I'm finding I'm getting issues where the Z leadscrew washers are just too close together and they end up binding in certain parts of their rotation. It's definitely the washers brushing against each other that is causing the issue, and not something to do with the X carriage (I tried it without the X carriage). This happens on both Z leadscrews.

Specifically, it's the gap between the 8mm washers above/below the 608 bearing and the 4mm washers that hold the bearing in place that is the issue. See Section View thru Leadscrew (taken from the Mendel Frame wiki page).

I'm finding that the 8mm washers are just slightly off-centre and brushing against the 4mm washers. Adjusting them helps but I can never seem to get them 100% dead centre.

Things I have thought about so far include:
1. File out the slots on the Z-leadscrew-base part for the 4mm bolts that hold the bearing in place, thereby moving the 4mm washers slightly further away from the 8mm washers/Z leadscrew.
2. File the 4mm washers down somehow. Most likely putting a flat on one side/edge, and making sure this side/edge faces the threaded rod/bearing when tightened.
3. Trying slightly smaller imperial washers that still fit over my metric parts, that aren't as large a diameter on the outside (eg: 7/16" for the 8mm rod), assuming I can find any and/or make them fit.

Hopefully one of these will allow enough of a gap between the washers so that the Z leadscrews do not bind any more.

Any thoughts on this? Did you experience this? How did you solve it?

PS: My parts came from nophead, so it's not like they're warped or anything. I've not done any filing of any of the parts though, as it has seemed unnecessary.

I'd assume it's top and bottom, so elongating the slots slightly is the easiest solution. my RP parts needed extensive filing. It's a little painful on the fingers and it's slow, but you can use the a M4x40mm as the perfect size file. You probably only need to extend the slots a couple tenths of a mm.

I've actually got a fine round diamond file that is almost exactly the right diameter. If the screws still don't fit, I'll resort to using a screw to do the remaining file work.

Still happy to hear from anyone else with opinions on this or have experienced this problem first-hand.

Also: Yes it's on the top AND bottom washers, though the bottom ones always seem to be the worst off.

Can you measure the diameter of your washers. There is about 1mm clearance on my machine so all I can think is that your washers are bigger than normal.

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[www.hydraraptor.blogspot.com]

I'll do that when I get home. The only thing of note is that I have not seen any specs on just what the diameter of a washer is based on the hole size. I'm also guessing that the hole size on the 8mm washer is actually slightly bigger than 8mm, allowing it to wobble off-centre. I know there has to be a margin of error, but it's possible that in this case it's just too much.

Thanks nophead.

OK, some measurements of a random sample of washers (ie: one each plucked from a box of them):

8mm washers:
Inside: 8.4mm
Outside: 16.8mm

4mm washers:
Inside: 4.4mm
Outside: 8.8mm

Just looking at that, I'm guessing they're all on the large size, at least on the outside diameter. I know that they need to be SLIGHTLY larger to avoid being too tight, but perhaps the allowances are a bit big in this case?

They look pretty average according to this table: [www.roymech.co.uk]

I will do some measurements when I get home.

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[www.hydraraptor.blogspot.com]

I've filed the slots on the part the bolts go into slightly, but haven't assembled anything since doing so (yet). I found that where the parts were sitting on the heated bed when they were printed, the edges stick out a very small amount, where the rest of the plastic has shrunk slightly. It's not much, but it might just be enough.

The gap between the washers maxxed out at about a 1mm when it was touching somewhere else. The small amount I've filed should gain me about 0.5mm each side, so this should hopefully prove enough.

I'll see how things pan out soon. For now though, bed. Can't work on it tomorrow though. :/

My M4 washers are the same size as yours, but my M8s are only 15.8mm, so that is why I didn't have a problem. As long as I push the M4 washers to the outside there is plenty of clearance. Here is one hot off the machine: -



I must admit I don't like the design of those parts. Unless the bracket and the bearing are exactly the same size the bearing will be loose. Since the z-value of an object is quantised by the layer height, which is not specified, it is never going to be just right. There should be a rim to hold one side of the bearing.

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[www.hydraraptor.blogspot.com]

Definitely explains a lot. I'll see if other washers I can source are any different and use them just on this section.

Many thanks people.

Dropped past the place I prefer going to for fasteners and told them about the issue (too large O.D.), and they found me some washers whose O.D. is 15.8mm, so that should solve all my issues.

Thanks all. Might also be worth adding this as a note to the BOM re: O.D. of the 8mm washers.

I had the same problem, but solved it by pushing the m4 washers as far out as possible while centring the m8 washer.. A friend of mine got some m4 locking washers (the not-perfectly-flat type with dents in them) which was a lot smaller than the standard ones. Might be something to look out for.

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-Nudel
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New 8mm washers I procured with the slightly smaller diameter (same as nophead) seem to have done the trick. All going well. Now to just finish off the rest of my build