MakerBot Industries

Between the motor and the acrylic.

About the problem, you should set the metal pulley higher in the shaft of the motor.

Here are the active links for your pictures:

http://i.imgur.com/irJHo.jpg
http://i.imgur.com/5i53o.jpg

The pulley needs to come up on the axis as suggested by eried. The belt should be leveled. There is enough gear to hold it properly in place. The cork is in the right place and you need to tighten to screws down a lot more than you are doing. If all 4 are properly tighten (this is a lot more for tightening than you are tightening against wood) the motor shall not move (unless the cork is soaked in oil for some reason).

If you do want to remove any last space for freedom of movement you could use some M3 tooth lock washers (search for it at www.mcmaster.com). They will sink into the acrylic (scratching it) but that motor is going to be locked in position. Once again, there is no reason to do it in normal circumstances - just proper tightening with no washers at all should keep it in place.

There are also several tightening set ups in Thingiverse that you can print later in case of need. As soon as you can print make the Y-Idler support. It was the very first part I printed for my TOM. It does make a difference.

http://www.thingiverse.com/thing:7022

Remember to put a drop of 3 in 1 oil inside the idler before putting it all together. That is one of the places I found lubrication to be need more often (depending on how tight the belt is).

What difference makes the y-idler? I think it adds more kickback to the motion (I printed 2, one in pla and one in abs, and I ended removing it)

For me it helped to remove the stress from the acrylic (check for cracks everyone in while) and keeps the screw that holds the idler perfectly perpendicular to the belt rather than bending towards the Y-carriage. I have not experienced kickback problems.

It all depends on how tight you want the belt to be. In the case above the recommendation is to tighten things more, so the support would help keep things leveled.

Yeah, common sense tell us about those problems but have you seen cracks in the acrylic somewhere?

I ask you because I even feel that piece can add more stress to the belt system and to the wood rather than fixing a problem (the force in the acrilic is not so strong originally)

Since building it in March 2011 my TOM has developed cracks ( some as long as 20mm starting on the opening for the M3 nuts) on the MK6 acrylic parts and the constant heat from power supply and boards does not help the bottom plate either. I already have a set of MK6 spares from eBay. I have not seen any large cracks on the bottom plate and I believe that is because the stress has been distributed properly. I am not at the printer now so I cannot inspect it more closely. I will do that later.

I can tell you that there was already a noticeable "bend" to the idle screw when I set the support on it after a week of use and that distributing the force across the two top screws and front side rather than having a single perpendicular hold as original makes a difference in my TOM.

The issue is not present in the X belt because the top is secured to guarantee the balance and because the wood would not resist a similar effort as it the acrylic is subjected to in the Y-belt. A sign that the effort is not insignificant so I do not agree with you that the effort is not so strong originally.

Not necessarily in every time, but common sense usually prevails. :)