I need help sizing T slot aluminum extrusion for my build. I'm primarily trying to get some ballpark figures on typical real world forces involved to plug into deflection calculators plus any advice you may have would be ideal. I'm not looking for exact force calculations, just some concrete numbers that are good enough to decide between an extra beefy variant of 30mm base profile or medium grade 40mm or to determine that anything less than 80mm would be a waste of money........ At the moment, I'm trying to finalize the type and general layout of my aluminum extrusion frame elements so I can start iterating through the other design decisions. My next step is to select a suitable aluminum profile and redesign my frame to incorporate it.

Due to pandemic, I have more time at home these days, so I'm attempting to get as much done on this project as I can before other responsibilities require my undivided attention. So, I'm not rushing this, but I am really trying to get at least the linear guide and ballscrews ordered from China sooner than later, and I need to size my machine frame elements before I can determine specific rail lengths (and then revise design based on available parts and cost).

Sorry about the length of the braindump below, not sure what info you might need for my questions. I am not a mechanical engineer and it has been decades since I took physics and statics classes, so at this point I'm mentally atrophied enough to be a total lay person. On the long term, I'll relearn the math and physics involved, but this ol' brain takes longer on the uptake than it used to, so need assistance getting my frame up to speed. Suggestions on the subject are much appreciated.



General DIY Build info:
I'm building this for personal use and for the sake of learning every nitty gritty, PITA detail of making machines like this hands-on, and at the end of the build I'll have a machine that can do an ok job making parts for itself, other machines, projects, or whatever I feel like cutting at the moment (with limitations on material type of course). This project is intended as a concept design that incorporates a bunch of different ideas, more or less an experimental platform that I need to actually work at some point. I have to keep my budget as tight as I can, but not at the sacrifice of practical utility. So, I'm cutting corners where I can in order to spend a little more on having beefier critical elements, etc.

Machine Type and footprint:
CNC router with some cost effective attention to more rigid milling requirements, and CO2 laser combo with mostly enclosed optics to protect from swarf/etc. Dual gantries oriented length-wise to accommodate oversized material: one slow-ish for spindle, one optimized for speed and laser engraving. Separate Z axi for spindle and primary work envelope/platform. Yes, it's basically a medium sized cnc router mashed up with a laser engraver, but with an economical attempt to beef up critical parts of the frame a little to be a bit more milling friendly. I'm in an apartment with concrete floors, no garage. I have space for exactly one decently sized machine, thus one of the reasons this build is a spindle/CO2 laser combo instead of separate machines. I have other reasons for the combination, but they're more on the messing around and experimenting side of things. I have looked around at other people's builds and some commercial some commercial machines for ideas and starting points, but AFAIK, I have not seen any DIY combo builds that incorporate a full size spindle and full size CO2 laser instead of a diode, so this is a completely from scratch design.

Target quality/precision/materials:
I do not expect to get machinist-quality precision and repeatability. I want picometer precision and repeatability for $ zero dollah, but my slightly more realistic goal is to match or exceed quality of some of the cheap-ish chinese ebay CNC kits like the 3040/6090 kits, NOT the ultra cheapo plastic 3018's. "Materials" target is "good for DIY" precision/repeatability drilling and "ok" milling for aluminum plate up to 20mm thick plus any less demanding materials. I have a one-time project with stone I'd like to try, but stone is not really my target. Sooner or later I'll at least attempt any other material types and depths I can get my hands on, but a machine that can reliably cut ANYthing is waaaay outside my budget, so doing an ok job with 20mm aluminum seems like a decent arbitrary target.

