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ekh

Some comments on the production of UM2

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I have had an UM2 for 2 months now, I have some suggestions to the production of the UM2.

But first I have to say that you guys at Ultimaker do a great job IMHO.

It is no easy task to start a company and grow as fast as you have and keep everything perfect.

Also the way you selected for your busyness model is very positive and along what is suggested here:

http://www.thrivemovement.com/the_movie

I recommend you watch the Thrive movie. If you have no knowledge of the issues the movie puts light on, watching the movie can change the life quality for yourself and others in a positive way. The planet needs change.

But back to the subject.

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My first comment is: Do you make "burn in" of the printers.

The display on my UM2 failed after approx. 6 hours of printing, I returned the UM2 to the shop where I bought it, and had to wait nearly 2 weeks to get it back.

Electronic failures follow a "bath tub" curve where many fails occurs in the first hours of operation. Then follows a hopefully long period of a very low failure rate. Eventually at the end of product life, the failure rate goes up again.

I will recommend that when you have assembled a printer, you set it to "print" 48 hours in 40 degrees C room temperature and no filament.

The "part" contains movements and nozzle and bed temperatures as when printing for real.

If it stil works OK after the 48 hours, you insert filament for the first time and do a real test print before shipping.

If it does not work, you have saved a customer from an annoying experience and you can correct the problem at the lowest cost.

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The axles supporting the print head were not parallel to the rotating axles. The errors were 1 mm and 2 mm for the two axes. That part of the assembly ought to be done better.

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The X motor is not mounted sufficiently accurate, so the toothwheel grinds the toothbelt so that rubber smudge falls down on the x motor.

A guy in the shop has also seen this, so it is not only my UM2.

Apart from reducing toothbelt lifetime, this extra friction does not improve print quality.

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The tootwheels are too bad a quality, the holes are too big for the axles. When the screws are tighthened, this results in excentricity giving an position error depending on the angle of the wheel.

This was also the case for my UMO.

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The tolerances for the linear bearings in the print head are not acceptible. In one direction the play at the tip of the nozzle was 40 to 50 um. I'm taking of free play here, not forcefully bending something.

I could not find long 6 mm bearings on Ebay, so I bought 8 short bearings and selected the best 4 bearings.

I measured the existing head and made new drawings for the black plastic parts in order to use 4 short bearings instead.

After printing the new parts, I replaced the plastic parts and the bearings.

That improved the print quality.

I have attached a 3D view of my new printhead. I could fiddle more with the tolerances, but to me this is not a final solution. I am in the process of designing a new print head with the extrusion feeder in the head, using 1.75mm filament.

Designing a 3D printer is a big compromise, where you have to select specific solutions. There are many good choices in the UM2, but for the printhead I disagree.

I expect the new design to weight only slightly more than the existing moving parts.

I will do my best to solve many issues about print quality with this head.

It is no easy task with risc of failure, but if I succeed in making something useful, I will share drawings and STL files here.

I will make another post about this subject later.

I have attached a 3D view of the intermediate printhead design.

intermediate-printhead.thumb.png.d1cd42e89cc7f7140fb1733b11c67206.png

intermediate-printhead.thumb.png.d1cd42e89cc7f7140fb1733b11c67206.png

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