CNC ROUTER TABLE FLATNESS

[Bravin Neff]

You have a machine shop that can fit the entire machine in, after welding and true the top rails and the bed? A $100 shop rate is cheap, don't forget the setup time is going to be billed out also. Post the name of that shop maybe others would use it?

How is this machine going to mill or grind the table of a welded up frame, where the rails are 10 inches or more above the table?

A boring mill is *designed* to do work like this. Ask me how I know (I grew up running them). That machine you've linkied to has 60" of Y. Plus whatever table it has. There are tons of these old machines around, smaller and *far* larger. As I said in my original post, it would take a couple of hours including setup. I live in the Detroit area. There are tons of high tech CNC machine shops, but this is *not high tech*, this is decades old tech. This is the 60 year old crusty guy that never graduated to CNC but it doesn't matter because he only ever does one offs. They are still around. Try Hawk Tool (Wixom), or Three M (Commerce). Stapels Manufacturing (Troy) has a couple boring mills. Central Gear in Madison Heights has a couple boring mills. And a floor mill that will do a machine base 5 times larger than the one in this thread. These are all within a 10 mile radius. Probably a dozen more I'm forgetting.

[Bravin Neff]

Oakland Machine (Pontiac). Hallmark Tool (Wixom). The other Three M (Wixom) has (4) huge G&L floor mills.

[Bravin Neff]

I didn't look closely at your rendering, but it looked like just flat surfaces, maybe some edges for the rails, drill and tap some holes. If that's the case, a boring mill is the way to go. And a good devlieg is the Cadillac of boring mills. It will be as flat as anything modern. I'm dead serious about that. I work with and sell the best machine tools on planet Earth (Okuma), including the huge $4 million bridge mills like seen above. They are fantastic for a bajillion reasons and will command a very high shop rate, but they are *barely* more accurate than a good devlieg.

But don't just shop for a devlieg, any good boring mill will do it if the guy is good.

[wmgeorge]

I would be nice for others reading if you guys listed the State your in? I think one is Michigan? Heck I go there a couple times a year and if I needed grinding I could drop it off and pick up on the way back. Nothing like that in Iowa for sure. Thanks guys.

[routalot]

I had an email telling me this thread had been updated and having clicked on the link I wondered if I had been taken to the Practical Machinist forum.I don't know if there is an offer to pay shipping from England to any of these amazing shops of if the enquirer would be willing to be parted from his part built machine for that length of time.

We also don't know what type of work the machine is intended to carry out and what level of dimensional accuracy is needed.I have had conversations over the years about accuracy with all sorts of people.What I always ask them is "If you find your fence has been demolished by a falling tree,how accurately do you need it's replacement to be built?".I explain that the technology exists to replace the posts to a few thousandths of an inch or they could just use a length of string and a tape rule.The high accuracy approach will cost much more quite obviously and there might be a sense of pride in achieving such accuracy,but the fence won't work any better for it's intended purpose.

[mactec54]

I had an email telling me this thread had been updated and having clicked on the link I wondered if I had been taken to the Practical Machinist forum.I don't know if there is an offer to pay shipping from England to any of these amazing shops of if the enquirer would be willing to be parted from his part built machine for that length of time.

We also don't know what type of work the machine is intended to carry out and what level of dimensional accuracy is needed.I have had conversations over the years about accuracy with all sorts of people.What I always ask them is "If you find your fence has been demolished by a falling tree,how accurately do you need it's replacement to be built?".I explain that the technology exists to replace the posts to a few thousandths of an inch or they could just use a length of string and a tape rule.The high accuracy approach will cost much more quite obviously and there might be a sense of pride in achieving such accuracy,but the fence won't work any better for it's intended purpose.

These same machines are all over the UK and in most countries so you should not have a problem in finding them the UK was the birth place of big machines like this

Again you have no concept of what is required, it is nothing to do with accuracy as I said before, It's a requirement if you choose to use Linear Rails They need a flat machined surface to be mounted on

[Ntl]

Agreed you have to have a flat surface or you will be fighting all kinds of problems. Take it from someone that has been dealing with the effect of buying a table that has linear rails mounted to a non machined surface.

