Quote Originally Posted by Juranovich View Post
Now, I don't want to go into to much detail before i break the 10 post threshold and can post pictures, but considering I'm planning to make the frame 1000x800mm (effective working area approx. 750x600mm), should I use 1605 ball screws on all axis, or is it better to use 1610 on X and Y (and possibly 1605 on Z)? With belts, I guess, it doesn't matter as much since I could always gear it to suit the purpose, but am I unnecessarily restricting myself if I choose one over the other? I'm thinking of using nema 23 2.4nm steppers (in case it's relevant info) and mainly work with wood (hard and soft) and occasionally soft alloys e.g. aluminium..
Either could work - and there are builds showcasing both - which you lean towards depends on what you want to cut. For woods + plastics, you'll want to lean towards the 10mm pitch screws on that size of machine. If its more fine detail work and metals (in which case you might consider building a mill rather than a router...) you'd want to lean towards the 5mm pitch screws. Its not about how quickly you want the machine to finish jobs, its about cutting at the right speed for the material.

Belts offer some flexibility with ratios, but there are a few things to consider. First, your pitch defines how fast you can go before screw whipping becomes an issue. Look at the following page, and click the blue link at the bottom to open a calculator:

https://www.zappautomation.co.uk/ecalculators.html

A 1605 or 1610 screw will have a root diameter of ~12mm. Using a BK BF setup, a 1000mm screw can get to around 1500rpm before whipping is an issue. That limits our rapids to 7.5m/min on a 1605, or 15m/min on 1610.

Typical stepper motors will be falling off in torque dramatically above 1000rpm = 5m/min 1605 or 10m/min 1610. This is where your belts come in, its about allowing the motor to stay at appropriate RPMs for the speed (or torque multiplication).

Now, I'd personally aim for rapids in the 7.5-10m/min range for a wood router, which suggests 10mm pitch screws, but some people are happy with the 5m/min.

As for the Z axis, the travel is massively reduced so large rapids arn't an issue. A finer pitch should give slightly higher accuracy and holding torque at the correct Z location, so I'm all for fine pitch Z screws. 1605 should be fine.

Those motors sound a little weak to me. You should use the motor calculation sheet to determine what you need. Mines a similar size, and I use 2x2010 X screws (2x4nm low-inductance nema23 steppers) and a 1610 Y screw (3.1nm).