Ultimaker original bed springs

[antiklesys 3]

Hi,

I wanted to ask what is the purpose of the springs under the UM bed?

Shouldn't I need to remove the bed now and then, what would be the best solution to have it fixed in place and have to avoid any future bed levelling needs_

Thanks,

Alex

 

[tommyph1208 55]

Dosn't the springs allow the bed to dislocate when/if your printhead hits it... instead of just ruining nozzle and/or print bed?

[IRobertI 520]

The purpose is to keep the bed pressed against the washers of the leveling screws.

I doubt the springs have anything to do with you having to occasionally re-level your bed. More likely it's simply the wood moving around with temperature, moisture and just plain old settling into place. Wood is a living material and it tends to move with time.

A secondary purpose is to make the bed "give" a bit in case the head moves too far down. Instead of hitting a dead stop the bed can move down a little bit to avoid damage to the printer.

 

[antiklesys 3]

What would you advise to be the best bed levelling and z stage improvement?

With stock bed (no heated bed)

 

[drayson 75]

Hi guys!

IMHO - mod to 3-point leveling...

It's so easy to level the bed.

Take a look onto youmagine or thingiverse, there are a few mods also applicable on the original bed.

[tommyph1208 55]

Some easy and cheap stuff to experiment with:

You can quite easily change it to a 3 point leveling system by drilling a new hole in one of the sides of the build plate and z-stage plate, beween the existing holes and moving one of the bolts with springs in there, discarting the other... or use longer bolts like and some sort of finger grip, like:

http://umforum.ultimaker.com/index.php?/gallery/image/3387-img-0734/

Some people also claim to get better results with a flexible z coupling rather than the fixed stock version... something like:

http://www.ebay.co.uk/itm/5-6-6-35-8mm-Flexible-Shaft-Coupling-CNC-Stepper-Motor-Coupler-Top-Tight-D20L25-/370631482123?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item564b5b9b0b

The harder and much more expensive way is to conpletely recreate the entire z-stage structure for a more solid/rigid/stable design...

[jhertzberg 19]

Hi guys!

IMHO - mod to 3-point leveling...

It's so easy to level the bed.

Take a look onto youmagine or thingiverse, there are a few mods also applicable on the original bed.

 

Can't agree more. I went with this one. The design calls for three strong ball magnets that hold the bed consistently in the same place. I hardly ever need to relevel after swapping the bed out. I also replaced the acrylic bed with glass. I had two panes cut for me locally. I use glue stick instead of blue tape, and get glass smooth bottoms.

 

[antiklesys 3]

Hi Tommyph,

I already went with the flexible Z coupling as I had a spare coupler after switching to direct drive.

I have to say the quality has slightly increased after that.

What are exactly the benefits of a 3 point leveling VS a 4 point system?

Wouldn't the 3 point make it less stable?

 

[Dim3nsioneer 557]

3 points define a plane. 4 is one too much.

About the flex coupling for the z axis: I once used one too. But then I realised that the z position is never properly defined with a flex coupling. In the meantime I switched to an Oldham coupling and added quite some weight to the z stage.

 

[nallath 1,120]

Three point leveling is far better. Thats why the UM2 uses 3 points. The (re)leveling has nothing to do with the springs; If this were the case, the screws would have to change length.

As noted before, in most cases it's because small warpings in the wood. This is also one of the reasons why the UM2 has a metal bed (Heated bed being the other).

 

[drayson 75]

Can't agree more. I went with this one. The design calls for three strong ball magnets that hold the bed consistently in the same place. I hardly ever need to relevel after swapping the bed out. I also replaced the acrylic bed with glass. I had two panes cut for me locally. I use glue stick instead of blue tape, and get glass smooth bottoms.

 

I used this successfully also for a while - before switching to an alu plate with my own designed leveling system (http://www.thingiverse.com/thing:247552)

Can recommend it in case you don´t want to change to a different print plate setup :-)

 

[antiklesys 3]

Looking at those pictures the bed springs you have seem twice as long as the ones I have.

Did they change in lenght across different UM1 releases?

 

[jhertzberg 19]

Three point leveling is far better. Thats why the UM2 uses 3 points. The (re)leveling has nothing to do with the springs; If this were the case, the screws would have to change length.

As noted before, in most cases it's because small warpings in the wood. This is also one of the reasons why the UM2 has a metal bed (Heated bed being the other).

 

True about the releveling being caused by the wood warping. The 3-point design I referenced anchors the two front points to the thick z-stage arms rather than the thin board in the middle.

 

[jhertzberg 19]

3 points define a plane. 4 is one too much.

About the flex coupling for the z axis: I once used one too. But then I realised that the z position is never properly defined with a flex coupling. In the meantime I switched to an Oldham coupling and added quite some weight to the z stage.

 

I like the Oldham coupling idea. I seems to be a more straightforward way to deal with a not quite straight lead screw than getting fancy with the z nut housing. Given this, did you take the play out of the z nut housing?

 

[antiklesys 3]

I managed to take the play out of the Z nut by putting a spare piece of plywood covered in tape in the socket of the Z stage. The Z nut is now stuck as intended

Any link for Oldham couplings on ebay EU? I saw they are going for roughly 20€ each

 

[jhertzberg 19]

I managed to take the play out of the Z nut by putting a spare piece of plywood covered in tape in the socket of the Z stage. The Z nut is now stuck as intended

Any link for Oldham couplings on ebay EU? I saw they are going for roughly 20€ each

 

In a stock Ultimaker Original, the play is intentional, to allow the smooth z rods to keep the bed moving straight, even if the lead screw is not exactly straight. If you start to see bands on your prints every 3mm (the period of the screw), take the spare plywood out and see if print finish improves.

 

[Dim3nsioneer 557]

I like the Oldham coupling idea. I seems to be a more straightforward way to deal with a not quite straight lead screw than getting fancy with the z nut housing. Given this, did you take the play out of the z nut housing?

 

Yes, I used your cardboard method (thanks!) in such a way that the threaded bar is as vertically as possible and does not see major forces during one rotation. So the Oldham coupling has to deal with just with an excentricity of a few tenths of a millimeter.

But today I received a ball screw I ordered for replacing the threaded bar. I will have to design a connecting piece between the z stage frame and the ball head. This piece will be fixed to the z stage with no play. However, I will still use the Oldham coupling.

 

[antiklesys 3]

jhertzberg, the level of play i had was way above "intentional". I don't have any band or backlash issues with my prints as of now (everything was gone with flexible z coupling, direct drive and spring belt tensioners for the long belts).

I'm planning to move to 3 point magnetic bed levelling, but I also want to increase bed levelling accuracy, hence I'm thinking of adding an ultrasound distance sensor on the printhead and see if i can make it work for fine tuning.

For X Y bars I'm upgrading the blocks but it would be nice to upgrade the bearings to better ones (even tho they are bloody expensive as they have to allow movement in two directions)