Monthly Archives: December 2014

ShapeOko 2 tutorial – Dominion turntable – part 10

If you missed part 9, please find it here.

New design

While I was in the process of milling the last quarter of the Dominion turntable, my friend changed his mind about the layout. He realized that he needed one of the holes in the outer ring to be the double depth of the rest of them.

Fortunately, that was no problem since I wasn’t finished milling that quarter, so I changed the design and the g-code accordingly and started over. Here’s the new design:

Dominion turntable - new layout

Dominion turntable – new layout

EDIT: A new OpenSCAD file with this new design can be found at the Woodworking Plans page or here.

Part 11.

ShapeOko 2 tutorial – Dominion turntable – part 9

If you missed part 8, please find it here.

Moving the lumber

After milling one quarter of the turntable it’s now time to move the lumber and start milling the second quarter of this half of the finished turntable. In short the process is like this:

  1. Power up everything (computer, Arduino, g-shield and stepper motors)
  2. Move the cutter -274 millimeters in the y-direction
  3. Move the lumber -274 millimeters in the y-direction
  4. Set this position as our new zero

Powering up everything and move the cutter -274 millimeters in the y-direction is easy but moving the lumber is the real trick. Since I put the lumber against the frame of my ShapeOko 2 in the x-direction, I don’t have to worry about movement in the x-direction as long as I keep the lumber against the frame. All I have to worry about is then moving the lumber -274 millimeters in the y-direction (step 3 above).

Basically, what I do is this:

  • Put a pencil mark at the lumbers current position using a square and the frame of the ShapeOko 2 as a reference point
  • Put a pencil mark 274 millimeters from the first mark
  • Move the lumber so the last pencil mark aligns with the frame

I’ve tried to take a few photos to illustrate the process:

Initial pencil mark

Initial pencil mark.

Making the new pencil mark 274 millimeters from the first one

Making the second pencil mark 274 millimeters from the first one.

Aligning the last pencil mark with the frame

Aligning the last pencil mark with the frame.

After securing the lumber to the ShapeOko 2 again, we’re ready to start milling the next quarter.

Part 10.

ShapeOko 2 tutorial – Dominion turntable – part 8

If you missed part 7, please find it here.

Milling the cutout of the quarter circle

At this point we’ve finished milling the surface of this quarter of our Dominion turntable and there are two things left to do, before we can continue working on the next quarter of the Dominion turntable:

  1. We need to mill the outline of this quarter – but just the curved part and the straight part along the y-axis. The straight line along the x-axis is not milled.
  2. We need to prepare and move the lumber to a position where the next quarter of the Dominion turntable is going to be milled.

This way we can mill half the turntable without having to glue two parts together.

InkScape

We need to make a svg-file with the path for the cutout. For that purpose I use InkScape. If you’re not familiar with InkScape you’ll find several tutorials here. We need to draw an intersection of two quarter circles with the smallest having the same radius as our Dominion turntable, i.e. 274 mm. The larger circle has a radius of 279 mm leaving us with a 5 mm gap between them. Furthermore, we need a rectangle with dimensions 5×279 mm. Putting it all together in a combined path it looks like in the photo.

Cutout path made in InkScape

Cutout path made in InkScape

Last but not least we need to place the figure in the right position. That is: we need to place it so that the upper inner corner of the rectangle is placed at (0,0). Then save the figure as a svg-file.

MakerCam

I use MakerCam to create the g-code. Go to http://www.makercam.com to start MakerCam (there is a beginners tutorial here).

First we need to setup MakerCam so it fits the svg-file created by Inscape. In the upper right corner I select cm instead of inch. Then select Edit -> Edit preferences to open the preferences dialog shown in the photo.

MakerCam setup

MakerCam setup

Set the value of SVG Import Default Resolution (px/inch) to the value 90 and Machine Tolerance (in) to the value 0.001 and press Ok. Then select File -> Open SVG File, select your file and press Open.

Select the path (it will turn orange) and select CAM -> Pocket Operation and MakerCam will show the dialog below.

