Step 21: Improving machining

posted in: Construction CNC DIY | 4

The last ship model was well done, but I still can improve more things in the operations.
So, I decided to do a real model of the ship, that is, the two parts, glue them, and sand them to have a finish part. Let’s see if me and the CNC machine are able to do it…

With the model already done, I only need to design the symmetric part. I will program the machining code separately.

First step in programming is generated what CATIA says Rough Stock. I’ve created it overdimensioned, in order to not have material problems.
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As you can see, the model is inside the material. The inferior plane matches with the inferior plane of the rough stock, so while machining, tool will reach the base, and will cut also the surface where the piece lay. That’s why I’m going to use a throwaway support. That’s it, an extra support which I don’t mind if the tool cut it. When it becomes useless, I will change it, but in that way I won’t damage the main table.
After this, I configure the process: Selection of what is going to be the rough stock, what is going to be the piece, the machine, and some exportation options for the G-Code.

Now we can define the machining operations. First, i’m going to do a roughing, with 1mm offset, to avoid problems.

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Here I can define the surfaces to machining, I’ve selected the entire model. The security planes, things as the tool path, zig zag paths, etc… Also the deep, by my experience, with 3mm will be enough. The percent of cutting tool i’ve defined 60%
Feed rate, without machining 1000mm/min, and machining 700mm/min. This speed has been defined with my experience, kind of tool, and material. Logically, the most high feed rate the better, but always inside the security, in order to not burn the material, or not to have too much vibrations. I will also configure the kind of tool, giving the number I already asigned to it in the control program, for the tool change, and for the tool compensation.

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This is the tool path in the first rough operation with a Ø10mm tool.

Next, i will program a contour operation, to do the piece perimeter. This is an easy operation, just define the splines I want to go over, and some reference planes. As the other operation, i will define also the feed rate, deep, etc…

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So it looks like this:

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Now comes the funny part. The finish operation. I’m going to use a spheric tool, because we have a stepped part after the roughing operation. This operation is the Sweaping. After the last post, I watched that the front and rear part was bad defined, so I decided to machining this surfaces separately. That is, the central part of the ship machining with a zig-zag along the Y axis, but in the rear and front part along the X axis. The results is better, and the surface best defined.
The cut conditions very similar to the last operation, I select the surfaces, etc… Every zig-zag path with a distance of 1mm to each other, so I will have a good definition, and as the tool is spheric, surface will have a very good quality. As I wanted to try new strategies, I decided to do this operation in two steps, to not to overload the tool. I realised that with only one step would be more than enough, and I would save 10 minutes machining.

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So, It’s all ready to simulate the machining. In the next video you can see this simulation, and it’s very close to reality. This option is very usefull, because if there is any movement that goes for where he mustn’t, you can see it clearly. I insist, fundamental.

Then, I proceed to prepare the machine and the rough stock, which it’s screwed at the table. I open the program, adjust some data, as the tool number, and something important: Every tool change, i raise the tool to Z=75, in order to have space to mount and dismount the tool, of course. I make the origin where I must, (i’ve already explained this in other post) put the first tool, and let’s go!

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Finish machining starts

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Once the fisrt finishing machining is done, let’s go with second. I realise that with only one finish step it was enough, but well, it will take more time.

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And I repeat the same process with the symmetric part, so we have both parts:

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You can see here the finish surface, logically, the most close the path, the better surface, but it takes too much time.

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Otherwise, it has a really great quality, also in precision as in surface quality. For me it’s great!

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With Loctite I’ve glued both parts, so now I can see the final model finished. That’s great. Now i can sand if by hand, with a 180 sandpaper.

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The most sand the better, but I was tired to sand, and I left like this. But it was just a test, but in a profesional work, I could left a great finish. I’m really happy with this results, of course, this CNC machine works great!

Continue with Step 22: 4th Axis (Design)

4 Responses

  1. Bernardo

    IMPRESIONANTE!!!
    Muchísimas felicitaciones por tu proyecto…llevo ya algún tiempo pensando en construirme alguna y conforme ahorro algo de dinero voy recogiéndome cosas para fabricarla, pero me asaltan muchísimas dudas. Me preguntaba si te importaría pasarme el CAD y decirme las características de los motores (no vaya a ser que compre algunos que luego no muevan el “bicho”) que has usado. Me ayudarías un montón ya que necesito una máquina así para mi fin de carrera.
    ENHORABUENA!!!

  2. Oscar Terrer

    Hola!
    Gracias por tus comentarios. Los motores no sabria decirte que tipo son, yo los compre en una empresa llamada Sucarmo. Aqui tienes el kit: http://www.cnc-robotica.com/index.php?cPath=23_53
    Como no tenia ni idea, lo que hice basicamente fue llamar y preguntar. Para mecanizar un tipo de material, con las medidas de la bancada, etc.. y me dijeron que con los motores del kit tendria mas que suficiente. Si necesitas datos, los motores son:
    Motores 2,5 A. 180 N. 8425

    En cuanto al CAD, bueno, mandame un correo privado y veremos que puedo hacer 😉