Almost completed but a fastener problem

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2YRRAH
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Almost completed but a fastener problem

Post by 2YRRAH »

I am closing in on the last few things to complete my machine. I had hoped to start calibrating this weekend but I've run into a problem with the bed fasteners. The kit has gone together very well for the most part but every issue I've had was a problem caused by the supplied fasteners (or not supplied in one case).

First I was unable to get the screws into the bottom of the PSU. They didn't seem to be long enough. I eventually eliminated the 4mm washers to get it secured.

The 1 3/4" screws used to hold the base cooling fan in place caused some trouble as well. Two of them went in no problem but the other two jammed tight just before they tightened on the fan. I could not turn them any more but they were still very loose on the fan. Not cross-threaded because there was about 3/16" through the nut smoothly until it suddenly jammed solid. I tried to back one out but it only twisted off. The other I forced tighter and it sort of snugged up to the fan. Good enough for now until I get some new ones. Later I noticed another unused screw in the same package that was very messed up. The 1/4" of starting threads were OK but then the majority of the shank had the threads completely stripped off. This is likely what I encountered with the fan without noticing...started to thread on OK and then jammed at the missing threads.

The Cheapskate package was missing the #4X3/8" sheet metal screws altogether. Fortunately the local hardware store had #4X1/2" screws that I clipped off to the correct length. Seems to be holding well.

And finally tonight, I have found that the supplied screws to secure the bed are simply not long enough. I have tried several different holes and screws but none of them will reach into the T-nuts on the base underside. Measuring the screws and materials shows why.

The screws are supposed to be 3/4" (0.75") but they measure 0.73"

Onyx bed .094"
spacer .160"
bed plate .260"
base top plate .260"

Total .771" (added) but measuring the stacked items gives .781" since multiple layers tend to "grow".

The T-nuts reduce this by about .110" so the total length the screw must reach is .661" (added) or .671" measured.

This allows .730-.671 = .059" of threading...about two turns of the screw. Theoretically enough but in practice not. 1" or even 7/8" long screws would have worked and there does not appear to be potential interference with anything that longer screws would cause.

So tomorrow morning I will be making the 40 minute trip into Calgary to Lee Valley to get some 4-40x1" brass screws (only material they have)...the only place I can get screws of that size on a Sunday.

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Outsider
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Re: Almost completed but a fastener problem

Post by Outsider »

Also try Lowes. I had to get screws and they had them in steel. We have a few stores here in Calgary

IMBoring25
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Re: Almost completed but a fastener problem

Post by IMBoring25 »

I found I didn't get the T-nuts fully seated with the hammer. I used the screws and spacers without the snowflake and bed to draw the T-nuts up the rest of the way. There's a lot of wiring in there. You don't want them excessively long.

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Outsider
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Re: Almost completed but a fastener problem

Post by Outsider »

I had that same problem. I did the same thing to solve it. Even with that, I came to the conclusion that the screws were just slightly to short. I have 4-40x 1" holding the bed down and there has been no problems.

2YRRAH
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Re: Almost completed but a fastener problem

Post by 2YRRAH »

So the screws from Lee Valley worked great. I like the brass finish next to the black Onyx. I might add some other brass-paint accents to the main body (black melamine)!

They only protrude about 1/8" from the T-nuts and they're tucked closely behind the base mounting panels so there is nothing for them to interfere with. I had much more worries about the way I had to brutalize the wiring to get the Rambo inserted.

So I would strongly advise SeeMeCMC to switch to 1" or even 7/8" screws to secure the bed assembly...but not necessarily in brass. ;)

The calibration is done and a I've run off a couple of calibration cubes that seem pretty good. So its on to printing the fan shrouds.

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dlbyers
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Re: Almost completed but a fastener problem

Post by dlbyers »

I received my kit within a few days of your original post so it is possible that ours are from the same batch. I encountered the same problem with the base fan screws and the PSU mount screws. Haven't mounted the bed just yet but may pick up some 7/8" screws to avoid the frustration. Thank you for the post.

TheIrishScion
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Re: Almost completed but a fastener problem

Post by TheIrishScion »

Same exact problem with my included hardware for the fan and the PSU as well (minus the Onyx bed, I haven't got that far yet though it sounds like I probably will)

I marked the problem with the fan mount down to overly aggressive nylocks locking up on the thread. I got one of the 4 to go on properly (as an experiment really) with a tiny dab of olive oil to reduce friction.

Sounds like the hardware choices are going through a slightly sloppy phase.

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Eaglezsoar
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Re: Almost completed but a fastener problem

Post by Eaglezsoar »

TheIrishScion wrote:Same exact problem with my included hardware for the fan and the PSU as well (minus the Onyx bed, I haven't got that far yet though it sounds like I probably will)

I marked the problem with the fan mount down to overly aggressive nylocks locking up on the thread. I got one of the 4 to go on properly (as an experiment really) with a tiny dab of olive oil to reduce friction.

Sounds like the hardware choices are going through a slightly sloppy phase.


As with virtually everything else manufactured the screws are most likely made in China and the quality control is virtually non existent which explains why some of the screws have bad threads.
The lengths of the screws could probably given a second look at by SeeMeCNC and if they need to be supplied a little longer they should and will do that once they discover the screws are too short.
They do offer the Max V2 fully assembled and although they probably do not sell many in that configuration, the person responsible for building them should make notes of which screws should be made
a little longer.
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TheIrishScion
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Re: Almost completed but a fastener problem

Post by TheIrishScion »

Eaglezsoar wrote:As with virtually everything else manufactured the screws are most likely made in China and the quality control is virtually non existent which explains why some of the screws have bad threads.
The lengths of the screws could probably given a second look at by SeeMeCNC and if they need to be supplied a little longer they should and will do that once they discover the screws are too short.
They do offer the Max V2 fully assembled and although they probably do not sell many in that configuration, the person responsible for building them should make notes of which screws should be made
a little longer.


