I feel bad that I haven't been keeping this page up. Since school has started I have only been able to work Saturdays on the cnc project. Its been developing slowly but surely.
First off, I got some more parts.
1> gecko had a nice sale at the end of August so I took advantage and picked up 3 of their basic stepper drivers. I also picked up some solid copper heatsinks to match at a garage sale! I'm hoping those will will provide enough power to get things going.
second, I've made a number of changes to the design of the machine.
I've reduced the cutting envelope in both the x and z axis in the hopes of increasing rigidity. Also, the old design called for the spindle to be cantilevered out on this long plate. I figure that will be a big source of vibration so I deep sixed it. Now the spindle rides right over the linear bearing blocks.
Finally, I've been analyzing the design in terms of inertia and gravity. I've moved the I've tried to put the center of gravity of the zy assembly right in the middle of the x cars so their isn't torque on the rails from just the assembly wanting to fall over all the time. Also, Initially, I was going to use the taig 1/4 continuous duty motor to drive the spindle. that thing is just too heavy. I'll use it for something else (maybe a small cnc lathe? ) I'm hoping I can find a dc motor that is sufficiently small enough to not throw off the balance of the machine but still put out the power. This is an area that I actually need help with. How does one determine the appropriate torque and rpm for a spindle? I've seen numerous equations but I always get mixed up with the differences between feed rate and surface feet/ min and the like. I have redesigned the plate that the spindle attaches to with a matrix of tapped holes. hopefully this will provide enough versatility to accommodate putting off the motor decision till after the machine is made.
here is the first finished part. It is a riser block to accommodate the size of the cnc dumpster leadnut
I will also upload a pic of the updated machine design |