My carbon fiber CNC gantry

[Zorbit]

That simply does not happen with properly made parts unless they are not designed with a wall thickness and shape that is appropriate for the load. Nobody should be trying to cut it close.

Making cf parts that are strong enough not to break is really not that hard. People here are doing just fine with cnc machines made from far weaker materials like plywood...

The sort of force required to break a cf tube made with 7 layers of fabric is immense. It is certainly more than the force required to break most of the end mills I use...

The point I'm making is that laminating CF and Glass together has to be considered carefully - the CF can be taking 90% of the load with the glass just adding weight, because the glass stretches so much more it does virtually no work until the CF fails. Adding a small amount of CF to "add stiffness" can fail badly.

[Goemon]

The point I'm making is that laminating CF and Glass together has to be considered carefully - the CF can be taking 90% of the load with the glass just adding weight, because the glass stretches so much more it does virtually no work until the CF fails. Adding a small amount of CF to "add stiffness" can fail badly.

That is true. I've seen that where people try skinning a wooden object with one layer of cf to "make it stronger". That sort of thing shows a misunderstanding of how the material works.

I have also seen plenty of examples where people misinterpret or misunderstand things like the Young's modulus when comparing two materials. They see a chart showing that one is higher or lower for strength or stiffness and use it to choose their material.

It is important to understand that critical part design is far more complicated than any one piece of data. Strength and stiffness is affected by part shape, part design, wall thickness, the manufacturing process, choice of resin etc.... as well as choice of material.

If you ask most people here, "what is stiffer, a steel or an aluminum cnc machine frame?", most would answer "steel". But, what if the steel frame had a 1/4" wall thickness and the aluminum had 1" walls? What if one used plates and the other square tubes?There are at least as many complexities with composites. With a well made composite, there is synergy between multiple materials. A poorly designed ones could easily see one material drag the other down.

[peteeng]

Goemon - any news on this machine? Peter

[peteeng]

Hey Gaemon - Any news on this CF router? I know this is old so maybe you have sawdust by now? Peter