“This instructable explains how to make an A4 plotter using three servo motors and an Arduino UNO R3.
Construction is simple … all you require is a hacksaw, a sharp knife, and a 3mm drill.
Two plotters are described:
The first version, shown in photo 2, uses MG 996R metal gear servos.
A second lightweight version using SG90 servos is shown in photo 5
Both plotters use the same software which features an onboard g-code interpreter that is Inkscape compatible. 
The MG 996R plotter features a vacuum hold-down and a simple pen-lift. The reason that the sample plot in photo 6 looks weird is that servo1 is faulty … I have some replacements on order. 
While waiting for the replacement servos to arrive I built a lightweight plotter from two SG90 servos to verify the inverse kinematics discussed further on. The sample plot for the SG90 plotter using these equations is shown in photo 7.
The plotters work … but not as well as my digital versions.
I am publishing my results in the hope that the construction details and solutions to issues that I have encountered are of help to others.
The estimated cost for the MG 996 plotter is less than $100.”