[joeavaerage]

Hi,
you could make the table.

Here it costs about $6NZD/kg for profile cut steel. Thus a 50mm piece of steel 600 x 400 would weigh 96kg, or cost $576NZD.
Then you'd need to put it on a mill and face both sides, and trim the sides, would guess 2hrs. Then mill the slots, probably another hour.
If you provide the T tool, say $200NZD, then the T-slots will take another two hours or so, for a total of 5hours or $500NZD approx.

Thus I would expect to pay around $1100NZD + $200NZD for the tool,for such a table. This is where the costs of such a big machine become evident. If you reduce the size of the table
to 400x300 then the steel comes down to 48kg or $288NZD, and the machining likewise reduces.

Craig

[NordicCnc]

I am trying to finalize some of the expensive materials/parts.. Now trying to select epoxy granite.
Following are some of the options I picked from various threads.

1. ResinL + GL2 from R&G and Silimix 282
2. Sika-212 HP
3. SikaGrout-3350
4. https://www.uscomposites.com -> 635 THIN EPOXY SYSTEM

I can see some successful builds that use 1 and 4. But could not find any build that use 2 and 3. And what other options do we have? Especially ones that are available in USA or UK?

Also, has anyone in this forum checked their machine's accuracy after 2 years to see if there any issues in the frame?

Have you considered UHPC from Durcrete, specifically Nanodur E80 recipe? It has a modulus of more than 80GPa (more than aluminium) and is very easy to mix and cast, because it requires no vibration. Comes in at 2€/kg.
https://www.moertelshop.eu/buy-nanodur-cement-cheaply_6

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[peteeng]

Hi Sus - Well sand is as old as the earth so it will be stable. Sand (quartz or silicon dioxide has a modulus of 70GPa same as aluminium) Blue metal is different and is stiffer. I personally would not use a mixture of sizes. I would use the smallest or medium. I disagree with the ratio that produces a "dry" mix that is stacked into the mould. I recommend a mix that flows so can be poured. Or dry stacked then filled with very thin epoxy. I think that grout is the go. Its a premade product to a specification. Sika3350 is 58GPa which is better than you will get if you add sand or blue metal to epoxy. I expect you will get 40-45GPa in epoxy granite. The sika3350 quotes a void ratio of 1.5% which is really low. The grouts are self deairing. If you use a graded mix in the EG and vibrate it or even pour it, it will segregate (that's my experience). The grouts are designed for this sort of thing so I'd go there. The only reason I'd go epoxy is if I used aluminium powder or steel grit. Then once cured this can be machined. So it then can be milled and drilled. I have done quite a bit of those for small scale parts. I think the main issue with grout and epoxy is the initial exotherm. This can get to 60-80degsC plus. Which means it will expand a bit putting pressure on the mould. So we need a product that cures over a long period of time so the exotherm is released over a long time and the temp peak is low so the mass growth is small.

The other aspect of EG is that epoxy does not get along with water and sand and gravel will have a lot of water in them just from the environment. I use vacuum casting/manufacture a lot and have found that bonding various things in vacuum gets rid of the water barrier and even things kike polished aluminium can be bonded together that would not work in ambient. So using a water based product like grout sidesteps that one. Keep at it. Peter

edit attached is Rampf - their EG is 40GPa their concrete is 45 and solid granite is 65.... I'm sure a company like this, if they could would get their EG above 40.

[ardenum2]

Rampf - their EG is 40GPa their concrete is 45 and solid granite is 65.... I'm sure a company like this, if they could would get their EG above 40.

EG's final specs depend on the largest stone size you use. Rampf has a variety of epument types depending on that size. EPUMENT 140/5 with max 5mm stones is 30-35GPa, 140/8B with 8mm stones is 35-40GPa, 145/B with 16mm stones is 40-45GPa. I'm pretty sure grading stone size is a must so that every void is filled with a particle.

[peteeng]

Hi Ard - Yes and if you use one solid stone (the [sic] "largest stone size") its the highest E. Grading is a big big subject and there's lots of discussion but few tests. The concrete and grout is graded at a nano particle size that's why it has a reasonable modulus. Plus the active ingredient that bonds the whole mass together has a E=30GPa vs epoxy at 3GPa. But chasing E is only one part of the issue and Pippin has designed a gantry with E=35 that was stiffer than a steel section. It works because the thick sections have no local shear deflection issues.

You cannot fill "every" void and my own tests on establishing actual solid fractions show little delta with using one small grain vs using large grains with grading. Its simpler and simple is best in CNC world... Peter

[suspension]

Hi,
you could make the table.

