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Slipping Z axis?

PostPosted: 2013-Jul-Sun-15-Jul
by bringho
I've started printing 8-)

The first print was the 5mm Calibration Cube Steps by MCroucher from Thingverse (thing:24238) and though it did not come out looking great it was a sucessful first print.

It was done using the instructions in the online Simple Getting Started Guide and it looks like I need to add a fan to cool the part being printed.
blob.jpg


I later found out that I had inserted the wrong filament diameter into Repetier (1 instead of 1.7 because I used a comma instead of a dot as the decimal separator) and have yet to try with the correct setting...

Then I lowered the print height to 0.2 and added support and tried to print out the Printrbot Simple Bed Leveling Screws by JohnSL from Thingverse (thing:103519) but that did not work out well so I reversed to 0.3 layer height and even though the control over the support feels strange I managed to get a second print that I could clean out quite easily so those are now installed.

I tried to slice the Harry Potter Gryffindor Crest by Imminentfate from Thingverse (thing:123282), scaled down to 33% of the original but both test prints failed at the start of layer 9 with that layer being moved roughly +20 mm in x axis... No Idea what could be wrong but I've saved the file if anyone is interested to have a look at it.

Then I decided to print the swirly shot glass by profgizmo from Thingverse (thing:36103) and then I found this strange behaviour which I would guess is due to z-axis slipping if it were not for the fact that the shot glass measures almost exactly the expected height?!?
First image shows layer 72 of 148
strange_printing_behaviour_1.jpg


Secon image sows rougly layer 120 (still of 148 ;)
strange_printing_behaviour_2.jpg


Any comment appreciated.

Re: Slipping Z axis?

PostPosted: 2013-Jul-Sun-18-Jul
by Tdeagan
My first guess would be inadequate current settings for the z steppers.

Wouldn't hurt to lube the lead screws (I use lithium grease.)

Re: Slipping Z axis?

PostPosted: 2013-Jul-Tue-16-Jul
by bringho
Thanks m8!

I've bought and applied lithium grease but I still have the z-axis problem.

I've found that there are some cables near the z-axis coupling and will take a closer look to ensure that's not the problem before I start adjusting the current which seem to be a pain in the ... on my production Simple.

Re: Slipping Z axis?

PostPosted: 2013-Jul-Tue-16-Jul
by Tdeagan
The current adjustment should be easier than it sounds. Each of the motor drivers on the Printrboard has a tiny trim pot.
Image
Use a jewler's flathead screwdriver to turn it (in pretty small increments, say 30 degrees clockwise.) Try out some printing, or even just run the Z axis up and down a number of times. Feel the temp of the Z motor housing. You should be able to increase the current up to the point where the motor starts running hot (which is undesirable.)

Re: Slipping Z axis?

PostPosted: 2013-Jul-Wed-12-Jul
by bringho
Thanks!

Before dismantling the Simple I found out that the controller board is quite simple to get to when the extruder is in top position ;)

I then noticed that the bottom part of the z-coupler (the one connected to the servo) had popped up so the strap did not secure it to the axis... which most certainly is the reason for slippage. I pushed the tube in place again but before I had a chance to test it I managed to break my PSU :x so now I have to repair / get a new PSU before commencing my trials. :cry:

Re: Slipping Z axis?

PostPosted: 2013-Jul-Wed-17-Jul
by Tdeagan
Good catch on the troubleshooting. Bummer on the PSU. But, better it fails now than in the last 10 minutes of a three hour print :P (been there.)
good luck!

Re: Slipping Z axis?

PostPosted: 2013-Aug-Fri-17-Aug
by bringho
My new (expensive) 'VOLTCRAFT ' 8.5 amps PSU arrived the other day and I've been doing some more testing :D

Slipping seem to be a thing of the past with the tube firmly pushed down on the motor axis. 8-)

Link for any European who wants/needs a new/better PSU:
http://www.conrad.de/ce/de/product/514003/VOLTCRAFT-NPS-150-USB-Notebook-Netzteil-Laptop-Netzteil-146-W-12V14V16V18V185V19V195V20V22V24V-85-A-max

Thanks for all the help !!!

Re: Slipping Z axis?

PostPosted: 2013-Aug-Sat-08-Aug
by REPRAP SQUAD
If you guys ever have any probs with the x and y axis I've found that a little shrink wrap helps to grip really well.

Re: Slipping Z axis?

PostPosted: 2013-Aug-Sat-23-Aug
by MDW
REPRAP SQUAD wrote:If you guys ever have any probs with the x and y axis I've found that a little shrink wrap helps to grip really well.

Can you please explain this one a little more? You wrapped the belt in shrink wrap, I guess? Doesn't the gear tear that up?

Re: Slipping Z axis?

PostPosted: 2013-Aug-Sat-23-Aug
by REPRAP SQUAD
Im refering to slippage on the x and y axis that uses vinyl tubing for the spectra line.