Drives and SteppersThese CNC machines require:
The image on the right is of two NEMA 23 steppers and a NEMA 34 servo
motor. The small steppers are ~2.5 inches wide and 3.5 inches long. The machines work better with steppers over 250 oz.in. The Xylotex 425s work well with lower thread count Acme leadscrews and/or with dampers. |
 The next image is of drives from Geckodrive and Xylotex. The Geckos are at the top, and each one of the units drives one axis. They are ~2.5 inches square. The Xylotex drive board is the one shown at the bottom of the picture. This one unit is a four axis drive; there are 4 drives on one printed circuit board. Xylotex also sells 3 axis drives which are used with the machines in these plans. The fourth axis can be used when 2 steppers are slaved together or for a rotary table or similar. The plans for the rack and pinion/leadscrew machine have a slaved axis option, but otherwise all machines in the plans require 3 drives. The drives are sometimes called amplifiers because that is largely what they do. They amplify a few milliamp computer signal into a higher current that turns a motor. Some builders make their own drives and scrounge the steppers from old equipment. I recommend buying a package-deal (steppers, drives and power supply) from one supplier if electronics is not your strong suit. The drive and stepper have to be sized to match the capabilities of each other. It is also becoming harder to find used parts at bargain prices. Demand has driven up the price; plotter steppers and the like are not as available as they once were. |
 The third image is of 2 power supplies. The left one is home-made and is for the steppers. The larger unit on the right is from Antek and is for the servos; it like the servo above, is shown for comparison. Milling metal with any speed requires components of a different scale. The machines in these plans are for wood, not metal. The power supply has to be sized to match the stepper(s) and drive(s). One power supply can power all axes when it is properly sized to accommodate the load. Likewise, a separate power supply can be used for each drive and stepper. This is frequently done for a variety of reasons from cost and availability of parts, to the loads on the axes. All of the axes do not have to be moved by identical motors and drives. |
 The image on the left is of the power supply, drives and steppers from HobbyCNC. The power supply is on the far left; it is plugged into the wall outlet, and is attached to the drive board. The drive board is in the middle of the image. Like Xylotex, the HobbyCNC system combines the three drives onto one printed circuit board. The drives are attached to the computer's parallel (printer) port, and each drive is attached to an individual stepper. A pair of wires connects from the computer's printer port, via the parallel port cable, to the drive of each stepper. One wire of the pair controls the Step signal and the other wire controls the Direction signal for each drive. Other wires from the computer's parallel port can be used to control the spindle, vacuum systems, lubrication and cooling systems, hold down clamps and most anything that can be controlled with a relay-switch. These options, like the step and direction signals, are set-up in the computer's controlling software. This information is given by the controlling software's supplier. It is up to the builder to decide which axis is given which pair of wires; therefore it is possible to alter the axes so, for example, Y could be the longer axis and X could be the shorter one. The options are wide open and can be arranged to match the table's capabilities, the perspective of the user and/or the configuration of the G-code. Generally the Z moves up and down and the X and Y move horizontally. X is usually left and right (East West) and Y is North South in the map analogy. The machines in these plans consider the longest axis to be the X axis, and the Y as the shorter gantry axis, with Z as the up and down axis. This is not set in stone and the tables can be set-up however the builder desires. ........................
A note about steppers and drives: Steppers can be powered well beyond their nameplate voltages. Therefore smaller drives such as HobbyCNC and Xylotex will not always be able to power steppers to the steppers' potential. These smaller drives cannot handle higher voltages; the excess power will cook their electronics. Since Gecko's drives are capable of handling higher power they can push smaller steppers beyond the stepper's potential and damage the stepper by overheating. Geckodrive's documents give details on sizing/matching steppers with power supplies, and on building power supplies. Their pdf file is an excellent resource and is linked on this site's links page. |