[Nothing]

I've been researching cnc's for some time now to see what would be post suitable for a DIY machine that would machine aluminum and steel and I've chosen to make a VMC out of UHPC (ultra high performance concrete). This was inspired by builds like https://grabcad.com/library/uhpc-fix...-cnc-machine-1 and https://hackaday.io/project/181258-3...g-machine-uhpc. The problem is there isn't much info on these the most I got was from the grabcad link with a 3d file, I was just wondering what would be the best way to approach this, I'm not looking to make anything massive just a 45x30cm work area? I know the parts I want to add just not the shape of the frame. I would appreciate any advice you guys have and any links on where I could learn about cnc design choices to see how to make mine. Thank you

[Mr-MaW]

https://grabcad.com/h.w.ma-1/models

You can take a look at my products and hope to inspire you. For questions about mineral castings, you can send messages and emails at any time.

[Nothing]

Your stuff looks great, that's a monster machine, I'll certainly message you soon

[ardenum2]

whats the budget

[Nothing]

I am hoping to do this for relatively cheap since it is quite small, something like 1600$ without the spindle. I can go over by a bit if I have to but the concrete shouldn't be too expensive and having small linear rails and ball screws should keep the motion stuff to about $600 I believe, depending on quality obviously.

[peteeng]

Hi Nothing - Look for an engineering grout in your area. The ones that are double compensated is what you want. Generally called a Class C grout. Its compensated for drying shrinkage and plastic shrinkage. So shrinkage is very low. They also use CSA in it which means if cured correctly it won't crack like Portland cement. 1600USD is a bit slim to cut steel... Peter

If your in the USA try some of this grout. Its a 100% CSA grout non shrink... Peter
https://www.ctscement.com/product/ul...=Professionals

[Nothing]

I'm in Canada, from my research most people use durafil from a european company, it would be really expensive to ship here but I found UHPC locally called ductal made by a company called lafarge. I will look into the grout you are talking about too and compare them. From other builds the budget does seem slim but I'm assuming as I get more and more into it, it will expand, but I don't want to open that door right off the bat. Heres a video of ductal to give you an idea of it's capabilities https://www.youtube.com/shorts/LYpIhXgDufQ depending on the mix over 200 megapascals of compression force https://www.ductal.com/en/about

[ardenum2]

$1600 would get you a router from small to medium extrusions at best, good luck nevertheless.

[peteeng]

Hi Not - Ductal is Class C concrete with steel fibres. The concrete suppliers have a range of plastic and steel fibres that can be added to any concrete. Totally agree with the approach. Ductal has a modulus of 48GPa which is quite good. For machine parts don't worry about compressive strength look for its stiffness. Here's its data sheet for interested parties. Peter

[Mr-MaW]

The price should not be a problem, I am worried about the freight, after all, shipping 1000KG things from China to Canada is a lot of costs.
However, if it is well assembled in China and equipped with an electrical system, it should still be advantageous to transport the equipment in good condition.

[Nothing]

Oh ok thanks for letting me know, the guy from the grabcad link in my first post says that he used a special mixture to get 80GPa so I'll check out what modifications I can do to raise that.

[Nothing]

The price should not be a problem, I am worried about the freight, after all, shipping 1000KG things from China to Canada is a lot of costs.
However, if it is well assembled in China and equipped with an electrical system, it should still be advantageous to transport the equipment in good condition.

The concrete I would get locally, I don't have too much time to make this, so waiting for shipping would take a while and it takes a month to set, plus like you said the shipping price would be very high. With locally sourced concrete that shouldn't be a problem. I would get the rest of the stuff like the electronics, motion system and the spindle from china. I'll try to get them in a bundle to keep shipping price low.

[Mr-MaW]

The concrete I would get locally, I don't have too much time to make this, so waiting for shipping would take a while and it takes a month to set, plus like you said the shipping price would be very high. With locally sourced concrete that shouldn't be a problem. I would get the rest of the stuff like the electronics, motion system and the spindle from china. I'll try to get them in a bundle to keep shipping price low.

I know what you think, but I still want to help you analyze some issues, after all, it is better not to go wrong, because the cost is too high and it is likely to lead to cracking and scrapping.
What kind of structures are you going to make? C-shaped, gantry bridge shape?
What is your three-axis travel? What is your estimated weight?
Regarding the 80Gpa you said, I think this is theoretical data, the laboratory measured is not so large, please believe me, because I have tested.

[Mr-MaW]

Oh ok thanks for letting me know, the guy from the grabcad link in my first post says that he used a special mixture to get 80GPa so I'll check out what modifications I can do to raise that.

And have you seen my drawings? Which product do you prefer?
Those are the products that I make.

[Nothing]

Yes I have taken look at your grabcad profile, the machines are quite large for my needs, I will be replicating this machine https://grabcad.com/library/uhpc-fix...-cnc-machine-1

which is inspired by

https://www.youtube.com/watch?v=k4BrAcZ3spQ . It's a horizontal mill which seems ideal since making the bed move on two axis would be too complicated and the spindle should be light enough to be moved. I've also read that horizontal mills are good for accuracy and repeatability which is good since I'm hoping to make quite of few of the same items. It has two molds the arch and the base, steel parts are placed in the mold with bolts on the back so they will be one with the concrete at the end, they are faced to be flat when cured so linear rails and everything else can be mounted properly. For the elasticity I understand that 80GPa is probably under best condition but that also means that the concrete mixture that I'm going to use which is rated at 48GPa is under best condition so having a higher value is still good since the real value will be lower for both. The molds seem pretty simple but if I am not able to do them that is what I would ask you for, since it seems you are good at that and because they will be made out of wood it shouldn't be too expensive to ship them.

[peteeng]

Hi Not - Both of these are verticals not horizontal. V or H refers to the orientation of the spindle axis. The "arch" is called a gantry or bridge. Bridge is usually used for a fixed part. Some describe it as a fixed gantry. There is no agreed industry term for many of these configurations. Peter

[Nothing]

Thanks for letting me know, I've heard of gantry/fixed gantry before but not bridge, good to know. Do you perhaps know what type of mill this is called, it seems that there are a few vertical mills types but what is it called when the spindle is on the x axis and the bed only moves in the y.

[peteeng]

Hi Not - The conventional notation is if you are standing in front of the machine: side to side is X, going away from you is Y. Z is up/down. But this is not always the case The most common description for your machine (I think) is moving table, fixed gantry. Some companies call it a double column for instance. Others call it a Portal Mill. Technical people call it a cartesian co-ordinate robot Go figure. As long as you can describe it and the other person gets it, it seems to be Ok.... Peter

[Nothing]

I've done some more research and it seems that every diy mill that doesn't take years to build and haven't had thousands poured into them aren't really suitable for steel. I've found a pretty good deal locally for a taig micro mill which has been converted to a cnc, it comes with lots of extra necessities and a micro lathe which just needs the motor hooked up (the motor comes with it). Thanks for all the help

[peteeng]

Hi Not - Well done. You will be able to use the Taig to make your next one when the itch starts again! Peter