- What bearing options do people use for the arms and what are their tradeoffs? (I've seen ball bearings and magnets, but I haven't seen any discussion on WHY some of these designs offer desirable properties and what they are)
Traxxas are much simpler and cheaper to implement.
Yes, bearings and magnets are precise, they also weigh a lot, cost quite a bit and are a challenge to get right.
Despite what many think, the magnets aren't even that much better IF you do things right and think about what you are doing.
First off, magnets cannot handle high speeds. Before any of you complain, I've had them, at some of the speeds I run at, they will simply not hold on. It just won't happen. Some of this comes down to what you expect speed-wise. I had them chatter on small infill at 150mm/s, which is about the absolute slowest speeds I run my printers at these days for infill.
Second, if you want them for precision, you are probably running slow speeds anyhow. If you slow down any printer, slop and tolerances become less of an issue. Granted excessive slop is a problem, but if things are decent, your quality should be decent regardless of which rod end system you use. However, if you need a little extra precision, rubber bands on the rods will tighten it up when necessary (I use hair ties).
My biggest issue with them though is safety, I've had mag joints separate and the effector come off in my hands when I wasn't expecting it, luckily it was cold at the time. I don't like the idea of flinging around something that hot, untethered. It won't fly across your room, but it could land on something and start a fire or burn someone/something pretty bad.
- How important is the mass of the print head?
Depends on your priorities, if you want precision, it probably won't matter as your speeds will be low anyhow.
If you go for speed, then it does matter. Higher weight means slower acceleration and problems bringing it to a halt as well. This is a problem with mag joints.
- How accurate should positioning of the three axes be?
Using a probe and some software can tell you exactly how far off things are without a lot of effort. Probes make deltas much easier to use.
Traxxas are much simpler and cheaper to implement.
Yes, bearings and magnets are precise, they also weigh a lot, cost quite a bit and are a challenge to get right.
Despite what many think, the magnets aren't even that much better IF you do things right and think about what you are doing.
First off, magnets cannot handle high speeds. Before any of you complain, I've had them, at some of the speeds I run at, they will simply not hold on. It just won't happen. Some of this comes down to what you expect speed-wise. I had them chatter on small infill at 150mm/s, which is about the absolute slowest speeds I run my printers at these days for infill.
Second, if you want them for precision, you are probably running slow speeds anyhow. If you slow down any printer, slop and tolerances become less of an issue. Granted excessive slop is a problem, but if things are decent, your quality should be decent regardless of which rod end system you use. However, if you need a little extra precision, rubber bands on the rods will tighten it up when necessary (I use hair ties).
My biggest issue with them though is safety, I've had mag joints separate and the effector come off in my hands when I wasn't expecting it, luckily it was cold at the time. I don't like the idea of flinging around something that hot, untethered. It won't fly across your room, but it could land on something and start a fire or burn someone/something pretty bad.
- How important is the mass of the print head?
Depends on your priorities, if you want precision, it probably won't matter as your speeds will be low anyhow.
If you go for speed, then it does matter. Higher weight means slower acceleration and problems bringing it to a halt as well. This is a problem with mag joints.
- How accurate should positioning of the three axes be?
Using a probe and some software can tell you exactly how far off things are without a lot of effort. Probes make deltas much easier to use.
