[AndyL]

Hey folks,

Please don't take this as blasphemy... or come after me with (chair)

Looking for a tool recommendation, building a fairly typical moving gantry router. Construction is HSS steel (channel and tube). Mostly will be using it for thermoplastics and acrylic. As such, planning to use a rotozip style tool for its 'regular' cutting.

However, I know I'm going to throw some steel plate (1/2" x 6" flatbar usually) at it a few times a month - to cut simple bearing plates and adapters.

Could you guys recommend a more appropriate cutting tool for this type of work? I don't mind building another tool holder to swap tools. Ideally I'd like to be able to dry-cut if possible, but I'm pretty sure I could retrofit a liquid cooling system in relatively easily if needed...

Thoughts / recommendations?

Thanks in advance,

Andy

[dertsap]

how heavy of a router are you building in order to cut steel ? rigidity is a definite must , at the speeds a rotozip runs(20000 -30000rpm ) i couldn t even begin suggesting endmills , those speeds will kill any hss , you definitely need carbibe
on our horizontal for example i am running a job doing pocketing with a 1/2 carb ballnose and a 1/4 carb ballnose at 9500rpm feeding at 110 imp and 99imp on structural steel ,and i wouldn t push it much faster ,or without the heavy flood coolant ,
you may be ok with some coated carb endmills light cuts , heavey feed with a heavy airblast , or your tools will no doubt suffer rapidly from thermal breakdown especially if you try to flood the tool

[joecnc1234]

I ran a $500,000 5 axis router cutting aluminium hydroform dies the chances of cutting steel 0......

[AndyL]

Now call me nuts - but using the correct tool (spindle, drive, whatever you prefer to call it) + the correct bit... One would be able to cut steel no?

Why I'm asking about tools and bits... I realize a rotozip is unlikely to be able to cut steel, but being barely beyond design phase - it's easy to add another tool mount to the design.

[dertsap]

if your using linear rails you should be able to make something rigid enough , a larger scale router with some decent torque and adjustable speed it may be possible , but you will still need to be taking light cuts
i just picked up a router that can go as low as 8500 rpm which is slow enough not to burn out tool if a guy goes about it properly , i can t see it not working if you make a good setup , but if your planning on doing any hogging i'd say forget about it

[AndyL]

Routers actually small - cutting area will only be 12x12, built out of 3" x 1/4" channel. Dual 1" acme's on the x and y (had it lying around...) Still working out Z - partly depends on tool(s). Haven't gone with linear rails - modified version of the skate bearing & angle

Which router did you find that would go down to 8500?

[dertsap]

Which router did you find that would go down to 8500?

some china dealey

[in2steam]

Hey folks,


Looking for a tool recommendation, building a fairly typical moving gantry router. Construction is HSS steel (channel and tube). Mostly will be using it for thermoplastics and acrylic. As such, planning to use a rotozip style tool for its 'regular' cutting.

Andy

HSS(high speed steel) thats rather expensive(does it come in tube form?) to building a machine with, I just use it for my tool bits I would consider using a-36 tubing. You will find that anything more then .002 , and you will flex your gantry unless its several inches think, I would either consider another different design or another machine.

chris

[AndyL]

Hollow Structural Section... Chances are if you look around a commercial building you'll see a lot of it used - it is your basic structural steel you may alternatively know it as c-channel, i-beams, angle iron, as well as tubing.

I'd have to sit down to work the math - but in the current design, the bearings should fail long before the gantry flexes. But thanks for your thoughtful reply.

[joecnc1234]

have you ever seen a milling machine before?
ground hardened ways with Meehanite castings at the low end. You think Hollow Structural Section is not going to flex when you put a load on it, now there is a load.

[dertsap]

funny hss normally has a whole other meaning within these forums ,

concidering the stuff is made to hold up concrete buildings and such
how anyone can assume flex is well beyond me , which brings me to question if you ever worked on a milling machine ? ive used a fair amount of structural steel and such to make fixtures in order to to cut large steel parts , and flex or vibration was not an issue
i can take a die grinder and put in a 1/4" endmill and cut weld preps or what have you on steel , its not a magical material , a guy just needs common sense thats all
i would strongly suggest moving away from the skate bearing idea and going with linear rails , for that small of a system they should be cheap enough even if you do ebay

there are a lot of good guys in the forums who will post to help you out to create a good design ,don t get discouraged ,JUST MAKE IT WORK

[AndyL]

Yeah, HSS has various meanings - I'm in construction, I deal with both HSS daily and can use both terms in the same sentence without thought; generally assume others do also. Possibly my fault on that; tho I did mention channel and tube in the original post...

We've got a desktop mill at work; don't find much use for it myself other than the occasional need for very precise drilling. The rest of the time - I've always found it easier/faster to freehand my work (grinder/drill press). However there's a few projects coming up I'm thinking I'd like a more professional/clean look.

Design itself has been designed in consult with a mechanical engineer - discussing deflection with him at lunch (and his reviewing this thread) - to get that .002 deflection on the gantry (haven't mentioned it but it is a pair of 3" channels ~5" apart) would require roughly 8200lbs of force, the bit would shear long before reaching anywhere near that load.

Skate bearing type (not actually using skate bearings - my shop is millwright in nature - i've got lots on the shelf to pick from) we still think would work nicely, also leaves the top of the frame open for mounting of the X axis screws - keeping the slop to a minimum.

[dertsap]

to get that .002 deflection on the gantry (haven't mentioned it but it is a pair of 3" channels ~5" apart) would require roughly 8200lbs of force, the bit would shear long before reaching anywhere near that load.

- my shop is millwright in nature - .

i agree you could probably run it over with your truck and do more damage to the truck than that size of channel

easy to assume skate bearings around here they're quite popular

sounds like youve got all the right resources
how do you plan to design the rails ? round bar ?

[AndyL]

Excuse the poor rendering - still learning this magic cad/cam stuff (Never saw the point until this past year - pretty pictures on a computer didn't do me much good in the workshop; never even tried to learn... Having a way to spit that out is enough encouragement to learn).

2x2 angle for the slides is the plan, angle has 1/4" plate welded to the open side, mounts to the side rails w/ 5/16 bolts at 3" O/C. Base is pretty well done at the moment; gantry design is up in the air till I sort out how to power cutting on steel.

I think a truck would do pretty good number on it...

[in2steam]

Hollow Structural Section... Chances are if you look around a commercial building you'll see a lot of it used - it is your basic structural steel you may alternatively know it as c-channel, i-beams, angle iron, as well as tubing.

I'd have to sit down to work the math - but in the current design, the bearings should fail long before the gantry flexes. But thanks for your thoughtful reply.

I was doing that more in jest then anything else, although to say that buildings don't flex would be in error, are not most buildings desgined to sway? At any rate just be careful welding, introducting to much stress onto the frame may cause you untold problems even for a small machine as you are looking to build, H.S.S. esp in the tube form is DOM (drawn over mandral) welded and has its own built in stresses, I am sure you have cut a piece of seam welded material, it springs apart some. You would be best off not weld all that much and when done send it out to get stress relieved. I would cut the frames with a process that uses/creates the least amount of heat, preferably water jet of cold saw. Just some thoughts.
chris

[AndyL]

Yep, all steel flexes, all buildings flex.

There's a big difference between a 20'- 60' span and an 18" span though. The loads to acheive any substantial flex across 18" are insanely high in comparison.

Other than the tabs (for mounting) on the backside of the 2x2 for the X slides - haven't found any other place where welding is needed. Machines been designed as bolt together.