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Posted · Ultimaker - Black Edition

About the space frame: yes, a filled construction should be at least as rigid (for the size of parts and forces we are talking here. For larger structures the weight of the structure would have to be taken into consideration, so that for a large construction the space frame would be better, but for our topic here that is irrelevant)

About the crossed tongues: yes, one vertical and one horizontal could be twisted. But as soon as you have, say, 2 horizontal one vertical, you should be fine.

I am not even sure if any of that is really needed or if you current structure would be rigid enough already, given the fact that you havepanels in all 3 directions ? But you might want to ask someone else about that.

I'm really looking forward to get a peek at that baby once the first prototype is tehre!

 

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Posted · Ultimaker - Black Edition

Dang.. Got a problem with the triangular shape:

If I want to raise the lever attack point, it means that I have to raise the bottom plate with the arms. But that also raises the bearings -> no effect.

If I really want to do that, I need to separate the rear part of the bottom plate from the front part, meaning pretty much a complete reconstruction. But.. A good part of the stiffness of this construction comes from the fact that the same piece that holds the bearings also holds the platform. I don't want to lose that benefit..

So, I guess that I'll make my prototype with a more or less L-shaped arm. I can "fake" the T shape by mounting the bearings upside down and can then decide whether that is necessary or not. If it is, then I'll redesign the thing again and make a solid, triangular construction with a solid rear frame and a well attached arm. But the simplicity of the current design just calls to be tried out :)

 

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Posted · Ultimaker - Black Edition

Ok, version 1 of my z-stage is ready for prototyping.

I will make a prototype with 2mm acrylic. Won't be usable, but should look pretty cool :)

Z stage assembly V1

 

Z stage assembled V1

There is an error I just noticed after putting all the stuff together for Pic 2: The front is a bit too far recessed. I will move it further to the front a bit (making the "nose" where the front center hole for the platform sits) shorter. I experimented with multiple hole positions.

The hotend usually doesn't sit in the center between the x-y axes, but is somewhat offset. On the Original hotend, the nozzle is offset about 10mm to the right and 10mm to the front.

Anyways, I figured it's not necessary to put 9 holes there so you can correct offsets in all possible directions, but instead I went with 2 holes (center + 1 correction). Now, you just have to turn your hotend the right way so that the offset fits.

I made the arm as triangular as reasonably possible. As discussed, making it triangular downwards doesn't work.

On the assembled picture, I added some quick dummies for the bearings (top only). As you can see, they protrude about 4mm, and that is their short side. They can be mounted upside down so that they protrude 16mm. That works for the top, as well as the bottom bearings.

This is why I lowered my "cage" height again.

If you go with the bearings upside down, then the arm can be made "thicker" by up to 16mm. This will make it stronger if necessary (if no steel is used).

So, on wednesday I'll see if I can lasercut the parts @ the Zurich FabLab. If they fit together and the construction seems sturdy enough, I'll have them lasercut in steel within the next weeks.

/edit:

Just in case you wonder:

My offset correction goes to the front and left, instead of the right. That's because I'll be using Nick Foley's E3D integrated printhead which goes to the front and left. The UM original printhead can easily be assembled in the same way.

/edit2:

Just had a minor epitaph on the toilet! (should spend more time there...)

The bottom part is completely left-right symmetric. So I will just optimize the design for my "front left" offset and leave the centered hole away (this one is useless anyways). By just flipping the part, you can convert it to "front right" offset :)

 

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Posted · Ultimaker - Black Edition

What are you doing for the leadscrew nut cage? I spent a lot of time trying to find the balance between holding it tight in place and letting it float. Too tight, and I get z-wobble artifacts. Too loose, and it can twist a little and lose z height accuracy. The ideal is a mount that allows the nut to move freely in x and y direction, but with no twist.

 

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Posted · Ultimaker - Black Edition

I wonder if the stage is rigid enough, z wobble goes away and therefore the nut can be fixed to the stage.

 

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Posted · Ultimaker - Black Edition

What are you doing for the leadscrew nut cage? I spent a lot of time trying to find the balance between holding it tight in place and letting it float. Too tight, and I get z-wobble artifacts. Too loose, and it can twist a little and lose z height accuracy. The ideal is a mount that allows the nut to move freely in x and y direction, but with no twist.

 

I think the Ultimaker design fulfils this spec quite well, doesn't it?

