450x300 Aluminium extrusion build from scrap/used parts
Hello boys and girls,
After a long long time of promising myself to build a machine, I'm finally going to do it. I hope to mill/cut plastic, wood, and hopefully some aluminium up to 6mm thick. Accuracy I'm aiming for is around 0.1mm if possible.
Here is my machine plan. I would love some constructive criticism.
Specs:
Y-axis supports are 40x80 extrusion.
X-axis gantry is 80x120mm heavy duty extrusion.
Gantry side plates are 10mm aluminium plate.
machine base is a tooling plate of 10mm aluminium. It has a few holes here and there, which I've modelled in sketchup, so excuse those please.
Final working area is around 440x280mm, but if I can find a bigger base plate, that would be great.
Motors: I'm not sure, but probably around Nema 23 size, perhaps 4Nm?
Rails will be 20mm Hiwin, or Chinese, depending on price.
Ballscrews will likely be 1605.
Would someone be so kind as to critique my build please? Note that I haven't included the ballscrews for the x and z axes yet. Still working on positioning those. Ideas?
Re: 450x300 Aluminium extrusion build from scrap/used parts
Some initial thoughts.
First the base plate really should have a frame under it. You might get away with a frameless solution on a small light duty machine, im just not sure 280 mm qualifies here nore do i know your usage intentions. So i lean towards the need for a frame. An alternative on a small machine like this might be to simply close up the ends which would stiffen every thing up.
The connection between the gantry uprights and the gantry beam seems to be freating a littke shelf that fan collect swarf. This could be a real problem as the gantry sabble nears its travel limits. In general look for places in your design that might collect swarf and create an axis obstruction.
Usually we want to call the gantry the Y axis though there is argument about that. With the gantry though id just buy some extra pieces of extrusion to form the side plates out of. The extrusions will be stiffer.
The bearings supporting the gantry side plates might be a little too close together. T is hard to tell from your renders. In a perfect world the would be spaced about as far apart as the gantry beam is high. This can impact main table travel so you need to balance competeing issues.
As for machining aluminum the trick here is to make a stiff machine. This is why i would look closely at the main table rails and the extrusions they are mounted on and the tooling plate they mount on. This is the foundation of your machine and you want a solud foundation. Above it was suggested to close in the unit to create a frame on top of thevtooling plate. That is only one choice and has one bad feature in that long work can not be handled easily. There is an almost endless number of ways to address this issue from a frame underneath, to external bracing, to moving the linear rails to the tooling plate. In any event the base is where i would put a lot of thought. The aim should be to make it as stiff as possible with in your budgets capacity. Remember the T-slots in yiur extrusions are not the most robust of mechanical connection methods.
Re: 450x300 Aluminium extrusion build from scrap/used parts
My gut feeling is the base plate is going to need stiffening with some sort of frame. Also I might be inclined to beef up the extrusions under the long rails, 80x80 will give you more options on how to mount the rails.
Any idea where you're going to fit the other ball screws?
The gantry looks like a decently stiff extrusion. Heavier than most manage for a router that size.
I don't know how well profile rails work with T-slots, I think there is some debate on that. Do you have any plans to have anything to be able to straighten the rails? Profile rails are typically not perfectly straight from the factory, big mills usually have a machined surface that they get clamped to from the side. Are you planning any machining of the extrusions to make sure they're flat?
4 N-m should be more than enough. I've got a similar sized Chinese router (4030,) that only has a single stepper on the long axis and it's probably only a 2 N-m. 1605 ball screws are probably fine for that size. What are you thinking for a spindle?
450x300 Aluminium extrusion build from scrap/used parts
Note that I haven't included the ballscrews for the x and z axes yet. Still working on positioning those. Ideas?
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