Continued Progress on the MKX (project codename)

Reiterating the Tools available to the MKX:

• 3D printing Hotend (Jhead/E3DV6) 

•  Universal Paste Extruder - (Silicone, Chocolate, Frosting, Batter, Clay) 

•  Logitech C920 Webcam - (Serves to monitor prints via Octoprint, and as a 3D scanner)

•  Laser Engraver from DVD-RW computer Drive (Requires TO-18 5.6 laser diode case) 

•  Automated Putty Knife to remove finished prints. 

•  Pen/Pencil Holder

 On the Misumi 2020 frame, the vertical carriage will be 608 bearings inside of 608 Bearing Covers as well as the 608 for the vertical motion idler pulleys.

Controller board at this moment will be: Smoothieboard running Smoothieware.
I chose the X5 Smoothieboard because I require the 2nd extruder for the paste extrusion to push and retract the syringe. Smoothieboard seems much simpler than using Machinekit and LinuxCNC. It also can work with octoprint which is a must for me.

Speaking of Octoprint, I will use the beaglebone black to use Octoprint while offloading the Slicing from Cura to my private cloud as well as 3D photogrammetry. CloudScan and CloudSlicer. The BBB will require a usb hub to connect to the Smoothieboard as well as a wifi dongle.

I am still deciding the bed size, whether or not to use a mirror or a boroscillate glass sheet which are more expensive.

As a peripheral, Adding a LED ring underneath the base would be a nice addition to notify you of the temperature states.

That's all for now!

Automatic Tool Changer R&D

After doing some more R&D on the tool changing, perhaps there's a better way to change a toolhead than simply prying it off via plastic at the tool holder location, especially if the magnets are supposed to be strong to hold something as precise as a hotend. 

I came across a maglock and thought about its application here. Creating a fail-safe magnetic lock would be perfect for this situation(disengages when power is cut). 

At first, I thought a toroid with an air gap would work since its circular by design, but the magnetic field wouldn't apply very well here. 

So back to the basic, tried and true solenoid with a hollow (soft iron) core. As an example it would look like 

DGdo6.png

  
which should work. 

This would be located on the effector side. The effector would have the solenoid slightly recessed, with raised plastic notches every 5-10mm or so to help prevent rotational forces against the tool, specifically something as precise as the hotend. On the tool end side, there would be an evenly distributed pieces of metal to "lock" into the recesses. 

the basic magnetic force equation for a solenoid is: 

F = (N*I)2 μ0 A / (2 g2) 

N being # of turns of wire (will probably be 22-26 gauge wire) 
I = Current flowing through 
μ0 =  4π×10-7 
A = Area 
g = gap between core and wire 

I am not sure of the precise mathematical equation to deal with a hollow core material compared to that of a typical solid core, it is logically less permeable and therefore weaker. 

1.) I am unsure of any effects the magnetic field will have on the hot end as it will be in the direct center of it. I am using a jhead with a brass nozzle and ptfe. How that compares to something more complicated as having a E3D hotend which is (aluminum?) inside of a hollow iron core (target core material at this time due to low cost) is beyond my scope of E and M physics off the top of my head. 

2.) To control the attach/detach, it is possible to use a non-pwm fan input which are 12V. Does anyone know the current limits on the fan inputs for Ramps?

3.) Too many variables to determine ideal current load at this time. How much force required to keep hotend attached while moving at high speed and printing in the Z direction? Maximum current load for the solenoid? How many N turns of wire? Wire Gauge? Experimentation Required. 

4.) An alternate method is to use the 2nd extruder input (RAMPS 1.4)  to power the electromagnet, but I am trying to avoid that as that seems like quite a waste of an extruder slot, but it is available. 


Ideally, a script from Repetier Host / macro button from Pronterface would direct the tool to the tool holder mounted in the vertical space of the delta printer ( might as well use as much as we can right since deltas waste so much empty vertical height). Fan input would turn off, electromagnet would disengage and move to another discrete point to pick up a new tool.

Possible reconsiderations on MK-X upgrades

Currently building my 750/360mm Kossel Mini and am reconsidering the super scaled up size of the 1000mm/485mm MK-X whether or not to really use all of that space. The original plan was to use dual upper frames and then add additional space up on top to completely have a seamless extruder motor and filament spool holder.

Instead perhaps I will integrate the storage space within the 1000mm build system.


Interestingly enough, I discovered the Griffin printer and will use some of the great designs from that system

-Griffin Extruder
-Griffin Belt Tensioner
-Losi ball joint + Garden Stakes for diagonal arms
-Modified Griffin dual upper rail concept
-Griffin Vertical Carriage

This idea will combine with the SeemeCNC's Rostock Max v2 design of the belt running through the channels to reduce the loss of the build platform with the additional belts running above and below the frame itself.

The biggest change to the MK-X system is a revamp of the electronics governing the system as a whole. The Mega2560 is pushed to the limits with basic delta movements. As for future proofing, I will be switching over to the 1GB Beaglebone Black Rev.C (if it remains current)
as well as the Replicape. For simple usage, I will also be including the Manga Screen in the system

That's all the changes for now!