So I’ve decided to go down the road of building an MPCNC but having so issues with calculating the footprint. I will likely start with the recommended 12x12 to get a feel for the system and it’s capabilities before doing a rebuild to the machine I really want.
One of the main reason I want to build one is for use by the FIRST Robotics team that I coach. The staple of all of our builds is 1” x 1” x 59” and 1” x 2” x 59” aluminum tube stock. We either buy it with holes on a 1” space or will buy raw tube and do it all manually. Tube we buy https://www.vexrobotics.com/versaframestock.html
In addition to the normal spacing we are often pocketing holes into it to lighten the tube or allow us to put bearing blocks in place for various mechanisms.
Currently this entire process is done by high school students on a manual mill and while it’s an awesome experience we went to get a bit more modern and be able to advance our designs.
Done by hand
Designs we would like to do.
Speed isn’t really a concern for us and we don’t need super insane tolerances since most holes are to lighten the frame and the ones that we run bearings through usually get a plate added to square the holes.
So getting to my actual questions. If I wanted to build a purpose built machine to cut and pocket tube what dimensions should I build around. What is the smallest that I can go and still have enough room for the head of the machine to move around And not feel limited? Would something like this be feasible? Am I going to hate it later? Again I plan to build the recommend size to get a hang of the capabilities first.
How would you feel about just making a smaller Y and then moving the material through and doing multiple cuts?
If you imagine a 71" piece of conduit, and the router was biting or kicking back in the X direction, the stepper motors for the X could be 35" away from the bit. I think it would have a hard time fighting the aluminum.
With good CAM, the loads are very small, but it will occasionally bite, and when it does, if it moves too much, it will have way higher load, and you’ll get a bunch of chatter.
I love the idea of building an MPCNC with a first team. I think it is not only going to expand the kind of things you can build, and give the team experience with CAM/CNC. It will also be a good example of a bunch of interesting robotic solutions.
I think you’d be very happy with about 12"x20"x2.5" cutting area and a dw660. I think it would be very forgiving for all the learning curves it will have to handle. You would just cut 1/3 of the 60" at a time (and then flip it to do another side). You can also build your own connector pieces out of larger plates. Maybe out of ACM.
I am not an expert of metal, so I don’t know if that kind of aluminum is hard or easy to CNC.
Most of the time we’re never using a full 60” piece with the usual lengths being closer to 35” or so as the max so that may be the better way to go. The concern I had with repositioning is how to make sure you pick up we’re you left off. I know with printers this is usually done with some for of registration mark. Wasn’t sure how to do that same process with items larger than the build area on a cnc. I guess it would be similar to the process we do on a manual mill.
I also agree that it would be awesome to machine our own plates and such and that was one of the other issues with wanting to not only do tube stock but some other items as well.
One of the big attractions to the mpcnc was that I can build 2-3 machines at such a reduced cost and don’t mind building a purpose built machine for this reason.
It depends on the tolerances you’re ok with. You can easily screw down a rail fo the spoil board, and mark at 0 and 20". Then when you finished the first section, mark it at 0 and then move the mark to 20" and clamp it back down. If you can live with the error of a mark on aluminum, then you’re all set.
The max length and the z height will affect performance the most. I don’t see an advantage to making the smaller axis shorter than 12". But YMMV.
I think you’ll learn so much from the first machine that size. You will knoe everything you need to know when deciding how many to make and what sizes.
How big is the plate you plan to cut? The first machine should accommodate both unless you are planning to rough cut pieces to feed the cnc. If you want to do both materials on the first machine maybe you don’t want to limit the x as much.
A mark on aluminum is plenty of tolerance for most things today that we are making today. When you say 12” am I correct in assuming that is the useable space?
And that was my thought as well. The conduit is so cheap and it’s only time to rebuild why not start with the more default recommended size and go from there. I also figured start with conduit and move to the SS tube later for more rigidity.
+1 for this size, or perhaps 22-24" the long way so you have a bit of elbow room if youre doing 60" in thirds.
I dont have experience with drill bits but if you want a thru-hole I think your options will be to mill each side or use a drill bit. Or drill a pilot hole and manually (yuck) drill on a drill press.
As Jeff said, moving to SS tube will be a reprint of all the printed parts but that is a great reason to build a second machine for the larger size.
Honestly all great points. Thank you guys for the feedback. I hope to have most everything finished printing this week. I’ve got all the mechanical hardware here already excited to start putting this together.
And honestly I can see this first machine staying together and being used for wood signs and other projects and just an entire new machine being built. I really have no issues reprinting anything it’s just time and a little filament.
I already had 3 steppers from a different project that never got off the ground so I either need to get 2 more steppers of the same or just pick up a full 5 pack. One thing I noticed is that the ones I currently have are 45Ncm but I see that the ones on the store are a lot more torque. Am I going to be frustrated if I don’t get the more powerful steppers even if it’s on a “test” machine?
I figure I have them already might as well just pick up 2 more of what I have and see where I end up. Worse case is I have a wood machine and then my more customized aluminum machine.
