I would like to use my MPCNC to square off aluminium extrusions, similar to what this guy is doing
What is the easiest way to accomplish this? While I like the rig he built I can’t help thinking a CNC machine should be able to do this easily. Would I have to do this using a simple CAD drawing and Estlcam or can I use the controls on the LCD? The LCD interface has options to move in all directions but I don’t think you can control the speed. I would like to experiment and quickly try different speeds without having to upload a new gcode file every time if possible.
Honestly if you can manage to get your extrusion perfectly perpendicular to your X or Y axis you could just manually jog the endmill across the end face of the extrusion. Not here to discourage you but a simple wooden jig and a sanding block could get those ends nice and square too without all that hassle.
Personally, feel like reasonably squaring (and angling/tramming?) my chopsaw blade relative to the back stop was way faster than squaring my CNC. Used 12" Alu rafter square, nothing fancy.
Was recently struggling to assemble a square extrusion based frame with blind joints. This thread has me wondering whether anyone’s using steel cables to help do initial, and maintain, square extrusion frames?
Came close to printing/milling a jig to help square extrusion when fastening. My cabinet squaring clamps are too large for this situation.
You can put a little or a lot of work into this task depending on how many and often you want to do the job. As Brent mentions, the first task is to get the extrusion parallel with the axes of your machine. Personally, I use holes bored in the wood using my CNC and dowel pins to create my horizontal and vertical fences, but I’ve seen other, fancier methods.
I assume when you say LCD that you have an LCD display or you are running your TFT in Marlin mode. Here is a method/steps that accomplish the task.
Place your extrusion lightly against your fence with your router bit just off the end of your extrusion.
Run the script below. It starts by locking the X axis and pausing
Push your stock against the bit and clamp it down.
Pull your bit to just below the end of the stock
Optional: rotate the dial on the display. You will see a percentage that changes with the rotation. This percentage scales all feedrates. So, if you have the federate in the script set to 500 and the dial says 150%, then the actual federate will be 750. This allows you to test a bunch of feedrates quickly, then edit the script at the end to lock in the one you found best.
Turn on the router and hit the button on the display.
Script:
M17 X ; Lock X steppers
M0 Setup job ; Pause
G92 X0 Y0 Z0 ; Set origin
G1 X0.2 F500 ; Set the amount to "shave"
G1 Y50 F500 ; Make the cut
M18 Y ; Unlock Y steppers (optional)
The optional scaling in step 6 stays set until the electronics are cycled. This script turns off the Y steppers so you can set up a new cut without having to cycle the electronics. The 0.2 to shave is untested. Adjust as necessary.
I got to thinking about your task after your reply, and though a few additional lines might make the job easier. I added code to return to the beginning of the cut before disabling the Y stepper. This way the job can be run multiple times without re-clamping the stock. Each time, the job will shave an additional sliver from the stock.
M17 X ; Lock X steppers
M0 Setup job ; Pause
G92 X0 Y0 Z0 ; Set origin
G1 X0.2 F500 ; Set the amount to "shave"
G1 Y50 F500 ; Make the cut
G1 X-1 F1000 ; Move away from the stock
G1 Y0 F1000 ; Go back to the Y origin
G1 X0.2 F1000 ; Return to start of cut
M18 Y ; Unlock Y steppers
Unfortunately I didn’t have any luck squaring my extrusions using this method. While Robert’s script works great it appears the machine is simply not rigid enough to shave edges like this. I can clearly see the bit moving away from the piece while cutting, like it’s following the contour of the edge.
I had the same problem trying to square extrusions with my table saw - cuts are relatively straight when you cut in the middle but not when trying to take a bit off the edge.
This is the last thing I expected to trip up my Voron build. Next time I’m buying a frame kit instead of trying to save a few bucks
Nope not really…
Easiest way to get something “pretty darn close to perfectly square”? Yeah, ok, a good miter saw, correctly setup and with a good blade
If you want something dead straight, though, miter saw or table saws won’t cut it (pun intended)
For this, you need a rigid cutterthat won’t deflect under load, or sidetrack when it gets into a slot
That’s the very reason why jointers exist and we don’t square stock on the table saw (well actually you can, and it’s generally pretty much accurate and sufficient…)
So, indeed, using a mill (or router) for this is probably the way to go, but you’d need the cutter and the table dead straight and square themselves + extra-rigid to get a perfect result
Mills aren’t heavy for no reason…
But I think trying to get the result of a mill with just a palm router and aluminium extrusions wouldn’t get you anything better than a well setup miter or table saw actually…
If you want to go that route, at least use a full-sized router, rigidly mounted under a router table, and witha properly setup fence or sled to go with
Another way you could get away with though, is a stationary disc grinder
Make some sort of jig that holds the extrusion square to the face of the grinding disc (eg. referencing the edge of the table), and push the extrusion into the grinding disc slowly
This will shave small excesses of material, as aluminium is pretty soft…
