Hi, I’m in the market for small CNC to make alloy plates on while my work bee is busy making wooden stuff. The mini mill looks good but are there other open-builds options? Also, can the mini mill be modified to take linear rails?
You should be able to modify it for linear rails. You just need to model it up and cut some adaptor plates, or put additional holes in the plates that come with the kit so they can be mounted to your bearing blocks in the right location. I am currently modifying my CNC machine to be larger with a dual X beams and will be using linear rails. I chose aluminum angle to mount mine. The holes on the aluminum angles match the blocks on one leg and the Cbeam gantry plate on the other.
Fusion 360 free addition. Fusion 360 for Personal Use | Fusion 360 | Autodesk I like it because I can sketch up 2D dxf files for plates and other flat objects in a matter of minutes and export it for generating toolpaths with EstlCam or Openbuilds CAM. Fusion 360 also has an Openbuilds post processor (found here) if you want to generate the CAM inside of that program. Personally, I found Estlcam to be quicker and easier for me. It is very similar to Openbuilds CAM, but I purchased the license ($59) before Openbuilds came out with a CAM. One of the hidden gems of Fusion is the ability to upload editable models of McMaster Carr components. Need to 3D print a sprocket? Open a new drawing in Fusion, import the sprocket, modify if necessary, and export as an .stl. That is how I added the linear rails and blocks to the drawing you see above.
The C-Beam Machine was specifically designed for making plates for other machines. I prefer the C-Beam XL for its stiffer Y table though I see there is no kit you can search the forums for it.. A cheap alternative is to add a length of Cbeam (to the Cbeammachine kit) so there are 2 for the Y BUT use the existing end plates to space the 2 Cbeams apart, let the leadscrew run between the Cbeams, and put the guide wheels on the outside of both Cbeams so the support is the widest possible across the table..
Definitely a Mini Mill project. The smaller the machine, the more rigid it is and the higher accuracy and surface finish you get. There's an argument to be made for larger gantry machines if you want to batch-work, but extrusion machines and high-speed aluminum processing aren't a great match. Depends what your volumes look like.
Volumes are low, 10-20 plates a month tops and if they go up I’ll stump up for a more capable Machine. Bit pricey though….
If you're looking to beef up a minimill for harder alloys this is pretty much the ultimate guide: OpenBuilds MiniMill Review (mostly for cutting aluminum) - YouTube
Assuming ~5-10 minute cycle times, I'd run a mini mill "SS" with linear rails, ballscrews and a fixture plate/palletization/vaccum plate comfortably up to 700 units a month (4 per hour, 8 hours a day, 20 days a month is 640, not a hard figure to hit even without a very short part change time), possibly a lot more if I were getting blanks in either pre-sheared to rough size or laser/waterjet to exact outside dimensions and didn't have any processing work to do. If you could feed it with a robot, you could add an order of magnitude to that- 4000/mo is doable with very high uptime- volumes only limited by the amount of plates you can keep stacked for the robot. After that- assuming worst case scenario of no automation and no pre-cut blanks- I'd go to a smallish, highly rigid gantry machine- less than 500mm X travel, maybe 600-700mm if it's a really solid gantry- and buy in sheets as a move to batch-work. Mostly just to avoid operator fatigue, increase those cycle times and allow easier operation of multiple identical units. Workholding would be tricky though inasmuch as you'd have to account for tabs, or run a fairly large vacuum system. If there were automation... I'd just keep adding Mini Mills in a line, let one robot feed them all. Sky's the limit.
Yes, that’s It. It’s going ok thanks, I’m selling a wooden one now it’s time to finish off an alloy version and start promoting it. It’s had a complete redesign using 3D printed parts but now I need to make them in alloy. One plate in particular needs12mm alloy machined down to 6mm in several places, drilled and threaded. so I thought I’d get a more suitable machine sorted out.
you didn't mention Pierson Workholding or LEAN (-: the secret to throughput is minimizing per part operator interaction.
Ha! I like Pierson, but I don't have enough Z travel to use their products yet. They're a little tall. Lean is an interesting one, because I think of it as one end of a line, with "resiliency" on the other end. And while I like *process* optimization, I'm not a huge fan of the anti-resiliency efforts when it comes to stock and inventory. It assumes an expectation of the supply chain and/or workforce that isn't guaranteed- as we've seen in the last year. But I do think V-Slot has the potential to be a great parts loading gantry robot base, it's something I've been thinking about for a couple of years, and three Mini Mills in a row would probably be doable for a single 1500mm stick to keep up with. With an extra go-between computer reading switches (end-of-run g-code motions) or serial comms, it could even be run on grbl. I probably wouldn't, because a linear rack & pinion gantry machine with the available digital IO to interact with multiple mills is an easy low-end (read: single Mesa card) LinuxCNC project. It's true. This is why palletization beats vises, or why vacuum has the potential to beat everything, sheet-goods-wise. The fewer screws you interact with, the better.
