steel frame as a basic diy guy

[reefy86]

been reading alot regarding steel frames and aluminium frames, after reading a nuber of posts about how much work has to go into the steel frame to make sure its completely straight/flat as its not just a simple matter of buying the size steel needed and just bolting together then bolting your linear rails on top of the frame,

so looking at aluminium the price is nearly 3k in uk money so about 5k for you guys and thats just for the frame bed lol. how hard is making a steel frame for the first timers that dont know how to weld and has never delt with steel before.

cheers

ash

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[ger21]

First, let me state that I don't know how to weld, and have not really worked with steel, other than drilling and basic cuts in smaller pieces.

Having said that, I think that if your handy with tools, it's not that hard as well.

Plenty of guys with zero metalworking experience have built mechmates. On the UK cnc forum, building with steel is the preferred method. The one thing to amke life easier that's commonly done is to use epoxy to pour a self leveling surface for mounting rails to.

Steel is cheap, so get a welder and start practicing. It's not that hard to get serviceable joints.

[reefy86]

so on the y axis (3000mm long) i just make a dam and then pour epoxy resin along the y axis and no matter what imperfections there is on the steel the self leveling resin will auto fix so leaving a perfect flat top for the rails to sit on. im more scared of getting those mild steel beams perfect then i am welding

cheers

ash

[Eddard_Stark]

First, let me state that I don't know how to weld, and have not really worked with steel, other than drilling and basic cuts in smaller pieces.

Having said that, I think that if your handy with tools, it's not that hard as well.

Plenty of guys with zero metalworking experience have built mechmates. On the UK cnc forum, building with steel is the preferred method. The one thing to amke life easier that's commonly done is to use epoxy to pour a self leveling surface for mounting rails to.

Steel is cheap, so get a welder and start practicing. It's not that hard to get serviceable joints.

I built a 5' x 10' wood router with a steel frame with exactly zero welding experience. Yes, it is much harder than bolting together some steel and mounting linear rails.

I pretty much did what Ger21 described except my epoxy did not self level good enough. I tried two separate pours and couldn't get satisfactory results. What I ended up doing was using the gantry, which was ~74" (~1900mm) in length and professionally machined (cost <500$ US). After mounting the rails to the gantry I created a sled w/ a router and some linear bearings that I then used to mill my long axis mounting surface, including a reference edge. (good thing about epoxy is it mills easy) Each rail required two setups. I used a precision level and a test indicator to match the plane as close as possible.

BTW accurately drilling the linear rail mounting holes in steel along a ~3000mm length is very difficult. Once I had a reference edge it became doable, but it was nearly impossible without it. I ended up purchasing a mag-drill specifically for the project and even then it was not easy. I also used a home brew electric micrometer with led indcator coupled with properly tensioned piano wire to measure straightness over the length. It too was indispensable. (but it was cheap)

[reefy86]

I built a 5' x 10' wood router with a steel frame with exactly zero welding experience. Yes, it is much harder than bolting together some steel and mounting linear rails.

I pretty much did what Ger21 described except my epoxy did not self level good enough. I tried two separate pours and couldn't get satisfactory results. What I ended up doing was using the gantry, which was ~74" (~1900mm) in length and professionally machined (cost <500$ US). After mounting the rails to the gantry I created a sled w/ a router and some linear bearings that I then used to mill my long axis mounting surface, including a reference edge. (good thing about epoxy is it mills easy) Each rail required two setups. I used a precision level and a test indicator to match the plane as close as possible.

BTW accurately drilling the linear rail mounting holes in steel along a 1900mm length is very difficult. Once I had a reference edge it became doable, but it was nearly impossible without it. I ended up purchasing a mag-drill specifically for the project and even then it was not easy. I also used a home brew electric micrometer with led indcator coupled with properly tensioned piano wire to measure straightness over the length. It too was indispensable. (but it was cheap)

and my heads banging again lol

[awerby]

Steel is a good material for making CNC routers with, but yes, it does have a tendency to warp when welded. There are ways to minimize this, but not to eliminate it altogether. You can take it to someone with the equipment to grind it flat afterwards, but that's expensive. So bolting it together has a lot to be said for it. Even a bolted design won't be flat enough to mount rails to directly, though, which is where the self-leveling epoxy comes in. The alternative is to make the frame as best you can and then mount some flat-ground stock to it, being careful to shim and level it as you go to keep it dead flat.

[wizard]

been reading alot regarding steel frames and aluminium frames, after reading a nuber of posts about how much work has to go into the steel frame to make sure its completely straight/flat as its not just a simple matter of buying the size steel needed and just bolting together then bolting your linear rails on top of the frame,

There is absolutely nothing stopping you from building a bolt together steel frame. In the end it wouldn't look much different than some of the aluminum T slot frames. The main reason to consider steel is the cost where steel is often substantially cheaper than aluminum.

By the way aluminum extrusions really aren't flat enough for machine axises. This is why some companies offer machining services for their extrusions to flatten the linear bearing mounting surfaces. In many cases the flatness of a steel beam is comparable to that of an extrusion. Admittedly extrusions have tighter specs but the idea they are absolutely superior isn't really true.

so looking at aluminium the price is nearly 3k in uk money so about 5k for you guys and thats just for the frame bed lol.

