How good is a sub ?100 3d printer ?

[Roberts_Clif]

When I got lines like it was because of the lead-screw coupler.
I order for this too be what is happening you would have to have a 1.25 - 2mm pitch lead-screw.

Lead screws 3.jpg

From left to right T8-8 4 start lead screw 8mm pitch turned one revolution.
Center is a T8-2 single start lead screw 2mm pitch turned one revolution.
Far Left is a standard 8mm all thread used as a start lead screw 1.25mm pitch turned one revolution.

If you are using something like the two on the right then it could be that the lead-screw is not centered in the coupler.
I have to do this with my couplers wrap a single layer of tape around the lead-screw the press it into the coupler.
This allowed my lead-screw to turn truer, I also had a coupler that was sprung and wobbled this too required replacing with new coupler.

Now my Z-striping no longer exists. Hope this information helps you.

[curious aardvark]

okay, yep not sure about the revolutions. but I am still just using the plastic tubing, which is not perfectly centred on the spindle of the motor.

That makes sense. So basically need a better way to connect the screws to the motors.
Cool - cheers :-)

So this is what I need ?
https://www.amazon.co.uk/Samje-Coupl...ateway&sr=8-21

And probably these as well:
https://www.amazon.co.uk/KFL08-Align...ateway&sr=8-33

[curious aardvark]

If I get both from china, it'll be about 8 quid. Which just about keeps me under the 100 pound mark. And that should be the final mods :-)

6.77 pounds with postage.
It'll take 2-3 weeks, but there's no rush. Ordered 2 5-8mm couplers and 2 of the bearings I can just screw to the top of the frame.
Hopefully that should finish the machine off.

[hutchouk]

These are the couplers I used, currently at 69p each:

https://www.aliexpress.com/item/3281...27424c4dsjGCaf

I bought a pair of 5x8mm since I changed the lead screws. If your keeping the stock threaded rods, you'll need the 5x5mm ones. They should absorb some more of the wobble, but I've heard that these can stretch and knacker if misused, so it may be worth getting a few spares too.

I also discovered that many other users recommend spider couplers, which are more expensive but don't stretch or damage whilst still adsorbing a bit of the wobble.. These are ?5.54 for two including postage, so I'm trying out the cheaper ones first.
https://www.aliexpress.com/item/32888355543.html

The lead screws I bought where these (300mm with nut) at ?2.26 each:
https://www.aliexpress.com/item/3295...27424c4dBLyWKQ

I changed both at the same time (rookie mistake I know) and have seen an improvement. I may of got the same improvement by merely changing the couplers, but who knows!

I still get a little bit of wobble on the left hand z axis which i still need to investigate. This could be down to one of the cheap couplers being off centre. However, I also notice the left hand linear bearing is a little bit loose in it's bracket, which allows the lead screw wobble to affect the print. I'll probably try to fix this by padding or clamping the bearing in place a little better.

I also read on a couple of sites that holding the leadscrew in place at the top with bearings can exagerate the wobble, so it may be worth holding off on those flange bearings.

[Roberts_Clif]

Alignment is the key, I tried a solid coupler that I 3D Printed it was the worst coupler that I had ever used.

s-l1600.jpg

I use these couplers, though they can get stretched out of shape an cause this same issue.

My 3D Printer was working great though it needed to be disassembled, while it was disassembled somehow the couplers got sprung.
Thinking nothing about it re-assembled only to find that it was giving me this Z-Axis stripping.

2mm Layer Shifting.jpg
left was 3D Printed using a new coupler the Right was 3D Printed with sprung coupler.
Using a T8 single start lead-screw 2mm per turn rise (pitch).
You can measure the stripes at 2mm

[curious aardvark]

measured the screw rods they are 8mm and the stepper shaft is 5mm - so why would I need a 5mm=5mm coupler ?

Yeah aliexpress doesn't let you pay via paypal and I'm not giving my credit card details to the chinese :-)
how can an aluminium coupler stretch ?
I must be missing something here.

Printing some - now that' a good idea, I would have thought.

So aren't the couplers I ordered solid ?

As far as the flange bearings go. I wasn't planning on screwing the grub screws in, just going to use them to stop the screw wobbling at the top. Keep meaning to make some, but as the mini delta is currently giving me problems, don't have anything else with a fine enough nozzle to do a decent job.

[curious aardvark]

Figured I'd have a go at making some solid couplers anyway :-)

The side holes are 3mm. print it at .32 layer height and they will be deformed enough to give a really tight grip. Shouldn't need a nut inserted.

Figure it's worth a try :-)

[curious aardvark]

Ah, I see the ends of the threads are thinner than the rest.
lol, one of these days I'll measure things before ordering.
right cancel the 5-8 and order the 5-5 :-)

Aso change the plastic couplers too lol

[hutchouk]

If you're unable to cancel the 5x8mm couplers you can just turn the existing lead screws upside down.

[curious aardvark]

no problem cancelling.
claims they post in 2 days and I cancelled in about 10 minutes :-)

Then got 4 5-5 couplers these: https://3dprintboard.com/attachment.php?attachmentid=13158&d=1561725614&thu mb=1