Tribed: a fully automatic bed leveling and tool height adjustment, with FSR and 3 Z screws

This post is the continuation of my preliminary analysis regarding bed tramming and automatic tool height adjustment. So far I never made the step to redo my bed, even though it was on my wish list for years. Now it is a reality :)

Early testing of the complete setup : starting with a properly calibrated bed,

corrupting it manually, and letting the system auto-calibrate it again.
A faster / realistic movement is here, since speed was not a concern above.

So why now? A few months ago, someone came and talked to me about his wish to design a new, open source, user-friendly printer for the prosumer market. Please check this as your opinion counts!

All in all, it was an excellent reason to realize my idea of a fully automatic bed leveling. And since the new printer will also be opensource, here is the work, design and my analysis. How nice: not only I was given the possibility, but I was asked to do so!

As said, this improvement is part of a longer effort towards a user-friendly printer, for more reliability and less manual tweaking. My Ultimaker itself may eventually be ditched one day. Huh. No, I am joking. Well.. unless the new one is really is obviously better... Damn, that's exactly what it is all about :/

Thoughts and hints around hot ends

This post finally documents ideas and hints I had during the design of two hot ends I made last year.

My extremely small "cheesy hot end" (all-metal and actively-cooled), here with an Ultimaker printed support.
This hot end was very easy to make (only used basic tools) and also because the barrel is quite short.

At the time I already had ordered an E3D hot end, but the lead time was so big that I decided to give it try myself. Actually, since I attached it with this tiny E3D support on my Ultimaker, I almost never swapped my hot ends anymore because it is just so reliable... The only drawback is that the efficient heatsink could be made almost half the size for more Z space, less vibrations and less weight (hence my smaller, low cost --and low quality-- copycat by the way, see below). And it does not mean I stop thinking ;)

Features and improvements for a would-be homemade Ultimaker 3D printer

How would I re-design the original Ultimaker?

Quite some changes on the back of
my Ultimaker Original (aka v.1)!

The Ultimaker 1 (aka Original) is a well-built printer. It is probably one of the oldest and still best designs as proved by its incredible longevity.

I bought mine two years ago and, still, I feel quite confident that it would compare favorably in many aspects against a 30K€ FDM printer that a client bought last month. Is Stratasys really serious with this beast? May be there are better properties (eg. less warp due to fully enclosed?) But it also features a smaller build volume, a ridiculously limited and exceedingly expensive printing set of material. They also solved warping ABS by printing on... ABS beds (just try to remove it now when you forgot the in-between support!). You bet they bought Makerbot: overpriced "serious business" printers ought to be past, crappy obsolete printers. Too bad they are polluting MKI with greedy business practices though, and not the opposite.

OK, back to our subject. The "UM1" is one of the few printers you can take around you and which will keep printing very reliably without the need for re-calibration. It is also the only one I still blindly recommend... once the user knows that it is not that trivial to 3D print something. The new UM version is probably better in this regard, but it loses some "hackability" that I am fond of...

Still, the Ultimaker printers are big and they sometimes do not suit all my needs. If I was to re-design a clone, there are a few cosmetic but also structural modifications I would make, especially to the original design. Actually, many of my designs are all about improving the printer. Time to summarize what I did and what I would like to do!

Help yourself: compatible 3D printer parts that are easier to swap!

Why would I ever re-design a working part of a printer?

It does look robust, but hard to disassemble! (Escher)

Most of customers and users do not tinker with their 3D printer. After all they paid for a robust printer and spent a lot of time setting it up properly. Once done, it stays so (well, at least with the Ultimaker). Sure, it is a desirable feature, especially for the "boxed/walled" frames. But it may get really annoying when you are trying printer part alternatives in the first place, which is the subject of this post.

By the way: there are really two main usages for a 3D printer: the obvious first is to print objects... while the second is to print replacement parts for the printer itself! Sounds weird, eh? "So what are you printing with your amazing printer? - Well, most of my time-consuming designs are printer part replacements!"...

Now back to the question: why shall I sometimes just re-design a part of the printer with no added value beyond the ease of manipulation?

Rollerstruder: a filament feeder / driver / extruder

The rollerstruder filament drive system on an Ultimaker

Almost one year ago I got rid of the plywood Ultimaker filament drive mechanism. It is an extremely important part of the FDM process as it pushes the (cold) filament towards the (hot) end. Any malfunction at this stage systematically leads to a bad print. So when not reliable, you have to stay close and react quickly to fix troubles, for example by feeding the filament further manually (btw check this if you are still doing it on an Ultimaker).

