[switch2472]

Jeez, time really flys by, doesn't it?

Between my last post here and today, I've gone from working as a machinist, to running my business out of my home shop, to taking a day job working as a machine tool teacher.

Finally picked up some 1" plate steel to start work on the base and Y axis of the machine. Hopefully I'll have time to post up some progress again!

[Mr-MaW]

Hi Switch - Interesting article. Their material only gets to <14GPa flexural stiffness. Its nearly not worth using at that stiffness and tensile is only 6.5GPa which is only double that of the epoxy... If this is the trend with quartz then I wouldn't use it. UHPC starts at 30GPa and is much cheaper then epoxy... Until you model the machine from tool to bed and then get its static stiffness its hard to tell how good your machine rigidity is... The Z axis is the stiffness killer.. Peter

Peter...this IS the Z axis. There is a reason I'm working on it first.

The material being used is "red granite", not quartz, in the linked article.

Take note also, the simulation shown above is *with* the "nearly not worth using" material, and it's an order of magnitude better with the fill than without.

UHPC is still water-bound, and will always and forever be prone to rusting a steel component in contact with it, and will not maintain stability over humidty and temperature changes due to this water content. Non-water-bound UHPC is just...epoxy granite with fancy aggregate.

Hi Switch - so why are so many companies making machines from UHPC? Granite is 70-89% quartz with some alumina so should be stiffer then 100% quartz (its red because of some iron in it ). The gain in stiffness by increasing the steel thickness for the same cost of the epoxy granite is a much better strategy then using the EG but you are now committed to your steel size. I buy plywood that is stiffer then 14GPa (F27 is 18.5GPa)... I agree about the rust I have samples here that have steel fibres with rust. The proof will be in the pudding, I'm sure your machine will be a good one... Peter

New thoughts.

I've been given a cast iron column from a Hardinge-Handsvelt sinker EDM. It's 39" from base to the top of the casting, and 10.5" x 8.5" across the column. It does have a big cast in L-shape that is nicely ground cast iron on the top. The column wall thickness is about 1/2"-13mm, and the corners are increased to about double that thickness. It does have some internal ribs but it's mostly hollow.



https://imgur.com/yGcqM1C

It's the same size as the welded steel column. I'd have to do exactly the same machining to it to mount the rails, and I'd have to mount the rails or the blocks on huge risers to fit the ballscrew in between them. It would scrape in much faster than the welded steel, though.

The question is, Is it going to be more advantageous to use my welded steel column, with it's slightly less than double Young's modulus, or the cast iron pillar? (Steel at 200GPa, vs cast iron at 124GPa). My welded column weighs almost the same, and yet I still need to weld in the top cap and internal brace in the welded column.

Basically, all I can see the iron casting having over the steel weldment is 10 times better damping, and 3" more height.

I feel that what you (Switch) said is not right, there is some deviation in understanding.
Mineral castings and Steel blocks do not rust.You can take a look at their products.

https://reiden.com/en/products/30/rx10

And you can also look at my work, but I can only show you pictures.
https://grabcad.com/library/ma-miner...inear-motors-1