1 Topic by mmiller7 (edited by mmiller7 2015-10-08 11:09:45)

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Topic: Questions about replacing Z-screw

I've been battling Z-axis banding, finally traced the problem to a bent lead-screw (I can see the motor and printer-bottom flex and wiggle, exactly like this just less severe).

Question 1: This is non-fixable, I have to replace the Z axis screw/motor, correct?
Question 2: After installing the new motor/screw, will I need to "adjust" anything with the control board?  I know I read there was something about XY axis work that may require tweaking potentiometers to get circular circles, will I have to adjust anything like that for the Z-axis motor?
Question 3: Is there anything I can do to prevent this in the future?  I'm guessing it happened either removing a "really stuck" print, or while transporting the printer, but I'm not entirely sure how it happened.

I've watched the guide from Solidoodle at https://vimeo.com/61632393 but they don't seem to mention adjusting anything just to re-assemble it.

2 Reply by AZERATE

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Re: Questions about replacing Z-screw

Have you taken a look at this thread? http://www.soliforum.com/topic/2154/fix … aded-zrod/
It is a sticky in the Hacks/Mods area.

A1: Nothing can fix a bent screw. You can combat all you want, but a jacked up screw is a jacked up screw. My #1 has a pretty big wobble to it, but I print just fine with a well nut.
A2: To be clear, I have not done this mod, so I will not give false advice. However, if you were to upgrade to something like an M5 rod, you will have to change your Z steps per/mm in EEPROM.
A3: You have a shaft on either side of the Z rod, so I doubt fighting a stuck print would be the cuplrit, though I suppose it is possible if you used a mallet big_smile

On the topic of stuck prints, if you are printing direct to glass, just put the glass in the freezer for a minute or even on a cool surface for a few and the part will come right off.

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3 Reply by jagowilson (edited by jagowilson 2015-10-08 16:10:04)

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Re: Questions about replacing Z-screw

Steps to remove the Z platform:

0. Disconnect the motor, thermistor and bed heater from the motherboard; bring the wires into the frame.
1. Loosen the 4 screws on the bottom of the frame holding the motor in place.
2. Loosen the 4 hose clamps or shaft collars holding the two Z rods in place.
3. Remove the Z rods from the frame.
4. Pull the entire assembly out.
5. Remove the platform from the motor+screw assembly.

Now you have to remove the Z screw from the motor. Here's how I do it:
1. Go find six 5/16" square nuts
2. Put the nuts on the shaft, all the way to the bottom, until they fall off and onto the motor front plate
3. Keep doing this until there is no more empty space for nuts to fit.
4. Tighten the final nut as hard as you can--the rod will pop right off the motor shaft.

Now you need to install a new rod. Regardless of if you use an M5 or another 5/16", you will need a coupler. Use a flexible 5-to-5mm or (5-to-8mm if you use a 5/16" rod instead of a 5mm). Make sure you get one that pinches the coupler together, NOT one that secures the coupler in place with a set screw on the shafts.

When I get home I will send you a design wardjr worked up for an M5 shaft, which will work for you only if you are using the wooden platform.

It's likely this happened in transit. When you transport your printer in the future, put the Z axis all the way at the bottom.

4 Reply by Claghorn

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Re: Questions about replacing Z-screw

Here's my experience replacing my Z axis with a small M3 threaded rod:

http://tomhorsley.com/hardware/solidood … dle-z.html

P.S. The note at the end about having parts come out too tall was apparently a one-time glitch. I tried to reproduce the problem to see what was going on and everything I did after the first print came out the expected height.

Claghorn's Website

5 Reply by mmiller7

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Re: Questions about replacing Z-screw

AZERATE wrote:

Have you taken a look at this thread? http://www.soliforum.com/topic/2154/fix … aded-zrod/
It is a sticky in the Hacks/Mods area.

