Modifying the X-Carve - Part 1 Adding more Z-Depth

In recent weeks I've become more interested in milling three dimensional molds Using Fusion 360.  At Hammerspace I have access to two 3 axis mills, my personal 1 meter square Inventables X-Carve, and a 8 foot by 10 foot frankenstein of a machine that I've taken to calling 'The Beast'.  

'The Beast' in action at Hammerspace.  This CNC is so big and heavy, they had to build an extension to the workshop around it.

'The Beast' in action at Hammerspace.  This CNC is so big and heavy, they had to build an extension to the workshop around it.

The Beast had a cutting area of approximately 10 feet x 8 feet x 2.5 inches deep. It is really more of what is called a 2.5D CNC machine, intended for cutting slots and tabs in sheet material like plywood and aluminum.  This machine had been lobotomized and rebuilt around a Mach3 controller, so it is capable running G-Code directly from Fusion 360.  I'm going to use The Beast for some of my experiments, but to mill anything more then 2.5" tall, I'll need a different tool.

The X-Carve is an inexpensive tabletop CNC carver intended for enthusiast and light duty work. It's working area is 3.2 feet x 3.2 feet x 2.75". The X-Carve has its quirks, but i've had good luck running 3 dimensional G-Code exported from Fusion 360 on it.  Like The Beast, this machine is intended to be a 2.5D carver, but with a few advantages.  This is my personal machine, so I can freely make modifications to it, and the X-Carve is open source, so all the files and drawings for it are available on Inventables GrabCAD page.

For the first stage of the Modifications to this machine, I'm going to add more z-clearance between the bottom of the X-Carve's gantry and its spoil board.

The easiest way to do this, is to replace the four corner brackets at that connect the Makerslide rails to the spoilboard's frame with taller one.  I downloaded the drawings for the original brackets from GrabCAD, and added three inches to their height in Fusion 360. The new brackets were cut out of 1/4 inch thick aluminum plate on The Beast. If you'd like to create your own extra tall brackets, you can download the DXF files for them HERE

The new X-Carve Brackets add 3 inches to the Z-Height of the gantry.

The new X-Carve Brackets add 3 inches to the Z-Height of the gantry.

 A Big Thanks to Tom Newell of Sainsmart and Oni Technologies for doing the cutting for me! Cutting plate aluminum is still a bit out of my wheelhouse.

To tell the story of installing this modification, I've made a short youtube video to take you through the steps.


Until next time, when we'll adjust the reach of the Z-Axis to take advantage of all that newly added depth.

Thanks for Reading!


Fixing the SketchUp Involute Gear Plugin

Long ago, there was a simple plugin for SketchUp that would make Involute Gears quickly and easily. Called 'gear.3.rb' I used it on countless simple mechanical projects.

The SketchUp Involute Gear Plugin in operation after some quick repairs to its Ruby script

The SketchUp Involute Gear Plugin in operation after some quick repairs to its Ruby script

Recently I wanted to revisit one of those projects, and found that the original download site for the plugin was gone. So I dug the script out of one of my old SketchUp installs and discovered that it won't load into SketchUp 2015. It looks like there is an error in how the plugin adds itself to the menu system. 

After adding the script to my sketchup plugins folder, it failed to load do to a missing 'GetString' Method in the script. 

I pulled the Ruby script open in TextWrangler, and found the UI section.  It looks like the code is using and out of date function to add itself to a UI menu that doesn't exist in newer versions of SketchUp...  

The Offending Section of the Ruby Script that was keeping the Gear.3.rb plugin from loading into Sketchup 2015

A quick search of the SketchUp Ruby resources led me to the documentation of the Menu Class. It looks like the class was simplified at some point, and this plugin never got rewritten to use the new tools. 

Screenshot from the documentation of the updated Menu Class in the Sketchup Ruby Documentation

The Fix to get gear.3.rb working again seemed straightforward. Rework the items in the plugin's Ruby script to match the strucure of the updated commands. To keep things simple, i'm just going to add the two commands from the Involute Gear plugin to SketchUp 2015's 'Tools' menu, and add a menu separator to make them easier to find.  Based on the Ruby documentation, the changes were straightforward.   

The Modified UI section of the gear.3.rb plugin's Ruby Script

Nothing left now but to Save the script, reload SketchUp, and check the Tools menu...

The Two commands from the gears.s.rb script added to SketchUp 2015's Tools menu, with there own menu separator.

Holy Shit... It worked.  

Did I mention I have never written or modified a Ruby script before in my life?  

You can download the repaired SketchUp Involute Gear Plugin gears.3a.rb here.  You'll need to follow these instructions to get it installed.

A big thanks to Doug Herrmann, the original author of this plugin.  I don't know where he is now or why his site is gone, but I'm happy I've found a way to keep the tool he created running.


Aliens M41A Pulse Rifle - The Stock

The stock of the Pulse Rifle is, at its core, a piece of metal u-channel with a slot pattern cut into it. The stock extends forward under the rifle's body work and it's mounted to the top of the Thompson's upper receiver.

It took me a little while to realize the slots in the stock are not purely ornamental. The slots on the top are close to lining up with the holes where the Thompsons rear sight use to be attached. Our Stock will be designed to be bolted to the Thompson through these holes.

Reference model on the left. Measured model of the back of the Thompson on the right.

Reference model on the left. Measured model of the back of the Thompson on the right.

To verify my measurements of the Thompson, I printed the test objects I created in the last step and fitted them onto the gun's body. I had to modify the 3d model a bit and reprint a few times to get the fit I wanted. It was time well spent, now I know my 3d model is accurate and how much allowance I need to incorporate between the Thompson and the final printed parts.

I doubled the thickness of the stock's walls in comparison to what's in the reference model. The extra thickness will add strength to the stock and make it less brittle, a critical improvement for a part 3d printed out of PLA. The cutout in the right front of the stock lets the Thompson's charging lever move freely. The inside of the stock, the part that touches the Thompson, is shaped to match the geometry of the test piece I printed earlier, so I know it will fit in place properly.

Screen Shot 2015-07-06 at 3.03.20 PM.png

The final part is a 278mm long and will barely fit onto the 285mm x 153mm build area of my MakerBot Replicator 2. To add strength to the finished part I set it to print with 4 outer shells and 50% infill.  I also turned the stock to print at a slight diagonal, so that the layer lines on the flat surfaces wouldn't be running parallel to the direction of force.

The final printed stock fits marvelously. Its not so tight that its deforming the plastic of the Thompson, but there is good surface contact on all sides. Ther charging lever can move freely into the slot without any problems and the higher print density made the part really strong.

For now, i just used two bolts to hold the stock in place. They pass through the slots, through the sight mounting holes, and into the upper receiver where nuts hold them in place. There are many advantages to this over just glueing the stock on.  I can adjust its location, remove it for sanding and painting, and easily replace the stock if it gets broken.

Next up, The hard part, building the primary body components!