A Laser Guide for CNC Alignment

After working on numerous CNC projects, I have found the aligning the machine to the workpiece zero location can be a bit annoying. For most projects, finding the workpiece zero doesn't need to be done precisely. You need to get the router bit near the bottom left edge of your workpiece. However, if you are too far off, you might waste some of the workpiece material or run out of space.

Since the router is usually at the top of its Z travel when you are finding the workpiece zero location, just eyeballing the corner of the workpiece when the bit is 2 inches above is tricky. I often find myself grabbing a small square, checking the alignment, and then jogging the machine until I am satisfied with the XY location of the bit. Many times, I found myself measuring, jogging, and then repeated over and over again.

Almost every drill press on the market has a laser guiding system to help you align your drill bit to the wood. There are aftermarket guiding systems for older drill presses as well. These are all based on using two lasers "line modules" to project an illuminated crosshair on the workpiece. Since the projected lines come from two different angles, the intersection point of the two lines is aligned to be directly under the drill bit.

I decided to create a laser alignment module for my CNC machine. Once you have a good design for the laser holder, completing the system is relatively simple. I just 3d printed the parts using PETG, soldered the modules to a switch and a battery holder, and then installed it into the plastic piece.

My version of this project is designed specifically for an X-Carve with a DeWalt 611 router. It works nicely with its dust collection system. However, modifying the project for you own us is pretty easy after you have played with Fusion 360 a bit.

I ordered all the parts for this project from Amazon. However, Amazon only sells the battery cases and the switches in packs of 6. Even with the extra parts, the total cost for the electronics for this project was about $22. A Single-Pole Single-Throw switch would work fine with this project, but the DPDT happened to be at a better price point when I bought it.

• 2 x 1.5V AAA Battery Holder Case Box
• Focusable 650nm 5mW 3-5V Red Laser "Line" Module Diode w/ driver Plastic Lens (2 Pack)
• 6 Terminals 2 Position DPDT Toggle Switch
• One (or two) M5 x 12mm bolt
• Access to a 3d printer with PETG filament - or equivalent
• Access to Fusion 360 - if you need to design a different frame for your CNC machine.

aeeworkTo design the frame to hold the lasers, I took a series of precise measurements off of my CNC machine. The phone above shows some of the critical areas:

• The diameter of the router - below its spindle mount
• The diameter of the spindle mount
• The location and dimension of the screw holes on the spindle mount
• The location of the bit lock button
• The locations of the dust mounting rails and system
• The diameter of the laser module

The foundation for any design in Fusion 360 involves drawing sketches and then extruding them. The extrusions form the basis for the next drawings. You can use extrusions to add or subtract features in your body. There are so many other things you can do with the software, but understanding the core workflow can help with designing something like this.

Using Fusion 360, I began with a drawing that defines the circles associated with the router and spindle mount diameters. I added an outer ring to determine the thickness of the mounting system. With these critical features defined, I added rectangular features to align with the vertical rectangular elements of the spindle mount. I also added smaller circles to specify the location of the laser module.

After drawing these features, I used the Fusion 360 extrusion tool to make a vertical outline of the essential elements that define the basic framework. You may notice that the original design is wrapped entirely around the router. I ended up modifying and editing the system after I created prototypes.

After creating the main vertical structure, I drew in the screw holes at the correct locations on the spindle mount. Using the outer face of the spindle mount as a reference plane, I specified the inner dimensions to be wide enough to fit the AAA battery case (27mm allowed sufficient clearance) and then added 3mm on each side. The interior space in the battery box was about 27mm x 84mm x 27mm.

On the top face of the battery box, I drew another sketch to define a groove to hold the access panel in place. It was about 2mm on a side inset by about 1mm from the top of the box. The battery box lid was 0.5mm narrower than the groove so it would slide easily into place.

Getting the layout right was tricky and did involve about five iterations with my 3d printer. The beautiful part of the Fusion 360 + CAM process is that you can make incremental changes with minimal effort. Plastic is cheap, and I did most of the printing without direct supervision. The time between the design modifications was only about 30 minutes, although the printing time was about 10 hours.

The overall design process in Fusion 360 is very straightforward - once you understand the basic flow. Basically - create a drawing, extrude it, modify the extrusion, and then use it as the basis for additional sketches. There are excellent tutorials for the beginner. In 3-4 hours, you can design complex parts.

When you are creating the design, make sure to account for a bit of extra space any tight fits. I generally allow about a 0.1mm to 0.2mm tolerance to account for the accuracy of my printer. The gap you need might depend on the printer you use, but this is easy to adjust as you iterate on your design.

When your final design of the framework is complete, export it as an STL and send it to your 3d printer. I used PETG filament with an infill of 20% for my mount. Since the frame is not subject to any large physical stresses, I didn't find it necessary to reinforce with more infill. The printing time on my Prusa I3 MK3 was about 8.5 hours using 0.15mm optimal settings. It took about 1 hour to print the lid.

The STL files attached for this project fit my machine - an Inventables X-Carve.

If you do end up creating a similar piece for your CNC machine, please share your files with others! There is no reason to have others start from scratch if you have a working design for their machine.

Assembling the electronics is simple. I pressure-fit the laser modules into the frame and then soldered the wires with the same colors together. Using two short pieces of red and black hookup wire, I fed the connections to the laser module through the access hole in the frame. I attached the black wire directly to the battery pack, and then connected the red wires from the battery pack and the red wire from the laser module into the switch.

Before installing the batteries, I used the M4 screw to attach the frame to the spindle mount. Since the groves and frame precisely fit the system, a single M4 screw is enough to lock the system into place.

Once you attach the frame to the spindle, install the batteries, place the battery case into the battery box, and close the box with the lid. When you flip on the switch, the lasers should project the two laser lines onto the workpiece.

The final step is aligning the beams.

Before you can use the laser guide, you need to align it to your router bit. Turn the laser on, and twist the lenses until the lines are in focus. Once you have focused the beams, you twist the module itself within the frame such that each line bisects the router bit. Using a smaller diameter bit might be helpful in this step. Once you have focused and aligned the lasers, press the module and the lens upward until they are nearly flush with the plastic bracket. The lens on my module was reasonably loose, so I needed to lock it in place. Pressing the laser module upward into the plastic seemed to work well - although a drop of glue could have held the lens in place.

If you lower the bit closer to the workpiece, you will notice the lines are eclipsed more and more by the router bit. The laser lines indicate the rough vertical offset of the bit in addition to the position over the workpiece.

Once you have the system aligned, using it is easy. Just jog your machine toward the desired target. Again, I did not design this system for the type of precise alignments you need for two-sided carves, but it can help you get set up and started on your project faster and easier than doing this with the job, measure, jog cycle.

I created the project to accommodate the standard X-Carve dust collection system without removing the lasers. Just turn the laser off and attach the system into its rails.

I know that many of you won't have the same model of CNC machine, but I encourage you to give this project a try. Doing the design, prototype, modify cycle with Fusion 360, and a 3d printer is very satisfying. You can achieve a perfectly engineered part with very little time and effort.

This project was a lot of fun for me to create. It is a simple but practical addition to a CNC system. Designing and building the framework was a great chance for me to sharpen my 3d design skills. I hope you enjoyed this, and post your remakes so others can use your STL files for their projects!