Steel frame cnc router design/build

[kingcreaky]

Chaps - i'm dithering about with the gantry quite a bit...can't come up with an approach that i'm happy with yet.

chaps, im going to stick my neck out here, and before I even say anything Ive only made one machine... but what I do have in common with CraftyGeek is I am also DIY, so this was my gantry approach, slate it if you will, its not perfect but it was all done by hand with pillar drill hand punch and ruler.

[JAZZCNC]

Firstly - do I need to be concerned about weight. ie, am I ok using steel box or is this something that I may regret later?

No but within reason, weight is your friend when cutting has it allows deeper depths of cut, obviously there's a limit and it affects other areas of machine like motors, drives, screws etc if you go too heavy. Stay within 80Kg and you'll be ok with steppers.!!. . . Heavier than this and you'll be into servo territory.

Secondly - Jazz, the mock up design that you posted earlier in this thread - the gantry on that has 2 lengths of steel box attaching to vertical end pieces. I assume this would have to be a weld - my concern here is alignment & the lack of adjustment. Is there another way of going about it?

Doesn't really matter because all the adjustment is taken care of thru the rail mounting and were gantry sits on X axis bearings. . . The only requirement is that it's not twisted.

There are several ways to do different and I just drew this quickly to give an idea of easy and strong which go with single screw.
Really how you go about it depends on the job in hand, like in creakys case it was simple but would only really be suitable or woodwork type cutting any harder material like aluminium or if higher accuracy say for fine engraving, by that I mean in brass or Aluminium, PCB's etc where required then this is when weaknesses show thru quickly. . . . Resonance and vibration being the enemy has hollow aluminium box isn't stiff enough.! . . . It's also only works with twin screws and with single screw wouldn't be very good at all.!!

Your problem or complexity/weakness comes from using single screw.!!

[JoeHarris]

Yes there's a 10mm thick plate with holes tapped it.The holes in legs are drilled oversize for clearance. The 10mm plate is tacked in place to hold.

The main bed frame is heavy so there's 4 lead screws (2 each side) to help lift up and down and roughly get into position. Then there's 8 angle plates(4 each side) fastened to bed frame with 2 holes in each so 16 Bolts total that bolt into uprights with 10mm tapped plates inside.
It's simple and easy thou to be honest it's not something you do very often has usually you'll settle on a position that allows 90% of what you want to do.!. . . . It's just nice having the flexibility to do oversize things when needed.

Cheers. What thread are those then? I think I read somewhere that you favour m5 due to number of threads but they look bigger? What do you tend to use for plated connections?

[reason I ask is my 4.2mm bit is knakered and I'm looking at replacing it with a taper bit as my chuck is not the best... If m5 is not the way to go I may not bother just now..

Joe

[JoeHarris]

Your problem or complexity/weakness comes from using single screw.!!

Get onto old Chai he'll sort you out with an extra screw for a bargain price and you won't look back!

[JAZZCNC]

Cheers. What thread are those then? I think I read somewhere that you favour m5 due to number of threads but they look bigger? What do you tend to use for plated connections?

[reason I ask is my 4.2mm bit is knakered and I'm looking at replacing it with a taper bit as my chuck is not the best... If m5 is not the way to go I may not bother just now..

Joe

They are M10 Joe. I only use M5 for linear rails where they tap direct to steel box. Most other stuff like Z axis then M6 or M8 depending on plate size.

Wouldn't use a taper drill for threads there not accurate enough really, Ok for general holes.

[CraftyGeek]

On the x-axis I am going to use 2 leadscrews with a single motor.

Ok - i'll draw up a revamped steel gantry...I have a slightly revised approach in mind now...i'll be back with a design for you to tut at later :-p

[JoeHarris]

They are M10 Joe. I only use M5 for linear rails where they tap direct to steel box. Most other stuff like Z axis then M6 or M8 depending on plate size.

Wouldn't use a taper drill for threads there not accurate enough really, Ok for general holes.

Thanks Jazz, What about where you are joining the various sections of the steel frame together? I am going to be tapping directly into 3mm wall steel for most of my connections...

[CraftyGeek]

Ok - I have a gantry drawn up now that i'm feeling much happier about.

Weight as it stands currently is approx 28.5kg...obviously z-axis & spindle etc still need to go on.

Motor mount shown is rough & a guide only.
Leadscrew is guide only.

Teal parts: 75 x 50 x 3 steel box
Green parts: 60 x 5 steel flat bar
Bearing mounts: 15mm ecocast
Front vertical plate: 5mm aluminium plate
End braces: 15mm aluminium plate
Rails are mounted on 50 x 10 aluminium flat bar

Hopefully this is a decent blend of strength, precision/alignment & weight.

Bracing for impact...thoughts?

[jcb121]

here's another idea for the ganrty, a bit more expensive solution though as the sides need to be machined/watercut.

Attachment 9513
Attachment 9514
Attachment 9515

so 20mm alu plate reinforced with solid 25mm square bar. 20mm plate all around.

to attach the ballscrew nut, you'll need some sort of hanger or place the ballscrew on top of the linear rails and make it go through the gantry 20mm plate :D

saves material and very elegant .

all criticisms welcomed / encouraged!



what software are you using? it looks interesting.

[CraftyGeek]

Interesting approach - but I think it'll work out a lot more more expensive than the current draft above. As it stands above its about £78 material cost...I can't see that aluminium version being in double figures.