blackToe 4'x8' routing area Version 2.2 CNC Machine Kit without electronics: Depreciated (
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See the section below for an itemized part list with prices
About the blackToe 4x8:
Update: The blackToe is up to version 2.2 with one enhancement. There are now side supports on the gantry sides to reduce or eliminate any side to side vibration.
Roller chain is the primary method of moving the x and y axes. Roller chain is my chosen method for two reasons. First, the cost is relatively low. For the users of this site, cost is a big factor. It's hard to scrounge-up money with garage DIYers and hobbyists. Second, for a 4'x8' machine, lead screws appropriate for the travel lengths are cost prohibitive and the lesser diameter lead screws have a tendency to whip.
My tests with the roller chain proved to be highly successful, but there have been challenges. It is impossible to find sprocket hubs for 1/4" diameter shafts, so I used a collar as a spacer between the shaft and the bore of the sprocket. An idler sprocket is also used only to provide a good grip for the drive sprocket. Another challenge was the need to sculpt the parts as I assembled everything together. During the design phase of this version, I did not allow access to the set screws, so out came the jig saw. The new parts for this machine will have access areas provided for ease of assembly and maintenance.
The video provided show the mechanism in action. The roller chain and sprocket allow for very fast rapids at 1000+ipm. I pushed it to 1500 ipm without problems. Of course, with faster speeds, the resolution (steps per inch) decreases linearly. The steps per inch calculation is based on the pitch diameter of the driver sprocket (the sprocket connected to the motor shaft). At one quarter microstepping, the steps per inch is approximately 174. This is like saying 174 dots per inch. At 1/64 microstepping, the resolution is approximately 2,784. These numbers are typical for machines of this size due to their drive mechanisms (rack and pinion, belt or roller chain). With this purchase, you will receive a machine that will open up a whole world of automated fabrication.