“belt needs to be tight enough to make a noise like a guitar string”
That isn’t very specific… how tight does this belt need to be exactly? How do you know?
When the belt is in motion one side of it will stretch while the other side will go slack, you want it tight enough that when that happens the teeth remain completely engaged in the drive pulley.
The rough rule of thumb is that it should be tight enough that when you pluck it it sounds like a low guitar string. There’s no specific note to tune to, you just want to start at tight enough to have it make a sound when plucked then tighten as needed if the belt skips during fast reverses.
Can it be too tight? Also, having a hell of a time lining up the idle, stops, and the motor in with the axis
Tune to G#
If it’s too tight it will just wear faster. You simply want it tight but not ridiculously tight. Like the others said, if you pluck it while you tension it, when it starts to sound like a guitar string you can stop tensioning it.
@Jordan_Cohen yes, it can be way too tight. Bass guitar string or lowest tone on normal guitar. I actually get very good accuracy with no resonance on surfaces from what I would have considered not very tight belts when I started out. heavier systems need tighter belts but it can become a ‘dog chases tail’ situation. the axles for the pulleys and the mounts they are on need to be able to take whatever tension you put on them as well, things that need to be considered. So tight it makes things out of alignment is not good. cantilever axle pulleys only supported on one side that are found on some machines do very badly with over tightened belts. perfect belt alignment to the linear motion axis, least offset from the moving parts center of mass to the point they are pulled from, pulley axles supported on both sides, and moderate tension. General description of what is desired on axis using belts (X and Y on an i3 for instance).
Ahhh ok. So I loosened it one more tooth and aligned each side. Looks better. Should it be hard move the bed? Like should it be effortless?
@Jordan_Cohen it should be as effortless as possible, should feel very smooth. what machine is this? my i3 clone I had to rearrange some things, add spacers and change out m5 screws to longer ones and reverse them from the stock install, to create perfect linear alignment in the Y axis. For i3 I have a mod and a tip post on thingiverse here:
edit: Never mind on machine type MK2 Prusa i3, I see it in the OP now. that thing should not need much beyond tensioning they are designed with all the right things, aligned and supported correctly.
At best you should basically only feel the resistance of the motor when pushing. To tight belts will pose problems with bearings. The moment it starts sounding like a guitar string it is already pretty tight.
One of the first things I did with my prusa i3 was print belt tensioners for x and y. I also printed new bearing mounts with an adjustment a screw for Z height. And frame stiffeners. The quality is much better now. And the effort taught me a lot about printing.
@AlohaMilton I hear you, but they don’t give you any measurements for how far away the rails should be, they just tell you to use the frame as a rough guide. I wish they provided some inside dimensions and even printed little holes in all the parts to stick your calipers in.
All this guess work and ‘by eye shit’ has my inner ocd engineer freaking out.
Here is how I tune the belts on my printers. At a distance about 3" from the idler bearing (21mm) I should be able to pinch the belts about half the closing distance between them. If the belt is too lose I can touch them. If it is too tight I can’t pinch them far enough. The sound will be different depending on which side of the belt you pluck. On the side with the bed connection it is a low base sound. The beds move with almost no resistance. You also need to make sure the drive gear, the idler bearing and the bed attachment points are all in the same plane.
I noticed the bearings by themselves wheren’t all that ‘slidey’ on the rails. When I was testing things out before putting it together.
To help lower the resistance in the bearings I use silicon lubricant spray (plastic safe) on the rods and inside the bearings. You can apply it afterwards as well just don’t get it on your bed or nothing will stick. The bearings glide on the rods as you tilt the frame. Another advantage of silicon is that it repels dust.
That is a good goal to shoot for
@Jeff_Parish can you recommend
a silicon lubricant spray?
Any silicon spray that is plastic safe will work. I am currently using Liquid Wrench brand. http://www.liquidwrench.com/products/#!/2
yep, need a new hobby : )
The MK2 kit in particular shouldn’t have its Y belt tightened too much, as it will flex the Y motor out of alignment.