Wood Pointilism

Objective
The goal of this project is to create a mechatronic machine that is capable of drilling a series of holes of different diameters in precise locations resulting in a pointillism piece of artwork. In order to complete this objective, a study, precise mechanical mechanism needed to be created which would work reliably without human intervention. The total costs of all mechanical and electrical systems were required to cost under $250.

Frame
The frame of this CNC drilling machine is made from ½ inch 6061 aluminum stock and 2.5” by 1” extruded box frame aluminum. The fasteners used to hold the support together are ½ in. long ¼-20 hexnut fasteners. All of the holes were done on a milling machine in order to ensure precise placement within .002”.
Bushings
This assembly uses oil impregnated bronze bushings as the running surface on the shafts. These bushings were machined in order to be press fits in the aluminum housings (+.005”) and running fits over the shafts(-.001”). This allows the bushings to hold firmly within the housing and to slide effortlessly over the steel rods.

Rods
The rods used were ½” diameter steel rods on the lowest axis of motion, and 3/8” diameter steel rods on the other two axis. The larger rods were used on the lowest axis in order to prevent deflection over the large span, and to ensure the no deflection occurred when the drill made contact with the working surface.

Lead Screws
Instead of the standard ACME leadscrew, we used 3/8” 16 threaded rods with hex nuts to provide linear motion. These create more error than leadscrews, but they were much cheaper to buy and easier to machine. The hex nuts were pressed into position using an arbor press.

Rotary Tool
A 120 volt, .07 amp rotary tool with an tapered abrasive bit was implemented as our cutting tool. This tool was chosen due to its light weight, high rpm, and relatively low torque. We wanted to ensure that the torque output wasn’t low enough in order to ensure the safety of the operator of the system.