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The CNC Explosion
I am absolutely amazed at how far home CNC has grown since the early 90's. Today there are programs Such as Mach3 CNC and DeskWinNc that are superb programs at a very low cost. Similarly, the cost of step and direction Servo Amps and Stepper drivers made by Gecko Drives has made CNC a real alternative to the small businesses, home shop machinist and entrapuers. Half of the credit must go to NIST that developed the program called EMC ( Enhanced Machine Controller) and half goes to Gecko Drives.
EMC was developed as a free, open source machine controller than ran under Linux. The first versions were somewhat problematic in that there were some problems with the pulse stream that it put out for parallel port applications. Quite a few interested persons started working with the guys at NIST to eliminate the bugs and improve it performance. This Ultimately led to the group to develop; the Brain Dead Install ( BDI) version that made loading this very powerful and complex relatively easy. Concurrently, Art Fenerty and Karl Carken obtained the free source code and developed their interpretations of the EMC program fixing many of the problems and making it run much faster and better. Art ( www.artofcnc.ca) solved the problem with windows timing issues with the parallel port by using a internal timer found on most motherboards. This smooth out the pulse stream and now made using windows 95,98 and XP a viable alternative. His latest version called Mach2( cost $150) is and awesome program that is divided into to portions.One is for Lathe operations and the other is for milling, plasma cutting, routing etc. Karl's version solve the pulse stream problem by using a pulse shaper such as a PIC microcontroller to read the pulses and then run them at a steady rate relative to the G code that was ordered. This required an interface board that connects to the serial port. The board consists of a PIC microcontroller, a 7805 voltage regulator and a few other components. Cost is $225. Both programs will run pulses up to 44000 steps per second. Both are working to improve their products with ever more features and improvements. Either is a excellent program. I use both programs and find both programs fairly equal.
Gecko drives was the other reason for the exploding growth of CNC at low costs. They came out with the G201 micostepper drives rated at 7A and did 10 microsteps for $99. This was at least 1/3 of the cost of other microstepper drives in that amperage range. They then came out with the G210 which is a G201 but has a daughter board internal that has jumpers. It can be set for X1,X2,X5 or X10 which multiplies the microsteps so that it takes fewer steps for applications where the steps per inch would be too slow for a program to work properly. For example the G201 with ten microsteps would take a standard 200 step per rev motors and cause it to take 2000 steps per rev. If this were commented to a 20 TPI leadscrew that would mean there would have to be 40000 steps to the inch.In Ausgust 2008 they came out with the tiny G250/G251 and G540 step motor drivers. They are awesome for their size.
On the other hand the G210 with the rate multiplier set would have a steps or 200,400,1000 or 2000 steps per rev and with a 20 TPI leadscrew would have 4000,8000, 20000 0r 40000 steps to the inch depending on the jumper setting. One additional feature of the G210 is that it allows for using common signal ground for the step and direction pulses. Whereas the G201 only supports using the +5 from the PC for the signal return path. I prefer the common signal +5 because it is better. Gecko drives also came out with one of the first low cost step and direction servo amps called the G320. This neat little servo amp can run servo motors with a power supply up to 80VDC but it is recommended to stay at around 72VDC and can carry up to 20A load. I am currently using these on my Enco 8X36" knee mill with three axis and the parts that are listed on my product page. Performance is silky smooth, quiet, very accurate and without a doubt better than the older stepper systems I had installed. I have been running them for several years without burning one up. I have run the table into the stops but the 5A fuse and err/res circuit performed it function and prevent a burn out amp. The interesting thing about my set up is that I am using a 600 oz in servo motor to raise and lower the knee. With a 2.5/1 ratio timing belt and the knee .2" pitch it raises about 400 lbs with awesome power at about 30 IPM. I have ballscrews with zero backlash ballnuts for climb milling. Generally, I can bore a hole to within .001 TIR.
Dan
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