Monday, November 3, 2014

Testing.

The Shapeoko2 first tests were a success.

The electronics had already been tested before assembling the machine, as suggested by the instructions, so I expected all the motors to rotate and the communications between the computer and the Arduino controller to work fine.

After assembling, it was important to test if both Y motors were rotating in the same sense, so I connected them one at a time and used the Universal G-Code sender software to check them.

It is important to remember that the electronics that comes with the Shapeoko2 kit will burn if turned on without the motors connected. You must verify all the connections before turning on the machine. At least this is what the instructions say. I believed.

The first carving attempts worked almost fine. For 2D tests the workflow is simple. You can use easel (www.easel.com) that is developed by Instructables and works fine. I could draw something at Easel and send it to the machine but I used a piece of pine to carve on and this material is not on Easel list of materials. The machine went too fast inside it and also tried to move faster than it could carve, so many steps were lost and the result was not consistent. You can change the parameters on the software, but you have to guess them first. My second guess is to divide everything there by two.

But the mystery really started when I tried to do 3D carving. There are many pieces of tutorials around trying to explain how to get from a cad drawing to a set of instructions for the carving machine, usually written in G-Code. After a lot of search I learnt the following:

1) OpenSCAD is free and can produce STL files. You use this software to do your 3D project;

2) You need something to translate from STL to G-Code. This something can be paid (like MeshCAM) or free (like PyCAM). MeshCAM works fine but is not cheap. I’m trying to install PyCAM now and will tell you about it later;

3) The software you need to use cannot be made for 3D printers. Those ones build something by adding material. You need to remove material, which is the inverse operation.

4) After you load your STL into the software, you need to tell it how to carve and which tool you are using. There are many, many options. I tried the standard ones, with a 1/8” flat end bit and only roughing passes. The 3D object I tried to carve was a fairly simple one but the generated G-Code had, like, 5000 lines.

5) Having the file with G-Code, you must load it to Universal G-Code something, home the machine (lower left corner, almost touching the material) and hit SEND;

6) If something goes wrong, you must be able to abort the operation, but the only option that works is the pause button. The STOP option does not stop the machine 3D movement. This is a real problem. The solution I found was to unplug the USB cable.

7) The machine needs limit switches. They do not come on the kit, but are really important. I will buy some and try to install them. Hot glue will be the fixing option, probably. But where to connect them is another mystery. The Shapeoko forums probably have a lot of information on that.

8) You must read this: http://lcamtuf.coredump.cx/gcnc/ There is a lot of information on this webpage on CNC milling. Useful information.

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