In my opinion you have a few options:

Jig it up weld it up and have it machined.

Don't use linear rails if the machine frame is welded steel.

Or you could do a hybrid style table like the shopbot, where it's a steel frame with aluminum extrusion, or a full extrusion machine.

That's my personal opinion and if it's not a huge machine, I would just build it out of heavy extrusion that can be easily machined prior to assembly. Doing it that way you can get everything to line up perfectly and not deal with binding and worn out mechanical parts.

Dan

[hughes674]

Ok

Having had a few days to digest all the advice given it appears that there are only a couple of people that have actually read the original question. I am fully aware that having the frame machined is the best solution but this doesn't illuminate other potential issues that have been pointed out. Eg (Stress relief, Competence of machinist. ETC). It would be easy just to get the table heat treated then ground but unless there is a means of checking the end result we are back to the original question and we haven't got a clue exactly what tolerance our machine bed is. The point of finding a method to mount rails precisely would illuminate this and take away any guess work of exactly how accurate our machines are.
If having the bed and rail mounts ground is the only way, how do we check the accuracy of the work carried out costing $000,s. Or do we just say it's accurate to 0.05mm because the guy that ground it said it was.

Cheers
Mick

[Ntl]

I don't understand the question then. The rail mounting method is easy to find from the manufacturer of the rails you are using. As for the tolerance, you would need the shop to show you when you pick it up that they meet your specs. If it doesn't and you supplied the shop with drawings, then you have them fix it or don't pay.

With your last question, I think you may want to just buy a premade router from a reputable company. You might be getting into to big of a project for the tools you have. You more than likely will find it's more cost effective to just buy one anyway unless you have a big budget and are doing it for fun. You need to decide if you want the machine to be your project or the parts you cut with the machine. I've seen guys on here with router's they started building 15years ago that still aren't cutting anything.

Just my opinion don't take any offense by it.

Dan

[wmgeorge]

What Dan said above /\ . What is the intended purpose of your router? Is if for wood, if so you need to understand what you mill or rout today can and will change the next time the temperature or humidity changes. If your not understanding that then you need to forget a CNC wood router.

[mactec54]

Ok

Having had a few days to digest all the advice given it appears that there are only a couple of people that have actually read the original question. I am fully aware that having the frame machined is the best solution but this doesn't illuminate other potential issues that have been pointed out. Eg (Stress relief, Competence of machinist. ETC). It would be easy just to get the table heat treated then ground but unless there is a means of checking the end result we are back to the original question and we haven't got a clue exactly what tolerance our machine bed is. The point of finding a method to mount rails precisely would illuminate this and take away any guess work of exactly how accurate our machines are.
If having the bed and rail mounts ground is the only way, how do we check the accuracy of the work carried out costing $000,s. Or do we just say it's accurate to 0.05mm because the guy that ground it said it was.

Cheers
Mick

Most of the large machine shops that do this work can check the surface on the machine, as for stress reliving these same shops do that before the machining, any machinist that runs a big machine like this is competent, machine beds are normally with in .0005" or better

It is easy to check how the surfaces are using test indicators, if you have a shoulder machined for the Linear rail register you can then mount a rail and with ( 1 ) bearing carriage mounted on the rail with the indicator mounted run it along the whole axes checking the machined surface, most I have seen are within .001" in 12 feet if that is not good enough then you would have to hand scrape the surface

[stepanova80]

wmgeorge, Thanks for sharing video. I will share my product which is made by routertable. and jono5axe, Thanks for this information. What was the actual cost? Can you share the numbers?

[Goemon]

I wrestled with this for a while but mainly because I either wasn't capable (or could not afford) to follow the best advice for achieving the hyper precision that people were talking about. In the end, I found that the best option I could afford was to mount my rails on used NSK and THK actuator bases.

I just bought a bunch of used actuators and replaced the old worn out 25mm rails with the ones I bought for the job. I figured that there was no way I would ever achieve comparable flatness, squareness or parallelism to what those NSK guys can do. With a little patience, they can be found for very little money (even super long ones).

