I just had my 2nd rear lead screw nut strip out on my H2 which began life as an H2D and I upgraded to an H2C. The first was about 1,500 to 2,000 hours in and happened about the time I received my H2C upgrade kit, so I replaced all the lead screws and nuts at the time of the upgrade and greased the lead screws. I am now at 137 hours of printing after the upgrade/lead screw replacement and have had the rear lead screw nut strip out again.
I have submitted a ticket but since it’s the Chinese New Year (Kindly note that during the Chinese New Year Holiday (From Feb 15th to Feb 23rd), there will be an additional delay of 4–5 days in our response time due to limited resources in our customer support team.) I thought I would post here to see if anyone knows if there is any alignment process, I may have messed up in replacing the last ones.
I just find it hard to believe that a greased lead screw would strip out in 137 hours of printing. I have read many online posts of the H2 rear lead screw nut stripping out and wonder of something else is wrong.
Ooof, I’m assuming they supplied new lead screws with the nuts. I know I got a set of LDO lead screws for a home build kit and the threads had burrs all over them. What else could chew up a brass nut that quickly?
Yes, BL Support was very good about sending out a complete Lead Screw kit. I replaced them all and greased and have the same problem with the same lead screw. Its a little frustrating but BL support is usually pretty good to work with from my experience except for the delays and the H2D to H2C serial number upgrade process. I am hopeful they will be able to help me I just need to wait for them to get back from vacation. My main concern is finding out what is the root cause of the issue so I am not having this problem on a regular basis.
Since all three screws are driven by a common belt, they all turn synchronously, one screw can’t turn any further than any other screw. But there is also “phasing”. Each screw needs to be in the same rotational position with respect to its nut. If one nut (say, the back one) is a thread higher than the others, the system will work perfectly (since we can’t see bed meshes, you wouldn’t know the back was high) but that nut is going to be under a lot more load and that load is likely to wear it out faster. The higher the “phase error” the greater the load, the faster the nut will wear.
That being said, a leadscrew should be able to take some load and not wear out quickly. If it wears out quick, even when properly greased, I think that means the surface roughness of the screw is too high, it’s not finished correctly, or the nut does not have enough threading for the load it needs to bear (the more threads, the less stress each thread bears and the slower it wears out).
Can this be theoretically fixed by “ramming” the bed down until lockout on all 3 lead screws? I have a separate bed-slinger machine that has independently driven Z-axis screws moving the entire X-gantry up and down. To “tram” the X-gantry, it basically rams it all the way to the top which has a fixed metal plate, until both sides lock out, presumably at the right spot for the lead screw nut.
I’m thinking the same can be done to get the three lead screws in phase with each other and the corresponding nut, but I could also be very wrong in how it works mechanically. Perhaps, the first lead screw to lock out would then lock the rest out without actually shifting the phase of the others since they are linked by the belt.
I couldn’t say. But the procedure for replacing a screw/nut should include consideration for this. I haven’t looked at the WiKi to see if it does. It may not be explicitly called out, it could be implicit in the way the job is done. But I don’t know and I’m too lazy to go look.
All very good thoughts. I followed the wiki when I changed them out but I could have messed something up and not known it. I’m just concerned that I fix it again and it happens again.
Almost certainly something else is wrong. The lead screw nut should not strip out unless the nuts have a material failure in their manufacture - and over batches and time that is highly unlikely in a well run manufacturer. The other source is some other defect is putting undo stress in the nut causing it to wear out , and replacing the nut won’t fix that.
They are sending me another lead screw kit, hopefully this one lasts longer then 137 hours. I can only assume that I did something wrong when I replaced it the last time as I agree, it shouldn’t wear out like this.
I didn’t think it was too difficult. I do wonder why they strip out so soon, I have maintained mine and greased them regularly. I had the rear screw strip twice while the two front screws have been fine.
My rear nut stripped at about 3000 hours. Replace it and about 1 month later the front right one went out. Replaced both front ones. 1 month later the rear went out again. Replaced it, and today the left front went out, even though it was only about 1 month old. Getting frustrated with this……
Wow! Seems like there is an issue with these lead screws and nuts. I have to assume that they will get it figured out and rectified. Other than having a wait a day or two or more between responses on desk tickets the customer service has been pretty good. I don’t understand why it takes so long between responses but the overall service has been decent.
There is clearly something going on. Lead screws should not wear out like this. Or if they do, they should all wear out at the same rate.
But it doesn’t appear to be happening a lot since there are (at this point) probably 10Ks of BBL printers in operation world wide and only a few reports of nuts wearing out.
This is almost certainly a defective component issue, the quality of the screws or nuts. Most are OK, but a small percentage are clearly not OK…
It’d be interesting (to me, anyway) to take a look at a bad screw under a microscope to see how the threads look. Gotta think BBL is doing this already, to figure out what’s wrong and correct it.
I agree, I have to believe BL is investigating this. My experience has been the hard metal screw has held up its the yellow metal (soft metal) nut that strips out as I assume it was designed to do. It’s just stripping out very soon. Maybe thread design or something elase.
Precision lead screws are typically hardened and then ground to final dimension (setting aside whirling) - the lead nut is always a softer material such as brass, bronze, or even HDPE.
If the screw is properly finished and is correctly sized for the application, there should be verrrrrrry little wear over the lifetime of the device. There could also potentially be a phasing issue in a 3-screw arrangement being driven off a single belt, but I would expect the design should make it easy to set phase while the machine is being assembled.
BL should probably just upgrade everyone to ballscrews just to be on the safe side tho😋
For all the people whose Lead screw nuts have failed, how often and how did you clean and lube and did you use Bambu grease on the lead screws? Be honest. It would be good info.
