Steel frame cnc router design/build

Quote:

---

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.

Attachment 9497Attachment 9498Attachment 9499Attachment 9500Attachment 9501Attachment 9502

Quote:

---

Originally Posted by CraftyGeek

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.

Quote:

---

Originally Posted by CraftyGeek

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.!!

Quote:

---

Originally Posted by JAZZCNC

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

Quote:

---

Originally Posted by JAZZCNC

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!

Quote:

---

Originally Posted by JoeHarris

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.

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

Quote:

---

Originally Posted by JAZZCNC

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...

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.:concern:

Bracing for impact...thoughts?

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.

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.

Bumpety bump for my gantry design above...any thoughts?

Quote:

---

Originally Posted by CraftyGeek

Bumpety bump for my gantry design above...any thoughts?

---

Erm.!! . . . It's ok but there's not much holding or supporting that top rail piece. 5mm Ali has no strength in it so your gaining nothing from that really and the Steel plate doesn't add any strength.
The triangle piece on the X axis is about the only thing supporting it and that's not enough it will flex under cutting and transfer to finish quality.
At the very minimum I'd have 2 triangle pieces at each side, really i'd make the gantry sides wider and tie the end of both rails into sides has well as double triangles on each side.

On a plus note you could drop those pieces between the rails and steel has you can drill & tap the steel directly. You only really need those when using Alu profile.

Beef the holding of the cross rails and it will be ok.

Quote:

---

Originally Posted by JoeHarris

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...

---

Joe I've drilled holes just less than dia of M12 nuts so tight fit then knocked the nuts into holes just below surface with bolt in threads to protect then weld in place then grind welds flush.

Edit: That was for in middle of sections. At the ends were I could reach I just drilled M12 hole for bolt put nut on inside and welded from inside.

Quote:

---

Originally Posted by JAZZCNC

Joe I've drilled holes just less than dia of M12 nuts so tight fit then knocked the nuts into holes just below surface with bolt in threads to protect then weld in place then grind welds flush.

Edit: That was for in middle of sections. At the ends were I could reach I just drilled M12 hole for bolt put nut on inside and welded from inside.

---

Little more involved than I was Intending but I guess m6 with only 3threads engaged is a bit measly when I think about it! Are those bolts in your photos earlier on this thread m12 then? They look smaller somehow.

On the x axis RHS presumably you don't weld bolts in place - what do you do there? Hope you don't mind giving away all the trade secrets!!

Cheers
Joe

Quote:

---

Originally Posted by JoeHarris

Are those bolts in your photos earlier on this thread m12 then? They look smaller somehow.

On the x axis RHS presumably you don't weld bolts in place - what do you do there? Hope you don't mind giving away all the trade secrets!!

Cheers
Joe

---

Actually they could be M10, I've forgot now but I've still got one frame part built so can check.!!

To be honest Joe I could have saved loads of time and made things easier by just using large hole cutter creating access holes on out side of frame for access with a Socket and bolting together, I just think it looks neater. In your case it may be better to take this route and put rubber grommets in the access holes.

Regards top rails then yes I welded the middle nuts but could have easily done the same thing here. I wasn't concerned if the top rail distorted because I epoxy level the top rails anyway.

Quote:

---

Joe I've drilled holes just less than dia of M12 nuts so tight fit then knocked the nuts into holes just below surface with bolt in threads to protect then weld in place then grind welds flush.

---

I've got M12 bolts in 3mm box steel holding bearing blocks in place and never moved?

Quote:

---

Originally Posted by Swarfing

I've got M12 bolts in 3mm box steel holding bearing blocks in place and never moved?

---

You Lucky bugger it wouldn't work for me that's for sure it'd strip for sure guaranteed. .:disgust:

Loctited in position and no real forces so fine for my application :whistle:

Quote:

---

Originally Posted by Swarfing

Loctited in position and no real forces so fine for my application :whistle:

---

Should have known.!! . . . Parcel tape and chewing gum. .:joker:

Jazz my ex misses is on the prowl in wakefield tonight so bang one of your 16mm ballnuts in for me and tell her the backlash is way toooooo sloppy will ya :triumphant:

Quote:

---

Originally Posted by Swarfing

Jazz my ex misses is on the prowl in wakefield tonight so bang one of your 16mm ballnuts in for me and tell her the backlash is way toooooo sloppy will ya :triumphant:

---

Listen mate been there done all that (well not done her. . Lol) Honestly she's not even worth the words your typing.!!

LOL! why do you think i left her for a CNC machine?

Tighter ballnuts and no backlash? G.

Thats the ticket Geoff :thumsup:

Quote:

---

Originally Posted by JAZZCNC

Should have known.!! . . . Parcel tape and chewing gum. .:joker:

---

Haha cheers guys! Trade secrets eh?!

Ok - V2...

Inner end pieces are 15mm plate
Outer end plates are 20mm
bearing blocks also beefed to 20mm
Front plate is still 5mm - more to keep crap away from the leadscrew than perform a major structural role...although should help with twist & sideways flex.
Rear stell plate removed - although that was there more for a convenient flat mounting surface rather than anything majorly structural.

