Steel frame for 8' * 4' cnc bed ?

[JAZZCNC]

Hi Ian,

Completely agree it's not neccesory to spend £800 to get the machine you want.

Regards your question of do they setup professional machines on site then yes they do and to a very high degree taking a great deal of time using very costly precision levels etc, also they are bolted to the floor more often than not on shock dampening feet.

Obviously good build quality is required but Setting up the machine while in situ is the key to an accurate machine, time taken here will make or break the machine.
The heavist machines built from quality cast iron still bend and twist requiring carefull leveling and setup so don't think for one second 80x80 is substantial and won't move or require setup.!. . . In real machine terms it's banna material.!!

Also regards Epoxy, Yes it will self level to a high degree but it still requires the machine to be fixed and levelled to high degree before application and will only be accurately level to that one spot.

Basicly what I'm saying is if you want good accurecy then Yes 80x80 will do what you want it to do and with good build quality and attention to detail will give the accurecy you require but the machine needs to be fixed down with adjustment built into the design.

If good strong design with carefull welding and attention to detail is used, mixed with very carefull setup then you will easily surpass the accurecy you desire without having to spend £800 on surfacing.

£800 would be far better spent on using quality components.!!

[JAZZCNC]

What sort of tolerances do you require as that it what determines if machining the rail surfaces perfectly parallel is necessary? You can compensate for it perfectly well in software.

Oh god here we go again.!!! . . . Don't talk soft you can compensate for un-parallel rails in software.!! . . . How.???

Jonathan I'm not wanting to get into a fight with you again but you are miss-leading folks and plan wrong by promoting software can compensate for poor build quality. . . . please stop it because it curdles my noodle. (And I'll always challenge just for the sake of newcomers.!)

[flanagaj]

Hi Ian,

Completely agree it's not neccesory to spend £800 to get the machine you want.

Regards your question of do they setup professional machines on site then yes they do and to a very high degree taking a great deal of time using very costly precision levels etc, also they are bolted to the floor more often than not on shock dampening feet.

Obviously good build quality is required but Setting up the machine while in situ is the key to an accurate machine, time taken here will make or break the machine.
The heavist machines built from quality cast iron still bend and twist requiring carefull leveling and setup so don't think for one second 80x80 is substantial and won't move or require setup.!. . . In real machine terms it's banna material.!!

Also regards Epoxy, Yes it will self level to a high degree but it still requires the machine to be fixed and levelled to high degree before application and will only be accurately level to that one spot.

Basicly what I'm saying is if you want good accurecy then Yes 80x80 will do what you want it to do and with good build quality and attention to detail will give the accurecy you require but the machine needs to be fixed down with adjustment built into the design.

If good strong design with carefull welding and attention to detail is used, mixed with very carefull setup then you will easily surpass the accurecy you desire without having to spend £800 on surfacing.

£800 would be far better spent on using quality components.!!

You have answered a fundamental question for me here. I always thought I could get away with having a meaty frame welded together, sent off to be milled and the linear rails attached to then come back to me on a lorry, into the workshop and straight to work without any further alignment required. You have basically told me that this is not possible, so I need to have a rethink.

I have read the MadVac web site on how he aligned his linear rails and it makes me weep as it seems such a laborious process that seems very hit and miss. I was hoping that I could just pay to have that part of the build done for me.

[Web Goblin]

Do you think that is over sized ?

No I dont think the material is oversized.
If you want a really sturdy machine then you cant really oversize the frame material, within reason I might add. Box section steel itself isnt really that strong unless you start going into heavy wall thickness stuff and as Jazzcnc has said getting your construction right to start with will make all the difference and would save you £800 on machining.

Ian

[Jonathan]

Oh god here we go again.!!! . . . Don't talk soft you can compensate for un-parallel rails in software.!! . . . How.???

In mach3 go to "Function Cfg's" then "Formulas". If you can measure the error (dial indicator etc) then it will be possible to work out a forumula to compensate, and eliminate it.

Of course it is better to get it right to start with, for obvious reasons, but if after doing all the things we suggest it turns out that there is a small error or, as is likely with a welded frame, it gradually moves, that's something you can do to compensate. Better than nothing.

Surprised Jazz didn't mention this as he has before ... but to damp resonance on a steel frame you can fill it with sand.

[JAZZCNC]

In mach3 go to "Function Cfg's" then "Formulas". If you can measure the error (dial indicator etc) then it will be possible to work out a forumula to compensate, and eliminate it.

