The Roland iModela is a small-scale craft mill, used primarily for jewellery and other small scale hobby projects. It works in a very similar manner to our large CNC mill: you feed it g-code, it moves a 3-axis tool based on your instructions. Using a combination of EAGLE, pcb-gcode, and Roland’s iModela Controller software, we can make small (2″ x 3″ or smaller) printed circuit boards with ease.
You’ll have to start by laying out your PCB in EAGLE. Certain parameters should be followed when preparing a board for cutting using the iModela: you want to give yourself forgiving clearances and trace widths, so that variations on your PCB surface don’t result in bridged traces. I set all my traces to 0.9 mm. I wouldn’t go any smaller than 0.6mm, for risk of your traces thinning out during etching. If you’ve already set up all your traces, you can change them all at once. First, use the group tool to select all of your traces. Next, click on the change tool and select width from the popup menu. If you click on the ellipsis (…) at the bottom of the list of suggested widths, you can enter your own custom trace width. Lastly, right click on one of your traces and select “Change: Group“. This will apply the change to everything in your group.
You’ll have to run a Design Rule Check on your board layout to make sure your clearances are in order. Type the command drc or click on the design rule check button to launch the configuration menu. Refer to these settings when configuring your design rules:
If you wind up with any errors, click on the errors button and EAGLE will show you each of the clearances that need to be adjusted. Once these are all dealt with, you’re ready to output your board to pcb-gcode
Make sure you have the pcb-gcode script installed on your machine. It can be grabbed here. You’ll also want to grab the imodela gcode profile, which can be found here. You’ll wanna put that file in the profiles folder where pcb-gcode is installed, typically eagle/ulp/profiles.
To run the pcb gcode setup, type in the following command: run pcb-gcode-setup . You may first be prompted to select a profile, in which case, choose the imodela.pp profile that you just downloaded. Use the following settings when setting up PCB-gcode:
Be extra sure to turn off the “spot drill holes” option, otherwise you’ll plunge your etching bit into your board and ruin your pads.
The Machine tab is where you set up all the important details. Z Up is the amount the bit is lifted above the board when it is transported. Make this at least 1mm. Z Down is how deep your etching tool plunges into the copper clad. This is one you’ll wanna tweak if you notice your cut is too deep / not deep enough. With the 30 degree v-bit, I found -0.2mm was sufficient. Drill Depth refers to the depth needed to get through the board. I measured my copper clad to be around 1.6mm, so I set it to 1.7mm, but you’ll probably want to check your stock with a micrometer before starting.
Confirm that the GCode Style tab still has the imodela profile selected, then hit “Accept and make my board”. This will spit out two files, one for the drill program, that ends in bot.drill.tap, and another that contains the etching program, which ends in bot.etch.tap. Since the iModela doesn’t have any tool changing capabilities, you might want to go through the gcode file by hand to remove any vestigial tool-changing instructions – if you don’t, the drill program will still run fine, it just might have some redundant Z-axis instructions.
Once your files are prepared, you can start setting up the iModela hardware. The unit “unfolds” so that you can easily access the workpiece table. There should be some scrap material between the plate and your copper clad – a piece of acrylic should work fine. Use double sided tape to affix your PCB material to the plate.
It’s important that your copper clad is level with the cutting tool, otherwise your etching will be uneven. I was able to level out the plate by applying more double sided tape on one side of the board, raising it slightly.
You’ll want to start by drilling your holes – select a drill that is large enough to fit your components through, but not so large it will eat up your pads. Using an allen key you can loosen the chuck on the motor so that you can swap tools. Don’t insert your bit too far into the chuck, otherwise it won’t be able to reach the board! Make sure the bit is tightened snugly, then fold the iModela unit back up and secure the green latches at the front of the unit.
The iModela Software requires a Windows machine, so you’ll need a PC or a mac running Parallels/VMWare Fusion. When you open the iModela Controller software, you’ll see controls from every axis of the mill. First you’ll need to zero in the X/Y coordinates. Boards set up using PCB-Gcode in EAGLE need to be zeroed into the right-front corner. Select the G54 item from the popup menus on either side of the screen.
When your tool is hovering above the right-front corner, press the X/Y button in the Set Origin Point panel. Do not touch this button again once your x/y origin is set!
Properly zeroing the Z-axis is crucial, as your drilling and etching depths all refer to this point. To set this origin point accurately, I like to lower the bit onto a piece of paper, wiggling the paper from side to side. When the bit catches the piece of paper and it no longer can be wiggled, you have found your zero point and can press the Z button in the Set Origin panel.
To initiate your drills, press the Cut button. This will allow you to select the GCode file you’d like to drill from – in your case, the one that ends in .bot.drill.tap. Selecting Output will initiate the job. Lights on the top of the unit will light up indicating the power consumption of the tool. When all the lights go out and the drill stops, the drill sequence is complete.
At this point you can unfold the iModela and replace the drill with a v-bit – the 30-degree v-bit is recommended. Set a new zero point for the Z-axis – again, it is crucial to accurately set your zero point – you want your etches to be deep enough to cut through the copper, but not so deep that they eat away at your traces. Once properly zeroed, you can hit Cut again, selecting instead the .bot.etch.tap file. When it’s all done, brush away the dust, and pop your board out with a blade to release it from the double-sided tape.
OMG, DIY PCB!