I now have precision actuators with 25mm square rails and ground C3 ball screws on all axis. And... most premade actuator bases come with pre-drilled and threaded mounting holes which is a huge time and error saver.

For the machine base and gantry face, I used (and had good results with) epoxy leveling. I use epoxy every day in my day job though so I know how to do it right. It's certainly not an easy process and It's no surprise that others had issues. Choosing the right resin and following the correct process is key. Anyone expecting to simply pour resin over a table and wait will find themselves disappointed.

Anyway, before spending weeks and tons of cash on making new parts, it might be worth taking a look at what is available used near where you live. There are tons of options for precision flat surfaces including (but not limited to) old machine bases, granite surface plates, old coordinate measuring machines, granite inspection tables, old industrial milling tables, machine tables, precision welding tables etc. I have seen precision flat granite tables up to 12 foot x 8 foot...

[wmgeorge]

Flatness is one thing, cutting square is another. Flatness, I used a 6 ft level and leveled my machine both X and Y directions, yes I reversed the level to make sure. Flatness as cutting a board flat, the Same thickness? Use your spoil board cutter and set your router or spindle up to finish your spoil board. Its the same height from one end to the other, making it flat or on the same plane with your gantry. Is that not all you need to do?

You end up with a board or whatever the same thickness and I do it all the time. Think about it.

Why do you need to surface grind the table, its not a milling machine, its a router.

Added: Since you have a spindle mounted and running, why not just mill your table flat instead of the spoil board? Use a 1/2 carbide end mill for steel, zero it out on the lowest part of your table, take sensible light cuts and just surface it level or actually on the same plane as your gantry?

Use some common sense and don't try to take off or true a table thats .250 or 6 mm off!!


Cutting square is another issue.

[mactec54]

Flatness is one thing, cutting square is another. Flatness, I used a 6 ft level and leveled my machine both X and Y directions, yes I reversed the level to make sure. Flatness as cutting a board flat, the Same thickness? Use your spoil board cutter and set your router or spindle up to finish your spoil board. Its the same height from one end to the other, making it flat or on the same plane with your gantry. Is that not all you need to do?

You end up with a board or whatever the same thickness and I do it all the time. Think about it.

Why do you need to surface grind the table, its not a milling machine, its a router.

Added: Since you have a spindle mounted and running, why not just mill your table flat instead of the spoil board? Use a 1/2 carbide end mill for steel, zero it out on the lowest part of your table, take sensible light cuts and just surface it level or actually on the same plane as your gantry?

Use some common sense and don't try to take off or true a table thats .250 or 6 mm off!!


Cutting square is another issue.

I suggest that you do think about it

There are people that build machines that would say other wise

The regular Router spindle could not run a 1/2" end mill milling steel, all it would do is make a big mess as many have found out

What you posted does not correct how the machine is going to cut, the Gantry has to be parallel in both planes to the table then the Spindle has to be tramed to the table after the Gantry is aligned to the Table, it will never cut correctly if not, you can not correct it by just cutting the spoil board, or cutting the Table, it's all about the Gantry and the Spindle being aligned with the table

So if you where able to machine the table frame with the Gantry and spindle not aligned and tramed, then you would have a messed up table

[wmgeorge]

Really? My router cuts true and flat, I am wanting to hear from others who know. PS Its never been heat treated and ground with a surface grinder....... just as it came from FLA.

Yes my Z carriage and spindle was Trammed with a dial indicator in all directions,

[mactec54]

Really? My router cuts true and flat, I am wanting to hear from others who know. PS Its never been heat treated and ground with a surface grinder....... just as it came from FLA.

Yes my Z carriage and spindle was Trammed with a dial indicator in all directions,

Nobody needs to heat treat and Grind /machine the table if it is built right and has no twist in the frame the table will be fine

It's not only the Zaxes and Spindle that needs to be true to the Table the Gantry has to be also, if the Gantry is not parallel in X and Y plane and you Tram the Z axes and spindle it will not cut true and flat as you say, if the Gantry is not on the same Plane as the Table, you may have got lucky with your machine others have not been so lucky