Hello all,

As the title suggests, I am building a large bridge type CNC mill from DIY UHPC.

I am currently part way through the build, so there is too much to cover in one post. I have already built the UHPC frame components, and intend to work on leveling and assembly of these parts while awaiting delivery of the needed components. I am now at the stage of looking to select and order components, such as linear guideways, ball screw systems and servos etc. I am hoping to get some advice regarding this aspect of the build.

The work envelope of the machine will be appoximately 1250mm x 1050mm x 600mm, and the design mindful of the ability to upgrade to 5 axis capability in the future. It is intended as an all round prototyping machine, with the possibility of doing light production work to get going. This means cutting everything from foam to steel, though I do not yet know what I am likely to do most. I am considering the possibility of using interchangeable heads, though I intend to begin with a cheap spindle, as my first project won't require any hard material and this will allow me to learn CNC machining without risking a valuable spindle.

I have encountered various difficulties with developing a DIY UHPC, but have read well over 100 academic papers on the subject and have used software to help me design the mix, so may be able to offer some valuable information on this subject. The result of my mix design is a coarse UHPC, which can be mixed effectively in a drum mixer (though a pan mixer is preferable) and is self compacting - can give an excellent, almost glossy finish. I have also utilized a thermal curing regime based on employing the concrete's own heat of hydration, the principles of which were tested and proven in an academic study. This serves to bring an end to long term shrinkage (confirmed by numerous papers). Many people have used proprietary UHPC mixtures for DIY CNC builds, often using nanodur compound 5941, however this is based in Germany and not readily available elsewhere. there is nothing particularly special about nanodur compound however, it is still a portland cement based binder (albeit with careful particle grading and a pozzolan).

I imagine more UHPC info will naturally arise in the thread, so will save that for later.

Here is a basic CAD visualisation of the design. I will show some other progress photos in coming posts.