I had considered buying a CNC and the more I read about this project the more it kept haunting me. I love digging into complex projects and trying to figure them out. It gives me something to do while my wife is watching 90-day fiance.
Anyhow, my end goal is a 30"x30" workspace and I will be primary doing wood project and also drag bit on acrylic. I think I lucked out as there is a metal supermarket only a couple miles away so I should be able to source the rails without issue.
I currently don’t have or know how to do 3d printing, and I am looking to do that first thing. I am willing to learn by recreating parts if necessary.
So I am planning a 30"x30" work area with a 4" z axis using 1"OD DOM .065 tubing. I will start with a makita 7 series router and potentially move to a spindle to quiet things down.
Worst case I can buy the printed parts. But will the specs work for what I want to do? I hear a lot via the forums about keeping it small.
Sorry for the ramble but just want to ensure I am not missing something.
30" is on the large side for a Primo, but doable. Mine is 25" by 37" larger means you need to be a bit more careful in how you lay out your projects and makes cutting harder materials more difficult than it needs to be. I will be cutting mine down in size as soon as I get more organized.
Keep in mind that your effective Z is limited by your router bit. Most of mine are good for 1/2" max and my deepest is barely over 1" cutting depth. A table where I could drop the cutting area would make taller projects possible.
It’s a fun project! I will look forward to seeing your build.
My working XY area on my Primo is 26" x 32." I’m probably paying some penalty for the larger size, but it works fine for wood. I rarely used that much area for routing, but lately I seem to be pushing the size with my laser work.
The Z height has a lot of impact on performance, so I compromised and made the Z height adjustable. The Z axis and the legs allow for Z working height of 5", but I cut a hole below each foot in my base board and allow the legs to drop through. I use 3D printed spacers to keep the four legs the same length. Most of the time I leave my machine at its lowest setting, typically only raising it for carving 2" foam board. Note that the Z working height must accommodate both the material and the length of the bit below the nut on the router, so I need 4+ inches of working height if I want to do contour cuts in 2" foam.
.I will start with a makita 7 series router and potentially move to a spindle to quiet things down.
A Makita router is comparable to 1KW spindle in terms of power, and spindles of this size are rare. The cheap spindles (400W to 600W) don’t perform as well as the Makita, and you will pay a cost and mass penalty for the larger spindles (1.5KW, 2.2KW).
Is the z-axis impact due to lever action on the core? I can understand the longer spans having flex but is the higher z-axis impact from this x/y flex or from lever action (sorry my term for it).
I could potentially do with a working size of 28x20ish, Would this make a sizable difference in rigidity? I would mostly be working with 1" or 3/4" stock as well as 1/4" plexiglass but didn’t want to limit in the case I was doing something with thicker stock like a 2x4. In that case I would not be cutting through just engraving or vcarving.
That’s the big part of it, yeah. The taller your machine, the farther down the z has to travel to get to the bottom. There is also the levering against the legs, but if you can accurately bore holes for the legs, you can mitigate that somewhat by setting the legs into the table. Some of us have used easy tools like 1in hole saws, drills, or spade bits to cut two holes through two stacked pieces of wood, and used those to locate the legs by screwing them down to the table. Don’t know how much it helps, but it helps more than nothing, lol.
As for the 30 in length, it’s big, but inside the realm folks have done. I ran my primo at 24x48 for kind of a while, and I’ve seen others, plus a 36x48. You really have to be careful with your CAM though, because it is FLEXIBLE.
Here is some video and then slow mo of my 1in, 1/8-wall DOM 4ft span before i epoxied a 1/2 emt inside it.
If you’re doing 30" x 30" I would say increase to 0.120 instead of 0.065. Welded tube is fine too.
The “lever action” of tipping the router away from vertical is the killer when it comes to height. For a given load at twice the height, the tipping torque is doubled because the lever arm is twice as long. And then for a given torque, the deflection is twice as much, again because the arm is twice as long. So the effective compliance (deflection relative to load) is 4x worse.
So you really want to minimize the Z to the shortest that you can tolerate. Note, if you prop up your workpiece, this can be somewhat mitigated, since it’s not the legs that really deflect. You just want the upper surface of the workpiece to be as high as possible.
F* me, that’s where my chatter is coming from. I run a 55x75 cm Primo and was thinking about why it was happening. You can’t see it in the cuts, but this is the reason… Since I installed a dragchain with a L-profile it has become less as well. Thanks for the unintended solution to my problem.
My build area is around 24”x24” and it seems to be fairly rigid but 30”x30” will be pushing it if you plan to cut harder materials.
I try to locate my cuts as close to a corner as possible to improve stiffness. I’ve only cut wood and plastic so far but I eventually hope to cut aluminum.
I built a drop table so I can cut larger parts, not necessarily deeper if that makes sense, so that is an option for you as Dan suggested. Here’s an example of one of my projects.
There are a few other table examples on the forum. If you’re interested you can probably seach for “drop table”.
I try to have the workpiece as close to the top as possible while still allowing for easy tool changes to minimizes the moment effect on the core. But that doesn’t help with any vibrations that are due to a large span.
I also located my cable management at the trucks (above the table) so I can slide in larger parts from any side (max workpiece width ~32”). If you go this route you would have to index your part in such a fashion to repeatably locate the next cut. For example if I want to cut a 30” square I would cut ~22” then rotate the workpiece 180deg and finish the cut. But accurate locating and work holding may be a challenge.
So if I were you I’d probably try to make a list of as many projects that I could think of that I would want to do and size my build based on the majority of them. If it turns out that most of your parts are in the 30” range then it may be better to jump up to a Lowrider 3.
There can be a bit of analysis paralysis. The advice I would give you is that none of it is permanent. If you are finding the size a sticking point, just go smaller, learn what you need to learn, and then build it bigger. Or do the opposite. Nothing is glued down and if you cut the tubes too short, they are the only parts you need to replace.
You’ve read the arguments, you will be able to tell if it isn’t working. It is your CNC machine. Make it yours.