A1: Nothing can fix a bent screw. You can combat all you want, but a jacked up screw is a jacked up screw. My #1 has a pretty big wobble to it, but I print just fine with a well nut.
A2: To be clear, I have not done this mod, so I will not give false advice. However, if you were to upgrade to something like an M5 rod, you will have to change your Z steps per/mm in EEPROM.
A3: You have a shaft on either side of the Z rod, so I doubt fighting a stuck print would be the cuplrit, though I suppose it is possible if you used a mallet big_smile

On the topic of stuck prints, if you are printing direct to glass, just put the glass in the freezer for a minute or even on a cool surface for a few and the part will come right off.

I figured as much and placed an order for a new Z axis motor/rod...fairly affordable though I feel a bit sad tossing a perfectly good stepper motor so it'll probably sit forever in a parts-bin.  I'm a bit nervous doing major mods like replacing the Z-steps, I've already had some run-ins trying to flash firmware to get bed PID and now it only works with the auto-reset jumper "open" (no idea, but I don't want to replace the system board).  Ended up using ISP because I never got it to flash thru USB.

My Solidoodle 2 is basically "stock" other than a couple very minor things...like an "on-off" switch on the 12V input and PVC spool holder above the machine, plus some plexiglass/poster-board enclosure.  I've added bed-PID in the firmware but that's about the most ambitious I've become.

The bed is just plain kapton tape - somehow it's still the same tape the printer shipped with even after 2+ years of use (!) though I am thinking I may need to replace it soon as it's getting more bubbles and "un-sticking" from the aluminum bed in places.  I have more kapton pad just dread changing it...so far cleaning with acetone has been sufficient to re-use it.  I was going to try glass but it seemed like more trouble than it was worth and I gave up.

To remove prints, most pull off or I can slip the edge of my Leatherman blade and "pry" against the bed (I've become really good at matching the angle and not nicking the tape).

6 Reply by mmiller7 (edited by mmiller7 2015-10-08 20:30:26)

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Re: Questions about replacing Z-screw

jagowilson wrote:

Steps to remove the Z platform:

0. Disconnect the motor, thermistor and bed heater from the motherboard; bring the wires into the frame.
1. Loosen the 4 screws on the bottom of the frame holding the motor in place.
2. Loosen the 4 hose clamps or shaft collars holding the two Z rods in place.
3. Remove the Z rods from the frame.
4. Pull the entire assembly out.
5. Remove the platform from the motor+screw assembly.

Now you have to remove the Z screw from the motor. Here's how I do it:
1. Go find six 5/16" square nuts
2. Put the nuts on the shaft, all the way to the bottom, until they fall off and onto the motor front plate
3. Keep doing this until there is no more empty space for nuts to fit.
4. Tighten the final nut as hard as you can--the rod will pop right off the motor shaft.

Now you need to install a new rod. Regardless of if you use an M5 or another 5/16", you will need a coupler. Use a flexible 5-to-5mm or (5-to-8mm if you use a 5/16" rod instead of a 5mm). Make sure you get one that pinches the coupler together, NOT one that secures the coupler in place with a set screw on the shafts.

When I get home I will send you a design wardjr worked up for an M5 shaft, which will work for you only if you are using the wooden platform.

It's likely this happened in transit. When you transport your printer in the future, put the Z axis all the way at the bottom.

Drat, guess I have to be more careful moving it.

How do I know when it is "all the way at the bottom"?  Is there concern of either damaging the motor pushing it down to far, or bending the rod running it past the "bottom"?  This was my fear when I tried to transport it and why I didn't run it *ALL* the way to the floor.

Mine is the Solidoodle 2, basically stock with all-metal platform.  That was one reason I went with this model printer, I was not convinced the wood-based ones would be that dimentionally stable in my apartment - we have HUGE humidity swings and lots of gaps to the outside (but we don't pay for heat/AC, it's included!) so winter humidity is maybe 25% with humidifiers pumping out ~5 gallons a day, and summer is around 60% humidity and I have no idea how to lower that (no idea where I could put a humidifier and not trip circuits).

Do you think getting a "5-to-5/16 coupler" and using the same motor would be better than replacing the entire assembly?  If the coupler claims it's "flexable" would this mean maybe I can just allow for the "give" and use the same leadscrew in spite of the minor bend?

Also, do you know if I would have to "tweak" the PCB any if I do just swap the whole motor+rod?