Here it costs about $6NZD/kg for profile cut steel. Thus a 50mm piece of steel 600 x 400 would weigh 96kg, or cost $576NZD.
Then you'd need to put it on a mill and face both sides, and trim the sides, would guess 2hrs. Then mill the slots, probably another hour.
If you provide the T tool, say $200NZD, then the T-slots will take another two hours or so, for a total of 5hours or $500NZD approx.

Thus I would expect to pay around $1100NZD + $200NZD for the tool,for such a table. This is where the costs of such a big machine become evident. If you reduce the size of the table
to 400x300 then the steel comes down to 48kg or $288NZD, and the machining likewise reduces.

Craig

Hi Craig

1300NZD is half the cost of the option I checked. Two issues though, without me being there is there a way to order this? And the shipping will be huge! Still, I will research this path. I may be able to find an ocean shipping forwarder. Thanks for the information.

Sus

[suspension]

Have you considered UHPC from Durcrete, specifically Nanodur E80 recipe? It has a modulus of more than 80GPa (more than aluminium) and is very easy to mix and cast, because it requires no vibration. Comes in at 2€/kg.
https://www.moertelshop.eu/buy-nanodur-cement-cheaply_6

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I haven't. Will UHPC be as good as epoxy? I've read that concrete will be shrinking all the time and also can get micro cracks. Is this not the case with UHPC?
Also, would any decent quality UHPC work? I can check with my local construction good supplier if this is the case. In any case.

[suspension]

edit attached is Rampf - their EG is 40GPa their concrete is 45 and solid granite is 65.... I'm sure a company like this, if they could would get their EG above 40.

Any idea where I can buy their concrete? and prices? Cannot find much info online.
But my guess is that this will be as expensive as EG?

[ardenum2]

Any idea where I can buy their concrete? and prices? Cannot find much info online.
But my guess is that this will be as expensive as EG?

they sell the EG to private customers directly, the concrete epudur only to companies. Avarage price for epument depends on the max. stone size, cheapest ones were $4.5-$5.5 per kg in 2022. This includes both resin and graded stones, just need to mix the two together.

Direct contact person is [email protected], email him he will send you current prices and shipping info.

[NordicCnc]

I haven't. Will UHPC be as good as epoxy? I've read that concrete will be shrinking all the time and also can get micro cracks. Is this not the case with UHPC?
Also, would any decent quality UHPC work? I can check with my local construction good supplier if this is the case. In any case.

I dont know, I have only read about Nanodur 5941 and the recipe for E>80GPa. Dyckerhoff recommends usage of retarder to minimise shrinkage and prevent microcracking. I read somewhere that shrinkage is 1‰ without retarder and half of that with retarder. In my mind that is negliable, but I have not tested myself. My next build will be with UHPC, whenever that happens... Here is the link to the recipe.
https://www.google.com/url?sa=t&sour...VpF2nL4B2MvHu5

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[ardenum2]

I dont know, I have only read about Nanodur 5941 and the recipe for E>80GPa. Dyckerhoff recommends usage of retarder to minimise shrinkage and prevent microcracking. I read somewhere that shrinkage is 1‰ without retarder and half of that with retarder. In my mind that is negliable, but I have not tested myself. My next build will be with UHPC, whenever that happens... Here is the link to the recipe.
https://www.google.com/url?sa=t&sour...VpF2nL4B2MvHu5

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I suggest going with durcretes recipe, dyckerhoffs was formulated for construction, durcrete further modified it for machine tools, they added a shrinkage reducer on top of dyckerhoffs recipe and made a bunch of other changes, for questions about the full e80 recipe email [email protected]

Also watch the webinar to avoid any mistakes in the design

https://www.youtube.com/watch?v=au3eD3ZmAvI

[peteeng]

Hi - Sika3350 has 0.025% shrinkage. I consider 1% even 0.5% shrinkage a big shrinkage... Peter

[joeavaerage]

Hi,
well bugger-me....I've had cast iron axis beds for a little over two years, no shrinkage that I can measure. Do you know what, I've had steel for years and years
and it doesn't seem to shrink either.

Craig

[peteeng]

Hi Craig - When steel and iron is cast it shrinks quite a bit too eg the steel allowance is 1/4" per foot. This is 2% shrinkage. CI is 1-2% as well depending on its flavour. This is the plastic shrinkage discussed. Once stable grouts and epoxy don't shrink either. Peter

[suspension]

Hi Ard - Yes and if you use one solid stone (the [sic] "largest stone size") its the highest E. Grading is a big big subject and there's lots of discussion but few tests. The concrete and grout is graded at a nano particle size that's why it has a reasonable modulus. Plus the active ingredient that bonds the whole mass together has a E=30GPa vs epoxy at 3GPa. But chasing E is only one part of the issue and Pippin has designed a gantry with E=35 that was stiffer than a steel section. It works because the thick sections have no local shear deflection issues.

