Issue With New 3D Printer (Reprap Prusa i3)

[mavlock]

Hello all,
I recently purchased a 3D printer, and it seems there are some issues. There is a connection between the Z motor and the threaded rod using a beam coupling. The issue is that the stepper spins alright, except the rod doesn't start spinning, and then suddenly starts spinning and moves off the stepper and starts moving up off the 3D printer.

https://www.youtube.com/watch?v=TtlYJFSl_pY

Please help!

Thanks

[printbus]

I don't see the Z-axis doing much of anything in the video. Are the motors being driven with the usual reprap driver with a voltage adjustment? If so, have the stepper motor drivers been adjusted to ensure the motors are being driven properly? Do you think the Z-motors are trying to drive in the right direction?

That type of shaft coupler is notorious for not gripping the threaded rod very well. The issue is the threaded rods are technically undersized a bit compared to a smooth shaft. There's a similar shaft coupler that uses set screws to grab the shafts that does better, but many of us improve the grip with the kind you have by adding some foil or metal tape onto the threaded rods.

There's a problem in the Y-axis too, leading to what sounds like the Y-motor either skipping steps or if belt driven, the gear on the Y-motor skipping teeth on the belt. That could be a number of things wrong in the setup, from home/zero position and bed size definition in the firmware to wrong endstop switch position or setup, or incorrect motor direction, or...?

[MiniMadRyan]

I second printbus' comments. It seems like your Y-axis either doesn't have an end-stop or that the end-stop isn't connected properly, leading to the the horrible grinding noise you hear. I would think it your issue on the Z axis could be similar to the Y, as it appears the motors are wanting to turn, but are stopped by something. (is the X carriage crashing into the top of the frame?) Call me crazy, but in that video, does the z-motor not turn in the direction of raising the x-axis and not actually dropping it (thus homing the printer) Sounds like the motors are reversed and there may be some issues with the end-stops.

[mavlock]

Hey guys, I appreciate the replies,

I purchased this off someone so I don't know exactly what the issue is with the end stop and how to fix this. In regards to the Z motor, they are both spinning in the same direction, it seems there is a loose connection between the rod and the motor caused by the coupling. I unscrewed it and I saw that they were rotating the same way, and sometimes as I said, the rod 'spins off' the motor and moves up with the platform. How do I connect these solidly?

Thanks

[printbus]

As I said before, wrap the threaded rods with foil or some metal HVAC tape to make them a larger diameter than they are. That'll make it easier for the coupler to clamp onto the threaded rod. It may seem like it, but the couplers are not threaded. They are meant to clamp onto smooth shafts. Loosen the screw that closes the clamp on the threaded rod. If you have a thin screwdriver, try wedging it into the clamp slit and pry it open some. Reinsert the threaded rod after applying the foil or tape to it. Tighten up the screw that closes the clamp onto the threaded rod. If the threaded rod still spins, you'll need to try again, adding more foil or tape in order to improve the grip between the coupler and the threaded rod.

Again, there are different couplers that grab the threaded rods better, but you should be able to make these work.

[JohnA136]

If you newbies would just include your location in your posts or profiles, you might find someone local that might help? I am sure once you solve your coupling and end stop issue, you should be able to get some good prints going.

p.s., we use plastic tubing and zip ties on all our Prusa i3s and then never slip?

[mavlock]

Hello guys,

I appreciate the help. Basically it's sorted, the connector wasn't tight enough (silly me) and it seemed the manufacturer didn't put the stopper far enough forward, so pretty much it was rendered useless. However, another issue has occurred. it seems when it starts printing, it moves in the moves in the shape of the model, though no plastic is extruded. I know for a fact it's hot enough because plastic is oozing out when it's on the preheat, but when it's moving nothing comes out.

Thanks

[printbus]

Can you post a picture of the extruder assembly so we know what you have? They're not all the same. If you have one with a large gear in the back, do you see the gear rotate when you start the print? Which way does it turn?

Two things come to mind - the extruder could be pushed down onto the glass essentially blocking the nozzle or the extruder motor is rotating in the wrong direction.

Do you have an LCD control panel on the printer, or a computer hooked up to it that would allow you to do some manual operations through software like Pronterface or Repetier-Host?

Giving us more insight into what you have for a printer would make it easier to help you. It appears to be box-style Prusa i3, but that's not much to go on.

[mavlock]

Hello,

Thanks for all the help I have received. You'd be glad to hear it's working now and I am getting some promising results! The issue previously with the extrusion was that I was sent a free sample of filament, which was ABS, and my settings were for PLA so it wasn't melting.

I have been using hairspray on the bed and here are my completed prints (the fan cover is the first one I did, a bit rough done on 0.3mm print quality with 210c on extruder and 70c on heated bed.

photo 2.jpg photo 1 (1).jpg photo (7).jpg

Any tips on making them smoother whilst printing just let me know!

Thanks for everything! Wouldn't be working without you, so feel pride in knowing that these are a result of your knowledge!
Markus

P.s. Ignore the pump which was randomly attached and I cannot remove!

[printbus]

1) Calibrate the extruder so plastic is being extruded at the expected rate. 2) Make sure you've got the process for a good first layer figured out. If the first layer isn't right, it can mess up layers above it. 3) Understand the retraction settings in the slicer software and how to make the use of them.

There's lots of information to be found on these. Also, it's a good idea to figure out your optimum settings using various calibration test prints.

Good luck with the printer!