cnc router frame, steel or alu?

[LCY]

hello to all the pro-builder here

i need some advise, im planning to build a 2'x4'x8" router, able to machining pvc sheet range to some steel plate, my question is the frame rigidity, wat material should i use? please advise

[Master of nun]

Hi Mate,

Not that I'm a pro builder....or pro anything for that matter

I guess it all comes down to the steel plate you want to cut.
What thickness steel plate do you have in mind?
How many passes would you be happy cutting that thickness plate?

When you say Aluminium, are you refering to an extrusion like the 80/20 system?
If so, one thing the 80/20 system has goining for it is the ease of assemley if tools are limited, however it can get expensive on a larger machine.

I've only cut steel on a manually operated drill/mill, someone with router/ steel cutting experience should give you some further advise.

Liam.

[LCY]

hi and thanks for reply

the thickness like 1/2" but i really dont mind how many pass it will have to run, ofcourse i will be happier if it can do cut with lesser pass

the structure i will use steel flat bar 3/8" thick, plus angle at the join

i had google a lot and i see ppl dont mill steel with router, why? bcuz linear shaft not rigid as slide?

[LCY]

not finish yet but i think this will give u better idea wat im talking

[Master of nun]

1/2" steel plate is getting pretty serious for a router, Maybe you should do a few sketches or CAD drawings and post them for people to comment on.

I think 1/2" steel will need a Steel Router to answer the first question.


Liam.

[LCY]

i tot with more pass it will still do the job will it? ie mill away 1" of steel with thickness 1/2" with 50 pass, or may be 100 pass? im not a machinist i never mill any metal, my job is totally unrelated to machining, i have very limited knowledge.

[Master of nun]

Sorry to say this but, that does not look rigid enough to machine steel plate.
I would think a heavy wall RHS 100x 50x 6mm, rather than 3/8 flat bar.
The gantry will only be stiff in the longitudinal axis....side to side it will flex and allow for vibrations.

If you look at a milling machine for inspiration, They are very heavy to absorb vibration....you could fill the RHS with sand, this will absorb high frequency vibrations much better than 3/8 flat bar.


What is your budget for this router?
What do you intend to use for a spindle?


Liam.

[LCY]

budget like 2.5k usd for frame, balllscrew, and shaft only, (i found some taiwan ballscrew are really good price, still donno the quality yet) electronic will be gecko g540, stepper nema23 ,i hope it can handle this.. spindle might use some chinese onefor routing. for milling spindle i dont know yet. is 1hp enough for milling?

sorry for my bad english, im not english educated

[CarveOne]

Originally Posted by LCY hi and thanks for reply the thickness like 1/2" but i really dont mind how many pass it will have to run, ofcourse i will be happier if it can do cut with lesser pass the structure i will use steel flat bar 3/8" thick, plus angle at the join i had google a lot and i see ppl dont mill steel with router, why? bcuz linear shaft not rigid as slide?

Machining of steel is normally done with very heavy cast iron milling machines of the Bridgeport type knee mills due to the stresses involved. Rigidity is everything when it comes to getting a decent finish on steel. A wood router style machine can cut steel but it won't give good results due to chatter and resonances. It also has to take very shallow cut depths and maybe use what is known as "pecking" to cut it at all. A wood working router or spindle is the wrong device to be cutting steel. The bearings won't last very long and the RPMs are way too high.

You can probably find a used milling machine that will do a much better job for less than you can build one of these router machines and not be happy with the results or speed of completion. This type of wood router design is just not a good choice for milling steel for a lot of other reasons.

I have two milling machines and two wood routers. Buy the milling machine for steel and other metals. Build or buy a wood router for wood, and maybe light use on aluminum, but no hard metals. You'll be glad you did.

CarveOne

[Master of nun]

don't worry, you Engish is MUCH better than my Bengali!

I think you need to do some more research, Feedrate for steel is much lower than what you will require for PVC, so small Nema 23 steppers geared down for steel may burn pvc at slow feedrate.Also spindle speed for steel will be slower for steel than for PVC, You may be able to use a (cheaper) slower speed spindle for the steel and save some $$ even second hand from old milling machine.

You will need to think, will I use this router for 80% pvc, 20% steel.
or.... 20% steel, 80% PVC.....or 50% 50%



Another alternative is to find a large Mill and convert to CNC.


Liam

[Master of nun]

Thanks for that Carveone

LCY, You are really talking two different machines.

Infact in the time a router type machine will cut steel, you could have done it on a manually operated mill with much better results.

As for your budget, it's hard to put in to perspective....i'm sure your dollar goes much further for manufacturing in Bangladesh than in Australia or the US.

I have cut PVC on a mill, allthough not ideal....it works. You should be building a machine with steel in mind.....the key, MASS


Liam

[LCY]

thanks both of you this is really a good place to learn

i guess its clear now, i will get a used mill later, but for this router, i should able to mill alumium, right?

i got a plan if this router works, i will make a second machine which will cut acrylic with laser, will build the frame with aluminium, so i can save a bit more than the first machine