Having gained experience in CNC machine basics through building a Tevo Tarantula 3D printer kit (AliExpress https://tevo.aliexpress.com) I decided to build a CNC router. After some research I opted to base my first machine on the Ox originally designed by Mark Carew (Ox example https://openbuilds.com/builds/openbuilds-ox-cnc-machine.341/). Being short on funds (available kits were outside my budget) I did some searching on AliExpress where I was able to purchase:

a set of Ox plates
a z-axis rail assembly
a 1.5kW water cooled spindle and controller
four Wantai Nema23 Stepper Motors and DQ542MA drivers
numerous wheels and bearings
end stops, cabling, cable snakes, power supplies etc.

Remaining items such as rails, machine screws and other items I purchased locally.

Basic specifications:

Working bed size: 1300mm x 900mm with a maximum z range of 130mm. 1.5kW spindle with ER11 collet.

I used an old Dell Desktop PC to drive the machine using Linux CNC. Here’s a couple of photos of Mark 1.

Review of Mark 1

Overall I’d recommend the OX design but I did experience a few issues that I’ve detailed below. I used the Mk1 machine to build all sorts of things including the 10mm Aluminium plates for Mk2 – so I consider this first attempt a success.

Issues

LinuxCNC is an excellent controller but unfortunately, living only 100 metres from the Pacific Ocean, the power supply of the PC did not survive. A subsequent replacement also failed a few months later. That needed a rethink.

The OX uses two stepper motors on the belt driven Y-axis. Variations in wear on these two belts and the slipping that occurred when one belt got too loose led to less than ideal results.

With a 1500mm X-axis made from three 60×20 profiles, the torsional flex in the Z-axis was unacceptable so stiffer design was needed.

Time to redesign core parts 🙂

Mark 2 – a much stiffer and more reliable ‘Ox’

The changes I made for Mark 2 are described in the following sections. These changes were made incrementally so I present them in the order they were made.

Y-Axis

To overcome the problems with the belt drive I decided to change to dual 16mm ball screws, each 1200mm long. I also decided to replace the 80×20 V-slot side rails with 20mm linear rails. This required some changes to the stepper motor mounts and the design of new supports for the rails and ball screws. Nothing complex and all achieved with hand tools.