First Build - Yet Another Alu Profile Router - 900 x 800

[Voicecoil]

He who dares wins.

[JAZZCNC]

How about a variation on "C", bring the 2 80x80s close together (ditch the crap collecting gap) and plate them front and back to make say a 90 something x 160 section? You could even slip a drop or 2 of epoxy where the extrusions meet if you were feeling keen

Doesn't need to go that far because there's more than enough strength in profile, he'd just be adding weight. The epoxy would just be a waste of money and offer nothing in terms of strength.

If he had a little more length and could afford slightly wider bearing/gantry plates I'd suggested going with 160 flat with 160 on top and with rails in same front and top positions. You have to think about the direction of cutting forces. The wider bottom profile makes the gantry stiffer in the direction of cutting forces.

[CaptainBarnacles]

If he had a little more length and could afford slightly wider bearing/gantry plates I'd suggested going with 160 flat with 160 on top and with rails in same front and top positions. You have to think about the direction of cutting forces. The wider bottom profile makes the gantry stiffer in the direction of cutting forces.

Like this?



That's certainly more beefy than I had planned but I'm in this to build the best machine (supposedly within my budget but that vanished ages ago!) I possibly can. I don't want to start cutting and immediately regret compromising on something critical.

My gantry riser plates are currently 210mm width so this arrangement would fit. My concern is that the CoG of the router would then be well in front of the forward Y-axis carriage. Is this what you mean when you said about wider bearing/gantry plates? ie. I'll need to widen them to bring the CoG back within the two Y-axis carriages? Which would then mean a reduced cutting area?

[JAZZCNC]

Like this?

My gantry riser plates are currently 210mm width so this arrangement would fit. My concern is that the CoG of the router would then be well in front of the forward Y-axis carriage. Is this what you mean when you said about wider bearing/gantry plates? ie. I'll need to widen them to bring the CoG back within the two Y-axis carriages? Which would then mean a reduced cutting area?

Yes but not so much because of COG but more the loss of travel. COG isn't a big deal as your probably thinking and you are not exactly hanging it out into outer space.
That said I'd also consider looking at 160 flat with 80 on top and rails top n bottom. You'll lose some height between bearings but gain in stiffness.
End of the day it's down to what you need in terms of clearance between gantry and bed, along with travel required. Also what you are wanting the machine to do.?

My suggestions are based on what profile you have, however, if I was building it and wanted a very strong gantry at this size I would use 80x120.

Option E will work fine as well if you cannot afford the length. I wouldn't stress over any of them because each will work fine for a router.

[CaptainBarnacles]

I've been taking stock of this project over the last couple of weeks. It occurs to me that I was getting a bit bogged down and getting a bit obsessed with building the ultimate machine first time around. I took a look at my design and looked for ways to simplify it and design a machine that I, with my limited tools and experience, could actually build in a reasonable timeframe.

A few late nights at the computer (I'm finally starting to get the hang of Fusion 360!) and I have this:





The gantry is 2 qty 80x80 stuck together (though I may still add an additional 40x80 on the flat for more of an L shape profile), 40x160 for the Y axis frame, 40x80 for the bed with MDF over.

It's not a million miles away from some of my earlier designs but it feels more mature and I feel happier with it. I have my 150mm Z axis travel, I lost a little on the bed size but I can live with it for now. Time for less procrastination and more building (when the workshop warms up a little).

[pippin88]

C would be best IMO.

The ideal gantry profile is square.

The gantry is subject to vertical force, horizontal forces, and torsional forces.

When the Z axis is all the way down, it acts as a lever and tries to twist the gantry.

[Kitwn]

You may like to mock up some parts of the construction in ply or MDF before committing to expensive aly plate. This works especially well for complex structures like the Z axis and is easy to do with hand tools only. In fact I spent yesterday finally building my Z axis in aluminium plate after running it as a plywood 'mockup' for the last 18 months.

I'm also changing from microswitches to inductive sensors for limit switches and they're going to resemble sore thumbs, whether I like it or not. Andy's right about working out these details in advance if you can.

[CaptainBarnacles]

Some really amazing advice and words of wisdom, thank you so much guys.

I had a go at mocking up a couple of components in ply and it was useful to help visualise assemblies before commiting to cutting aluminium. That was a while back and since then my CAD skills have moved on a bit so I am more inclined to model it in CAD now than in MDF or ply (although sometimes it would definately be quicker to just go and knock out the part in ply!).

I will certainly be using CAD with a different midset going forward. Back when my CAD skills were very limited I was using it as a way to visualise the overall machine and give me an idea of what the finished thing would look like. From the advice here I can see now how it's real power is the ability to precisely model the real world and to resolve issues and conflicts before I go anywhere near a power tool.

Looks like I'll be spending this rainy weekend in front of the computer and trying to lock down the design as much I can. I'm really itching to get started with the build but I now appreciate how much time and heartache can be saved by spending the time on the design (although it is starting to annoy Mrs Barnacles - every time she walks past I'm staring intensely at a virtual CNC router. I told her it would only take a few weeks to build, that was over two years ago!).