I am assembling the z carriage, and can’t get it so slide freely all the way to the bottom. It slides ok up and down, but when it gets an inch or so from the bottom it tightens up. It will go all the way down without too much force, but it’s noticeably tighter toward the bottom. I’ve tried loosening and tightening everything while sliding up and down, but still tight at the bottom. Any tips or tricks to get it smooth top to bottom?
Hello,
You did not indicate in your post if you were using the stepper motor to drive the z axis or just trying to get the z axis to slide on the rods manually without the motor drive and threaded rod installed.
In my kit the steel rods were coated with some sort of rust preventative (I’m guessing) and the linear bearings felt a bit rough, just sliding an unmounted rod through the linear bearing. White lithium grease was the solution to this. The other thought is the “squareness” of the frame. If the frame is not “square” 90 degree corners that could cause binding. Check the corner braces at the top of the Z axis (the part that does not move). Also check that the vertical aluminum channels are exactly the same distance from the ends of the horizontal aluminum side rails.
I hope this helps.
Cheers,
NeilRG
I’m still on chapter 4, just trying to get the carriage mounted on the two vertical rods without binding at the top or bottom when sliding by hand. I’ve taken measurements and believe the rods are slightly further apart at the top and bottom (81.3 compared to 80.9 in the middle). I’ve rearranged the mounting posts and bearings and tried many tightening sequences. I saw someone else say he drilled the holes in the plate a tad to allow the bearings to be further apart. I’m mulling whether I need to do that? Was thinking I might try M3 bolts first to pick up a little more wiggle room? Thoughts on all that?
Hello again,
The structural aluminum parts in my kit were all cut nice and square, and the guide rods with exception of the threaded z axis were also true. This i determined by rolling them on my kitchen counters.
I sense that you are trying to be diligent in your efforts, so I would suggest that since the rods are accessible that you roll them on a glass table to to confirm they are true.I interpreted your measurement to mean that the one or both of the rods is bowed out of true.
Mark the rods on the ends in ink so you can them apart As you roll them slowly you may find that there will be a point at which one of the ends seems to lift off the glass surface. use only one hand as you do this and where your fingers are located at the point the rod end lifts clear you have found a bend in the rod right under your finger. Work with it a bit and you will be able to pinch the rod clear of the glass without turning it further, put a mark at that point opposite where your finger is.
If the rod is found to have a few tenths of a gentle bow, you may be able to true it up by supporting it on between two wooden blocks and TAPPING the area where you made your out of true mark. Use another wood block with a small hammer, never a metal hammer of the finished rod surface directly. If you put a knick in it, you are done, that rod is scrap.
Then repeat the rolling on the table test. Mark it. Tap it then roll some more. Much easier to actually do this then to write about it I assure you.
I hope this helps.
NeilRG
Thanks again for your input and help. I’m an old pool player (billiards) so already tried rolling the rods to confirm they were true. They are. The real issue is that the center line of the bearings can’t get more than about 80.9mm apart, whereas the plastic parts that hold the rods in place put the rods a little over 81mm apart. The carriage sides ok in the middle of the range – I assume because the rods are flexing a tenth of a mm or so – but when it gets close to the top or bottom, the plastic clips keep the rods forced apart a tad wider than I can get the bearings, so the carriage stops sliding nicely.
I saw someone else say they drilled the holes in the carriage plate a little bigger so the bearing can sit a tiny bit further apart. Another thought I had is to sand off a tiny bit on the end of the plastic clips so the rods are tiny bit closer together. However, I did not want to modify the parts in the kit until exhausting all options. As such, I bought new bolts that are a little bit thinner so that the bearings can sit a tiny bit further apart. I used #6-32 bolts, and now the carriage slides very smoothly all the way up and down with all bolts fully tightened. #6 bolts are a standard size in the US, and are almost exactly 3.5mm in diameter – so just half a mm thinner than the bolts that come with the kit. M3 bolts presumably would work also, but I figured I’d use the biggest bolts that work. All seems good now, but will report back if there are any unexpected problems with this solution.