L51 wrote: ↑Sat Jan 13, 2018 10:18 pm
What would be a good acceleration to set?
Not to be glib, but, whatever gets rid of the ringing. It's not really an exact science, and everyone's machine will differ.
Ringing occurs because there is elasticity or play in your printer. The print head's inertia causes it to overshoot the corner (slightly), then it bounces back and forth (slightly) until it dissipates, like ripples in water.
There are a bunch of contributing factors:
- if the belt is loose, the rubber's stretchiness will allow the print head to bounce around. Proper tensioning removes most of this stretch, so there's less room for the belt to wiggle. Think of it like a rubber band - loose, it's really springy, but if you pull it taut it becomes... taut. There will still be *some* stretchiness no mater what you do - even a steel cable will stretch somewhat - but you want to minimize it as much as possible.
- if the speed is too high, you'll have too much inertia, making it harder for the print head to stop moving. Think of a high-speed car crash vs. bumping into a car in a parking lot. Reducing the acceleration reduces the speed, which lowers the inertia and reduces any potential wiggle.
- if the jerk is too high, again you'll have problems with inertia with the print head being yanked in a new direction before it's stopped moving along the last axis. By lowering the jerk, you give the print head more time to settle down. On the other hand, if your jerk is too *low*, the details will become soft and indistinct, because it takes too long to change directions.
- you can also have problems with harmonic vibration. If the surface your printer is on is bouncing and shaking, it will have to compensate for that as well as its own mechanics.
So eliminating ringing is mostly a balancing act, and you mostly just have to experiment to see what works best for you. Start by making sure your belts are properly tensioned. It's also worth checking your printer for loose bolts. Then start reducing your print times until you get reasonable results. Then start adjusting your jerk settings to see if you can bump up your print speeds (or, if you're not getting acceptable results at 20mm/s, the problem may be the jerk more than the speed). And if your printer is bouncing around when it's printing, try putting it on a more rigid surface.
I don't have an A8 so I can't give any specific settings, but there are a lot of A8 user groups out there - facebook, reddit, thingiverse, discussion groups - that can probably give you some settings suggestions to get a starting point. Although as a DIY kit that often gets heavily modded, it's *really* going to be down to your specific printer.