So whats the formula to get Mach to stop loosen the rails eliminate binding and tighten back down.??? . . . Your talking tosh and again passing on missleading vaguely accurate impracticle information which just sends wrong signals to newcomers who only discover this far into the build when it's too late.!. . . . End result being they can become disspondent and give up.

Much more helpfull to give sound advice encouraging good accurate build quality than saying just build it and don't worrie because software will compensate for your shity work.!!
Software compensation and formulas etc are last ditch work arounds which never work correctly or has desired.!!. . . . .Effectively they are weak bodge's not to be encouraged IMO.

[Jonathan]

So whats the formula to get Mach to stop loosen the rails eliminate binding and tighten back down.??? . . . Your talking tosh and again

I think you're missing the point I'm making. I said in my last post that obviously it's better to get it right to start with and that software compensation helps if and only if it is a *small* error. I didn't think I needed to state that by small I don't mean binding or tight rails as you'd be foolish to try and run a machine like that for obvious reasons.

Software compensation and formulas etc are last ditch work around

Exactly ... which are better than nothing. If the machine is running smoothly then I see no reason not to use maths to improve it.

No matter how well you build the machine you will never get all axis perfectly true and perpendicular. The best you can get is the error being negligible compared to the tool deflection. If it's only just over negligible then the machine may well run smoothly and if so you can use the formulas to compensate.

Much more helpfull to give sound advice encouraging good accurate build quality than saying just build it and don't worrie because software will compensate

I thought I did say that in my previous posts ('it is better to get it right to start with') on this thread. If not I'll not bother.

[blackburn mark]

Oh god here we go again.!!! . . . Don't talk soft you can compensate for un-parallel rails in software.!! . . . How.???

In mach3 go to "Function Cfg's" then "Formulas". If you can measure the error (dial indicator etc) then it will be possible to work out a forumula to compensate, and eliminate it.

So whats the formula to get Mach to stop loosen the rails eliminate binding and tighten back down.???

i think you changed aurguments there jazz, its unfair of you to talk like your "THE MAN" when your not man enough to admit that you were unaware of mach's ability to compensate..... surly it would be better for you and the rest of us if you had said
"sh*t... how the hell do you do that?" then you me and all the uninitiated you keep going on about might learn some brand new shit

[JAZZCNC]

i think you changed aurguments there jazz, its unfair of you to talk like your "THE MAN" when your not man enough to admit that you were unaware of mach's ability to compensate..... surly it would be better for you and the rest of us if you had said
"sh*t... how the hell do you do that?" then you me and all the uninitiated you keep going on about might learn some brand new shit

No Mark I'm very much Man enough to admit when I don't know something or indeed I'm plain wrong. . which in this case don't feel I am. . . . I'm also very open to learning new shit, Which I do every day.!!
I also know very well about Mach's compensation features, also know they have very limited affect and difficult to impliment. Even Art fennerty Mach's designer agree's they are unrealiable and only to be used in case's or when all else fails and expect limited success.!!

Know I don't really give a flying F@#K what YOU, Jonathan or anybody else thinks about my comments. . . . I do care that people should be mindfull that newbie's will be reading and soaking up these missleading post's and it can and does cost people valuable time and money, even leading to discourageing them to try again when it doesn't perform as expected.

My comments are not in anyway personal to Jonathan, believe me I would be them same regardless who it was and will always challenge information I feel is wrong or missleading.

Not every one likes posting on forums, I know from experience helping those that have had the good sense or courage to ask for help that this is particularly true in both the young and older generations.
They sit back and prefer to skim post's soaking up information both good and bad like sponges, they latch onto anything that seems to fit the bill for there particular needs or requirements.
Comments inferring software can compensate for less than ideal build quality along with other urban cnc myth's like bigger, faster is better etc are latched onto and implimented into first time builds often with disasterous expensive results.

All I'm asking is that influential posters consider what they post and instead of trivialising the need for care while building and they promote and emphasise the advantage good build practice makes instead.!

Jonathan I'm Sorry if I've up set you and know your comments are ment with the best of intentions but I feel you really do need to be more mindfull new people will be reading your post's. A bit more explination and clarification of the short comings of some the suggestions would be more helpfull.

Now with that said I don't want this to escalate any further as it's distracting and not fair to the original posters thread.! . . . For this I do appologise to Justin because I was the one who jumped on Jonathan and started it all but please let's leave it here.!! . . . . . If you feel you must rebuff me then please feel free to PM me.!

[blackburn mark]

jazz, maybe in future "you" will be more mindful and PM the people that you want to tare a strip from... besides that i think we are all open to critisism if its unagressive and done without an air of superiority.

i also appologise Justin for my part in hijacking this thread.