Funssor (ChaoticLab knock off) All Metal Z-Tensioner

I bought an all metal Z-axis tensioner for the Voron 2.4 from AliExpress, not knowing at the time it was a knock off of the Chaoticlabs design (I should have bought it directly from ChaoticLabs which may also have saved me a bit of trouble setting it up). 

So this is NOT a post about the official ChaoticLabs Z-axis Tensioner, but a review of the AliExpress "Funssor" version.  When I received the parts, I thought they looked OK and were well made.  However when I went to swap the printed Z-axis tensioners, I ran into the first problem.  The shoulder screws which were included did not fit the stock GT2 20 tooth (9mm) idlers.  I measured them and found they were about 4.97mm in diameter so they should have fit, however when I checked the point where the threads stop and the shoulder begins, I noticed a very slight bump in the profile of the screw (under a microscope).  

​I ran the screws in my drill and used a small hand file to bring down this area and then used some fine grit sandpaper to clean it up, which fixed that issue.

The second issue which is gonna require parts, is that the idler will grind to a halt if I snug down the shoulder screw that holds it in place, even just a bit.  I was able to reduce this problem if I added another M5x8x1 flat washer to the stack, however they only include four of these washers in the kit (so I would need four more).  I think some blue threadlocker is a must on this as well, since even with the extra flat washer, the screw cannot be tightened down due to the design of the tensioner.  One trick to use when assembling the idler into the part, is to stick the edge of the washer to the idler using some tape, and then when the screw is started into the threads, pull the tape out.  Otherwise getting the inner flat washer installed is a bit of a pain.  

So I am again waiting on parts and re-installed my printed Z-axis tensioner, which will work just fine.  The advantage to the Chaoticlab design is the knob, which will allow much simpler adjustment of the tension.  They have made the design files available for printing as well.  I'd suggest if you plan to buy these, try the official version from Chaoticlab instead of saving a couple bucks on the AliExpress knock off like I did, since it can't be worse than the knock off, and is probably higher quality.  I'd suggest picking up some extra M5x8x1 flat washers in any case, since they could be handy and are easy to lose during assembly.

It's gonna be a while before I get the washers, so will update when these are finally installed.

Update 5/4/2023: I received the washers and installed the tensioners and have mixed feelings about them.

Pros:

• Aluminum construction should be stronger than printed
• The knob is much easier to use than tensioning using an allen wrench

Cons:

• The construction is not great, the shoulder bolts required filing, and the knob feels crunchy.
• Required ordering washers, which only helped somewhat.
• I'm not a fan of the way the pulley is held in.  The shoulder bolt which holds the pulley cannot be fully tightened without seizing the pulley.  The retaining bolt is also somewhat cantilevered, since one side is only supported by the bolt head.  They could have just used the same design to retain the pulley as stock, and it would have been better. 

Overall I would not recommend these.  They look nice, but for the cost, they should operate smoothly and installation should not be such a pain.  Since I was unable to fully tighten the bolts for the pulleys, I have little doubt that I will need to re-tighten them regularly or design some other solution.  Again however, it should be noted that these were AliExpress knock offs, and are not Chaoticlabs branded tensioners, so I do not know if the genuine article would improve on the problems I experienced.