 

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Posted · Ultimaker - Black Edition

I think the Ultimaker design fulfils this spec quite well, doesn't it?

 

I can't quite agree. When I first built my UM Original in January 2013, I had severe banding artifacts every 3mm. This was probably a combination of a not-quite-straight leadscrew, and a tight nut capture cage that transferred the screw wobble to the bed. I had to take a file to the wood in the cage to loosen things up, then add some cardstock folded in an accordion shape to keep the nut from twisting. Owen posted a design that solves this here.

 

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Posted · Ultimaker - Black Edition

I can't quite agree. When I first built my UM Original in January 2013, I had severe banding artifacts every 3mm. This was probably a combination of a not-quite-straight leadscrew, and a tight nut capture cage that transferred the screw wobble to the bed. I had to take a file to the wood in the cage to loosen things up, then add some cardstock folded in an accordion shape to keep the nut from twisting. Owen posted a design that solves this here.

 

Very interesting. Is it possible that you post a picture of your cardboard solution? My imagination still is a bit limited in the morning... ;)

 

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Posted · Ultimaker - Black Edition

I'm going for total rigidity ^^. The nut is simply clamped to the top part with 4 screws and a little plate that you can see in the last picture. The screws are positioned so that the nut fits exactly in between them, and the screws will need to be tightened pretty hard in order to hold the z-nut immovable, but I will see how well this works...

On my first UM1 kit there is definetly something odd about the leadscrew. The further down I move the z-stage, the further the leadscrew leans to the front, eventually touching the slider blocks.

I hope this will go away with my construction which holds the leadscrew exactly in parallel to the shafts. The 12mm shafts should be absolutely immovable - so keeping the leadscrew in line with them should keep it straight. There might be some tension building up, I hope that's not going to be a problem.

Using a flexible coupling on the z-motor would probably be good, but I don't know if there's a kind of flexible coupling which doesn't allow play in axial direction (the usual flex couplings don't work, I know that).

There are several different kinds of flexible couplings - and I don't know most of them. They are very expensive (30 to 50 EUR per piece) if you're buying from Misumi, so I don't want to just buy some of every kind and test them, as long as I don't know that it is necessary.

I'll could try asking Misumi for free samples, or information on which coupling would be ideal for that application.

Or maybe someone here in the forums knows which would be the ideal coupling?

By the way, yesterday I found that the small linear bearings for the printhead are just as bad as the big ones. There is a lot of room for improvement here...

 

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Posted · Ultimaker - Black Edition

Hi everyone

I think it would be very nice if there would be a similar list of improvements for the UM2!

If there are some!!

Could be also a help for UM2-Beginners like me, because I have some problems with the filament.

Sometimes the printer has no feeding because the filament has "knotted"!

Printed two different models and on the half the filament stopped, unfortunately I was not there to handle it!

I saw models on YM for different materialfeeders and filamentholder, but are there some experiences about them and which helps realy good!?

Any news about improvements for UM2 would be nice!

Thanks a lot

 

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Posted · Ultimaker - Black Edition

Very interesting. Is it possible that you post a picture of your cardboard solution? My imagination still is a bit limited in the morning... ;)

 

It's nothing to look at, just some cardstock folded under to damp the motion of the nut and to keep it from twisting into a locked position in the cage...

gallery_1856_870_161073.jpg

 

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Posted · Ultimaker - Black Edition

Thank you! I just tried something similar, but I had some problems with a blocking z axis. After some adjustment, it might work right now...

 

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Posted · Ultimaker - Black Edition

Update!

I received the Trespa panels today:

Trespa Panels

Only 76kg of the most awesome building material I've ever seen :)

I'm working hard on finishing the UM black edition design (it has become so big that Sketchup is getting really laggy when I view the whole thing...).

By now, I've redesigned the complete machine, pretty much down to the smallest screw...

The bad thing is, there is just about zero compatibility to the orignal Ultimakers. But as this is not an upgrade kit anymore but instead a complete replacement, it doesn't matter...

I'm expecting to start CNC-milling tomorrow. The bulk of the design should be finished by the end of this week. Expect more pictures soon ;)

 

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Posted · Ultimaker - Black Edition

I can't quite agree. When I first built my UM Original in January 2013, I had severe banding artifacts every 3mm. This was probably a combination of a not-quite-straight leadscrew, and a tight nut capture cage that transferred the screw wobble to the bed. I had to take a file to the wood in the cage to loosen things up, then add some cardstock folded in an accordion shape to keep the nut from twisting. Owen posted a design that solves this here.

