bertho

Taking a step back, never mind manufacturing problems, what would an ideal heater/nozzle/Bowden system look like? I have been playing around with measurements and there are drastic force changes if I feed too slowly or wait a little bit between measurement. Presumably the melt zone extends up higher and the plastic starts to cool and there is more friction against the walls.

There are many good points here but I like to disagree about the one piece barrel and nozzle suggestion. Yes, leaks are frequent in some designs but that just shows poor design. There are millions or more industrial metal to metal joints using orders of higher pressure that works perfectly. The problem is twofold: Poor joint design and machining of the parts and wrong assembly technique. The nozzle should be tight against the barrel and with clearance to the aluminum block. That ways the critical joint is formed at the correct place.

That is the required extrusion force that I was referring to above. Maybe using Joergen's and alaris2's numbers as an upper practical printing speed for testing. I wonder at what printing speed the heater runs out of power? That is another interesting data point.

Real CNC equipment has a speed adjustment setting up or down in % of the G-Code setting. It also has Tehran % adjustment for the spindle speed. I have not looked but I think there is at least an option in Marlin to vary the speed. Presumably both adjustments ought to be in Marlin. This brings back my argument about do not change correct values. If the steps/mm value is correct, do not lie about it to change the the print result. I guess we are back discussing a "Packing" fudge factor.

Thanks Alaris2, Yes, the next question is how much force do we need vs. printing speed and materiel & temperature..... Knowing that, I can then calculate speed and spring force and gear ratio if needed. Happy printing, Bertho

Instead of printing I ended up spending too much time to satisfy my curiosity. Here is the result: http://www.vinland.com/Extruder_Drive_Force.html Note, the sample spring can be even further compressed than what is shown in the data. Bertho

It was my first uploading to Thingivers and also posting on the forum so I guess I overlook that. Happy Printing!

All the files are in the zip file, including the STL files. Good luck!

Thanks for the nice words. It is good news that it works well for you. Look for a stiffer spring though so you can obtain the needed force while still having a range of compression. That way it will also be insensitive to filament thickness. I have not had time to do any further testing, as usual business is interfering with my hobbies. Tolerances: I wish here was more space but the gear wheel is very close on one side. I have calibrated my printer and by using the independent X_Y_Z scaling option in Netfabb, the size comes out very accurate. I do not like to adjust the Solid model, just the printing process. The major problem I have with Cura is undersized holes so I have to open them up.

Thanks Alaris2. Please let me know how it turns out for you.

Since I needed to measure the spring used for the Ultimaker Upgrade, I documented the steps both for a high accuracy measurement procedure and a simplified one. http://www.vinland.com/Spring-Testing.html Note, the spring for the upgrade is not critical. There is a tremendous adjustment range. Bertho

Joergen: A smaller OD bearing will move the shaft very close to the plywood body of the drive. If I remember correctly, the roller blade bearings are too wide to fit in-between the plywood sides which is why I chose the 3.5mm wide bearing. I intended to put an external grooved sleeve on it but that would be a machined part so I left it off for this Thingiverse version. The bearing can be found here for $7.41: http://www.mcmaster.com/#standard-ball- ... gs/=i853dw It is a Dynaroll SMR128ZZ A5 The spring OD is 7.72mm, has 8 turns of 1.14mm wire, and a free length of 20.9mm. Sorry, no part number since it came from my big junk box...

I finally got got my upgrade ready and posted it on Thingiverse. The detailed info is available here: http://www.vinland.com/UM_Extruder_Bearing.html Please let me know if there are any questions or suggestions. The ball bearing is 12mm OD, 8mm ID & 3.5mm thick. Bertho