Plotter

This is a homemade plotter. All parts were developed separately. This allowed adjustments in the assembly as well as smaller changes in case the design of one or other part become required.

Focus on low cost and use of materials easily accessible in the local market.

(click on the pictures to enlarge)

Screws and supporting rods made using 1/4 inch threaded steel bars. Very low cost and easily available in hardware stores. Of course, the threaded steel bars are not comparable to commercial screws but they are compatible with the purpose and expected low cost of the project.

Holders of bearings obtained by sawing up the corners of a plastic box. Difficult to obtain but easy to handle for both making the passages of the screws or making the hole where the bearings are packed. The bearings were mounted under pressure (fitting) without glue.

The bearings were bought in a junk shop at Timbiras Street (Santa Efigenia Area in São Paulo - Brazil). The threaded steel bars goes through the bearings without rolling off. Easy assembly and good precision supporting them. This solution saved much time and headache.

Without any pretension to achieve perfect alignment between the bar and the threaded shaft of the stepper motor, silicon tubes were used to connect them. The tubes absorb any shear stress due to the misalignment of the axes while guaranteeing a good rigidity in the transmission of the angular movement from the motor to the spindles.

Rectified steel bar withdrawal of an Epson printer. Unfortunately, the bar and bushings that support the print head were the only parts that could be harnessed from this scrap for this project.

Frame constructed from one piece of phenolite plate. The same material used on printed circuit boards. Details of assembly of the car that comprises the X axis. Attachment / support made on the top and bottom of the frame. This solution allowed adjustments both in the width and the parallel adjustment of the frames.

Due to the total weight of the system that composes the X axis (the support bars, spindle bar, rectified steel bar, stepper motor and print head system), the whole assembly is supported by bearings. The screws becomes responsible for traction only.

Base made of MDF.

Bushes lined with strips of durepox over lines of phenolite to compose the sliding system over the screwed bar and rectified steel bar.

Stepper motors purchased in a junk shop at Timbiras Street (Santa Efigenia Area in São Paulo - Brazil).

The print head is made with strips of transparent plastic. The configuration adopted provides to the pen good rigidity against lateral movement and easy vertical movements.

The pen is lifted by a stepper motor. The solution adopted makes a reduction gear system not necessary and makes the programming of the pen movements easier.

Pen fixed by springs. This solution enables the use of pens with different shapes and diameters.

Drivers based on a PIC16F877 microcontroller. Opted to implement the motor drivers instead of using dedicated components like the Allegro A3984. This option was very didactic but a bad decision to the project. The engines can't reach high speeds without loosing torque and the steps are so discrete that causes high levels of noisy and resonance.

Positioning can be done manually without the need to connect to a PC. Up, Down, Left and Right. The center button raises and lowers the pen.

Interconnection between the PC and the circuit is made via optocouplers. Total electrical isolation between the PC and the circuit.

LEDs used during code debugging are now indicating the motors activity in the X, Y and Z axes respectively.