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X and Y motor mount screws specified too short

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In the assembly documentation here:

http://wiki.ultimaker.com/Ultimaker_rev.3_assembly:_X_%26_Y_motors#Step_2:_Mounting_the_X_and_Y_motor

it says to mount the motors using 20 mm long bolts. But, here is the stack-up that the bolt must go through:

washer - 1 mm

rear or side panel - 6 mm

7B spacer - 4 mm

7B spacer - 4 mm

7C spacer - 4 mm

---------------------

total - 19 mm

So there's only supposed to be 1 mm of bolt going into the motor?! That is too short. They should be 22 mm long to get a theoretical thread engagement of 3mm into the motors...

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Hi ,

You are quite correct, the specified bolts are far too short and on my machine only had 2 threads

of engagmement when using M3x20s

I replaced them temporarily with M3x30s and a washer stack.

I think the pefect thread length is something like 24mm. So probably M3x25mm plus a fat washer

is about right, or also M3x22 plus no washer also not too bad.

To be honest I am staggered by this, certainly I would be fired at work if I stood up in a meeting

and said that I didnt know that threads must engage by 1.5x diameter.

I suppose the only reason there are not dozens of people with Nemas having stripped threads is that

the wood will compress alot before that happens. But its still exceptionally poor engineering design.

Calum Douglas

Cologne

Germany

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I suppose the only reason there are not dozens of people with Nemas having stripped threads is that

the wood will compress alot before that happens. But its still exceptionally poor engineering design.

Compressing the wood after putting on the right short belt tension is good. This makes the washers digging into the wood, keeping the motors in place.

Anyhow, instead of the wooden spacers you should add normal round spacers, same as found holding up the electronics, this reduces noise.

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I suppose the only reason there are not dozens of people with Nemas having stripped threads is that

the wood will compress alot before that happens. But its still exceptionally poor engineering design.

Compressing the wood after putting on the right short belt tension is good. This makes the washers digging into the wood, keeping the motors in place.

Anyhow, instead of the wooden spacers you should add normal round spacers, same as found holding up the electronics, this reduces noise.

How much of a difference does this really make ?

I've dug through every little bag of parts and haven't come across any black motor spacers.

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The black spacers come in new kits, if you have the 7A/B/C wooden parts, then you will not have the spacers. The difference in noise is noticeable, but how much, no idea, didn't measure it.

The motor mount holes also have moved slightly in new kits, so the motor no longer sits against the sides of the printer. Which also reduces the noise from those motors. The material feed mechanism has also changed a bit so that motor also no longer rests against the case, and the woodn parts from the feed have less contact points with the case. Which also helps in noise reduction.

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This should be a new kit as It came with both the v2 hotend and the extruder upgrade, but I do have parts 7a/b/c as well and the "quality note" says it was "the laser pack was packed on 16-08-2012".

I've pretty thoroughly investigated every nook and cranny of this kit now and the spacers were definitely forgotten. Do you have their full dimensions, tolerances, and what they are made of ?

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The kit upgrades is a constant process, so a few months old is already an "old" kit. But 08-2012 will still have the wooden spaces, and I think it also has some of the V1 hotend parts as well as the old extruder next to the upgrades. The latest kits no longer contain the old parts, that's the newerst kits. I think they are dated from 10-2012 (but I work at R&D not production)

If you want spacers, they are 11mm long round black electronics spacers with an inside diameter of 3mm.

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Well it was really nice to get shipped an "old" kit then.

I have a feeling my kit was just put together on a Friday afternoon. The soldering and connectors on my circuit board look like crap (and it's marked 1.5.6 vs. 1.5.7); the holes in a couple of my limit switches were drilled out too much so they can't be held in place with the M3 bolts; crooked drive gear on the extruder motor; and these missing spacers. Even if the laser cut pieces were from 08/2012, you were posting on here earlier in this thread at that time saying to use the plastic spacers instead of the wood pieces.

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When I said to use plastic spacers we didn't include them in the kit yet. It was just something people where upgrading on machines to reduce noise. Ultimaker later changed the kits (changing production takes time)

Seeing your timeframe by looking at your other posts, it looks like you have one of the latest bit older kits. (Which is still a few versions ahead of the machine I have at home, which is a year old) There is nothing wrong with this kit, and we've shipped it for quite a while before the newer version. We are continuously updating the printer. I can guarantee that an Ultimaker you buy now isn't the same as the one you buy in 6 months.

The limit switches are causing a few problems, in 95% of the cases the switches work fine. But sometimes the threads won't hold, or people screw them to far and the threads get stripped. The Z switches can be secured with 16mm bolts and nuts, and the X/Y can be attached with 12mm bolts instead of the usual 10mm. (But there are very few spare 12mm in the kit) Using 16mm in the X/Y switches won't work as they will block the sliderblocks. The X/Y endstops won't come very critical, so you could also glue them in place.

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Another thing to consider while installing the stepper motors is the possibility of upgrading to a heated bed in the future. Although the standard placement of the motors will function with a heated bed, they will run considerably warmer than without a heated bed--especially if you use bubble wrap or other material to make walls to retain heat in the build chamber (often worthwhile when printing ABS).

If you might possibly install a heated bed someday, you should consider installing the stepper motors to the outside of the UM frame during your initial assembly. The only downside is aesthetic but the extruder motor is mounted externally, regardless. You can choose an appropriate screw/bolt length and even install a short spacer, if that helps with noise (I didn't). The pulleys are easily positioned in appropriate location on the motor shaft to keep the drive belt running square. The two pairs of four wires in each of the two motor wiring bundles must also be swapped. Swap the red wire with the black wire in the plastic white connector shell of each motor's bundle and also swap the other two wires (I don't recall their color).

There is strong motivation for doing this on initial assembly. In order to re-route the wires, they must be pulled through the sleeves. You may as well remove the white connectors and do this during initial assembly. I think removing the white shells is easier than trying to push or pull the shells though the sleeves regardless. Document the wire positions and use a sharp dental pick or very small screwdriver to depress each metal connector tab to disengage it from the white shell and pull the wire out. By wrapping a small piece of blue tape around only the wire bundle (without the white shell) while also capturing another small wire or string in the bundle, the wires can be pulled through the sleeves much more easily.

I drilled a 1/2 hole next to the motor on the left side of the frame to route the wires. Use a wood drill and drill slowly to not break through the plywood, damaging the edges. The motor on the back can use the same hole the hot end and extruder wires use.

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