CNC Gantry Build. The $1 mistake that started it all.

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Originally Posted by ChipsBFlyin

Pete,

Have a look at how they pour this machines base. I'm not saying that this is the route I am going to take, these are just commercially available small CNCs

https://www.langmuirsystems.com/mr1/base

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The base pour looks good, the rail mounting and the base supporting structure not so good, being a small machine, it most likely won't matter too much, the general concept is good that anyone could build a similar machine.

Hi CBF,
do you not think the claims of Langmuirsystems seem a bit optimistic?. I have seen others link to their site and viewed their products and I question whether the reality
matches the claims.

Craig

Hi Joe et al - In the video doing deep Al 100% cuts the general machine noise is good, but there is a wobble in the noise which means it could be stiffer. Not as good a sound as a full VMC but that's expected. They do have various specs which seem to be high on the site for an assembled machine. have to look closely at it and see if their forum has any feedback....Peter

Mactec,

Based on the videos I seen of them so far, they look alright. I don't really plan on running heavy slotting cuts like some of the demos, but if it can handle that, then I don't see why my machine wouldn't be able to. Then again this is my first machine build of this size, so what do I know.

Craig,

I do question the longevity and claims being made for those machines, but for what they sell for I guess you can't complain.

Pete,

I don't think those machines have shipped yet, I think they just did a pre order for them.

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Originally Posted by joeavaerage

Hi CBF,
do you not think the claims of Langmuirsystems seem a bit optimistic?. I have seen others link to their site and viewed their products and I question whether the reality
matches the claims.

Craig

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Yes, it's a lot of hype to make sales, to those that don't know any better.

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Originally Posted by ChipsBFlyin

Craig,

Thanks for your input. I am trying to consider all of my options. The cost of the Y axis rails mounts, including material, SR, machining/grinding is at least 2k+. Then I still have the dilemma of mounting them to the surface plate. I checked the surface plate and the sides are not square to the top to themselves or anything else. They aren't even flat, so my best solution for that so far would be to add jack screws to the Y axis mounts and use them to offset the steel mounts from the surface plate, then proceed to snug down the mounting bolts. I would then fill the gap between the surface plate and the y axis mounts with epoxy. I am questioning how this mounting method would work, so that's when I started looking into epoxy granite.

Pete,

I am in Brooklyn, NY.

I have no idea what material I would use for a casting yet, I have never heard of the grout option, but would like to hear about it. Is it prone to cracking? I do like the idea of UHPC, but I thought the concern with concrete is that it never fully cures and tends to move a bit? I don't know enough about these materials, I still have a lot of research to do. I did stubble upon a company called Basetek and they make castings, but based on the picture I see on their website, they don't look cheap.

I've seen some people mix in fiberglass and some mentioned carbon fiber into the epoxy granite. Any benefit in that?

Any recipes or commercially available products that have been tested would be greatly appreciated.

My process for making my casting would be:

1 - Build a mold around the surface plate.
2 - Hold the inserts in a machined jig that I can adjust to set as parallel to the surface plate as possible.
3 - pour the mold
4 - self level epoxy the Y axis rails mounts
5 - hand scrape the self leveling epoxy of the Y axis mounts to the surface plate.


Anyways this is what I have in mind so far.:

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Whoa what is going on?! are you pouring EG around the granite plate? You really are stretching the work area.

I'm really confused what you're trying to achieve here...

if you want cheap then UHPC but then you have to send the cast to machining $5000+, with EG you're looking at +$10000 cast+machining, prices vary but that's the general idea, UHPC much cheaper

if you don't want to use block inserts for the rails and only use bolt inserts and mount the rails on the cast then you have to send it to grinding instead

Is there a weight limit?

...and please no self leveling epoxy(forget about it altogether), it will deform under load. something like moglice in between, yes. Filling the epoxy with steel powder instead? maybe...

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Originally Posted by mactec54

Yes, it's a lot of hype to make sales, to those that don't know any better.

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I was under the impression that concrete and aluminum don't like each other and they cast it around the al work plate...

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Originally Posted by ardenum

I was under the impression that concrete and aluminum don't like each other and they cast it around the al work plate...

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Correct if it was anodized first it would be fine, and we don't really know what there mix is, they may have epoxy coated the aluminum before casting also

One thing I missed is the coolant drains will be a problem with those small pipes they will get blocked and will be a big problem to clean

ok so I had a read over and what you want is a huge work area?

then consider a double column raising gantry. You could have the block inserts machined and align them on the granite plate face down(to make use of the precision surface), make a mold around it and cast each part of this type of frame: It will be huge, insanely stiff and the cheapest option for a big machine.

https://www.youtube.com/watch?v=ebpIR1KiraM

Hi,
there is a guy here in New Zealand whom has built a very nice machine out of granite. He used a surface plate and then some granite parallels for the two upstands
on which the rails are mounted, and another granite parallel for the gantry.

https://www.youtube.com/watch?v=W_V8qp8zfCM

You may not have paid much for the granite surface plate, and that might come tumbling down when, or if, you buy granite parallels.....but if you did and bonded them
to the top surface of the plate then the top surfaces would be co-planar, no machining required.