 

Small note on this one, both of you are right. The design can work, but it depends on the thickness of the wood. So for most people it works fine, but for some people they can banding like jhertzberg.

 

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Posted · Ultimaker - Black Edition

Well, I hope I have this problem sorted out - this part is where I have made several big modifications. The z motor is on top. It is connected to the leadscrew with an oldham coupling, allowing it to shift to the sides slightly.

The leadscrew nut on the z-stage is fixed with a press-fit hole into a steel part and screwed down. No movement possible there.

Then, the leadscrew is supported on the bottom panel using a radial bearing and an axial bearing an angular ball bearing.

All this combined with the much stiffer frame and increased weight should eliminate any kind of wobble or banding. I'll see it as soon as it's completed. Timescale is still two weeks (still need to make that Misumi order...).

 

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Posted · Ultimaker - Black Edition

Well, I hope I have this problem sorted out - this part is where I have made several big modifications. The z motor is on top. It is connected to the leadscrew with an oldham coupling, allowing it to shift to the sides slightly.

The leadscrew nut on the z-stage is fixed with a press-fit hole into a steel part and screwed down. No movement possible there.

Then, the leadscrew is supported on the bottom panel using a radial bearing and an axial bearing an angular ball bearing.

All this combined with the much stiffer frame and increased weight should eliminate any kind of wobble or banding. I'll see it as soon as it's completed. Timescale is still two weeks (still need to make that Misumi order...).

 

I love the idea of using an oldham coupling. It moves the complexity of dealing with inexact alignment out of the nut trap, where space is tight. A few questions regarding the couplers you went with:

What benefit did you get from moving the z motor to the top? Cooling? Gravity assist in keeping the leadscrew plumb? More z height?

What material did you go with for the center disc of the coupling? McMaster has both Acetal and Nylon. My gut is to go with Acetal out of concern that Nylon might be too "mushy" for very small movements like with .06mm layers or jorised walls.

Did you go with set screw, or with clamp-on couplings? My stock double set screw couplings seem to loosen up every few months. Should I assume that clap-on couplings won't suffer this as often, or am I just being wishful?

 

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Posted · Ultimaker - Black Edition

I had to remove the oldham coupling in my setup. It turned out that the overlap of the coupling parts with the axes from the leadscrew and the motor axis were too short. Thus, the parts were easily tilted a bit which immediately led to the well known periodic horizontal lines in the print.

From my present point of view I can rather recommend to implement something to adjust the x-y-position of the brass nut in order to have the leadscrew at the right spot.

However, there might be better oldham couplings than I used with longer shafts and they might improve the situation.

 

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Posted · Ultimaker - Black Edition

I love the idea of using an oldham coupling. It moves the complexity of dealing with inexact alignment out of the nut trap, where space is tight. A few questions regarding the couplers you went with:

What benefit did you get from moving the z motor to the top? Cooling? Gravity assist in keeping the leadscrew plumb? More z height?

What material did you go with for the center disc of the coupling? McMaster has both Acetal and Nylon. My gut is to go with Acetal out of concern that Nylon might be too "mushy" for very small movements like with .06mm layers or jorised walls.

Did you go with set screw, or with clamp-on couplings? My stock double set screw couplings seem to loosen up every few months. Should I assume that clap-on couplings won't suffer this as often, or am I just being wishful?

 

I changed the setup mainly because I wanted to increase build height. My z-stage design reduces z-height, as well as the E3D hotend which is slightly longer than the stock UM. So, I threw out everything below the bottom plate and moved the bottom plate down 45mm. The electronics are now placed on the rear side of the printer, close to all the stepper motors. Motor cabling length is heavily reduced which should decrease EMI and maybe even improve motor efficiency.

Also, I didn't like that the z-motor actually has to carry the full weight of the z-stage. Motors aren't made for this kind of stress... And, my z-stage is MUCH heavier than the stock UM one...

The Oldham coupling I'm using is made out of:

Hub parts:

1.4301/X5CrNi18-10

Sintered Alloy

Spacer:

Aluminum Bronze

(Sold Lubricant Embedded)

I wouldn't recommend using any kind of plastic spacers..

