[jamesshuang]

Hi everyone,
I've been tinkering on an openbuilds ox-derived router for some time now, and I'm ready to step up to a bigger / more serious machine. My biggest frustration with the openbuilds router is that cutting aluminum parts takes forever, requiring just 0.25mm DOC to avoid binding up. I'm hoping to build a new router that can cut aluminum more reliably, and cut parts at least 2ft on each side.

I've designed a router based on SBR rails with SFU ballscrews, each 1000mm long. I've made some renders of my design here, albeit with a more modest 500mm travel. All the rails are SBR16, all the screws are SFU1605 (marked in green), and the rest of the silver parts will be HFS6 aluminum extrusions from Misumi. The blue plates are pieces I need to cut (very very slowly) on my current router.

I'm looking for some critiques of this design. I know the lateral SBR bearing loading is not ideal, but I'm fairly limited in the types of parts I can cut on my current machine (1/2" aluminum parts of that size would be nearly impossible on my machine, and I have no way to drill holes on the ends).

[pippin88]

If you want to cut aluminium, get profile rails.

Hiwin are available at good prices on aliexpress. I use BST Automation to get mine from.

[ger21]

I'll second that. There are builders here of machines made form wood, that found the round rails to be the weakest part of their machines.

[wizard]

IF you are serious about cutting aluminum then you best toss out that design. This especially if you are unhappy with slow tedious machine of aluminum on your current machine.

If machining aluminum is the goal you need to think more like a milling machine designer not a wood working tool designer. Ideally you want a machine that is at least ten times as stiff as a well designed machine for woodworking. We are talking a substantial woodworking machine here not a flimsy machine. In that regard unsupported rails are a no go an round rails ill advised. You need a machine designed around box sections, profile rails and ideally ball screws. The machine should be as stiff as your budget will allow for. One of the better materials to build such a machine out of is steel tubing.

In a nut shell if you want to move forward I'd scrap the current design. That might sound a bit excessive but you are already running a machine that can't cut the mustard so to speak, building another won't do you any good.

[jamesshuang]

Thanks for the recommendation regarding moving towards a mill design. I have no delusions about being able to plow through half an inch of aluminum per pass. My space is limited, and I still need to be able to cut fairly large wood signs and the like. I would be happy with the 0.5-1mm DOC in 6061 I've seen reported on similar routers.

I'm surprised that profile rails are such a huge step up. Is using profile rail on aluminum extrusion a valid choice? I've heard that you need to face mill the rail attachment to avoid binding the carriage.

[wizard]

Thanks for the recommendation regarding moving towards a mill design.

I probably didn't express myself well with respect to the "milling machine designer", the thought I was trying to get across was to design for a rigid machine.

I have no delusions about being able to plow through half an inch of aluminum per pass. My space is limited, and I still need to be able to cut fairly large wood signs and the like.

So this is more of a dual purpose machine.

I would be happy with the 0.5-1mm DOC in 6061 I've seen reported on similar routers.

I'm surprised that profile rails are such a huge step up. Is using profile rail on aluminum extrusion a valid choice?

That is a question that could lead to arguments. I've seen round rails used for all sorts of things so I don't have as negative opinion as others with respect to supported round rails. However as your expectations go up you can't rely upon round rails to deliver the results you want with respect to metal machining.

I've heard that you need to face mill the rail attachment to avoid binding the carriage.

Some suppliers of extrusions even offer machining services for the aluminum extrusions (at a price). It still comes down to what your expectations are, if you want to machine parts, and have flat surfaces come out flat then you need to flatten the surfaces that your linear rails bolt to. More so the stiffer you linear rails the greater the need to mount them to flat surfaces to prefer binding and premature wear. On top of all of that just bolting linear rials to T slots is a big pain in the butt.

The bolting issue is related to slop and the difficulty of torquing down the mounting screws to T-Nuts. You can have a tough time getting them parallel to each other and parallel or normal to that axises that they interact with. On top of all of that, many of the extrusions used to support profile rails aren't exactly the strongest profiles going.

I look at it this way, if you have to spend money on machining services, you might as well buy steel (which will be cheaper) and benefit from the positives of a steel structure. Do you want to machine the beams? I would have to say that that is pretty much a certainty if you have high expectations for straightness of an axis. When you first posted you seemed to be focused on machining aluminum, so my suggestions somewhat reflect what I expect out of machined aluminum components.