From Wiki: Generating Gcode Using MakerCAM

Note: This post came from the wiki and is a direct transfer.

Maslow (and almost all other CNC routers) use a file type called Gcode. A gcode file is a set of very simple instructions which tell the machine how to move as it cuts out your parts. There are a lot of programs out there which can generate gcode. You can find a list of free programs that our community is using here.

These instructions will show you how to generate gcode to cut out your sled using an online gcode generating program called MakerCAM.

Step 1: Download the files

You can download the files for the most up to date version of the sled by clicking here and using the “download” button on the right side.

Step 2: Open svg file in MakerCAM

Navigate to in your browser. If you are having problems with the MakerCAM website, check this thread. Click File -> Open

Step 3: A note about preferences

If you ever get to this step and notice that your file is not the right size, especially if the file was saved from Inkscape (as an “Inkscape SVG”), the issue probably has to do with MakerCAM’s preferences. Clicking Edit -> Preferences and then changing the value for SVG Import Default Resolution to 96 will fix the issue. You shouldn’t need to do that in this case, but I want to mention it because it is a common issue.

Step 4: Drill holes

There are three types of cutting operations that MakerCAM can do. It can
1.Drill a hole - When drilling the bit will move straight down to the target depth and then back up to drill a hole
2.Cut a profile - When cutting a profile the machine will cut around the edge of a shape on the inside or outside of a line. The width of the bit is accounted for.
3. Cut a pocket - When cutting a pocket a spiral or zigzag pattern is used to remove all of the material inside a shape

We will use all three of these operations to make the sled. Let’s start with drilling the holes.

Select each of the eight small holes on the file by holding control and clicking on each one. Tip: It can be easier to drag a small box across each one to select them instead of clicking on them.

Then to tell MakerCAM that we want to drill a hole at each of these locations click CAM -> Drill Operation. For the most part the default settings are fine. I changed the depth of the hole to .8 inches to be sure it goes all the way through my .75 inch plywood. I also changed the “peck distance” to .8 inches so that the hole will drill in a single pass instead of a number of “pecks”.

Click ‘OK’ when you feel good about the settings.

Step 5: Create Pockets

Next we want to create pockets or cutouts for the bolt heads. First select the four outer circles around the circles we just drilled like before. Then tell MakerCAM we want to pocket these by clicking CAM -> Pocket Operation

I adjusted a few of the settings from the defaults here. I set the depth to .25 inches because we don’t want to cut all the way through the plywood, just deep enough for bolt heads to be recessed. I changed the safety height to .15 from .5 because lifting all the way to +.50 before moving is excessive. I increased the step down to .10 because the default of .05 is very conservative, and I reduced the feed rate to 20 in/min because for small cutouts like these going a little bit slower won’t take much time and it will come out nicer.

Step 6: Create interior profiles

A profile cut needs to know if it’s cutting on the inside or outside of the part to correct for the width of the bit. First we are going to do our profiles which cut on the inside, then we are going to do the ones on the outside.

Select the large circle in the center and the three circles around it like before. The center circle will be for the router bit, and the other three circles will help us align our ring. All of these need to be cut on the inside.

Then click CAM -> Profile Operation to tell MakerCAM we want to cut along the profiles of these parts.

In the settings I changed a couple things from the defaults, most importantly switching to tell MakerCAM we want to cut along the inside.

Step 7: Create exterior profiles

Finally we need to cut around the outside of our parts.

Select the big circle and the outside edge of the brick holders, then choose CAM -> Profile Operation.

I was a little bit more aggressive this time around with the step down because these parts do not have a lot of small features and we want to cut them quickly. Other than that, the settings are all pretty much the same as before.

Step 8: Export gcode

Before we export our gcode, let’s make sure everything looks right. To do that click CAM -> Calculate All and watch as MakerCAM generates the movements your machine will need to cut out the parts. Note that a green line will be appear showing where the center of the router bit will pass to cut the parts.

Note: if you would like to add tabs to hold the part in place you can do so now. Select the green cut line for the part you would like to add tabs to and click CAM -> Add tabs to selected. You can choose the width of the tabs (which must be greater than the width of your router bit), the thickness of the tabs, and how often you want them placed. Once the tabs are generated you can click and drag to move them around.

If everything looks good click CAM -> Export Gcode then press All to select all of the paths and Export Selected to export them to a file.

Step 9: Open the file in Ground Control

After that you should be ready to open the file in Ground Control by clicking Actions -> Open File and run it.