Howdy all. I’ve been lurking for awhile and am finally putting a thread together to get some feedback and hopefully document my build if I can get this project off the ground.

I’m planning to build a welded steel tube frame gantry router with epoxy leveled linear rail beds. I would like to have a working area of around 56”x48”x12”. Those may seem like odd dimensions, especially since the gantry axis (x) is longer than the fixed (base?) axis (y). However, I’d like to be able to cut larger sheets/blocks, without having a full 8-10 foot table, by repositioning my workpiece. I don’t have the space or money currently for a larger table.

My usage of the machine would be for cutting plywood, MDF sheets and laminated MDF blocks for molds, and possibly larger foam blocks for larger molds. Ideally the machine would also be able to do light aluminum work, but I’m not sure that’s a realistic goal. Not sure what I can expect my accuracy to be with Chinese rolled ball screws, but I guess I’ll get what I get and (hopefully) won’t get too upset.

I’ve attached a screenshot of my extremely rough frame design (still have no idea what I’m doing in Fusion360 so sorry for the absolutely garbage model), to give you a vague idea of what I’m envisioning. I’m still determining what steel tube is available locally, so exact structure is subject to change. Broadly, though, I’m envisioning a low gantry and a table with fairly high walls as shown above. I’m really not sure whether having a “flat” 2Dish frame is okay, or if I need to add some sort of triangulated structure below the cutting deck to keep the frame from “racking” if I move it after epoxy leveling the Y axis (and I will 100% have to move it at some point). Advice is appreciated.

Linear Motion: I’m leaning towards rails from BST motion on AliExpress. Any feedback on this option would be appreciated. I’d like to get rails that match the capability of my frame (and vice versa), so that I’m not wasting money upgrading one component when the other is already a limiting factor.
https://www.aliexpress.com/item/3301...24ce67b7Tp5PzQ

Actuation: leaning towards rolled C7 ball screws if I can find ones long enough, possibly also from BST automation? Advice on good vendors would be greatly appreciated. I’ve also seen a recommendation for linearmotionbearings2008 on eBay? I assume I would want something in the 20-25mm diameter range, and a larger pitch? Maybe 10-20mm pitch? I don’t think my cutting forces will be that high on most of the material I plan to cut, so seems to make sense to bias towards faster travel (and larger pitch will also hopefully help keep my screw RPM down to limit any wobble over long distance). One question I have is whether I should be looking at double ballnuts to reduce backlash, or whether that’s going to be overkill for my design. Once I have a better idea of approximate gantry mass, I will do the math to figure out if there is a combination of gantry mass/ball screw pitch/stepper motor torque that seems like it might work, but I’m still crystalizing my frame concept.

Spindle: I haven’t done all that much research yet, since it doesn’t really seem to affect the rest of the design at this stage, but I imagine I will end up going with something along these lines. I’ve had a small amount of experience with the capability of these spindles on a friend’s machine, and it seems to be a reasonable option for the price. I will have to investigate further as to whether a better option exists.
https://www.amazon.com/MYSWEETY-Spin...1282578&sr=8-9

Control: really haven’t gotten here yet, but Mach4 + ethernet smoothstepper + g540 + appropriately sized stepper motors is kind of my fall back. All I know for sure is I really don’t want to deal with a parallel port of any type at this point.

Well thanks for hanging in there for anyone who read all that. At this point I’d greatly appreciate any feedback on whether or not my overall approach is realistic/reasonable, especially with regards to how I plan to do the frame. Thanks again – David.