Assigning a profile to each pad size.
The first thing to do is to find the settings for your specific combination of paste, tip size and component pad size.
Put the dispenser in dot mode and follow the instructions in this guide for each size in your board. Each one will need to be saved to a different profile (menu item #5), for example 0603 component pads can be in profile #1 and 0805 in #2.
This can be done prior to connecting the dispenser to the 3D printer.
Profile 1: Dot mode ready for 0603 pads.
Profile 2: Dot mode ready for 0805 pads.
Profile 3: Manual mode for line dispensing.
Attach syringe to printer.
Now you need to fix the syringe and motor assembly to the moving carriage of your printer, the best solution is to design and print a little holder like this one:
It’s a very simple bracket that is screwed on the carriage, the internal diameter is 26mm where the syringe slides in.
Every printer and CNC machine is different, so you’ll need to find a way to attach the syringe holder securely in your specific case.
Connecting to the printer
Next the electrical connection, to do this the printer will simulate an external switch, the easiest way to do this is by connecting the 12V fan output from your printer like this:
(Image on the right is the dispenser input circuit and a 3.5mm cable with 4 poles. Image on the left are the individual strands of the cable)
You can also use a regular 3 pole cable, click here for a more detailed description of this connection.
Aligning the board.
Now you have to line up the PCB with the X and Y axes on your printer. There’s many ways to do it, this is just an example:
Put masking tape on the edge of the bed like this:
Now line your PCB directly above it and roughly in the center:
In your computer open your PCB file and pick an arbitrary pad to be your new origin:
It is best to choose the lowest pad on the far left to keep all coordinates positive and avoid confusion.
Now use the jog controls on your 3D printer software (in this case Repetier) to line up the tip of the syringe with the physical pad like this:
Make sure the tip is touching the PCB, don’t leave a gap in the Z axis like you normally would with the printer’s nozzle.
Now set this point as your new origin, to do this send the command: G92 X0 Y0 Z0
Your board in theory is now lined up (this is assuming your bed was lined up in the first place).
To check alignment lift the tip by 0.2mm in the Z axis then travel to a specific point of the PCB, in this case there’s a pad in the far right (coordinates X114.05 Y0) which we’ll move the tip over (after lifting the tip 0.2mm we send the command G0 X114.05 Y0 to go directly).
If you see that the tip is not inside the pad gently align the PCB, then move back to pad zero by sending G0 X0 Y0.
Keep switching back and forward between the two pads while moving the PCB very slightly until the tip stops right in the center of both. (while doing this don’t zero the Z axis otherwise you’ll drag the PCB along).
When you’ve finished, put some tape in the corners to hold the board in place while you put some more tape on the edge of the PCB as reference:
You can now use these guides to quickly swap between boards since the masking tape is already aligned with your printer, all you need to do with a new design is pick a new pad as the origin, set it to zero on Repetier and you’re ready to write the new gcode.