[raychar1234]

Hi all,

I have been reading cnczone for a long time, finally time to post.

I am in the process of designing an epoxy granite portal CNC. I will be using it for personal projects and research. (R&D, robotics applications)

I currently have 2 700mm thk ballscrews with mounts, 1 set of 40mmx900mm linear rails with 4 blocks, one set of 35mmx750mm linear rails and a thk kr46x250mm linear actuator. I also have most of the electronics. (PC, ESS, power supply, g540) I have a bosch 2hp router and a SuperPID controller.

I have several questions.

1. I am considering using a granite surface plate as the base for my machine, and then building epoxy granite supports and gantry. Is this wise? What is the best way to construct the gantry? Also, what machine mass would be necessary? I was estimating 400-600lbs.

2. I am considering using servos instead of steppers. I was thinking of getting the MB3 BOB from cncroom, or the c80 BOB, and then the DMM DYN2 AC 400W Servo Kit. (Or maybe the 750W. I need to do the calculations for my ballscrews.) What is the practical difference between good steppers with a g540, ess and servos? My goal is accurate to 0.001 with decent feeds and speeds.

3. I realized that my bosch router is not going to be suitable for my workload. I might want to do rigid tapping at some point. I am considering a jianken atc spindle or possibly a bt30 atc belt spindle with a 1.8kw servo drive. Would the lower rpm on the belt/servo drive impact my capabilities? I am planning to machine aluminum, steel and occasionally titanium.

I have a limited budget. I bought most of these parts a couple of years ago, and I am in no rush to get this done.
I have access to a machine shop and a waterjet. I have a pretty good feel for manual machining, and I have access to knowledgeable people.

Any guidance is appreciated! This is my first CNC build.

Thanks

Just similar as you, I prepared precision parts for several years which were bought from ebay which include 4 pieces THK KR33 and 1 piece NSK linear actuators with some small size linear rails. No extra ballscrews are needed. Easy servo stepper motors were bought also. Now, my router is under the building and was finished around 60%. The most critical and getting-headache portion is the precision alignments of those precision parts on the metal frame. As well, the required measuring tools like granite parallel and right angle triangular blocks etc are bought.