You cannot fill "every" void and my own tests on establishing actual solid fractions show little delta with using one small grain vs using large grains with grading. Its simpler and simple is best in CNC world... Peter

Hi Pete
I contacted Sika and they said they have two products. I attached their specs. Could you please let me know if these would be good fits for this purpose? They dont stock the exact product you suggessted.
Thanks
Sus

[peteeng]

Hi Sus - The monotop is limited to 50mm thick. It quotes it modulus as 25GPa which is a bit low and describes its shrinkage as "very low". The grout does not spec its modulus so ask what it is and its max thickness is 100mm. Its described as a dual compensated grout which means its compensated for the plastic stage and the cure stage. Ask what the actual total shrinkage is and the best way to achieve the lowest shrinkage. I expect the grout to be around the 30-35GPa mark. At first look I'd use the 214 grout. The 3350 has lots of european specs so I thought it would be available in EU. Any class C or dual compensated grout will be fine if you know the modulus so you can design it using FE. Peter

edit - ask if they have a 100% CAS grout....

BluCem HE80AG EARLY STRENGTH CEMENTITIOUS GROUT (bluey.ie) this is Bluey europe. email them and see what they have. The HE80AG is what I settled on here in OZ before I found the 3350

[ardenum2]

The 3350 has lots of european specs so I thought it would be available in EU.

it is weird, sika is a swiss company and it's products are hardly available even in germany. Best I can get is 35GPa from resellers, UHPC components on the other hand, no issues, too bad I need a low density product, E80 is 2.8g/cm3 almost as high as pure granite at 3g/cm3. E45 is 2.4g/cm3 similar to EG.

[NordicCnc]

Hi - Sika3350 has 0.025% shrinkage. I consider 1% even 0.5% shrinkage a big shrinkage... Peter

Shrinkage is not 1% for uhpc, rather 1‰ and half of that with retarder.

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[NordicCnc]

I suggest going with durcretes recipe, dyckerhoffs was formulated for construction, durcrete further modified it for machine tools, they added a shrinkage reducer on top of dyckerhoffs recipe and made a bunch of other changes, for questions about the full e80 recipe email [email protected]

Also watch the webinar to avoid any mistakes in the design

https://www.youtube.com/watch?v=au3eD3ZmAvI

Thanks, I sent them an email. Ill share the recipe with you if they send it to me.

I have watched the webinars several times, but I have to admit the automatic youtube translation is a little bit foggy, but I think I got the most critical points:

Minimum 50mm between UHPC edge and steel insert, or align steel insert with UHPc edge to avoid cracks.

800mm steel inserts is the maximum length, if you need longer then those should be separate ones to avoid tension induced cracks.

Threaded inserts should be hexagon style insert, i.e. hexagon shaped bottom transitioning into a smaller diameter and then to a larger diameter.

What I didnt find yet is how deep one should anchor the steel inserts. I assumed that minimum 50mm would be good and maybe maximum 80-100m. The 50mm coming from the same statement that a minimum of 50mm between steel insert and UHPC edge is recommended. Then if you anchor too deep, the tension is maybe increased when the UHPC has "more" material to pull, hence increased risk for cracks.

Is there anything else that I've missed?

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[ardenum2]

Thanks, I sent them an email. Ill share the recipe with you if they send it to me.

I have watched the webinars several times, but I have to admit the automatic youtube translation is a little bit foggy, but I think I got the most critical points:

Minimum 50mm between UHPC edge and steel insert, or align steel insert with UHPc edge to avoid cracks.

800mm steel inserts is the maximum length, if you need longer then those should be separate ones to avoid tension induced cracks.

Threaded inserts should be hexagon style insert, i.e. hexagon shaped bottom transitioning into a smaller diameter and then to a larger diameter.

What I didnt find yet is how deep one should anchor the steel inserts. I assumed that minimum 50mm would be good and maybe maximum 80-100m. The 50mm coming from the same statement that a minimum of 50mm between steel insert and UHPC edge is recommended. Then if you anchor too deep, the tension is maybe increased when the UHPC has "more" material to pull, hence increased risk for cracks.

Is there anything else that I've missed?

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For anchors I'm doing these https://www.aliexpress.com/item/1005004529261503.html screwing in a hexagon bolt 5mm in and then welding it around the thread. Threaded inserts m4 20mm, m6 25mm, m8 30mm, m10 35mm. Total length with a hexbolt 50mm for m4, 60mm for m6, 70mm for m8 and 80mm for m10. Cost is about $400 for a total of 300 inserts. Unless you can make them yourself, like in the picture attached.

The slides have english in them, but not everything is translated. What kind of a machine are you building?