Help with new custom printer - Prints have ringing around them

jumpedwithbothfeet

@mrawesome987 If you don't mind me asking what`s the purpose of the belt on the Z axis when you have two stepper motors on two lead screws? bed sag?

MrAwesome987

@jumpedwithbothfeet Just wanted to make sure both steppers are always synced. Is that a problem? It made sense when I designed it, is it overkill?

MrAwesome987

@siam I agree, it is likely the culprit, I just wanted to check with you guys before spending anything on replacement rods.

Do these often come bent like this? These were brand new when I purchased them.

jumpedwithbothfeet

@mrawesome987 I'm no way qualified to answer that to be honest, but I did run a very similar set up (without the belt) I didn't have any issues in that regard, I have had the same problem you have though but with 3 lead screws and that was because I hadn`t constrained my bed well enough.

Are your lead screws bent when not attached to the machine? i.e roll them on a flat surface and watch for wobble if they are good check for alignment issues on your printer.

SIam

@mrawesome987 said in Help with new custom printer - Prints have ringing around them:

Do these often come bent like this?

If they came from China, yes! I recommend ballscrews (not from China) these are not cheap, but it saves a lot of frustration.

MrAwesome987

@jumpedwithbothfeet Good suggestion. I will check this.

MrAwesome987

@siam Can you recommend a reputable place to purchase these? I may be willing to invest in some. Thanks!

SIam

@mrawesome987 I don't think that this will help you because is a German supplier I have my three ballscrews from https://www.dold-mechatronik.de/SFU1204-Standarbearbeitung

jumpedwithbothfeet

@mrawesome987 I noticed your using a flex coupling on at least one of your z stepper motors, good possibility that z belt of yours might be pulling the leadscrew out of alignment, worth checking with a print and the belt removed?

MrAwesome987

@jumpedwithbothfeet said in Help with new custom printer - Prints have ringing around them:

@mrawesome987 I noticed your using a flex coupling on at least one of your z stepper motors, good possibility that z belt of yours might be pulling the leadscrew out of alignment, worth checking with a print and the belt removed?

This is a good idea... I have not tried this, so I will do that! Thanks!

martin7404

I think your Z linear rods are not suitable for this or may get out of aligment easy. I would use full cylindrival bushings and roind rods

JoergS5

@mrawesome987 there could be additional reasons than discussed before

leadscrews being bent as discussed
the 4 supported shafts may have too high load, so pressure is built up and moves the bed sometimes
leadscrews can have different pitch (1/100 mm differences), so the bed is tilted a bit and builds pressure and releases it

A test would be to loosen 3 of the 4 shafts a bit (or the screws between organge part and aluminium extrusion) and check whether ringing is less then.

MrAwesome987

@martin7404 said in Help with new custom printer - Prints have ringing around them:

I think your Z linear rods are not suitable for this or may get out of aligment easy. I would use full cylindrival bushings and roind rods

I had not thought of this. Could you explain your thinking? The bed frame feels tight, and does not have any noticeable play in the X and Y axis. Thanks!

MrAwesome987

@jumpedwithbothfeet said in Help with new custom printer - Prints have ringing around them:

I noticed your using a flex coupling on at least one of your z stepper motors, good possibility that z belt of yours might be pulling the leadscrew out of alignment, worth checking with a print and the belt removed?

Just printed the same file but removed the Z sync belt. Results are MUCH better! Here's a before and after in the same lighting:

I'd say the issue is almost completely resolved, however, I think I am going to make a few adjustments to my design for permanent use.

Replace the lead screws with a better quality screw. Researching this now to find the best cost effective option. I looked at ball screws, but I don't think I can fit 1m ball screws in the budget right now. I am currently looking at Misumi screws. Are these of good quality for 3d printing?
Replace the flexible shaft couplings with solid couplings.
Design some sort of bearing mount for the top of the shaft that will allow the shaft to move slightly incase things aren't perfectly lined up.

Does anyone have any other suggestions or advice? Thanks again for all your help.

oliof

If haven't PID tuned your bed heater yet, now is the time. Bang bang controlled heating can cause enough expansion and reduction of the bed heater that you will get z banding artifacts.

JoergS5

This post is deleted!

martin7404

@mrawesome987 well this type of linear guide uses C shaped bushings and as far the rods are mounted on Aluprofile that is not straight in terms of hundreds of millimeter , so they can go slightly out of alignment .

jumpedwithbothfeet

@mrawesome987 glad you found the problem, it is looking a lot better do the lead screws still appear bent as they move on the machine? or has that gone now? as @oliof has suggested a bed PID tune is next it`s easy and most importantly free to do!

MrAwesome987

@jumpedwithbothfeet said in Help with new custom printer - Prints have ringing around them:

@mrawesome987 glad you found the problem, it is looking a lot better do the lead screws still appear bent as they move on the machine? or has that gone now? as @oliof has suggested a bed PID tune is next it`s easy and most importantly free to do!

The lead screws are definitely still looking bent. I'd like to replace them.

I am looking at the Misumi lead screws, but I'm having a hard time speccing what I need. The lead on my current screws is 2.54 mm, which is probably a bit low, right? They offer carbon steel and stainless. Any advantage to carbon steel?

Edit: I did PID tune the bed when I first configured it, although I PID tuned it for 60C, and I've been running it at 90C. Is that an issue?

mrehorstdmd

@mrawesome987 now check this video on fixing the Z surface smoothness:
https://www.youtube.com/watch?v=a3oQy6v3MrA