Play of the bed too high? (with video)

Snapmaker J1
1

Hello,

the print bed of the J1 has a play of about 2mm, and you can hear it “clack” when you move it up and down by hand:

play.mp4 - Google Drive (Video)

I am afraid it affects print quality during fast movements. Is this play normal? How can I fix it?

2

As far as I’m aware its completely normal, under normal circumstances there should be no forces pushing up from under the print bed. Unless your experimenting with non-planer slicing, fast print speed will not affect the bed in any way on a core XY machine since the bed remain stationary until the next layer change or z-hop. In fact I believe this “bed flex” is actually a safety mechanism so you are less likely to destroy your printer when things get under the print bed. Unless the flex is so bad that you cannot get the bed to level then that’s a whole different story.

3

I had three printers so far and none of them showed this issue while trying to push the bed up. Especially not in combination with noise.

As long as the bed is not moving during print (beside the normal x/y moves) and the level and printing doesn’t show anything wrong, i would not be too concerned

4

You need to look closely at which parts are allowing this movement.

1 Like
5

Hi,
thanks for your answers. As for my observations: I think the bearings on the left and right allow this play. I am wondering when the print head quickly moves back and forth on the y direction, the vibration by velocity changes actually points up and down. I’m just not sure if the weight of the print bed is high enough so it will keep down. Can anyone check if their J1 is having the same amount of play for comparison?

6

Comparing your video to mine it does seem like your bed have a little more flex then it should but not by much, perhaps 20~30% more? Granted I have no idea how much force your pushing against the bed but I was applying somewhere around 1~2kg of force to get any significant bed flex, which unless you’re printing more than half spool of filament in one go I wouldn’t even begin to worry about it.

So far I have put the printer through maybe some 100 hours of print time with about half of that on PLA+ on PEI and the other 50 trying to figure out how to get ASA to stick to the bed reliably and experimenting with HIPS supports for ASA. Currently what’s seen in the video is my best solution yet, double sided Kapton tape on glass.

I print my PLA at 0.3~0.2 layer height at 240mm/s for things that don’t require high precision fitment (±0.2mm) and my ASA/HIPS at 0.12 layer height 40mm/s perimeter and 80mm/s infill, do note this speed for ASA is with 0.2mm nozzle which I’m currently experimenting with alongside the fact I’m printing highly detailed figures for acetone vapor smoothing, I fully plan to do 100mm/s+ for ASA for normal functional prints as well.

Remember the little remark at the flex being a safety mechanism? Well I don’t know if the Snapmaker team intended for this but I had accidentally left my bed scraper under the print bed once and I came back to it and saw the tuning knob right on top of the handle of the bed scraper, I thought I had ruined the printer for sure but after pulling the tool out the bed just flexed right back into position and after a quick releveling I was back to printing in 10 mins and its still doing just fine.

Point is I highly doubt the bed flex you’re experiencing will cause you any grief with high speed printing, the fastest I’ve done on my machine is 280mm/s with PLA and the only reason I didn’t push faster is because of the table I’m currently using resonates hard at speeds higher then 240mm/s during infills. I have no failure caused by the printer’s kinematic system so far even with such small layer heights, although I do admit my prints rarely go over 200g per run.

In my humble opinion, if your not experiencing any issues caused by the print bed now, you should not worry about it and just try to do whatever it is that you want to do. I was originally worried about the bed being supported from only one side too when I first got the printer but given just how well its doing 10+ hour prints now at speeds my old bed slinger wouldn’t even dream of, my previous skepticism is now completely gone.

1 Like
7

Hi,
If you hear kind-a clacking sound while pushing cantilever bed up- and downwards by hand, the most likely this is about play in linear bearings. I have tested the same on my SJ1 - frontal “freedom” is about 1.5mm. I just made a rough sketch to explain how tiny play in bearings might introduce significant freedom at the front of table.

image
image1474×834 100 KB

On my printer Z-axis bearings are rather loose as well but I was not investigating it more deeply as “mother gravity” compensates for this problem rather well. As motion nut is also a bit loose, all table assembly moves up and down being well controlled by gravity. Could happen at some point this problem will need to be addressed more seriously. I have been running my SJ1 almost a year 24/7 and this by far is not the main problem with this machine :grinning:
Often linear rods are the ones being undersized (I have not measured on particular printer though). In particular printer I guess also the very Z-axis bearings are to be suspected for excessive play.
In the beginning I was a bit suspicious about cantilever design of table of this printer but in fact so far never experienced any printing problems that might be explained by flaws of this design.

1 Like
8

If you want to see a flimsy variant of the J1 table, do a search for “German Reprap Neo”.
That table and its corresponding z rods were weak! But even that one was well able to print without problems, even if you could easily bent it up and down almost by 10mm :laughing:

You need to always keep in mind that you exert a multiple of force when pushing on the table front with your finger in comparison to what a printed part might have.

The only thing that I would still strongly suggest is to make sure all four z linear bearings of the J1 table are properly lubricated.