G.Wimsatt Build Log

Holidays

2009-12-03T21:50:00.000-08:00

Received the 36VDC PSU finally from Hong Kong. Looks like customs damaged the aluminum casing when they were inspecting it. I was; however, able to repair the damage easily and the PSU works great. On a side note, the PSU came with a fancy hand-made Chinese charm/ornament, put it on the Christmas tree.

Wired up the PSU with the relay board and linear actuator, also works great! In doing so... I managed to break one of my control buttons for the lift.

Decided to go with a 0.25" PVC sheet for the top of the machine, it's much cheaper than a 48"x48" sheet of 16 gauge steel. The shipping for the steel was going to cost nearly twice that of the material.

Things are going to slow down until the holiday season is over (buying gifts and what-not). Will upload some new photos soon.

Misc Electrical

2009-11-14T19:55:00.000-08:00

12VDC and 5VDC PSU (old 250W computer PSU):

AC distribution bus, showing 125VAC varistor for surge protection (mounted on HDPE):

Currently in the process of finalizing the AC wiring between the main bus, control panel, and peripherals. Won't be finished until the 36VDC and 24VDC PSUs come in the mail.

Stepper Controller Evaluation

2009-11-14T19:34:00.000-08:00

I recently purchased a cheap stepper motor driver from ebay for about $17USD. It's based on the L298N stepper controller from ST, a CF745 micro controller, and a small 8-pin EPROM chip to store manual information. The seller rates the board for less than 2A, although the L298N datasheet shows it can handle up to 4A. I plan on using KL23H256-21-8B stepper motors, rated at 185 oz-in.

A pair of these controllers should work fine until I can afford a more sophisticated, micro stepping driver:

Control Panel

2009-11-14T18:32:00.000-08:00

The control panel is almost finished, just missing the USB interface to the CNC computer to upload media for engraving via a USB thumb drive.

Consists of:

Main power switch; enables power to everything except computer (computer can run while the rest of the machine is shutdown so one could render g-code while saving power); turns on the 12VDC (laser PWM and small cooling fans) and 5VDC PSU (stepper controllers) as well as the 24VDC PSU (stepper motors).
Computer power with power and HDD activity LEDs.
Cooling system; turns on phase change water chiller and water pump, air assist for the engraving head, sends power to an external plug on the unit's utility panel to control ventilation and to the laser enable switch.
Laser Enable; a key switch that can be used to lock-out the AC supply to the laser PSU.
Laser Fire; a push-on/push-off switch useful for aligning mirrors.
Lift Enable; can be used to lockout the AC supply to the 36VDC PSU that controls the z-table. Main purpose is to prevent an accidental nudge of a height adjustment button during engraving.
Lift up / Lift down; self explanatory.

Relay board that controls polarity reversal to the z-table linear actuator:

Z-Table

2009-11-14T18:10:00.000-08:00

This unit uses an adjustable height z-table to always keep the work surface at the correct focus distance from the engraving head. Motion is provided by a HARL-3624 linear actuator, pushing a scissor lift made from 3/4" steel square tube on ABEC-7 roller bearings. The actuator is connected to the scissors by a 1/2" dia threaded rod. The bearings roll on a track made from 1/4" x 3/4" aluminum flat stock.

Unfinished z-table chassis holding fresh steel square stock:

HARL-3624 Linear Actuator:

Finished Mechanism:

Chassis

2009-11-14T17:49:00.000-08:00

The chassis is constructed out of 11/16" sub flooring plywood and 2.5" x 1.5" pine boards. The unit rests on 4 steel casters rated at 485lbs each.

Chassis Specifications:

48"W x 48"D x 36"H (including casters)
Cabinet consists of 4 layers of plywood, reinforced with the 2.5" x 1.5" boards.
Painted white to seal the wood off from moisture.
Will be plated with 16 gauge sheet metal and angle aluminum on the corners.

Progress:

First Post

2009-11-14T15:16:00.000-08:00

40watt CO2 Laser engraving machine, targeting ~1000dpi

[This blog was created ~2 months into the build]

Specifications:

Made to accommodate a 27" x 27" work area, with a 27" depth z-table. More specifically, this engraver is designed to engrave most desktop computer cases on any side. The heart of the unit, a 40 watt CO2 laser tube.

The CNC computer:

Asus P4V800D-X
2.8GHz P4 Northwood CPU (Hyper threading)
1.5GB DDR400
GeForce FX5200 128MB
60GB HDD
Ubuntu 8.04 + EMC2 pre-compiled OS

Will eventually add a wireless card for software updates and to ease media transfer for engraving.