First Proper CNC Router

[diycnc]

The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.

Thanks for the stepper driver advice JAZZCNC.

How do you guys attach linear rails to a steel frame. Do you just drill and tap straight into the 3mm wall?
An M5 screw has 0.8mm pitch, so will be over 3 full threads in the steel, which is the rule of thumb iv come across a few times.

[JAZZCNC]

The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.

Don't get caught with the Critical speed trap doesn't often work out that way. So many variables come into play to screw the job up.

Let me put it this way you wouldn't find me using 16mm screws much over 1600mm on any machine I build and even then they would have fixed end BK bearings on both ends to help support.

Yep M5 screws are ok in 3mm box provided you don't swing on them with breaker bar. Make sure you loctite them.

[A_Camera]

The critical speed for these 16mm screws (assuming a 13mm min diameter) is over 2700rpm, thats a whopping 27m/min. I think 16mm will be OK.

I am using 1605 screws driven directly with NEMA23 motors and get more than enough speed with that solution. My X and Y has 9m/min and Z has 7m/min. Stalling speed is about 11m/m on all three. My machine is though a moving table type, which I think is better for DIY because it is easier to make and more rigid than a similar one with moving gantry would be.

Here is a short video, running all axes at 10m/min.



I am using analogue drivers, DQ542MA and it may be better with digital drivers, but the biggest difference in speed is made by the PSU which is based on toroidal transformer. The second difference is the external motion controller I am using (UC300ETH).

Speed wise I don't think Arduino would be an issue actually. I am running a 3D printer with Arduino and that 3D printer has even more speed than my CNC, currently has 15m/min on X and Y and 5m/min on Z but the Z is driven with simple dual 8mm threaded rods with 1.25mm pitch. Though I am using A4988 drivers, I am pretty sure that I could drive my CNC with the same Arduino but with the drivers from my CNC if I wanted to. Pulsing is generally not the problem, the problem is the drivers and the power supply. To get the speed I have in my printer I changed the delivered 12V PSU to a 24V PSU and that made a HUGE difference. Of course, if I'd run the CNC with the Arduino board (GT2560) I would not be able to use UCCNC or Mach3, but in theory it should not be an issue.