[Benonymous]

jaty97 Wrote: I don't really understand why it takes so long for some to build a machine.

I think there would be ample scope to build a machine quickly, especially out of a kit. Even if one was just to use a kit for the motion parts (motors,drives etc) that would make the process much quicker. My build has taken a substantial amount of time because I went custom everything, from the design in Solidworks all the way through. Add to this I'm using industrial servos and drives etc etc etc. After all of the big stuff is sorted, you've still got wiring and limit switches, software setup.

Most importantly for me, when i am finally finished I'll be able to take a couple of steps backward and say "I made that!"

[jayty97]

I think there would be ample scope to build a machine quickly, especially out of a kit. Even if one was just to use a kit for the motion parts (motors,drives etc) that would make the process much quicker. My build has taken a substantial amount of time because I went custom everything, from the design in Solidworks all the way through. Add to this I'm using industrial servos and drives etc etc etc. After all of the big stuff is sorted, you've still got wiring and limit switches, software setup.

Most importantly for me, when i am finally finished I'll be able to take a couple of steps backward and say "I made that!"

I looked at some of what you are doing. It looks like you are definitely building your baby!

I have a lot of the parts already for this mechanically that I have collected over the years and have a good idea of what I will be using. The drive system and electronics are the least of my concerns. After my last rebuild of my Gerber what I didn't understand, now I do.. I've made my mistakes and am becoming very comfortable with this stuff.

I'm sticking with steppers for simplicity, cost, familiarity.. as well as they have done me right thus far and i haven't needed the benefits of servos. I like using what I have on hand and any shortcut I can take I will, just not at the cost of quality. I always look to see what i can find that is similar to what I want to make and I could make work. That being said, it seems as though the gantry is the most import and part of the build, especially the uprights. That is were i see a lot of machines have trouble with as far as rigidity.

With concrete I could make up an accurate form and pour in a weekend. Welding up steel is going to take a long time. I can weld, but its not second nature to me like carpentry is. My faith in making an accurate form far outweighs my faith in my metal working abilities. I have done a lot of experimenting with casting parts.. even new gears for the Gerber. I know I could pour a good part, but am only questioning that part in service over the long term.

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[louieatienza]

Have you also given thought to using an epoxy-granite mixture of some type? I don't know how it'd work for a large gantry, but it's probably more impact and crack-resistant than regular concrete....

[shedbob]

Concrete(standard) is generally regarded as poor material for machine tools,
compared to other materials.Reasons given include:a Poor Strength To Weight Ratio,its
dimensionally unstable(eg absorbs water),never really cures,Poor Strength compared to
alternatives,has virtually no tensile strength,is susceptible to cracking(lowering
strength),brittleness and its properties deteriorate over time.There may be damping
advantages from the use of concrete.I am only aware of around a handful of efforts to use
concrete in machine tools.


https://www.jstage.jst.go.jp/article...4_1_1/_article
Concrete Machine Tool Structures - Hand Tools - Concrete Construction

For a comparison of machine tool materials see page 136 of this pdf.

DSpace@MIT : Manufacturing and testing of composite machine tool structures

Remember to that a tube is much more structurally efficient than a bar of the
same material and this is not reflected in a direct comparison of material properties
alone,multiplying the strength advantage of steel.

For info on concrete(strength) variations see.

Types of concrete - Wikipedia, the free encyclopedia

(There are perhaps 3 commercial machine tool builders using essentially uhpc,~= to
epoxy granite in specification,pc in the above pdf)

On beam design see these.
Reinforced concrete - Wikipedia, the free encyclopedia
Basic Issues of Beam Design - Yahoo! Voices - voices.yahoo.com
Breaking a Plain Concrete Beam - Yahoo! Voices - voices.yahoo.com
Deflections of an Uncracked Reinforced Concrete Beam - Yahoo! Voices - voices.yahoo.com


Apart from the possibility of beam failure,I see the biggest problem being the concrete gantry being
to heavy.If its significantly heavier than say a steel alternative then you
will require heavier duty screws,rails,bearing etc and that will surely cost more than you
save by using concrete.If it was me I would use the steel in the gantry and table and use
the concrete in 6 or 8 pyramid shaped legs.