Craig

Ardenum,

I would like 48" X travel and at least 20" on the Y axis. I'll look into that design and see what i can come up with.


Craig,

Fox3D's machine is the reason why I am in this mess. haha If you look at my original design, I thought about adding steel structures to the sides of my granite plate like he did with his surface plate, except he used granite. Here are some of the frames Haas makes. The frame looks to be tubular and plate construction.

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This is the latest and greatest idea. I don't even know what route to take anymore. haha

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Originally Posted by ChipsBFlyin

Ardenum,

I would like 48" X travel and at least 20" on the Y axis. I'll look into that design and see what i can come up with.
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That's possible, with this design you can get 48" in X about 25" in Z(vertical) and Y(length) as long as you want e.g 60" if you cast the bed in 3x 48" pieces. There is no better or cheaper frame to build. The stiffness will be an order of magnitude higher than a router.

I was planning on welding that frame, that is mainly made up of 1/2" flat stock and 3/8" steel sheets. Like I said, I have no idea of how to make the frame anymore, just coming up with random designs now.

Hi CBF - seems chips are further away at the moment. I'd cast parts on the surface plate. Start with a small part for experience then go for it. i think you will like "concrete" all the hard work is done in the moulds. These can be double checked and triple checked. Easy to correct. Once certain fill with grout and the jobs done. Peter note - devil is in the detail as usual but I think its less onerous then the metal path

Pete,

Yes, very far away from making chips. This was another option I was considering, a tube base (still a rough design) that was one piece or could be made in 3 pieces, but I am not sure if its rigid enough. Its made from 2" tube 1/4 wall. If it need to be done in one piece, I found a heat treater who can do large weldments.

Hi CBF - I used to work as a welder in the auto racing industry - I look at that and faint! Think thru the casting process. Much simpler. I think you need to write down your objectives and resources and figure out a trajectory based on those. Also consider that steel is convenient but most forward thinking machine builders don't go there anymore. Status quo is cold casting...They cold cast their bases and many of their structures.... Mineral casting, UHPC, composites that's the way to go....Peter (IMHO) :)

Pete,

Hahaha. I thought the same thing after I designed it. Welding nightmare.

Regarding UHPC, is the precision grout you recommended not a type of UHPC? I would also like to know if there are ways to optimize the casting, so I don't just end up with a solid block for a casting. Can I do webbing or pockets in some areas? If I can reduce some of the weight without affecting the performance, that would be great. Currently my casting weight estimate is at approximately 2.5 Tons. One of the concerns I have is that I don't think I am capable of mixing that quantity of material in a short period of time, if needed.

Hi CBF - There seems to be lots of names for "advanced" concrete. Engineering grout, UHPC, CSA etc etc. UHPC is a blend of Portland and CSA. You will find something local that's 100% CSA or a major blend. Look for a material that has the smallest growth/shrinkage.
1) You can honeycomb the mould to reduce weight. You can use foam "voids" to reduce weight. You can build it in pieces to reduce weight of the components. They then can be bolted together or bonded together depends on if you want to disassemble or not.
2) You can add styrofoam beads to reduce weight
3) You can foam the concrete. I have a client that does this for building panels and gets down to 500kg/m3 but then the modulus reduces proportionally
4) Look at cast iron parts to get an idea of how the "concrete" one will look. I want a word that gets away from concrete! it has a bad wrap... That's why I like the term UHPC . Your gantry can be cast... all the parts can be cast

https://foamconcreteworld.com/making-foam-concrete/
https://thumbs.dreamstime.com/z/gray...n-37003275.jpg

Moulds are generally made from white melamine coated MDF. Give them a good wax, say 5 or 6 coats then cast. Most people do not wax the mould enough. Design in everything you can into the mould so its done there not post cast....

Here's some test castings in CSA and EG that I have done. I have a few concrete trivets around the house. Peter


I design things with a 50kg limit so I can lift them. If you have a small engine crane then this maybe a bigger limit...

Parts can be epoxy "set" and still come apart. Bolts can be cast in usually use high tensile threaded rod for this or long HT bolts and use the head for extra grip. Bolts can be post fixed via drilling and epoxying in. Steel or brass inserts can be moulded (NY speak molded) in then drilled and tapped. You can make parts with recesses then epoxy in steel or aluminium inserts then take to machine shop and have post finished. many many ways to skin this cat....

some ideas - I disagree with the steel reinforcing but they are new to the materials. Peter

https://www.mmsonline.com/articles/i...ol-moonshot(2)