Still comes in under £100 - so that keeps me happy :rugby:

Better but still no inner triangle brace.!! See pic of brace on my machine. It's only a small thing but does help stiffen and dampen vibration more than it looks.

Don't let Money run this Build too much because you could easily find you spoil it for not much more money.!! . . . Better waiting and saving up to do it right than skimp. It's a lot of work building a CNC machine and just small things that don't cost the earth can make a big difference.

There is one inner brace already - 15mm plate & then 20mm outer on the end.

I'll look at doubling up that inner brace later.

I have to keep an eye on the cost as its already adding up to way more than I originally intended...& its going to take me months & months to sort out the finances for it - so yes, the budget is important. I appreciate that its not worth cutting some corners - but I can't shove a bottomless pit of funds at it.

Quote:

---

Originally Posted by CraftyGeek

There is one inner brace already - 15mm plate & then 20mm outer on the end.

I'll look at doubling up that inner brace later.

---

Yep but the more towards the centre you can support it the better, bring that inner triangle inwards the gantry side does the same job so it's not needed there. On mine it's only built like that for ease of fitting it's piece on it's own that bolts on could have easily done it like suggested you do and would work just the same.

Quote:

---

Originally Posted by CraftyGeek

I have to keep an eye on the cost as its already adding up to way more than I originally intended...& its going to take me months & months to sort out the finances for it - so yes, the budget is important. I appreciate that its not worth cutting some corners - but I can't shove a bottomless pit of funds at it.

---

Yep completely agree and understand but just understand it's here at this point when building frame you can't afford to cut corners. If you have a weak structure you have a Weak machine and it will always be weak or hard to correct without major hassle and expense at later date.
I've seen this often where folks think I'll do it on cheap then upgrade later only to find out it's not that simple or easy and end up scrapping and starting again. . . . It's called learning the hard way, I'm just trying to help steer around that.!

Right, the gantry is moving along nicely - i'm at the stage now where i'm starting to add the Z-axis. Its probably time to finalize rail/leadscrew choices before I go much further.

My thoughts have been
X - SB20 rail with 2x 1605 screw
Y - SB20 rail with 1605 screw
Z - SB16 rail with 1605 screw

I've seen mentions of clearance issues/fiddlyness when using SB16 with, I assume 1605 screws...should I just use SB20 for Z as well?
All axis will have a single Nema 23 motor & be driven by belts/pinions. Initial power setup will only be 24V - but I plan on upgrading this to at least 48V in the relatively near future.

Does this sound ok?...what about the Z axis setup?

No don't use 5mm pitch for X & Y you want 10mm so RM1610. Use Rm1605 on Z axis.

Either rails will work but your correct the 16mm are lower so very close without machining the plates to allow clearance for ballnut.

Dump the 24V ASAP.

That'll teach me for posting when i'm tired :-p
Brain said 1610, fingers typed 1605.

Ok - i'll go SB20 all round for simplicity sake.

24V will be upgraded - but it means upgrading the stepper driver boards as well...so it won't happen immediately, but as soon as its possible.

As i'm getting further into the design now & tweaking parts sizes to make leadscrew bearing housing line up etc i'm wondering about methods of assembly & tweaking the fit of parts.
This is a 2 pronged question..

Firstly - I see many mentions of shimming parts to get accurate spacings & alignment....what is normally used for shimming?

Secondly - some of the parts that i'll be constructing have a length of steel box with an end cap plate that needs to be welded on.
On the design, i'm drawing this as a neat, flush fit like this:
Attachment 9594

Given that i'll be completely new to welding (yes i'll be practicing first), the tutorial video that i've watched suggests fitting parts together like the next image so that the actual weld can fit between the box & plate.
Attachment 9595
That obviously makes getting accurate positioning very tricky & i'm guessing a bit of a nightmare.

So I was wondering if something like this would be a better approach...grind out some notches on the end of the box section - sit the plate flat on the end, then tack weld into the gaps that were created by the grinding...this should help keep alignment more straightforward & accurate?
Attachment 9596

If i'm missing something here please fill me in...or I could be missing something entirely :nightmare:

Could you not just make the green bit a bigger so that you can weld it from the other side to get your fillet weld ..Clive

Some of the joints extend on 2 sides of the box already - I guess it might be easier to tweak the layout slightly so they all do that.

If you practice on some scrap bits with no gap between & try increasing the Amps so you get better penetration, or try a weld prep on both parts(ie 45deg chamfer)

Quote:

---

So I was wondering if something like this would be a better approach...grind out some notches on the end of the box section - sit the plate flat on the end, then tack weld into the gaps that were created by the grinding...this should help keep alignment more straightforward & accurate?

---

what if you weld some wire on inside face and use them like a spacers?,
or just grind the end plate edges to get weld in

Thanks chaps - adding a chamfer to the edges could be an option. I'm off work on Friday - I think i'll take a trip to the steel yard & see if I can get some scrap, then have a play with a few different approaches.

Just a pity you didn't have a TIG setup, all you do then is strike the arc wait to get your pool and advance the torch, it make a very clean weld.

If i were you i would try just putting a prep on the box section, leave the end caps with square edge, then when you lay down your weld you won't(hopefully) melt the outer edge of the blank and it will look a lot better, i am fortunate as i have TIG so can just fuse the two together.
Regards
Mike