 5, 2013

Extruder wiring connections (Mendel90)

I'm building a Mendel90... A dimension of the prescribed design utilises a ribbon cable to bring power to the hot-end, extruder motor and fan(s) and carries the hot-end thermistor reading back to the printers motherboard.

The Kit version of this printer, designed and sold by Chris (Nophead), has quite an involved connector assembly between the x-carriage and the ribbon cable that connects to it. In scratch building the Mendel90 I came at this connector fresh and have gone with my own take on it, though the essence of the design, a ribbon cable to the x-carriage, is maintained.

I've built a functioning prototype using various connectors from my junk box. I'm using the screw-down connector for heavier wired hot-end power, and simple push-on connectors for the motor and fan(s). The under side has a spaghetti of wires soldered to the various pins.

 Two longer bolts replace the motor bolts, allowing the connector block to be mounted on to the back of the stepper motor. A piece of plastic is placed between the board and motor for extra insulation on my prototype.

You can mix and match connectors to your own preference. The screw-down ones are definitely a good idea for power to the heavier duty wiring on the hot-end, and multiple strands of the ribbon cable are needed to carry power to it. The push-on connectors are fine for fans. The 16 pin ribbon connector might do with some kind of retaining clip to prevent it working loose when printing. We'll see how it goes!

I don't have access to PCB etching or any way of producing a more professional PCB connector block, so this is probably as far as I'll take this idea. I'm happy to share it so others might evolve it if they wish.

There's lots more to blog about with the Mendel90 build. This is just to get things moving again!

Thanks for viewing!