[dikymon]

I'm in the planning and design phase of my first build and trying to do as much as possible myself. I am hoping to have a

machine with (slow) steel milling capability.
At the moment i am trying to figure out how to level the linear rails. I have read about people having moderate success

using self-leveling epoxy and others scraping epoxy flat using piano wire as a guide. But none being completely happy with

it.

So i had this idea of
(1) Use a hard but compressible material as a shim beneath the rail.

Attachment 213246

(2) Level (aided by a machinist spirit level) the rail using the mounting bolts to compress the shims.
(3) Pour epoxy to seat the rail in place.

Attachment 213248


Would this approach be feasible? Do you see any benefit over other epoxy leveling methods? Have others tried this method?

[wizard]

Assuming you buy epoxy suitable for leveling it should well set up level. Level being normal to the gravity vector at your location. Level isn't exactly flat which might matter on a really big machine. I suspect that the bigger problem with epoxy is that it is a bit on the soft side.

I'm in the planning and design phase of my first build and trying to do as much as possible myself. I am hoping to have a

DIY is what it is all about here.

machine with (slow) steel milling capability.

For this to even be remotely feasible you need to pay close attention to mass and stiffness. Some seem to think they are one in the same, this really isn't so. I'd might suggest that doing steel might be seen as a waste of time on most router designs.

At the moment i am trying to figure out how to level the linear rails. I have read about people having moderate success

using self-leveling epoxy and others scraping epoxy flat using piano wire as a guide. But none being completely happy with

it.

Explain this unhappiness? It is hard to respond without specifics. Maybe somebody screwed up. Maybe the design had weakness elsewhere. It is hard to have a discussion without more specifics.

So i had this idea of
(1) Use a hard but compressible material as a shim beneath the rail.
(2) Level (aided by a machinist spirit level) the rail using the mounting bolts to compress the shims.
(3) Pour epoxy to seat the rail in place.

I've never tried anything like that but I'm almost certain that it is a bad idea. Here are a couple of reasons that pop into my head.
1. Compressible material will compress more around the screws giving you a wavy rail.
2. If it is compressible now what would stop it from compressing more with time and load?
3. What good would the epoxy be if the rail is sitting upon a compressible material?
4. Being successful with round or profile rails depends upon this rails being mounted to a flat surface to begin with.

Would this approach be feasible? Do you see any benefit over other epoxy leveling methods? Have others tried this method?

I see only grief with this approach. Why not use epoxy to level in the normal way? Epoxy leveling does work to an extent.

Your other option is to enlist a machine shop to flatten the rail mounting surfaces. I assuming you are building up a frame here out of welded up steel sections and because of your interest in steel that this is a smaller machine. As such you may be able to mount your frame on a mill and have the rail mounting surfaces milled flat and in the same plane. Yes I know this is an additional expense but each step up in material machining difficulty requires that the machine be built to a higher standard of performance. What is suitable for routing wood signs would be useless for any significant amount of steel milling.

By the way what spindle are you going to use for this steel milling?

[louieatienza]

You cannot level the rail that way because the rail may not necessarily be straight. They're designed for at least one rail to be held flat and straight against a machined ledge. On commercial machines, blocking or bolts or such are used opposite the ledge to hold that rail tight and straight.

[dikymon]

Assuming you buy epoxy suitable for leveling it should well set up level. Level being normal to the gravity vector at your location. Level isn't exactly flat which might matter on a really big machine. I suspect that the bigger problem with epoxy is that it is a bit on the soft side.

The machine i have in mind is somewhat abnormal due to noise and space restrictions.

For this to even be remotely feasible you need to pay close attention to mass and stiffness. Some seem to think they are one in the same, this really isn't so. I'd might suggest that doing steel might be seen as a waste of time on most router designs.

Explain this unhappiness? It is hard to respond without specifics. Maybe somebody screwed up. Maybe the design had weakness elsewhere. It is hard to have a discussion without more specifics.

Steel is much, much cheaper compared to aluminium where i live. It's harder to machine and prone to warping i know, but my hope was to avoid some of these issues by bolting the structure together.

I may be wrong but the general impression i get from reading is that leveling epoxy does not set close to its theoretical "curvature of the earth".

I've never tried anything like that but I'm almost certain that it is a bad idea. Here are a couple of reasons that pop into my head.
1. Compressible material will compress more around the screws giving you a wavy rail.
2. If it is compressible now what would stop it from compressing more with time and load?
3. What good would the epoxy be if the rail is sitting upon a compressible material?
4. Being successful with round or profile rails depends upon this rails being mounted to a flat surface to begin with.

The thought was that once the rails were leveled, pouring epoxy would set it in place and thereby making the shims "obsolete". But if epoxy is "soft" then ofcourse this approach would not work.

I see only grief with this approach. Why not use epoxy to level in the normal way? Epoxy leveling does work to an extent.

Your other option is to enlist a machine shop to flatten the rail mounting surfaces. I assuming you are building up a frame here out of welded up steel sections and because of your interest in steel that this is a smaller machine. As such you may be able to mount your frame on a mill and have the rail mounting surfaces milled flat and in the same plane. Yes I know this is an additional expense but each step up in material machining difficulty requires that the machine be built to a higher standard of performance. What is suitable for routing wood signs would be useless for any significant amount of steel milling.

Machinists readily charge 100$ per hour where I live, so I'd rather try avoiding that option.

I am playing with a somewhat alternative idea; A box made from thick (12mm / ½inch) sheet metal bolted to a epoxy granite base. I have very little space and trying to maximize utilization which is why i am exploring other options.

Attachment 213682

By the way what spindle are you going to use for this steel milling?

I was thinking a chineese 2.2kw with a Hitachi VFD

[wizard]

With respect to those Chinese spindles most of them have little torque in the low end. Often the low end is way to fast also for machining steel. Unless of course you are doing engraving type work with very small cutters, the Chinese spindle probably won't make you happy.

If you want to avoid a machine shop get a largish piece of tubing and hand scrape it flat if it is really bad. I'd rather see you bolt your rails to a flat surface rather than try shimming a linear rail. By the way yes scraping is a lot of hard work but it can get you there if the tubing is fairly decent to begin with. In the end though I really think being stingy with a machine build is a bad idea, if a shop charges you a couple of hundred to give you flat mounting points for linear rails it will be money well spent.

As for a bolt together structure I have nothing against that but the nature of the material may lead you to having to weld some components. One consideration with aluminum is that you can recast aluminum fairly easy into the parts that you need. You may still need to do a lot of hand scrapping work afterward but cast parts in conjunction with steel tubing might be economical. Someplace on the web a guy has a site demoing just this approach. That is using a combo of castings and tubing to realize a router. This might be a way for you to get around the welding issues.

There is a series of books by a guy names Gingery that details building a machine shop from scrap. You don't want a machine shop but the info on casting and and scraping may be useful to you.

In any event I'm just trying to offer up ideas that might get you to where you want to be. If you want a machine to do precision work you have to have everything built right to begin with.