Extrusions are probably cheaper over here but the price differential remains. Beyond that steel offers some other advantages one important one being the mass of the steel.

how hard is making a steel frame for the first timers that dont know how to weld and has never delt with steel before.

cheers

ash

Welding skills suitable for this sort of work are fairly easy to pick up. Welding is preferred for many parts of a machine but don't assume that it is absolutely required.

If you imagine a steel frame built like many of the aluminum extrusion machines, it becomes obvious that welding isn't absolutely required. Imagine the designs where the frame resembles a ladder with the rungs underneath the X Axis. Assuming a smallish machine with large tubing, each "rung" of the ladder can be bolted each X Axis piece. Yes you would need some tooling here to execute such a frame, a long drill bit being one of pieces of tooling required. In the end though as long as you have a way to put the nuts on the bolts, a bolt together steel frame isn't an impossibility.

[Eddard_Stark]

Steel is a good material for making CNC routers with, but yes, it does have a tendency to warp when welded. There are ways to minimize this, but not to eliminate it altogether. You can take it to someone with the equipment to grind it flat afterwards, but that's expensive. So bolting it together has a lot to be said for it. Even a bolted design won't be flat enough to mount rails to directly, though, which is where the self-leveling epoxy comes in. The alternative is to make the frame as best you can and then mount some flat-ground stock to it, being careful to shim and level it as you go to keep it dead flat.

To add to this; As mentioned I had my gantry milled, drill, and tapped. I used a local guy who did it on pretty big Mazak VMC. Were I to build another large router I would probably go with a hybrid bolt/weld design. One of the reasons being the difficulty of mounting long lengths of linear rails in a DIY environment. The VMC he used, which he charged me $75/hr, had removable sides. It had 65 inches of X travel natively, but he says he can mill me something of indeterminate length due to the removable sides (which is how he milled 74" on my gantry). So if I were to do it again I would get 12' steel tube sections and have them milled, drilled and tapped. I would then bolt a welded framed to it with epoxy between the mating surfaces. ( I might even weld flats on the tubes and send them out for heat treating first) I figure I could have both long axis rails and the gantry done for around 1500 dollars. This would save an enormous amount of time and I would avoid any welding to the critical pieces of the structure. All that would be left is to make them co planar and parallel. The latter is easy to do.

Of course I might look into pricing time on a double column mill to have everything milled in place, but I suspect it would be more expensive and I don't even know where to find one.

[reefy86]

just before i go too deep into things is all this parallel rails precision and zero tolerence still highly advicable for high detailed 3d engraving in wood even on a rotating 4th axis?

[Eddard_Stark]

and my heads banging again lol

It's important to note that I used US Composites Thin Epoxy. I preheated the components separately to increase viscosity. Now that I have researched it more, people have been reporting better results using Precision Epoxy from a placed conveniently named Precision Epoxy Products (Precision Epoxy Products). I too was attempting to level two ~3000mm rails that were ~1900mm apart. I damned both of them and linked each rail in two places. My suggestion would be to try a test run of Precision Epoxy on something long and non-critical and test it for yourself. IIRC Precision has some documentation on how to achieve level pours.

[Eddard_Stark]

just before i go too deep into things is all this parallel rails precision and zero tolerence still highly advicable for high detailed 3d engraving in wood even on a rotating 4th axis?

Mechmate and Shopbot both get good results in wood using vee roller bearings which have less performance than profile linear rails but are cheaper and much more forgiving/easier to install. Also you can get different levels of tolerance in your linear bearings which will allow for more deviation in mounting the linear rails. I went with a pretty high grade HIWIN bearing and was cussing that decision many times during the rail mounting process. Now that they are in I'm pretty happy with them though!

[InMesh]

I made my 2 meter one out of steel 60mm x 40mm standing up then welded a piece of 6mm angle to the top to give it thickness and found a wash grinder down the road who ground the angle in a pair within a thou or two over the entire length ,now I have the strength of the angle on the tube and a very flat surface .

[reefy86]

think this maybe my final design using 90x90 5mm thick mild steel box, 100mm x 10mm thick steel bracing around the outside with corner angles for extra support.

what do you think?

cheers

ash

[wizard]

nice sketch. I like the design except for one thing, that is the flat steel bar around the perimeter which will reduce access inside the frame. if you are like me that space would get used to store something. That is if I could get to it. In fact I might add shelving on the lower horizontal frame members.

[rowbare]

Your frame looks good but I am not sure that the flat strapping adds anything to the table beside weight and cost.

This build by Hayen from a few years back is quite well done and has inspired many others. It is a bolt together design. Examine his use of pins and epoxy. The pins keep things aligned during assembly and disassemby and the epoxy fills in the mating surfaces to ensure good contact and rigidity. http://www.cnczone.com/forums/cnc-wo...ilt-steel.html

This is a really nice big router build:
http://www.cnczone.com/forums/cnc-wo...ter-build.html

Yet another well done steel build. He put a lot of effort into mounting his rails accurately.
http://www.cnczone.com/forums/cnc-wo...gineering.html

bob