MakerCam - Pocket operation

MakerCam – Pocket operation dialog

Set the following values:

  • Name = pocket 1 (default value)
  • Tool diameter (mm) = 3.2 (in my case I use a 3,2 mm flat cutter)
  • Target depth = -26 (in my case the timber is 26 mm thick)
  • Safety height = 5 (default is 15 mm but I see no reason to have that much)
  • Stock surface = 0 (default value)
  • Step over (%) = 40 (default value)
  • Step down (mm) = 1 (default is 1,5 mm but I prefer to go a little less)
  • Roughing clearance (mm) = 0 (default value)
  • Feed rate (mm/minute) = 1000 (this value is depending on your CNC machine)
  • Plunge rate (mm/minute) = 500 (this value is depending on your CNC machine)
  • Direction = counter clockwise (default value)

Press Ok to close the dialog. Then select CAM -> Calculate all to get MakerCam to calculate the g-code for the pocket operation. When the calculation is done, select CAM – Export g-code to get the dialog shown here.

MakerCam - save g-code dialog

MakerCam – save g-code dialog

Press Export Selected Toolpaths and save the g-code in a file with the extension .nc

Again, I view my g-code in a g-code viewer just to check that the code looks fine.

GCodeViewer showing the generated cutout g-code

GCodeViewer showing the generated cutout g-code

 Cutout

After a test run of the g-code, we’re ready to make some noise. 🙂

Part 9.

ShapeOko 2 tutorial – Dominion turntable – part 7

If you missed part 6, please find it here.

The final cut

After working our way down into the material it’s time to do the two final runs: one in the x-direction and one in the y-direction. Running one file takes well over three hours! I made a small video of the process:

After the final cut in the x-direction there are still some jagged edges as seen in the photo below.

After the final cut in the x-direction

After the final cut in the x-direction

To get rid of these rough edges I finally run the original file in the y-direction to get the surface as smooth as possible (I hope you can see the difference in the photos).

After the final cut in the y-direction

After the final cut in the y-direction

Of course I can’t make all these cuts in one day so I have do it over several days. The trick is to avoid changing the zero position so you can continue the next day without resetting the zero. When I decide to stop working, I do the following:

  • Stop the spindle and the vacuum cleaner
  • Shut down Grbl Controller
  • Shut down the computer
  • Finally, cut the power to the g-shield and the stepper motors

This way the stepper motors will hold the position until the last minute. Then the only problem is to avoid touching the machine until the next time. When I want to continue it’s only a matter of the reverse procedure:

  • Power up the g-shield and the stepper motors
  • Turn on the computer
  • Start Grbl Controller
  • Connect to the g-shield in Grbl Controller

When power is turned on and everything is running, the Grbl Controller will set the current position as the zero position and all I have to do is to adjust the z-axis and continue. 🙂

Part 8.

ShapeOko 2 tutorial – Dominion turntable – part 6

If you missed part 5, please find it here.

The material

My friend chose to have the Dominion turntable milled from glued laminated timber called Acajou – a type of mahogany with a very nice reddish-brown color. This particular piece of timber is 26 mm thick and is cut to a width that fits within the frame of my ShapeOko 2.

I pushed the timber against one side of the frame and clamped it down in one side and tightened it against the side with a couple of small wedges – I had no room to do it differently.

Milling

Now, we start by running the Limit=-17 file in the x-direction, then the Limit=-16 file in the y-direction, then the Limit=-15 file in the x-direction and so on – alternating the direction all the way down to Limit=-1 which I run in both directions.

I do this to get as close to the final surface as possible. If I just ran the files in one direction I would risk to have to cut one or two millimeters off the sides of the holes in my last run, because VisualCADCAM will always move the cutter by 2,8 mm (the step distance in this case) each time it makes one pass across the timber – whether it fits the edges of the holes perfectly or not!

I made some films just to show you the process. They all play at 8 times the normal speed. In reality it takes from about five minutes for the smallest files to 25 minutes for the largest files to run.

Part 7.