10. Mechanical Design, Machine Design¶
For this week we had to:
-
Group assignment:
- Design a machine that includes mechanism + actuation + automation + application
- Build the mechanical parts and operate it manually.
- Document the group project
-
Individual assignment:
- Document your individual contribution.
This week, the team of Fab Lab Armenia Dilijan worked on a joint project: CoreXY machine with 3D printed axis.
Since we were the first to print the Armenian alphabet on paper, the machine was named by Mesrop in honor of Mesrop Mashtots - the creator of the Armenian Alphabet in 405.
Details of our work can be viewed on our group page
Our work can be divided into several parts:
- Dismantling the printer, removing stepper motors
- Creality CR30 Belt Printer Assembly
- Printing the necessary parts on a 3D printer
- Design of the electronics unit
- Various experiences
- Machine assembly
- Programming
Dismantling Printer¶
We started this week by dismantling the printer. There was an old decommissioned printer in our laboratory.
We removed a lot of interesting things from the old printer and tested them, end switches, solenoids, guiding rails, fans, electronic components, wires, bearings, screws and washers.
But the most remarkable were the stepper motors that we later used in our project:
But there was one caveat, stepper motors have rigidly attached gears on the shafts. But it is impossible to remove the gear so easily, for this reason I had to resort to the help of a grinding machine:
Printing an Axis on a Creality CR30 Belt Printer¶
Just in time for the Mechanical Design, Machine Design week, the Creality CR30 printer arrived. We assembled it and read the manual of the machine. We also watched lots of videos and reviews about it.
This was the perfect moment, because for this week we need to 3D print an axle for our machine. But the fact is that the 3D printers available in our laboratory up to this point are limited in size, and the Creality CR30 printer has a working width of 200mm, a height of 170mm and can theoretically print an infinitely long part.
We decided to make a machine using Urumbu CoreXY mechanism that uses kevlar zero strech wire instead of belts.
We decided to use this printer to create one of the long axises. We used Quentin Bolsée’s Beehive project that is a improved and 3d printable version of Urumbu design as basis. We had 4 extrusion rails from a dismantled Ender 5 we just needed one more axis to have coreXY assembly.
We also had just 10 625zz POM Pulleys so we had to modify Quentin’s design to use less pulleys. His design was using 4 pulleys for each, carriage so in total we would need 12. We reduced the number to 3 pulleys for a carriage and 9 pulleys were enough. That’s the reason our carriages are not rectangular and look like arrows. To determine the length of the movable axle, at the beginning I created an assembled 3D model of our future machine:
This assеmbly helped to decide the length of the missing rail. Then, focusing on the holes, I got the position of the holes for mounting on the axis:
And get the required axis for our CNC machine:
Then, in the same program, having received the STL file of our axes, I switched to the Creality Slicer program and received G-code
Since this was our first belt printer, there were many failed attempts:
The part was printed, but the tearing off from the table also happened. Then, looking at the comment of the user of this printer, we added the supporting part:
Although this affected the success of the print, the infill percentage also played a big role. The more infill we had the less chance there was for the part to stay attached to the belt. So we decreased the infill little by little and finally, we managed to get a successful print at 10% fill.
But later it was to be found out that insufficient ribbon tightening played the basis of unsuccessful printing attempts.
Replacing the carrying part¶
When assembling the CNC, a situation arose that the movable axis staggered. There are two options for resolving this issue
- Reprint the movable axis
- Replace carrier part
We chose the second option. In the FreeCad program, this part was replaced:
for this part:
This made it possible to fix the axle so that it does not wobble.
Assembling the CNC¶
As I mentioned above we had 625zz POM Pulleys that are specifically designed for v-slot aluminum extrusions. But we didn’t have the pulleys with grooves for kevlar wire, so we printed them and attached to the 625zz bearings using heat fan.
Block of electronics¶
After the CNC was assembled and fully operational, the electrical components and wires were sticking outside.
To hide the electrical parts and wires, it was necessary to make a case for electronics. And we decided to make a block for electronics on a laser cutter. First of all, it is necessary to make a drawing according to the following requirements and arrangement of components and wires.
I used online box generator makercase.com and added the holes and attachemnt positions with corel draw.
For correct attachment of the circuit board and the power supply unit, additional parts were cut separately from the plywood.
Also, beforehand, places were allocated for attaching the power supply unit and circuit board on the acrylic glass pieces.
There is also a place for a switch button.
If you look inside the block in assembled form, you can see it.
And if we look side by side, we will see.
There is also a place for cooling in the block for electronics.
Let’s take a look at the final version of the CNC assembled.
Conclusion¶
These two weeks have been pretty busy. I am very inspired that it is possible to create a working CNC machine within our laboratory. It was interesting to learn about the work of stepper motors. I also liked the CoreXY system. It is notable for the fact that the stepper motors are in their allocated places, and do not move along with the extruder.
Files¶
FreeCad file - CoreXY assembly