Some assembly concerns/questions.

[armstrom 0]

I'm moving along with the assembly of my Ultimaker but I'm running into a few areas that concern me.

1) Squaring the XY carriage. I don't understand how this is to be done using part 3B. The part itself has rounded ends and it's being pushed into a rounded corner (the opening in the top of the machine) and this is somehow supposed to give me a repeatable length? The pictures on the wiki don't seem to help as they are illustrating the very problem that I'm seeing.

2) The friction of the XY carriage is very high at the moment. I have all of the set screws loose in the pulleys so I know all the friction is coming from the copper bushings. I noticed the 6mm cross-bars (the ones going through the extruder) required significant force (more than I would have expected) when first inserting them into the linear bearings but once they were inserted they moved very smoothly. The font-to-back bar fell out as I was trying to mount the extruder in the machine. Granted, I have not yet lubed the axes so perhaps that will be a cure-all but I'm still a bit concerned.

3) When mounting the extruder and cross bars into the machine the instructions say to insert the left side first, Then "raise" the other bars up into the blocks. Well, that works for the front and back as the openings are in the bottom of the blocks but the right block is just like the left in that the bar can only insert from the top. This made for some tense moments as I saw the cross bar flexing slightly as I tried to get it into the final block.

4) Belt tensioners: The part C (little wooden cross piece with a 3mx10 bolt and nut on it) does not seem to be thick enough. It is able to move vertically inside the slot . This allows the nut to come up out of the groove that normally captures it. So now when I try to tension the belts the nut just spins freely. I "solved" this by wedging a small flat head screw driver between the wood and the nut so I could tighten it, but something doesn't seem right to me.

So far that's it. I've found some errors in the wiki but nothing too serious.

-Matt

[IRobertI 521]

1) Yeah I thought that was a bit silly myself when I read that step. Personally I used another part (or was it some of the scrap bits, I can't remember) instead to get a square edge on both ends. Then I simply got it as close as I could and it seems to work fine. I'd say get it as square as you can, try to print a few things and see how it goes. If you need to you can always print something to use as a squaring tool

2) My machine is also quite stiff. I think there's a video in the wiki that shows someone moving the print head around very very easily with just the tip of their finger. I think this was filmed with an early version and they stiffened up the whole mechanism quite a bit. As long as the motors don't have any trouble moving things around or it is extremely stiff I don't think you need to worry. My machine is far from silky smooth when moving it manually but the prints are great (at least I think they are ).

3) I honestly don't remember how this step went for me so I can't comment.

4) Yup, had the same problem. I later replaced them with these:

http://www.thingiverse.com/thing:17058

 

[armstrom 0]

Thanks for the feedback! I'll keep pushing through on the assembly. I just didn't want to get "done" and have to back up so far to fix something. Also, thanks for the link to the tensioner. I like that design better than the others I've seen that simply clamp onto the belt. However, the part I'm talking about is the screw used to hold the center lever down. If you look at this picture:

http://www.thingiverse.com/image:106571

It's the screw/nut that you can see on the right side of that block. As you can see in the picture the little piece of wood is thinner than the slot it sits in (it's all the way up at the top of the slot in that picture with a big gap underneath). The gap under the piece of wood is where the nut ends up. So when I'm trying to tighten the screw the nut just spins. If the piece of wood were the same size as the slot then the nut would stay captured down in the vertical groove and not spin. Oh well. Again it's something I can easily work around.

I think one of the first things I do (after printing the standard upgrades) is to design new blocks for the XY gantry. I don't understand why proper linear bearings are used in the head itself but copper bushings/slides are used on the fixed axes. I think I will design some blocks that use 8mm linear ball bearings and include a more robust tensioner system. The laser cut design is really cool and well thought out but something much easier to assemble/adjust could be printed pretty easily.

Edit: On a positive note.... I measured my fixed axes with my CMM and they are within a few seconds of square and parallel. Very impressive considering it's all located by laser cut wood The right and left axes were out of parallel the most.. only about 1 minute though.

-Matt