Three New Videos

MR-1 CNC Mill Assembly Tutorial: Y-axis Rail Course Adjustment

MR-1 CNC Mill Assembly Tutorial: Performing Checklist Before Pouring Concrete Base

MR-1 CNC Mill Assembly Tutorial: Pouring the Concrete Base

Baseplate seems set back slightly from early pics.




Uprights are 3 x 3 square tubing?
Worth using a vibrator for the concrete?
Steel rebar for additional strength?
How about filling the area between the stabilizer plates with concrete too?

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Bump for the rebar question. Is there any benefit? The whole time i was watching the videos i was thinking to myself “Self, I know I’m going to crash the machine and crack that concrete”. Are my fears legit or is concrete just that strong in comparison to my mistakes?

as for placement of the table, the video uses a preproduction unit and in your last pic, you can see that the spindle can go behind the table, so having it backed up is a good thing.

I’m just pointing out the inconsistencies. It may be too far forward based on the spindle location but the plate is 20” and the Y travel spec is 21.8”.
https://www.langmuirsystems.com/mr1#specs

If the plate is moved back so that the anchor bolts are behind the cross plate (approx 37” x 3” x 1/4”) that position the rail plate towers, the base could end up too far back. Just guessing at this point because I have no way to mock up the spindle, gantry, and all the rails to verify anything. Hopefully we’ll know in the next few videos because their page on the MR-1 base design shows a different mock up than the final result. Base Design | MR-1 CNC Gantry Mill | Langmuir Systems

Overall the page is a great sales pitch but I’m not sold on everything. I think there are more ways to improve on strength and rigidity without breaking the wallet.

Yes, concrete is strong…in compression. Not nearly as strong as iron or steel, especially under tension. And not all concrete is created equal. I’ve read recently strength can vary up to 6 times depending on the admixtures. I’m just learning about most of it so I can’t offer much advice but can pass on some references.

Food for thought.

Regarding baseplate position you are correct. Pre-production unit we had the baseplate biased to the front of the machine. Production units will have the baseplate centerline in the same location as the envelope centerline.

I think it’s worth noting that maximum strength is not a primary design factor for a CNC milling machine. Stiffness and damping are significantly more important. Considering that the peak loads imparted on the machine by the cutting action are never greater than ~150 pounds, the concrete is never loaded remotely close to its limit in either tension or compression.

Concrete is excellent for both stiffness and damping and that’s why it works so well in MR-1.

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I believe stiffness and strength are very much related. Can anyone explain the difference?

I know dampening with concrete and granite are much better than iron. See the link posted in the Cast Iron Plates thread. Includes a link about concrete tensile strength, which is only 1/10th that of it’s compression strength, and several references to UHPC being used in CNC machinery.

Mechanical strength (tensile, compressive, shear, torsion) is the resistance to breaking. Stiffness is the resistance to deflection. They are somewhat related, but a material can have very good strength but also very poor stiffness. Rubber comes to mind as a good example of that.

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OK, I think I get what you’re saying. I can look up the mechanical properties of any metal but I’m not going to find figures for stiffness or rigidity. Sounds like you’re referring to hardness. Metals use something like a brinell hardness test. Minerals use a scratch or rebound test.

Rubber and urethanes would use a durometer. Durometer / Hardness

Unfortunately comparing them would be a bit like debating politics in three languages. The scales aren’t designed for comparison of such dissimilar materials.

“Hardness is not a true property of materials, since it depends on certain properties of a material, such as ductility, resistance, rigidity, elasticity, viscosity, deformation, among others. Rather, it is a property that is attributed to any object capable of resisting change when it is suffers abrasion or scratching.”

The MR-1 uses a bit of everything. Metals, minerals, and plastics. No matter how well something works, there is always room for improvement and I think I can do so in several ways if there’s any interest at all. You never know…the brilliant minds behind the MR-1 might like some of my ideas and offer them as future upgrades.

My delivery is 3+ months away so I still have time for research. I’ve done a lot already and plans keep changing slightly as new ideas are always in motion. Best to sort them out before the concrete is poured and hardened.

I watched a couple MR-1 machining videos of 1018 and 1045 steel. How do they differ?
A good site for comparing metals.
https://www.makeitfrom.com/compare/SAE-AISI-1018-G10180-Carbon-Steel/SAE-AISI-1045-S45C-G10450-Carbon-Steel

What Daniel was talking about is correct, he wasn’t referring to hardness, although, that is another material property. You should be able to find mechanical properties for modulus of elasticity for pretty much any metal you want though, as long as it’s not some weird alloy that a specific company owns.

It’s concrete’s lack of elasticity that I’m trying to point out. The reason we don’t see bolts made out of concrete is because it’s extremely weak when it comes to elongation. It also takes a lot longer to fully cure than most people realize. In fact some say it never cures 100%.

