Maslow in GrblGru simulator

I first discovered Maslow two weekends ago, and ordered the kit a few days later. I know nothing about CNC, so tried to find a simulator, which I found GrblGru (to which you can add your own machine) over in the Shapeoko forum.

I downloaded the Maslow standard frame, and a prototype sled in one of the forum posts here (which I edited it so it was a much smaller mesh (my desktop is 15 years old!). Once I find the post I will credit the original sled designer)

Here is a screenshot:

Here is a link to download GrblGru:

Here is a zip file containing the Maslow machine:
oops, new users cant upload attachments

I took the coordinate system as the rear center of the sheet of plywood (I left off the frame backing plywood for simplicity).

At this point I need to learn Maslow and GrblGru! So if someone wants to try this, let me know where to upload the machine definition files. I’m not sure if I have designed the machine to operate properly in GrblGru, since I really don’t know CNC at all. So feedback would be welcome!


Welcome to our group. This is really great stuff. As a new user you will have some restrictions for a short while.

I’m interested in testing this. I will be working on my Maslow today but will move this to my PC tomorrow. As it’s a .EXE I’m going to assume that it’s windows based.

Thank you

I just opened a dropbox account, hopefully this will work to download the machine definition:

9mm sheet of plywood:

When GrblGru starts up select Full GrblGru Version,
Extras, machine manager, at the top type in maslow, new machine. Create a folder with the base,x,y,z stl files in it. Browse to that folder at the bottom of machine manager. Load stl files. For position Zt enter 161.189, accept data.

That’s as far as I have figured out yet!

I created a 9mm sheet of plywood as a separate stl model to import as a work piece. Loos like GrblGru is limited to ±1000 so in mm it doesn’t quite get to the ends of a sheet pf plywood.

If you figure out anything let me know!


First I need to credit MeticulousMaynard and his post “Prototype for New Z-Axis”,

I downloaded from the Fusion 360 cloud, and reduced the mesh as much as I could. Hopefully it is allowed to use in the simulator, if not, let me know and I will rework it, so as not to infringe on your drawing.

I realized the front of the sheet material should be the center of the coordinate system not the back. So the center of the sled is now at 0,0,0. The frame has been moved away by 1.5 inches, as that is the stated max thickness (still ignoring the backing ply thickness). I moved the optional piece of ply down by that much too. Might be useful as a backdrop to see your work easier, or if you delete the base.stl which consists of the frame, you can rename the ply base.stl and just use it as the frame to simplify the view. Also added a chuck, looks complete now.

New machine definition:

9mm ply:

Important if you are installing on Windows 7. I installed GrblGru on my Windows 7 work laptop to try and figure things out, turns out I was missing the area called Actual WorkPosition! I had to reinstall as administrator and then it appeared.

So for the new machine definition follow the procedure as above, but with chuck center set at Zt = 120.189.

After you accept the data, you go back to the first screen. With the chuck center set at 120.189, a bit length of 100, Actual WorkPosition should be changed to Z= -20.189, and then click origin. This will place the bit just touching your imaginary plywood workpiece at 0,0,0.

Had a screenshot here with the settings, but new users can only insert one image!

Taking a break, then I’ll post some more screenshots.
Edit: Taking a break, then I’ll post one more screenshot.

That’s what it’s there for. The Maslow is an Open Source machine, and I treat every modification I make the same way. Whatever improvements I make to my machine may be of use to the rest of you, so I like to make those available. Makes me feel like the time I take to design things is paying off :smiley:

Honestly I’m quite flattered that the project has received such praise from the community and I haven’t even built it yet.

This is quite a cool program you’ve made here. When I get time, I would love to play around with it a bit. I’m a Win 7 user, so I’ll make sure to run it as admin so that it works right :wink:

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After you accept the data, you go back to the first screen. With the chuck center set at 120.189, a bit length of 100, Actual WorkPosition should be changed to Z= -20.189, and then click origin. This will place the bit just touching your imaginary plywood workpiece at 0,0,0.


From the GrblGru author:

I included your STL objects into GrblGru today and made only a few small changes.

I created a new beta version V3.26.18 of it and put it on my dropbox at
This makes it possible for other Maslow users to easily use GrblGru. It contains a new machine “Maslow” and all settings are predefined in it.


Great news, thanks for this contribution!


I’ll start a tutorial to show how Maslow in GrblGru works as I understand it at this point. I am using the modified Maslow STL files that the author of GrblGru installed in the beta distribution, so I may not understand all his changes. Just as a reminder, I do not have a Maslow yet, although I did order the kit, and I do not know CNC, hence the need for a simulator. If you see something needs correcting let me know.

I’ll be covering this kayak rolling rib.


Maslow in GrblGru “rolling rib” tutorial, with no graphics, as I am only allowed one per post, and it’s a lot of work to add pictures!

Download the beta version of GrblGru which contains the embedded Maslow machine from here:

after installing GrblGru beta with maslow:
open and select Full GrblGru Version
Start GrblGru

goto extras->machine manager
in the top line use the pulldown menu to select maslow at the bottom.
Once you do that it will go back to the first screen with the maslow machine showing. You can click the large yellow question mark along the top right to clean up the graphc panel showing the Maslow. I’m using my laptop at the moment with a touchpad, so holding your right mouse or touchpad button you can rotate the machine in 3d.