I'm not buying that as an excuse. As with anything mass produced from China or elsewhere there are a range of quality grades available, from cheese-grade chinesium parts with no QC whatsoever, all the way through to milspec and aerospace grade hardware with full traceability, and everything in between. Regardless of whether it's the nut or the screw (or both) that's at fault, they're supplying the wrong grade of hardware in some of the kit, and the wrong length hardware as well (probably because the tolerances between suppliers are too high, the size machine screw they specified initially was perfect, but it was slightly long and now the replacement screw is made slightly short, or whatever).

Of course I understand that there's a price target to be hit, and I understand that the target audience for these kits is a _lot_ more technically inclined than most, and like me, most are happy enough to nip down the 'Despot and buy better stuff when needed. But the price delta between good nylocks and crappy nylocks when bought in bulk approaches zero. This is not where you want to cheap out, especially when you're turning, burning and squirting most of your custom parts in house already, so total materials cost on the kits should be manageable. If I was feeling really energetic (and less married with children) I'd BOM the kit for a ballpark parts cost, but I'd be surprised if the total materials cost was much over $450-$500. And if they were I'd be volunteering to help with sourcing :-)

Now, keep in mind that if they're selling the product for only 2x the parts cost, they're robbing themselves. Materials cost on most consumer products generally ranges between 10 and 20% of retail price. I suspect the SeeMeCNC kits are superb value for money even with an occasional iffy part.

While perfect may be the enemy of good, good enough can equally be the enemy of great. ;)

I'm probably way off the mark, and I say all this with love. Don't hate me, it's been a while since I committed manufacturing with intent.

///d
Last edited by TheIrishScion on Fri Feb 12, 2016 11:45 am, edited 1 time in total.

geneb
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Re: Almost completed but a fastener problem

Post by geneb »

TIL "Chinesium" exists. :D

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Re: Almost completed but a fastener problem

Post by bot »

Chinesium is an element discovered by the great American inventor, Midaf, who had the magical ability to make things better, simply by virtue of crafting them on American soil rather than anywhere else. This is called the Midaf Touch. The ability to make anything better, simply by being in America.
*not actually a robot

TheIrishScion
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Re: Almost completed but a fastener problem

Post by TheIrishScion »

Actually, given the choice I'll take my fasteners in finest cold rolled Swiss Unobtanium. ;-)

Eric LB
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Re: Almost completed but a fastener problem

Post by Eric LB »

Had the exact same problem with the 6/32 nylocs generating far too much friction and falling the threads (18/8 stainless (304) is VERY susceptible to galling. This happens on then fan installation because those nuts needed to be screwed in further on those screws. Solvable with stainless fasteners from my local hardware store for $1.72 , but annoying . JJ says they are "looking into it" as they have fielded several complaints. BTW, the solution for installing the vibration dampers on the steppers, is to get a Dremel tool with a cut off disc and cut two (for each stepper) of the supplied 10mm metric screws down to 5mm ( holding the screw clamped in a vise grip. Worked like a charm and takes only a few minutes. The Dremel cuts them off clean and there are no threading problems.

stillcopper
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Re: Almost completed but a fastener problem

Post by stillcopper »

See my post on 'Better Build Parts' in this forum.

Exact same problems with bad locking nuts and too short bolts for the hotplate.
Replaced nuts with standard using loctite, and longer hotplate bolts.
Appears it's been over a year now, given the age of this thread, and SEEMECNC hasn't corrected the problem.

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Windshadow
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Re: Almost completed but a fastener problem

Post by Windshadow »

if you look at my build thread from December 2015 I too reported the same problem with too short screws and i also had a problems with 3 or 4 of the captured lock nuts not holding in the melamine.

I think a higher level of QC should be looked at in the fastener area. One of the locknuts I was supplied was threaded undersized (the result of the fastener manufacturer getting too many nuts out of a tapping tool i expect) since i have a home machine shop in my basement I just ran a good tap through it to open it up but few kit builders will have access to a set of taps ( I have full sets of taps and dies in 5 different english systems including Whitworth and BA and ME as well as NF, NC, AF, AC, and partial collections (many home made to repair antique 19th century machinery) of quite a few other 'systems' well as metric of course but i have been assembling my shop for almost 60 years and a few bad fasteners in a kit can give a new builder quite a headache.

I reported these fastener length problems 5 months ago and I am rather surprised to see them still cropping up

RandomFactor
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Re: Almost completed but a fastener problem

Post by RandomFactor »

Glad it's not just me. Longer screws for the onyx bed mounting (or shorter spacers) would have saved me this weekend.

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Eaglezsoar
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Re: Almost completed but a fastener problem

Post by Eaglezsoar »

I hope that the the good folks at SeemeCNC are reading this thread and take the necessary actions so that future users will not have to keep going through this.
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Qdeathstar
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Re: Almost completed but a fastener problem

Post by Qdeathstar »

Feel lucky, had no problems with the bugs and bolts in my kit.

I even had a few extras. I found that the screws are extremely small, and several of them look similar to one another (eg, the cheapskate screws and the effector screws) if you aren't meticulous about screw tracking its pretty easy to get screwed.

My least favorite thing about the built was squeezing all those nylon locknuts into place. "Insert 47 nylon lock nuts". AAAARRRRGGHHH. Actually, toward the end I was beginning to like them.

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