CNC Router Plans and Projects

Computer

The original computer used on the first servo drive trial table was a $25 hand-me-down that turned out to be a 1995 Cyrix 6x86 133MHz.

This was plenty fast for using TurboCNC as the controller. TurbocCNC can be operated on an ancient 486, so getting started in CNC does not mandate a new computer.

Mach2/3 requires at least Windows XP. An entry level 2004 Compaq w/ AMD Sempron with 256 MB SDRAM is still used here with Mach2, and it works fine.

This is mentioned because there once was concern about the processing power required, but now even new cheap computers are fast enough.

Pendant

The unit resting on the back of the monitor is a USB numeric keypad. This serves as an inexpensive pendant that controls each axis. It is in a sandwich bag to protect it from dust.

A wireless keypad was tried as a pendant. However, its lack of consistency made it unsafe for all but the most basic moves.
The wired keypad has received the most use because it is dependable.

The keyboard and pendant arrow keys, 4, 8, 6, and 2, move the X and Y axes. The Page Up and Page Down keys move the Z axis in Mach.

The relays, diodes and FETs all came from mouser.com. They ship in small quantities.

It is important to note that when shutting down the controlling software, the parallel port pin that controls the spindle's relay can change state and turn on the spindle.

This happened here, and was resolved by placing a manual master switch, as well as a master relay switch, between the 5v from the computer and the bank of relays.

First Setup

The electrical components of this shop's first servo system were initially screwed to a piece of scrap plywood.
(Stepper systems as used in the plans are available as packages and do not necessarily require the work shown here.)

The cord that attached the computer to the drives was a standard printer cable with a Centronics connector at the printer end, and a DB25 connector at the computer end.

The break-out board such as it is, is simply a Centronics receptacle from a dead printer soldered to some terminal strips.

Note the DB25 printer cable pin order does not correlate 1 to 1 with Centronics. Pins 1 through 14 match but then they diverge for some reason. Only pins 1 through 17 are usually used, so there may be no need to connect anymore than these. It seems that the other connections from 18 to 25 vary among manufacturers, so be sure to check your own cables before soldering.

Package stepper systems do not require this work. The cables and receptacles are already assembled.

The components were moved to enclosures once it was clear that everything was working well.

Drive Enclosures

Here are some pictures of different drive and power supply enclosures that have been used over the years. Experience has taught that big boxes make work much easier.

The cases from old computers and home electronics are good raw materials for enclosures.

The components were initially put in panel boxes as shown on the top right, but the space was too tight for the relays, so a computer case was used. Second image on right.
The boxes below are made of scrap plywood, counter-top laminate, 1/8" tempered hardboard, and yup, that is an old speaker grill used as a vent cover.



Though not obvious in the photos, there are vent holes at each end of the boxes so air can pass over the components.

The boxes are not going to win any awards, but boxes, however crude and simple, are definitely a worthwhile ounce of prevention.
These last two images are of the cheapest drive and power supply box you will find. It is a plastic shoe box with the components fastened to the lid, now the base of the box.

Holes were drilled in the side of the clear plastic top to allow air to be inhaled and exhausted by the fan, which blows directly over the drive board.

The steppers are plugged into the receptacles that are mounted on the lid.

The entire assembly hangs off the back of the computer station or the machines by the keyhole hooks made of hardboard.

This hanging orientation keeps dust from falling into the fan holes, and permits the wires to hang without the potential for bending fatigue.