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Mendel90 build comments

Posted by Gronkwena 
Mendel90 build comments
April 15, 2013 06:15AM
Hi there,

I finished my Mendel90 over the weekend, and I am really happy with the first prints. Also the finished machine is surprisingly attractive in red and black. I didn't have very much experience with this kind of project (not soldered since I was 16) but overall I found it straightforward to construct, and fairly forgiving of error.

I can say this because pretty much every part which is possible to be put on upside down or backwards was put the wrong way round at least once as I built it. This is not a problem with the kit or manual, but more to do with my ability to check what I am doing properly! The net result is a very ugly looking pcb on the x carriage where I managed to solder on 3 pieces out of 5 the wrong way round, a snapped crossbar on the spool holder where I tried to remove it having forgotten that I had already screwed it on, and some white strain marks on the top z clamps from when the x motor/idler hit them while the limit switch z limit switch was the wrong way round (even though this is highlighted in the manual in bold...)

Some minor points of feedback from the build :-
1) It was initially very hard/ impossible to insert some of the nuts into the nut traps on the fixing blocks for the dibond. On the side with two nut traps, they went in easily, but on the side with one trap I couldn't get them in fully no matter how much force was applied. On closer inspection there appeared to be a very fine lip of plastic that looked like it had sunk/moved the part was laid down, and prevented me from getting the nuts in. I eventually resorted to using a small craft knife to remove a sliver of plastic, after which the parts fitted perfectly.

2) The manual refers to 271mm threaded rods, mine appears to be 300mm. This caused some searching through the packaging before I was certain there wasn't another size of rod hiding somewhere. Looking at the picture in the manual, I assume this length has been changed at some point.

3) When mounting the extruder fan, the nuts for the mount of the x carriage were not fully seated in the nut traps. I think I left the screws too loose and the nuts worked their way out of the traps as I was manipulating the carriage mount on other parts of the build. They are not visible once the carriage is in place, and its hard to check they seated correctly. As I tried to slide in the fan mount, one nut fell off the end off the screw. The only way to put it back in the nut trap was to remove the entire x carriage from the bars and belt, which was a bit of a pain! Although the manual says to leave the screws loose until adding the fan, I would recommend making sure they are fully tightened up, and only carefully loosening them once the fan is ready to be added.

4) When assembled I printed off the android without a problem. I then went to slice another model, but found when it went to print it did not work correctly (wrong temps, wrong scale, not extruding). I couldn't work out what I had done wrong until I checked the forums here. It looks like a few other people have had the same problem I had - I copied the mendel90 settings provided for the .skeinforge folder over the the defaults as instructed in the manual, but when I went to use skeinforge again I played around and clicked something, or overwrote the mendel90 settings somehow, and caused the slice to be with the default settings. I couldn't work out the issue until I checked here and saw a few similar posts. When I recopied the settings and resliced, the print worked fine.

Here are my first prints. I tightened up the belts and adjusted the z home after printing the android. I still need to do some adjustments to the z home/ bed levelling as there was still some spreading on the first layer of the gauge mount, but I want wait to for the dial gauge I ordered to arrive before I spend too much time on it.
open | download - PICT0027.JPG (426.3 KB)
Re: Mendel90 build comments
April 21, 2013 04:34AM
Nice write up.I got the same kit as you a few months ago, and really pleased with the results.
Re: Mendel90 build comments
April 22, 2013 03:52PM
I finished my kit last sunday and didn't have the problems with the nuts.
I had to push some of them in with a tool, but I never had to cut anything.

I managed to level my bed with only 0.02mm difference in height between the corners [using a digital caliper. should be enough, right?] and printed the android guy using the supplied gcode. The result was very good.
Then I tried slicing my own android guy (from the stl file) but I could not get it to work... I took me a whole day to figure out that I had to leave the setting at ABS instead of PLA. There is some PLA in the kit, so I assumed you had to select the PLA setting... It might be a good idea to change the default PLA setting to something that works, it would have saved me a whole day of frustrations spinning smiley sticking its tongue out

Printing large objects works pretty well. Printing small objects (or details) doesn't really work. I think the print speed is to high for small objects and details need to be cooled while printing... (just a guess)
I will figure it out someday. I need to learn all the functions and settings of skeinforge first. smiling bouncing smiley
Re: Mendel90 build comments
April 22, 2013 06:09PM
Yes I should update the PLA profile to be the same as the ABS one. I have never use the profile before as nothing changes apart from the temperatures in start.gcode.

You need to add M106 after the second layer to turn the fan on for PLA. It should automatically slow down for layers that take less than 20s as cool is active. The minimum layer time could also be increased.

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