[suspension]

Hi Pete

>> If you are designing "thin" parts you will need internal webbing to locally stiffen the section as it deflects. If the part is "thick" it maintains its shape at the desired max deflection. Thin and thick are relative. Early models are comparative only to gain insight and direction on how the part is best made. Depending on the manufacturing route will shape how the part looks.

How do you suggest I add webbing? Because the way it goes, I will probably end up with parts that are 100mm thick made of UHPC (or possibly EG). Do you use a metal?

Hi Ard

I am also comparing different sim runs in fusion. I also maintain an excel so its easy to compare multiple runs.
I guess what you are trying to do is to get the max stiffness out of a given mass of the material. Probably you have set the limit on mass based on the cost? But wouldn't it be a waste if the max stiffness you get from this is not enough for the machine? I am convinced that given the the effort, money I put to this machine, I do not want to sacrifice accuracy too much. And I like to get 50 as Craig suggested some time back.

thanks for the information on cement and products you found. Holcim is a major player in SL, so I will contact them to see if they have 'dynamax xrd'. The ones you have listed look promising too. Not sure why I missed those.
Also I found following two which is available in SL:

https://assets.master-builders-solut...ow-810-tds.pdf
https://cdnmedia.mapei.com/docs/libr...rsn=3af6b05b_0

As usual they dont have the elastic modulus specified, so asked the manufacturer but no reply yet.

CTS cement from US sent me attached test report for their product https://www.ctscement.com/product/cement-all. They dont have this info for the cement Pete suggested.

[peteeng]

Hi Sus - If you use UHPC you will be casting thick and using a void. No webbing needed. Talk to Holcim. The local supplier here has Dynamax and it quotes E=+40GPa. I expect plain grout to be about 30GPa and any with 3mm to 10mm blue metal added to get to 40. Peter

[peteeng]

Hi Sus:
1) I doubt you will get over 40GPa in a self made EG so I suggest you look for a suitable grout/concrete
2) You need to find a grout with high stiffness and this will fulfil your chasing of the machine rigidity at least cost
3) You may not achieve the rigidity you set out to achieve for various reasons. For instance If you want a machine to acheive 50N/um then aim at the model being 100N/um there are many inefficiencies in reality that are not in the model. It is technically possible to model the machine in Fusion very accurately, but I have played with the contact stiffness and the sliding and the simple models have not resolved. So there is a learning curve in modelling at that level... Keep at it. Peter

[suspension]

Hi Sus:
1) I doubt you will get over 40GPa in a self made EG so I suggest you look for a suitable grout/concrete
2) You need to find a grout with high stiffness and this will fulfil your chasing of the machine rigidity at least cost
3) You may not achieve the rigidity you set out to achieve for various reasons. For instance If you want a machine to acheive 50N/um then aim at the model being 100N/um there are many inefficiencies in reality that are not in the model. It is technically possible to model the machine in Fusion very accurately, but I have played with the contact stiffness and the sliding and the simple models have not resolved. So there is a learning curve in modelling at that level... Keep at it. Peter

Hi Pete

I am actually trying the model to get 100 in all directions so any issues in the model are compensated.

Wouldn't a grout have issues like shrinkages, cracks, etc? Also what properties should I check to select a suitable grout? Could you please let me know if the two grouts I mentioned in previous post are good enough?

Thanks
Sua

[joeavaerage]

Hi,
my understanding is that India and Sri Lanka have a good free trade deal....and India has a thriving foundry industry that rivals, maybe even exceeds China.

There is a good reason that cast iron is STILL the premier material for machines around the world. Why would you overlook the greaatest advantage your location offers?

Craig

[suspension]

Hi,
my understanding is that India and Sri Lanka have a good free trade deal....and India has a thriving foundry industry that rivals, maybe even exceeds China.

There is a good reason that cast iron is STILL the premier material for machines around the world. Why would you overlook the greaatest advantage your location offers?

Craig

Hi Craig,

But using cast iron would require a long stress relief period to my understanding. Years perhaps. Isn't it?

-Sus

[peteeng]

Hi Sus - Most metals post casting can be TSR. Some cast irons can be in mould stress relived. This is because in a sand moulding the sand is an insulator and as the casting cools there is an exothermic reaction and this heat is trapped in the part contributing to a low stressed part. Work with your caster to get the best result. Peter

Heat Treatment of Grey Irons | Cast Irons | Metallurgy (engineeringenotes.com)

[suspension]

Hi Sus - Most metals post casting can be TSR. Some cast irons can be in mould stress relived. This is because in a sand moulding the sand is an insulator and as the casting cools there is an exothermic reaction and this heat is trapped in the part contributing to a low stressed part. Work with your caster to get the best result. Peter

Heat Treatment of Grey Irons | Cast Irons | Metallurgy (engineeringenotes.com)

Ok, may be this is what @Ard is planning to do as well.
And also keen to know if commercial producers use this method (letting it cool down in the sand).