As an alternative consider there are many apparently successful builds in
steel including the mechmate and it is the material of choice for industrial router
builders(normalized I would think).This one looks good to me.

http://www.cnczone.com/forums/diy-cn...ext_cnc-6.html

[jayty97]

Concrete(standard) is generally regarded as poor material for machine tools,
compared to other materials.Reasons given include:a Poor Strength To Weight Ratio,its
dimensionally unstable(eg absorbs water),never really cures,Poor Strength compared to
alternatives,has virtually no tensile strength,is susceptible to cracking(lowering
strength),brittleness and its properties deteriorate over time.There may be damping
advantages from the use of concrete.I am only aware of around a handful of efforts to use
concrete in machine tools.


https://www.jstage.jst.go.jp/article...4_1_1/_article
Concrete Machine Tool Structures - Hand Tools - Concrete Construction

For a comparison of machine tool materials see page 136 of this pdf.

DSpace@MIT : Manufacturing and testing of composite machine tool structures

Remember to that a tube is much more structurally efficient than a bar of the
same material and this is not reflected in a direct comparison of material properties
alone,multiplying the strength advantage of steel.

For info on concrete(strength) variations see.

Types of concrete - Wikipedia, the free encyclopedia

(There are perhaps 3 commercial machine tool builders using essentially uhpc,~= to
epoxy granite in specification,pc in the above pdf)

On beam design see these.
Reinforced concrete - Wikipedia, the free encyclopedia
Basic Issues of Beam Design - Yahoo! Voices - voices.yahoo.com
Breaking a Plain Concrete Beam - Yahoo! Voices - voices.yahoo.com
Deflections of an Uncracked Reinforced Concrete Beam - Yahoo! Voices - voices.yahoo.com


Apart from the possibility of beam failure,I see the biggest problem being the concrete gantry being
to heavy.If its significantly heavier than say a steel alternative then you
will require heavier duty screws,rails,bearing etc and that will surely cost more than you
save by using concrete.If it was me I would use the steel in the gantry and table and use
the concrete in 6 or 8 pyramid shaped legs.

As an alternative consider there are many apparently successful builds in
steel including the mechmate and it is the material of choice for industrial router
builders(normalized I would think).This one looks good to me.

http://www.cnczone.com/forums/diy-cn...ext_cnc-6.html

Thank you for the abundance of information on concrete. It will take some time to read through it all! I won't give up on the idea before reading something with comprehensive facts against it... I have my work cut out for me!

If at the end of the day, concrete wont work. Epoxy granite will just be too expensive to use for the kind of volume needed. I've seen a lot of the projects done on this site and know most have been out of steel. I really hate working with steel. For one it is very hard to get good straight stock. Two, it takes a ton of prep and oil to drill and tap which I try to stay away from using too much in my shop due to contamination problems I get with my woodwork, etc. Lastly, by using steel, I would have to lay everything out by hand. I really want to utilize my existing router for critical layouts and steel is just not possible with this machine without oil coolants. Aluminum though more costly would be manageable, but still there will be a lot of fabrication involved to make complex parts and recesses for a belt drive system.

Maybe for me I would be better off building a laminated Baltic Birch machine... I could vacuum laminate the parts and have extreme flexibility in designing and cutting the parts. A 4" x 10" BB beam would have very good dimensional stability using the appropriate construction methods. I know there are drawbacks with this as well, but utilizing what I have on hand is of great importance to me if I'm going to go forward with a build. Plus, though I'm a good all around mechanic my familiarization and comfort level working with wood is far above anything else. This is where the desire to explore concrete construction originated from.

[OCNC]

Maybe for me I would be better off building a laminated Baltic Birch machine... I could vacuum laminate the parts and have extreme flexibility in designing and cutting the parts. A 4" x 10" BB beam would have very good dimensional stability using the appropriate construction methods. I know there are drawbacks with this as well, but utilizing what I have on hand is of great importance to me if I'm going to go forward with a build. Plus, though I'm a good all around mechanic my familiarization and comfort level working with wood is far above anything else.

This sounds like the best idea so far.

[peteeng]

Hi Jay - Did this machine work out? Concrete or birch? I've been playing with UHPC and its got many advantages...Peter

[WilliamACaines]

I can understand how hard it's for a beginner to sand concrete or cement if you haven't done it before. During my research on this topic I found this blog very helpful https://writions.com/how-to-sand-concrete/