Small rigid router - Design advise needed

**Boyan Silyavski** · 23-11-2014

Looks awsome. Will need a lot of patience welding.

**mitchejc** · 23-11-2014

Thanks Silyavski, yep that's going to be many many hours of welding. I'm a bit worried that the two square tubes on the front will bend a little during welding as its only welded on three sides but I'm hoping it will be ok. Maybe I'll only weld them top and bottom and not the back to prevent distortion. Do you think I need some ribs on the inside of the I-beam to prevent flex in the Y direction or is it going to be stiff enough with just the bearing and motor mount plates welded in?

**JAZZCNC** · 23-11-2014

Your making life much harder and expensive than it needs to be with all those rib plates.!!. .

Two large thick walled pieces of box section arranged in a L shape with a few triangle braces at the rear will easily match your gantry in strength and be much cheaper and simpler to achive. It will be much easier to achive accurecy as well because with that thickness of steel on those square tubes then heat from welding will almost certainly have an affect either pushing or pulling on the boxsection with so many braces to weld, even on just 2 sides.
If you used a Tig welder you may have chance but even then I'd be surprised if it doesn't.! You will certainly have to take it very very slow keeping welds short and leaving plenty of time between to stand any chance.

Your design will be strong but no stronger than more conventional setup and 3 times harder to achive and probably 3 times more expensive.?

Also Please don't tell me this is just for cutting wood with occasional aluminium use.?. . . .

**mitchejc** · 23-11-2014

Thanks for the input Jazz. I totally agree with the proven L shape being stronger per $. I'm not too worried about setting it up as the whole thing can be bolted together and adjusted before welding BUT I only have ARC. A bit of bowing of those tubes is not going to be the end of the world but if I get twist its going to be a throwaway so I'm seriously reconsidering my options. I can't get any square tube with walls thicker than than 3.5mm at my local steel shop so that's another curve ball I have to try and dodge with whichever design I'm going.

>>Also Please don't tell me this is just for cutting wood with occasional aluminium use.?

Yes, but I also want it gentle enough to cut little harts on pink mash mellows and then maybe the odd piece of brass in between :-)

**JAZZCNC** · 23-11-2014

Originally Posted by mitchejc

A bit of bowing of those tubes is not going to be the end of the world but if I get twist its going to be a throwaway so I'm seriously reconsidering my options.

Any movement of those tubes is bad news that will affect accurecy and take plenty of work to correct. This is the problem with such ridged design and complex setup that as limited scope to adjust out any build error.!!

Cutting marsh mellow can be harder than you realise..

**mitchejc** · 25-11-2014

Jazz I think if I use old bra straps to hold down those marsh mellows they are not going to be that difficult to cut ;-)

I'm pondering my choices here wrt to the gantry... my heart says go with the ribs and my mind says listen to these experienced gents :-) Blackrat on here got me into contact with a local supplier of the right epoxy for leveling so that will make things a little easier whichever way I go.

**Boyan Silyavski** · 25-11-2014

OK, now you have a nice picture. We could all agree it's the coolest design we have seen for a while.

Arc welder? Yeah I arc welded half of the first machine I made. But from now I am telling you it would be a mess with this design. Read my build where I changed at the last moment my gantry design cause I couldn't weld it as I designed it first. Luckily for the better.
And I have arc, mig, tag.

You should listen to your heart but also to your brain and your pocket.

At the end it should be doable in real life. That's the important thing.

**mitchejc** · 25-11-2014

Thanks for the good advice Silyavski. Fortunately I'm not building the machine to any deadline so I do have some time to rethink the design and if I have to redo the gantry design its ok, that's what I will do. You are right, the pocket is often where bad choices hurts the most :-)

**mitchejc** · 16-12-2014

Ok, I spend about three nights trying to redesign my gantry and every time I ended up starting to put ribs in :-) Got a quote on having the parts laser cut for the original design and it came to the equivalent of GBP120-00 so I decided to follow my hart and take a chance against good advice.

Ok, two weeks later and I can now say I FULLY understand what Jazz and sylyavski was trying to tell me and building this gantry design turned out to be a HUGE amount of work!

**mitchejc** · 16-12-2014

How do I convert this to a build thread?

Anyway, here's a few pictures of the gantry build. Took 3 full days to assemble and weld. I certainly know my little red arc welder much better now

Setting it up was relatively easy but took a lot of effort. Think 4x1m threaded rods + 88xnuts and you'll get the picture.

setup and squared.

test fit ballskrew before welding

Weld, weld, weld, weld... Remove flux, turn over, weld, weld weld...

Welding done apart from the 2 base plates which can only be done later. Very relieved it turned out pretty straight and no twist.

Would I recommend this approach for other first time builders? Well, if you are the kind of person that would describe three days of Chinese water torture as an interesting experience, then this is definitely the design you should go for...

Have to say its an amazing feeling to see the drawings turn into reality!