MPa x 145 = psi


.32 x 145 = 46.4 psi
.60 x 145 = 87 psi
Ultimate Tensile Strength of 1018 steel is 64,000 psi. You don’t usually see compression strength rating for steel but I’ve read it’s something like 200,000 psi.
Concrete is normally rated by it’s compression strength.
28.5 x 145 = 4,133 psi

You don’t have to look far to find alternatives, epoxy granite bases have been used in machines for some time, but its more complicated and more expensive. Thankfully simple 4000 psi concrete bag mix is more than adequate for what we are trying to accomplish with such a small machine.

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A few years back we made a few countertops and pool blocks where we tried out several different concrete mixes. One of them( I’ll see if I can find the recipe) used quite a bit of tite bond three glue, and fiberglass reinforcing fibers. It made for some insanely strong blocks that took a lot of abuse with no rebar.

GFRC concrete would be a good candidate- however, we have not had any issues at all using standard 4000 psi concrete and it is far far cheaper than the glass reinforced stuff.

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Ignoring the cost difference, is there any risk to using a epoxy granite mix in lieu of concrete? Is there target weight you are looking for that should be considered when trying to select an epoxy mix. Thanks!

I think they want rigidity first. Weight second

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This is a little late…

Modulus of elasticity(young’s modulus) is the mechanical property that relates material rigidity.

Deflection of a simple beam is calculated using PL^3/(48*EI)

P= Force
L= beam length
E = Modulous of elasticity
I = Moment of inertia

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New video tonight. Epoxy install on top of concrete . Oh boy…getting ready!

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Fiber reinforcements come in many forms and materials. Weight, costs, and percentage used in a concrete mix vary wildly.

Locally I can buy 80lb ready mix sacks at these prices.
“High Strength” 4000psi $5.67 x 6 = $34
“High Strength” 5000psi $6.97 x 6 = $42
“High Strength” GFRC $7.87 x 6 = $47 which is also rated 4000psi

Of course this is common hardware store GFRC concrete, likely with a very small percentage of glass fibers based on the price. If you want to get serious about GFRC or UHPC, Trinic has a very informative website and over 100 videos on YT. Trinic
They sell 20lb bags of GF for $55 which I think is pretty reasonable.

I’m not sure if the epoxy granite question was for members or LS. I doubt LS has done any research. There hasn’t been an agreement here, or any discussion for that matter on which is superior. IMO epoxy granite is a risk I wouldn’t be willing to take without extensive testing or verifiable proof that it is better than concrete. I would assume all risk falls on the person deviating from LS standard assembly guidelines.

Epoxy resin is pretty soft. Portland cement is easily 5-6 times harder when cured and both mostly rely on their aggregates for overall strength. Tensile strength may not contrast as much, haven’t looked into that yet. But compression strength and cost are the biggest issues.

Let’s say you build an MR-1 like this guy.
How to Build Epoxy Granite Machine Base

A 20% epoxy ratio would be 90 out of 450lbs. That’s going to be $600-1000 for epoxy alone. 90lbs of Portland Cement is about $13 so cost difference is like night and day.

This isn’t to say EG can’t be made strong. With carefully selected aggregates $$ and years of testing I’ve read about companies claiming 20,000psi can be achieved with EG but a DIY guy would be lucky to get half that number. You can buy 450 lbs of 20K+psi UHPC ready mix from Trinic for under $400 or make 12-15Kpsi GFRC for far less than that.

I have been researching epoxy granite and concrete mixtures for months and it has been like opening Pandora’s Box. No idea what I was getting into.

The 23 types of Concrete Admixtures(Additives)used in Concrete

Machine Beds with NANODUR®-UHPC

Constructing the Future with Ultra-High Performance Concrete

Sugar in concrete?

When I first read about using concrete for dampening and rigidity, I thought what a great idea. Later I was taken by surprise when I saw the anchors fastened to the bottom of the aluminum plates and just pushed into wet concrete. Then it was centered with a tape measure and some funky plates to get the table to the correct height to the rails.
In my simple mind I was thinking there would be a steel plate or flat bar bolted to the base (same as the “Y” axis rails) located in a precise position drilled a tapped to except risers that had threaded holes for bolting on the aluminum plates. Next step would be to pour in the concrete to the required level and bolt on the aluminum plates.
Some of my concerns are, will there be certain areas on the plate that will vibrate? One of the quadrants of the plate is not as rigid? Will the table (aluminum plates) be secure with anchors into concrete and not fastened to anything?
My experience is in machine shop and not construction of concrete slabs and anchors. I’m just looking for some feedback and reassurance from the experts at LANGMUIR.