I'm in the process of assembling workbee 1500x1500 (screw driven) and I came across of a strange problem. After assembling Y plates and moving the eccentrics all the way it should be to allow biggest clearance between the wheels, manual says that when i run any piece of C-Beam between the wheels, it should wobble a bit. In my case instead of it being wobbly, i hardly put that C-Beam inside. I think its too tight already. Shortest C-Beam which will be used for Z-Axis is not entering by itself by gravity. I must push it in. And it happens on both - left and right Y-plates assemblies. What should I do? Now I've assembled also z-plate with wheels and only one way to move C-Beam through (and it moves very smooth then) was to loosen all the M5 bolts so all the wheels are wobbly when I move them. Maybe that's the way it should be then? Have bolts loosened? Maybe I'm overthinking it? I will try to complete that build, then I will check if it's ok But still, that Y-plates wheels are still worrying me a bit. Also i've got another question. i've seen on openbuilds official tutorial video that you guys at Openbuilds are using maximum amount of wheels that are possible for that Y-Plates (and that was for 1000x1000 build). In Ooznest instruction i'm told to use 2 pairs on the top and 2 pairs on the bottom (like on my photos uplaoded). I's it sufficient for 1,5m x 1,5 workbee machine? I've asked Ooznest support too but it's saturday so maybe i will get faster some suggestions here.
There does appear to have been a design change - my workbee bought from Ooznest nearly a year ago has four wheelsets on top and three sets on bottom. However it is the outer wheelsets that will take the most of any torsional forces. My C-beam was a little stiff to start with - the tyres on the V-wheels will "bed in" with a little use. Better to be slightly tight to start with rather than loose - means you have more adjustment on your eccentrics as the V-wheels wear. If you can push the C-beam back and forth with a slight resistance you are probably OK. You definitely do NOT want your V-wheels to be "wobbly", but don't overtighten the bolts - the V-wheels must still be able to turn. There is always some variation in the dimensions of extruded profiles - if you think it is really a problem I am sure Ryan at Ooznest will sort it out. The movement of the C-beam in your second video looked fine to me and in both videos it looked as though it was behaving the same as mine did when new. I had to adjust the eccentrics after a few hours of use. Alex.
Thanks for the suggestions. I guess that loosing M5 bolts a bit is the right answer. I have good feeling about this
Only loosen the M5 bolts if you think you have overtightened them - the wheels should be able to turn, but not wobble from side to side. Alex.
You probably need to contact Ooznest - measure the outside dimensions of your C-beam as accurately as possible and the centre - centre spacing of the holes in your gantry plates where the V-wheels are mounted. I'll let @Ryan Lock know about this conversation so he know what has been said. Alex.
Space from center to center of the v-wheel bolt = 99,65mm (this time i've measured z-plate, as i'm assembling it now) Complete v-wheel diameter = 23,95mm C-Beam height = 80mm( in the side where is that ACME nut-blocks space), and 79,85mm on the whole-alluminum side, which is bottom in the picture below) C-Beam width = 40mm Well, dimensions of the C-Beam are probably the same as shown on the picture below (checked some of them and everything looks ok): I've used mechanical calipers so i't can be a little wrong. Will have electronic one's in about an hour. But on the paper and when measuring, everything looks ok. If I will assume that my measurement about right: beam height + 2 x wheel radius - 2x wheel recess on the C-Beam for the wheel = Space between 2 bolts 80mm + (2 x 11,975mm) - 2 x 1,8mm = 100,35mm (space needed for wheels and c-beam) So 0,35mm more than the distance between the centers of 2 wheel bolts. Of course it's true if accentric nut is in the center position. Accentric spacer can go max 0.79mm of the center (am i right?) So if i will twist it to the most wide position it should be OK. That was the math (my math skills are not good ) And in reality I will just need to have accentric's in the most wide position and leave it that way.
Actually did a litte mistake...on the bottom i assumed i have 100mm of clearance and i've measured 99,65mm between 2 bolt centers.
I think your maths is right - if you are still having problems check with @Ryan Lock at Ooznest that the plates and C-beam are within tolerance. If you leave the bolts fixing the V-wheels loose you will have two major problems; There will be side play on both your Y and X gantries which will make your machine inaccurate and unpredictable. Your V-wheels and bearings will wear much more quickly. The C-beam can be a bit hard to get in when everything is new, but the V-wheels will "bed in" with a bit of use and will get looser on the C-beam. If you can get the C-beam in and move it by hand then you should be OK. Also, expect the leadscrews to be stiff in the nut blocks at first. If they are really stiff, grip the end of the leadscrew in a portable drill (low speed) and run the leadscrew back and forth through the nut block until it runs reasonably freely - it should still be a bit stiff to turn by hand - and lubricate with a DRY silicone or PTFE based spray NOT an oil based one. Alex.
If modifications are acceptable to you the best suggestion here would be to drill out the holes on fixed side a very slight amount. Leave these wheel axle screws a little loose while inserting the C-beam and then tighten which will hold them in place at their outermost position.