[joeavaerage]

Hi,

.But using cast iron would require a long stress relief period to my understanding. Years perhaps. Isn't it?

Complete rubbish, you've been listening to too much myth and not enough fact. Cast iron is one of the most stable materials known to man....and has been for over five hundred years.
Even straight out of the mold its still damn good. Ideally it would be heat treated and aged, but its not necessary. Its stability will be better than grout and probably rivals granite, not to mention
being 300% stiffer than grout and 160% the stiffness of granite.

Walk into any factory anywhere in the world....and what do you see? Machines all made out of cast iron. Why do you suppose that is?

Craig

[ardenum2]

Probably you have set the limit on mass based on the cost? But wouldn't it be a waste if the max stiffness you get from this is not enough for the machine? I am convinced that given the the effort, money I put to this machine, I do not want to sacrifice accuracy too much. And I like to get 50 as Craig suggested some time back.

no, weight is my only limit, people move from place to place and I like cheap rent, I'm designing the machine so that it can be moved to any place, to any floor, by a bunch of dudes. That means a max 30-40kg per person, shape of the machine also determines how many guys I can fit around the machine to lift and carry it. Low machine weight is also crucial to making sure the floor doesn't crack under it's weight.

there will be no issues with accuracy. I'm using a high speed machining approach which puts very low loads on the machine structure, stiffness wise, won't be a problem even with 20N/um

Ok, may be this is what @Ard is planning to do as well

cast iron/steel is one of the things I'm considering. I can tell you from the get go, you being so close to india would save you a lot of $ in shipping costs, possibly thousands of $. one foundry in china quoted me $3000 to ship 500kg's china-germany.

the first thing you wanna find out is $/per kg of cast material, then things like lost foam vs. sand core casting. the columns I posted earlier are all compatible with both processes.

the best of the best of the best in iron casting will use a special casting/cooling process and label that product as a meehanite casting. to search for foundries start with key words like 'machine tool casting'

[joeavaerage]

Hi,
casting in steel works out a lot more expensive than gray cast iron. To cast steel you need a hard mold, and that costs bigtime if you are paying a foundryman. Gray iron can be cast
quite happily in greensand, the oldest and still hugely popular method. Lost foam is the new kid on the block, and is good for smaller parts where the foam does not deflect during molding.
It is economical in large volumes but quite expensive compared to greensand for one-off stuff.

For a 50kg part I'd expect to pay about $1000NZD for the molding, pouring and fettling, about $1500NZD for the same part by lost foam, and about $2000NZD for the part in steel, just ordinary steel at that,
nothing special like tool steel.

Craig

[ardenum2]

Hi,
casting in steel works out a lot more expensive than gray cast iron. To cast steel you need a hard mold, and that costs bigtime if you are paying a foundryman. Gray iron can be cast
quite happily in greensand, the oldest and still hugely popular method. Lost foam is the new kid on the block, and is good for smaller parts where the foam does not deflect during molding.
It is economical in large volumes but quite expensive compared to greensand for one-off stuff.

For a 50kg part I'd expect to pay about $1000NZD for the molding, pouring and fettling, about $1500NZD for the same part by lost foam, and about $2000NZD for the part in steel, just ordinary steel at that,
nothing special like tool steel.

Craig

I'm afraid I have to go one step further. I want to machine medical molds/implants. To do that in germany I have to sort of have a clean room. the main body can be whatever, but the front of the machine must be nontoxic so I have to either cast the spindle headstock or have it machined from solid stainless steel billet. whichever is cheaper. Usually I could machine on anything but I'd need to clean the parts afterwards with chemicals to make them viable. chemical baths is what I definitely want to avoid. A ram for the column I posted 65kg's would cost about $1200 to be machined from billet in 1.4301.

[ardenum2]

To cast steel you need a hard mold

are you sure about that? There's a stainless steel foundry 20km's from me that 3d prints molds for sand cores, then uses those cores to cast in ss.

[joeavaerage]

Hi,

are you sure about that? There's a stainless steel foundry 20km's from me that 3d prints molds for sand cores, then uses those cores to cast in ss.

You need a hard mold for steel. A hard mold is mostly a sand mold that is either chemically hardened or has a resin in it or is baked. Sand cores are often made with 3%-4% sodium silicate and are hardened
by passing CO₂ through it.

