[thunderdork]

Hi, i've been researching my machine. Its gonna have a large work area, 8'x4'. I've been reading the legendary MadVac build. He talks about a sandwiched approach to connecting metal to metal using epoxy and metal powder. I have two questions:

1. Does anybody have any links to a tutorial that shows how to do this
2. How do you make the sections for generally connecting beams together?
3. What's the best way to get them all square.
4. I'm going the cncrouterparts.com system of linear rails. How would I make a perfectly straight and level pathway for my 1/4" cold rolled steel for the tracks using this method?

[the_canuck]

http://www.cnczone.com/forums/cnc_wo...l_monster.html

I'm using the technique for my build as well.

I used West Systems epoxy mixed with AL powder and micro balloons to make the joint glue. I prepped the joint by acid etching one part and spraying mold release on the other part of the joint. I used 4 bolts for the main joints and 2 bolts for the smaller joints. I also drilled and reamed out 2 holes on each joint for taper pins to ensure alignment if I ever take the joint apart.

It's not the fastest way to build a table but it worked for me. The epoxy working time allows time to align the parts and verify that it's good.

For critical joints you could poor the epoxy into the joint after alignment.

I used molding clay to keep the epoxy from running out of the joints and making a huge mess.

Andrew

[louieatienza]

Do a google search for the MadVac CNC build.... He uses some of the techniques described to get pretty accurate surfaces and joints.

[thunderdork]

Yeah, madvac is where i got the idea from. Put a link to it in my first post. Problem is that I'm having a hard time visualizing the process. right now reading canuck's thread to see if he has some pics or vids of the process.

canuck, one thing that eludes me is "tapered pins". not quite sure what they are or how and why they are used...?

EDIT: another question too. I just read your entire thread. what is the purpose of the wire and how do you implement it? Is it just for visual reference when installing the rails? how deep is it in the epoxy? Do you remove it afterwards or something?

[rowbare]

Check out Haydn's build here. It is similar and has some good detail pictures: http://www.cnczone.com/forums/cnc_wo...ilt_steel.html

bob

[Kazik_Wichura]

Nice, I like those topics that you show guys here. Do you have any info that someone made DIY CNC frame only from EPOXY? I know one guy from France, and some info here. But maybe there is more about using EPOXY resin in DIY?

[PaulRowntree]

Nice, I like those topics that you show guys here. Do you have any info that someone made DIY CNC frame only from EPOXY? I know one guy from France, and some info here. But maybe there is more about using EPOXY resin in DIY?

With the cost of epoxy, I wonder what the motivation was? Plus, the stiffness (Young's modulus) of epoxy is similar or less than MDF, AFAIK . I think that the epoxy/Granite guys seem to want it for its damping properties more than rigidity.

Cheers!

[Kazik_Wichura]

With the cost of epoxy, I wonder what the motivation was? Plus, the stiffness (Young's modulus) of epoxy is similar or less than MDF, AFAIK . I think that the epoxy/Granite guys seem to want it for its damping properties more than rigidity.

Cheers!

Yes and no. Yes that rigidity is smaller but most of EG are heavy and have steel inserts. So in the end you can achieve high damping and good rigidity. Everything depend of project. EG machine can not be projected as same as steel machine.

Lucas

[eigstein]

check out moglice.com

sincerely ,

eigstein

[thunderdork]

With the cost of epoxy, I wonder what the motivation was? Plus, the stiffness (Young's modulus) of epoxy is similar or less than MDF, AFAIK . I think that the epoxy/Granite guys seem to want it for its damping properties more than rigidity.

Cheers!

The motivation is to get a ruler flat surface to mount linear rails too. thickness will probably be 3 to 6mm. Plus i'll have mounting holes drilled every 60mm held down with m6 bolts for the rails. It'll be a metal/epoxy/metal sandwich. I'm assuming that will add to stiffness.

[leix_99]

With the cost of epoxy, I wonder what the motivation was? Plus, the stiffness (Young's modulus) of epoxy is similar or less than MDF, AFAIK . I think that the epoxy/Granite guys seem to want it for its damping properties more than rigidity.

Cheers!

While reinforcing the epoxy with filling material, you get a much stiffer structure. However, my little material technology knowledgements require that i ask: does it really have a stiffness close to MDF? For the parts i made using this technique, it feels WAY, but WAY much more rigid and stiff than MDF.

No harm or offense in my question, just want to know why.

[PaulRowntree]

@lucas, ThunderDork, Liex_99 : notice that I questioned the value of a PURE epoxy build (not filled, not as a spacer, not as a leveller) as was proposed in lucas's post (#6 of this thread).

Do you have any info that someone made DIY CNC frame only from EPOXY?

Google YOUNG's MODULUS EPOXY then MDF and you will find some tables etc. Some unit conversion may be required.
Cheers!

[leix_99]

Oups, my fault, anyway, i don't feel like anyone is using just resin to cast an structure, at least a highly stressed structure.

[PaulRowntree]

Oups, my fault, anyway, i don't feel like anyone is using just resin to cast an structure, at least a highly stressed structure.

Quite so! I don't know anyone with deep enough pockets either!

[RomanLini]

Check the forum section devoted to making "epoxy granite" machine frames. The material is only about 15% epoxy and makes a result similar to solid stone, but less brittle.

It's close to the perfect material for machines if you don't mind the cost and weight.

Regarding glueing together steel using epoxy, I really hope the stell will also be bolted together?

If you are trying to make a strong vibration proof structure just with glue and steel that is a job for experts, and even they get it wrong sometimes. The thermal expansion coefficients alone can spell disaster.