Building the X axis
As I'm gaining experience building this thing, It seems to go faster and easier, maybe I'm seeing the finish?
Posts
Z axis mechanical drive
This is the most complicated thing of the whole enchilada. In order to move the whole beam up and down, it has two driving belts, one for each end of the beam, driven together by a shaft. To counter balance the weight of the beam and Y mechanical axis, I choose to use constant force springs, instead of weights for the purpose of reducing the inertia. The constant force springs are expensive, so for now I'm using a low-tech approach, bungee-cords.
Received printed idler gear
I have received the 3D printed idler gear today. Thank you Alex for printing them for me! They look really nice. Thank you Cristian for helping me modifying the source file so the model accepts 608Z ball bearings I already have. Working on the belt tensioner:
Linux CNC RTOS errors
Something is wrong with the computer running the LinuxCNC. As I generate steps in software I need it to be fast. I'm getting errors in the real time kernel. Eventually I figured it out: The thermal paste on the heat-sink have dried out and provided inadequate cooling to the CPU.
Building the frame
I've cut the aluminium profiles and started to build the frame. Here are some pictures:
Electronics
Motor drivers: I ordered TB6600 motor drivers and I made a simple board to interface to the parallel port. Schematics: Layout: I found an old computer and I installed LinuxCNC . It seems to be working fine.
Mechanical Movement
Motors: Choice was between stepper motors and DC servo motors; I decided stepper motors would be easier to control. I ordered 3 stepper motors from AliExpress: link I decided to use belts for converting rotational movement of the steppers to translational movement. They are faster, low noise, and cheaper than lead-screw used generally for this purpose. I found a nice site selling belts, gears and all kind of useful stuff: http://www.robotdigg.com/
Planning
The machine would have a fixed frame, as it offers more rigidity, having a table moving in X axis, a gantry moving on the Z axis and a tool holder moving on the gantry along the Y axis. A rotating axis "A" axis could be added to rotate the tool or on the table, rotating the work-piece. The frame: After some research I decided to build the machine out of "baltic birch" plywood. The sliding prismatic joint should be made by bearings on aluminium profiles. It should look something like this: I found some discarded aluminium framing materials, I decided to make the frame out of that, as it confers more rigidity and more important it is not subjected to warping as the wood is and also I can use it as a basis for the prismatic joints as well.
Scope
While building prototypes of concept model lip wing aircraft, presented on aliptera.com website, I run into cutting by hand complex curved shapes for the wings and fuselage. The work was tedious at least, the model didn't look very good and it took forever to make. I reached the conclusion I need a CNC machine to do the complex shapes I want. It needs to be able to cut foam in 3D, making complex shapes. For this I think a loop of nichrome wire of 1/4 -1/2 inch diameter would do nicely. To ensure rigidity of the loop some thicker gauge wire should be used. I would like to use it also for cutting/engraving aluminum, wood, plexiglass. Size: As big as possible. 4 x 3 x 3 ft would be nice.
Tests for the anti-torque control surfaces in front of the propeller
I'm testing the control surface effectiveness in front of the propeller. Since the propeller have a duct, theoretically the airspeed in front of the propellers is the same as the speed in the slipstream, so the control surfaces should have about the same effectiveness. This is to combine the strut and control surfaces in one element eliminating half of the surface drag.