Oversized plus primary work envelopes:
The spindle gantry is oriented long-wise to provide oversized work envelope: 50mm Z (barely enough for 1.5" material plus spoil board) and 4' wide plus elbow room, but requires doing a series of jobs and manually shifting material through iteratively. PITA, but hey, no limit to material length if its 4' wide or less. Primary work envelope implemented on a movable platform is 4' x 2' plus elbow room, with Z depth based more on budget than anything else, but figure at least 300mm. Due to laser and other project ideas I want to try out down the road, the main work envelope is on a movable platform and has it's own dedicated Z axis, in addition to the spindle's typical Z axis. When platform is at maximum upward travel, it is flush with the top surface of the frame 50mm under spindle gantry. Tentatively, a vice will be temporarily mounted on the platform when needed.

Tentative electrical/mechanical bits n pieces:
I'm in the US, but my apartment has 240VAC outlets available (Shhh!!! Don't tell the landlord!). Stepper motors to start with, might upgrade to a closed loop variant down the road pending additional $. I'm using open source controllers and firmware, but I have enough coding experience that this what I would do anyway regardless of budget. Unfortunately, the TMC5160 stepper drivers I already have are on those mini-pcbs so the maximum motor current is 4 amps per axis. I'm looking at steppers with a brake for both of the Z axi (both spindle and work platform).

Spindle gantry and axi:
"Hopefully Genuine" Hiwin linear guide for all axi, probably 25mm for gantry support and 15 or 20mm for everything else depending on price tag. Appx 1500mm gantry span with 50mm clearance. Dual ball screws for moving gantry, 16mm if I can get away with it, otherwise 20mm. Probably ball screw for spindle X axis, but not sure what's required for >1200mm travel, definately bigger than 16mm. Based on the costs I've looked at, I don't think rack and pinion will be an option. I want >= 10mm ballscrew pitch for something less-agonizingly slow, but I don't know what can be economically achieved with a 4 amp/axis (2 amp per stepper for dual ballscrew) stepper motor limit.

Laser gantry optimized for speed:
This is mostly TBD. I bought some C-Beam from OpenBuilds that I've been experimenting with. My current thought is to mount gantry with linear guide and use a minimal-load V wheel setup for Laser head X axis. The optics have to be protected and mostly enclosed, so I'm designing my own mirror mounts and laser head, so much of that will be directly integrated into the X carriage itself. Should be extremely low weight to move during laser engraving, just the weight of the plastic carriage and bearings, one mirror w/o mount, one lens w/o nozzle nor head, 3D printed minimum weight low pressure air assist nozzle, plus the drag of the air assist hose, and that's about it...

Work platform Z axis:
Lead screws for Z static load and XZ/YZ moment force, and probably minimally sized (12mm? 15, 20mm?) linear guide to deal with X/Y static load and XY moment forces, but I'm mostly throwing out fancy words since I'm not sure the most appropriate way to build and mount a platform like this. How many lead screws for a 4' x 2' platform?!? Well, at least 4. What diameter?!? No idea. Current thought is to use 12mm instead of 8mm for the sole sake of flattening the angle of the 2mm pitch thread a little to reduce backdriving force, but otherwise I have no idea. Feel free to make suggestions.

Spindle:
TBD, mostly determined by how much $ I have left over after everything else. Tentative target is a water cooled 2.2kW. I say "water cooled" only because I have the impression that it would be a little quieter than an air cooled spindle, thus less noise I have to dampen for my apartment neighbors' sake. No matter what, it will be a PITA to minimize noise pollution, so need to minimize any source as much as economically possible.

Laser tube:
TBD, mostly determined by how much $ I have left over after everything else. I've been considering many different options for this, including a possible dual tube setup with high >=120W and low <60W tubes. At this point, I just need to make sure I accommodate all the different options as far as my machine frame is concerned and remaining budget will determine the rest.

I have paper sketches and some preliminary CAD done, but nothing worthy of public viewing yet. I need to get the profile selected for my main aluminum extrusion frame elements before I get much more of the overall design out of my head and into Fusion.



Any help/pointers on T/V slot profile selection, and any real-world numbers to ballpark force estimation to plug into deflection calculators/etc to make De$ign Choice$ would be much appreciated. I freely admit my newb-i-ness, but am quick to point out that I'm working to fix that. Heh.

Thanks!