As for me, most of the trouble came from the old bolt that was shipped with my printer: it was grinding my filaments a lot, sometimes to the point it would stop moving completely and ruin the hour-long printable kalashnikov. It also lacked Bertho's addition of a ball bearing on the "idler arm", which soon became part of the official design.

In fact I just don't know about the new official drive mechanism (which seems way more reliable given the forum feedback), because I designed my own feeder that has to match my more efficient but unsual hobbed bolt. It suits me completely: months of intensive usage without a failure. And I learnt a lot of openscad and industrial design by the way.

Which hobbed bolt for a filament feeder? My homemade one!

Driving the filament with hobbed / knurled bolts

My quite efficient hobbed bolt :)

As all owners of 3D printers know, one item of utmost importance is the so-called "hobbed bolt", "knurled bolt" or "driving shaft". It is one necessary "vitamin" (ie. non-printable) item that is coupled to a motor and which rotation drives the filament into the hot end (check the whole setup).

Now, molten plastic still does not flow easily through our tiny nozzles (~0.4 mm), and the force to be applied is quite high. Pushing the filament manually gives a good idea, as one hand is barely enough. Since necessary value may be 15 or 20 Kg of traction, this is where problems start to arise given the small filament diameters (3 mm or even 1.75 mm).

Short belt tensioner for NEMA 17 stepper motors

How to tension the Ultimaker short belts once for all?

Upside version of the tensioner

The short belts that drive the main rods from the X and Y steppers must always be kept tight. Otherwise the print quality really gets bad. Two symptom that are easy to spot is non-round cylinders or "bouncing" waves in the surface of the print.

The usual fix is to unscrew the 4 bolts, push the motor downwards with a thumb and tighten the screws very hard while keeping the pressure...

I just could not stand this anymore, so I designed this thing and this derivative (with an additional spring).

Poll: what are the features you added to your stock Ultimaker ?

What are your Ultimaker features?

Here is an on-going poll motivated by this post on the Ultimaker google forum. So please keep your comments for the forum!

I finally developed my own blogger poll system after failures with the official and restrictive blogger polls.

Robust bowden attachment with a blind rivet nut

Using a blind rivet nut to fix the bowden tube once for all

Blind rivets nuts give you a nut where you cannot reach the other side of the support.

Replace the bowden tube

Replace the Teflon / PTFE / bowden tube

I ordered more Teflon tubing before running out of the original two pieces I received with the printer.

They had to be shortened regularly because they were getting damaged by traction in the quick connectors, and instead of popping out, some even was torn apart in the filament feeder plug !

The replacement I bought was a "teflon tube 4mm inner 6mm" (well, there is only one way to read the diameters). I got 12 ft for $19 with shipping on eBay.

Homemade heated bed

Why add a heated bed ?

After I made mine, I never had an object pop off by itself because of cooling retraction. Way less issues also when a small plastic blob gets hit by the head while it prints the next layer (which occurs almost all the time with tall and thin structures).

Now there is an update: in this post I explain about how I print reliably, and it works probably even with Nylon and a cold bed!

For the heated bed, I used a single power supply setup, that I attached on the underside of the printer. I now have only the mains and USB cable getting out of the printer, and I carry no more bulky external power supply (that I sometimes forgot to bring with me!). It also reduces the failures due to the tired stock power plug when someone bends over the printer...

Printed filament feeder small gear

The small stock delrin gear on the feeder stepper motor got some freeplay with time. I first replaced it with one I found on thingiverse made by Chasmaker. You can download my derivative here.

Replace the filament feeder big gear

I am not sure that the plywood I received was of top quality, because the wheel teeth started wear out pretty early.

Before it was too late, I designed and printed a drop in replacement. It is really working well, without any wear though I really made its life hard sometimes.

You may like also the small gear replacement.

Reduce friction on the rods and bearings

Reduce free play at the head rod ends

It gives a smoother movement and less noise when the directions changes forth and back.

I originally designed this to reduced a bit the useless friction that the standard plywood losanges were applying to the bearing and/or the X/Y rods.

This may not be significant. Also, a hole in the object would allow the bearing to be oiled also. To do so, you can also use the batman derived object on thingiverse(!), or as below:

Update: switched to these better end caps

Better, with a Nylon hub and free play adjustment (jwag55's excellent upgrade)

I printed the inside hub in Nylon to benefit from its nice properties (less friction, no wear, a bit of flexibility).

It is also a very good illustration why open licences such as Creative Commons are good, since this is a design by jwags55 inspired by mine (above). So I benefit from a free smart upgrade because I did not ask for money not prevented anyone from improving it.