Steels, including stainless, are not nearly as fluid as cast iron and shrink hugely (by comparison to iron) and tend to fracture the mold. As a consequence molds for steel needs to be good or
a molding failure will result in an expensive casting failure. The viscous force of a fluid steel passing through a greensand ie soft or unhardened mold will pull sand grains out of the mold polluting the casting.
In short; casting steels and stainless is a much tougher proposition than cast iron.

Small parts tend to be made with an investment cast where the wax pattern is repeatedly dipped in a ceramic slurry and then hardened by baking. The mold is strengthened by repeated
dipping in slurry and thickening the ceramic shell. Slow and expensive. Only for small high value parts. The ceramic shell is impervious and so the wax has to be melted out prior to pouring
otherwise the gaseous breakdown products of the wax were you to pour on top of it would outgas and wreck your cast.

Lost foam on the other hand are dipped or painted with a refractory ceramic and is dried in a low temp oven, so that the foam does not melt. The resulting ceramic is porous and has to be
so that the gaseous breakdown products can pass through the ceramic shell and dissipate into the sand backing. If the ceramic is not sufficiently porous the gas will bubble back through the casting
and out the risers/sprue/gates......and a hell of a surprise for the poor b********d pouring the metal as it blows back in his face!

For a machine of the type that you want I would say that is in the category of 'I need the best so to hell with the cost'. The stiffness of steel is so great that it even puts cast iron to shame and thus you could
make a machine very much more rigid for a given weight. Downside is cost, by my estimate about twice the cost of iron. Remember also because steel shrinks so badly you'll have to stress relive afterwards
to have any chance of securing the rigidity and stability that you have paid so dearly for.

If you think casting iron is difficult or expensive then casting steel will make you weep.

The most likely method/technique that a hobbyist might reasonably afford is greensand molded cast gray iron. Even SG iron ups the price too much. That is at least what I have found.

Craig

[peteeng]

Hi All - interesting video form herco. Peter

https://youtu.be/jgp2GOMwBrU


https://youtu.be/HVn93Brec0k

[Mr-MaW]

you are confusing me, what are you trying to do? just find a c frame you like and copy its shape, no need to reinvent a structure that's been done for decades. heres one mr maw designed, theres plenty of other c frames on grabcad

https://grabcad.com/library/cnc-1100-600-600-1

I'm glad you're interested in my product, Maw and MrW---It's all me,I don't speak English well and one account has been blocked.
I haven't had time to look at this forum because of the problems of visiting customers and attending exhibitions in China, and I find that everyone has a high level of enthusiasm and hope to continue to persevere.

In fact, my point is very clear, to practice your product as much as possible, there is an old saying in China "theory is greater than practice". Summarize experience in the process of practice,Including what material to use, what structure, these actually have the answer, as long as you bravely test he will have a result, and then continue to optimize.
As for what material E50 E60 E70 E80, all have its advantages and disadvantages, is the material has advantages and disadvantages, cast iron also has advantages and disadvantages, reasonable design, more practical data is the most important. So China's high-speed rail can be quickly laid across the country, and we have enough data, including collision data.

[Mr-MaW]

So China's high-speed rail can be quickly laid across the country, and we have enough data, including collision data.[/QUOTE]

For example, I hope you understand what I'm trying to say. In China, at the time you are discussing, I may have almost finished the prototype of this device, and this is efficiency.

[Mr-MaW]

So many products, will accumulate a big database, he helps us make better products. Mineral castings are serious in our company, not like E80, only providing materials, and dare not guarantee absolute reliability.

[suspension]

So China's high-speed rail can be quickly laid across the country, and we have enough data, including collision data.

For example, I hope you understand what I'm trying to say. In China, at the time you are discussing, I may have almost finished the prototype of this device, and this is efficiency.[/QUOTE]

I understand what you are saying. I had a look at your designs/work and they are quite impressive. What I may not like with this approach is the cost
This machine most probably be used for hobby projects (bit advanced ones) so I want to keep the cost low. Having said that I will get a quote from you once the design is complete (only for base/column cast) so in case it is with in my budget I can take that path.

[Mr-MaW]

I don't think anyone knows costs better than Chinese. Do you know Elon Musk?
Tesla electric car, why did he build the Gigafactory in China?
China should be the best cost-control of all countries.
So if you want to control costs, or mass production, you have to find the right Chinese supplier. Of course, we also have our own R&D center, and we also need to find suitable agents for us abroad, although these are not my responsibility.
I believe that soon everyone will see mineral castings from China.
Finally, I share a mineral casting product, which I currently consider to be the largest mineral casting product in the world, it weighs 29 tons.