Issues w/ assembling my Prusa i3
January 16, 2015 11:55PM
I purchased a He3D Prusa i3 recently, and the assembly has been a headache. The "detailed instructions" are a series of videos that leave and miss things, and the company's customer service can be a little touchy. Anyway, my current issue is with the smooth rods that it came with. the bearings don't freely slide on 3 of the rods. They feel like they bind up. If I just hold the rod verticle, the bearing doesn't move. If I use my hand to move it, I can feel the rod or the bearing wanting to rotate. The two rods for the y-axis seem to work, and one of the others is perfect.

My question is, is there a place where I can get individual rods to replace the ones that don't work, or is it just better to order a whole set? I've found some places that has the set of rods for $30. Is that about right, or are there cheaper options.

Thanks for any help
Re: Issues w/ assembling my Prusa i3
January 17, 2015 01:30PM
The rods won't help you. It's the bearings, you could try squirting a little sewing machine oil into the bearing before you place it on the rod.
Re: Issues w/ assembling my Prusa i3
January 17, 2015 01:44PM
Hi, you should give another try at your reseller's first. They should appreciate your problem. If not, the best way to get rods is to buy them online. Before to purchase anything, you may check again the rods, because maybe they're not to blame. Find a stiff flat surface (glass plate, kitchen top...) and try to roll the rods on it. If the rods runs properly, it's a bearing problem. Most of the LM8UU bearings provided in kits are cheap china ones; Some loose balls, some ball paths are a bit too tight. Anyways you need to lubricate them before use. I recomand a spray of dry PTFE based lubricant.

On my kit I thought the rods were bended, but it was the bearings. I recieved 12 LM8UU in my kit and 5 of them was damaged. For lost balls, there's nothing to do, but with some lubricant, it's posible to run some of them a while, event if the moves are not smooth and noisy. I changed for self lubricated Igus Drylin bearings, and it was a great improvement. If the bearings are to blame, try to find Igus bearings on ebay or amazon. You can also find quality LM8UU bearings with confidence in SFK or NSK brands, but they're pretty expensive (10 bocks each). You can also get some brass bearings which are cheaper and works pretty well too. Good luck.

Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)
Re: Issues w/ assembling my Prusa i3
January 17, 2015 09:25PM
Thanks guys. I did contact the seller, and they are sending out new rods.
I did check the rods and they passed the roll test. It's just when I put any of the bearings on the "bad" rods, they basically don't move, and when I do, they are hard to move. But when I put them on the "good" rod, they move just fine. They actually slide freely. I did test all of the bearings this way.
I did loose balls in a couple of bearings. The printer did originate from china. Anyway, I'll add bearings to my list of modifications/upgrades I want to do. Or maybe I'll just build a new better printer once I get comfortable with this one.

Thanks again
Re: Issues w/ assembling my Prusa i3
January 18, 2015 11:43PM
Does the problem follow the rods, or the bearings?

I suppose that it's possible that you got some rods that were rolled out of spec. Maybe they're 21/64" or something like that. (That's the size of the drill bit that I use to make clearance for an 8mm rod, because it's something like 8.33mm when converted, which is tight enough to hold things with minimal shimming, but loose enough to actuall allow the thing to fit.)

If the problem follows the bearings, then it's the bearing's fault.
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