I'm using set-screws for all the parts. Clamp-on is better (though mostly because it just clamps to the shaft better and more evenly than a setscrew), but considerably more expensive. Note that an Oldham coupling from Misumi costs 21 EUR, and a flex coupler costs 26 EUR (without taxes...).

You could just use some thread-locker to prevent them from becoming loose. Just have to use the correct one (especially with steel & aluminum combinations).

/edit:

By the way, I think I could just have used a solid coupler. I don't think there will be more than 0.1mm in displacement because all the parts are precisely machined (and I don't use wood). But I thought I'd give it a try...

 

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Posted · Ultimaker - Black Edition

I hadn't thought of the weight driving down on the motor, though I wonder if a lot of weight pulling down on the motor shaft is any better for it. I'm hoping that heated bed kit gets announced at the NY Maker Faire next month. I want to see what the company solution will be before doing anything more with my z stage.

I have been thinking of moving my electronics to back as well. Underneath my machine is about the dirtiest place in my home office, not the best place for an electronics cooling fan. It would also make it a lot easier to fiddle with the electronics if I didn't have to upend the printer every time.

 

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Posted · Ultimaker - Black Edition

The leadscrew is supported by an angular bearing in the bottom. I've simplified this structure (previously I was planning to use an axial roller bearing to support the weight) because the angular bearing I took is quite massive (26x10x8, OD x ID x H) and should be able to handle much more weight than "just the few kilograms of the z-stage".

The beauty of this (combined with direct drive) is, that all the motors are located very close to each other. Put the electronics nearby and you have less than 20cm cabling for any motor.

 

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Posted · Ultimaker - Black Edition

*Necromancer casts raise thread*

Finally got around to order the new rods from Misumi. Also ordering GT2 belts from them.

I am wondering what a good source for the GT2 pulleys is. The Misumi 8mm bore pulleys don't go down to 20 tooth.

 

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Posted · Ultimaker - Black Edition

*Necromancer casts raise thread*

....

 

* Templar cleanses the spell *

I get my pulleys from robotdigg.com. They are very cheap - but surprisingly well made. Perfectly round, made on a CNC lathe. I only ditched the setscrews and used stainless steel ones because usually the chinese have very bad standard hardware (screws, nuts and stuff). That's probably not necessary, but I have the setscrews around.

Btw, I'm completely redesigning the UMBE at the moment. Milling the frame panels is a PITA, and most of all it's much too expensive to sell them - it takes hours of manufacturing, broken tools and a lot of swearing...

So I'm switching over to making a frame from Misumi aluminum extrusion profiles (30mm enhanced ridigity - solid as a rock) and lasered stainless steel parts.

This sounds very expensive, but is actually cheaper in the end than the Trespa HPL panels. And that is simply because I can just design the parts and order them readily manufactured - no more post-processing or CNC milling on my side needed.

I've also made large improvements on my Z-stage. The first prototype wasn't satisfactory, but I learned a lot from making it. The second one should be very good.

 

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Posted · Ultimaker - Black Edition

How is this printer going? Do you have anything to show yet? :) Oh, and I was wondering what the difference between the Reptar blocks and the TwisterBlocks is, and why you have both listed.

 

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Posted · Ultimaker - Black Edition

Both blocks are listed because I couldn't decide between the two.

But you can ignore that list - it was never completed or tested.

I have instead re-designed pretty much every single piece of the printer and will be using only my own designs ("My own designs" sometimes being derivatives, of course. I'll take care for proper attribution when I publish the design).

As for the state of the UMBEv2 (the name is work in progress...), I'm now trying out a frame made from 30mm aluminum extrusion profiles. The Ultimaker gantry is - in it's theory of operation - unchanged. It is mounted to the frame using lasered 5mm aluminum parts. The z-stage has been completely redesigned (twice) and is now made from lasered stainless steel parts that hold two linear bearing cages (Misumi part number LHSSL12). These cages are basically an aluminum block that holds two linear bearings in alignment, with a total length of 100mm.

lhssl12

That's the core of the machine. The extrusion profiles will then be enclosed with some wall panels - probably plywood as wood is a good thermal isolator (and it's cheap as dirt).

Most of the materials now come from Misumi (which is probably the best stuff you can buy, like anywhere...) or from a professional sheet metal producer in Switzerland.

A little preview:

UMBEv2 Wip preview

Most of the parts are ordered and on their way to me. There will be more real-life pictures over the christmas holidays ;)

 

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