Grblgru, Lowrider 2, virtual simulation, 5 axis

Hi Ryan. I have been playing with Grblgru the last while. The author has made a program that can simulate virtual CNC machines as well as generate and run GCode suitable for Grbl, TinyG, G2core and now more importantly GRBL Mega 5X. This last flavour of GRBL Mega 5X you may know runs on a regular Arduino Mega with or without a RAMPS board and is easily capable of 5 true axes (and maybe 6 in the future). Most of us would like at least a 4th axis. I am running on both my MPCNC and LowRider V2.

Grblgru’s author has recently adapted his program to run with Grbl Mega 5X as well as simulate a true fourth axis for now. His manual has been in German but we have been working to make an English language version. He also has many YouTube videos.

He has made many ‘popular’ CNC machine models available within Grblgru but neither of the V1Engineering machines. What is required is an STL file for each axis, then he is able to generate an animated virtual version of that machine. He has never dealt with the way your machine axes work but is up to the challenge. I was wondering if you might already have such STL versions of the MPCNC and LowRIder V2 that you might be able to share with me or directly with Grblgru? It would save me having to figure out how to retroactively design the two machines and speed up the process. If not, let me know and I’ll try to make something appropriate but not as pretty as your photos ha ha. He usually colors the different axes as you see in the attached photo for all the different types he already has. Oh, BTW the program is fully functional and Free from


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That’s pretty neat. Unfortunate that it’s C# and so windows only… But… Maybe it’s just me that cares. :confused: .

It seems like the hardest part for a Low Rider or MPCNC is the length of the table and pipes varies. You almost need an openscad program to parameterize the size of the table to make the axis stls.

So far as unskilled as I am I was able to get a pretty good rendering of the Lowrider V2. I can’t animate it but maybe Grblgru can. He has a whole chapter in the manual on how to make these yourself so it’ll work in Grblgru but Ryans axes move differently that most CNC machines so we will see if a moving model can happen. I’m using TurboCad. I definitely don’t have control of my layers but one day I’ll get there.

Now on to the MPCNC…

Grblgru managed to take my sketch and animate it in his program. I’ll take a crack at my MPCNC next. Might be harder to animate.

They even got my name on there :slight_smile:

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FWIW, I bet if you took the gcode meant for a marlin machine, it would still do a good simulation in grblgru. They aren’t that different when it comes to gcode files (most of the difference is in the status updates).

Grblgru seems to be a general purpose GCode sender. I’ve loaded GCode from VCarve and it runs it just fine in the Virtual world. The program gets feedback from the Mega 2560 card and displays that beside the running GCode.

Grblgru originally designed this as a GCode simulator then started extending it from there.

WHOA, How did I miss this.

I’ve managed to make a model of my MPCNC. It has a hole on one side of the base and a place for my 4th axis. Grblgru is planning on trying to animate it this weekend since it’s supposed to be raining in Germany lol. He’s still proof reading his English manual. I have an Arduino Mega board wired to TB6600 drivers running my Lowrider and a Mega plus Ramps card running my MPCNC. They are both programmed with Grbl Mega 5X.

His Youtube videos are very helpful, particularly the ‘stand alone 3D simulator’ for orienting you to his GUI. They are also helpful for using items like his Box generator template. This will make finger joint boxes of any size. There are a variety of modifiable dxf templates included in the program that work quite well: gears, puzzle boxes, hole grids, circle of holes (for large holes), etc.

As an instructional tool Grblgru is a great program. You don’t need a real machine to play with the CNC world since it’s all simulated for a variety of machines and lathes. It will import or create dxf and STL files as well as basic management of bmp files. He has enabled the probe function to scan and record surfaces like the side of a bowl or incline and you are able to save that as a dxf for later use. Models are scalable if needed and can be projected onto a scanned or extruded surface.

The resulting GCode is ready to use since he has included a GCode sender in his program. The GCode can be saved for editing or later use. As an option you can enable a split screen to see the GCode as it runs, and the response from the controlled card at the same time in a window just beside the GCode window.

Loads of fun for the whole family! Lol

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Can the model of the cnc be adjusted for different sizes? Since everyone has different sized tubes, that would be quite helpful.

You can actually make and add a CNC model of your own for Grblgru. I wanted to make sure something of the MPCNC and Lowrider were in Grblgru so I asked him to help me get them set up. I’ll find out after the weekend maybe if there were any problems with getting the MPCNC model to animate I think the LowRider was straighforward. Colors of the components can be changed too. I haven’t tried to modify the Lowrider model in Grblgru yet (in the Beta download) because its mine! ha ha. Too bad for you…

The short answer to Jeff’s question is yes, but it requires making a custom STL model of what you want. You need 4 components saved separately as X.stl, Y.stl, Z.stl and Base.stl to import into Grblgru’s Model Manager. So start (designing) your engines Jeff.

Maybe someone who’s really good at openscad can make a parametric model to spit out x, y, z stls.

For my MPCNC model I just drag scaled it to make it a little wider in my Cad program. I imagine the same would apply to the Lowrider model to make it wider and longer as necessary then add a name like Jeff and you are good to go ; ) I don’t think high precision isn’t necessary for a cartoon-like model, just that it moves appropriately and you can see the results of the designs you’ve made.

With a rotary axis or two it would be nice to see any potential collisions before they happen. As Grblgru points out somewhere, virtual machines have saved a lot of real machine time in the industrial world proofing a production ahead of time.

Not parametric and very rough, but loads and renders:

It looks like none of the machine types support MPCNC, which is a parallel robot in the sense that each gantry constrains the position of the Z axis but they aren’t mechanically linked in series. I would imagine it should be fairly straightforward for Grblgru to add.

I might make this model more elaborate and parameterized although I’m not sure what practical use there is in having a fancy rendering of the machine.

Also the latest 3.41 triggers a few virus warnings, so I won’t be installing it. The older version 3.38 was cleaner so I went with that one instead.

[attachment file=109888]

One thing that would be hugely useful (and enjoyable as a simulation) is seeing the workpiece as the milling progresses. I know Fusion 360 has this and I saw an OpenSCAD script that can also also do it (although I suppose it is very slow).

Grblgru has indicated in other forums that he uses a commercial virus scanner regularly on his work. My antivirus has never tagged his stuff so far and I’ve been downloading the Betas too.

Maybe he can change something about the installer to get rid of the false positives. Here is a report that he might find helpful:


Thanks. I will pass it on.

The latest beta 3.41.6 now has a working model of the MPCNC as well as the Lowrider. It seems to move properly. He added a 4th axis at my request in the hole I made just for it. When I’m not using the 4th axis I have a larger spoil board covering the hole on both my machines.

He is aware of the installer trojan problem with false positives and trying to rectify it.

Grblgru has decided to post videos on his website because he can modify/update them there, unlike posting to YouTube.