Looking in the graphic window shows a tool tip height at 69.29. The author of GrblGru changed the coordinate system back to the rear of where the default frame plywood would go, therefore the sled base is at 38.1mm. We want to move the tool tip to the base of the sled, therefore in actual workposition, enter (69.29 -38.1) or “-31.19” in Z, then click origin. Each time you open GrblGru you will have to “calibrate” the actual workposition like this. Since the maslow sled rides on top of the sheet material, the base of the sled should always be the reference. If you change the length of the tool, you will have to calculate the new Z value.

Go ahead and download OpenSCAD, and install it.

I havent been able to make GrblGru reliably run openscad, but we can just run openscad, enter commands, save out the stl files and import into GrblGru just fine.

Run openscad. In line 1 enter:
translate([-1220,-610,0]) cube([2440,1220,30.1]);
This will give us a 4x8 plywood centered and 30.1 mm high, leaving (38.1 - 30.1) 8mm between the backing sheet ply and the sled, located at 38.1mm above the frame. You can preview it, then hit the Export as STL button and save as ply.stl.

In GrblGru >file->load stl-> and open the ply.stl file you created with openscad. the plywood should be located in proper position as a backing material.

In the left plane, if the graphics window is tool small, with the 3d tab open, you can click on each on configuration, tool, actual workposition, and control panel, to collapse them, which enlarges the graphics window.

Sometimes controller windows will open beneath the graphics, then just hit the show/hide controller windows button, to the left of what looks like a ruler with 2D below it. Make sure your tool tip is at the base of the sled, by zooming in on the tip of the drill, and using the different views available, front, top, side, zoom in and rotate as necessary.

I haven’t tried it yet, but at some point go to file->save project as: I don’t know what settings it saves, but get in the habit of backing your work up. As GrblGru is the work of one author, things may not work quite perfectly.

I’ll be using a rolling rib for a kayak I made a long time ago, cut out by hand. Shown here in the bottom image to the right of the coaming:

I’ll attach the dxf file.

In GrblGru goto file->import dxf-> locate rib 2d in mm.dxf and open it.

Go to the top view in the graphic area, and if you hold down the shift button on your keyboard, then go to actual workposition, you can move the sled out of the way, so you can see the 2d kayak rib. If you scroll through the different views the file should be at the base of the sled, and 8mm above the backing plywood.

Goto the “2d” tab.

Go to drawings and under that, hit the “+” sign next to rib_surface_215_9

Highlight “Toopath 0”. Right click->create job->cut mdf 8mm with 3mm drill bit.

Go down to jobs, highlight “job toolpath 0->cut mdf 8mm with 3mm drill bit”

At this point, just as a reminder, I do not know CNC, trying to teach myself the fundamentals, and get to know the simulator. Really just winging it!

Scroll down to 4. tool-> radius correction-> set to inside, click in the graphics area, and the image should change from an outside cut.

Select Highlight “Toopath 1”. Right click->create job->cut mdf 8mm with 3mm drill bit.

Go down to jobs, highlight “job toolpath 1->cut mdf 8mm with 3mm drill bit”

Do the same as above, change that to an inside cut.

Do the same with Toolpath 2.
With Toolpath 3, create the same job, but leave as outside.

Goto the 3d screen.

You may want to save at this point.

Click Show PreView, look’s like a yellow eye from the side.

Probably blew out your background ply. That’s ok, was only to learn the coordinates.

You may have multiple images of the intended 3d rib.

Try unclicking the STL file button near the Show PreView button (not the one with the ruler)

This should leave one image of the rib. No, I don’t know why this is.

In the Tool area, uncheck laser. We want a drill bit to show in the graphic area.

In Actual WorkPosition, press the Home button located in the middle of the 3d arrow controls, if you had moved the sled out of the way earlier.

Click on NC near the Show PreView button to show the calculated toolpath.

Then click on Show Toolpath, kind of looks like a snake, ready to strike.

The third mouse button (usually the scroll wheel if you push down on it), or if you hold both touchpad buttons down together the cursor should change to what kind of looks like an arrow pointing to the right acts as a pan button, to shift the view.

Go the the Control Panel area, might be easier if high speed simuation is unchecked at this point.

Hit Start, the machine will move to the upper right circle and then go down to start the cut. Hit Stop, and Exit. Zoom in on the area of the drill tip. Hard to see the forest for the tree (sled) at this point. I may redraw the sled as a hint of itself, as it is kind of hard to see the work area. You should be able to see the trace of the tool path as a yellow line. You should be able to see the calculated toolpath within the rib.

Once you are satisfied you can save the project, then save out the G Code for your review.

In the above directions if you skip Show PreView, you will be albe to see the dxf image, and calculated toolpath neatly tucked between the sled base, and the backing plywood. If you click the 2D button next to the Show PreView button, you can turn the dxf image on/off. If you click the NC button, you’ll knock out the G Code. Hopefully you saved it, then you can just reolad it. Playing with the various options leads to some helpful views.

The author of GrblGru is working on a new beta version, with an invisible base sled option, so you can actually see your work! I believe he would appreciate some input on any features specific to Maslow you would like to see? I am new to this, so really cant offer him any insight, so can someone try the software and see what features you would like?

There is an M in the toolbar you click to show machine. In this beta version if you hold down “Shift” it will toggle showing the sled base, so you can see your work.

From the author:

You can always download the current beta (test) version at the same address ->