Laser-cut test bench concept - what do you think?

[Valantar]

While tooling around looking for material and production options for the HTPC case I'm working on designing, I signed up for laser-cutting service Ponoko. Turns out they have a sign-up option where you get your first product for free if you order within ten days of signing up and the production+material costs are below $20. That's not much, but why not try to take advantage?

They have 181x181mm sheets of 6.7mm thick bamboo plywood which both look nice and ought to be quite strong. The size, as most of you've probably realized, is reasonably close to an ITX motherboard. So why not see if I can get a free DIY test bench out of this? I have a bunch of motherboard standoffs lying around, so why not.

This is my design:

As noted on the image, the "bench" has two wide legs, which mount (friction fit? One can hope!) to the outer edges. I made mounting notches on all sides so that they can be mounted on whichever axis is more stable. The base is slightly larger than the motherboard, but of course the legs have to be narrower than this to be cut from a single sheet of wood. One of the legs (2) has a hole for a C6 AC power receptacle and mounting holes for the side screws of a Mean Well RPS-200-12-C, with a small support plate that slots into the bottom of the leg and lies underneath the PSU. I'm guessing I'll have to epoxy in the standoffs, but if I could find some sort of threaded insert to hammer in instead (or similar), I'd take that. If friction fitting the legs doesn't work, it should be possible to either screw or glue them together. The bottom cutout is made large for easy access to CPU backplates and rear-mounted SSDs. I forgot to add this before exporting the image, but the first leg (1) should have a hole for mounting a 16mm momentary power switch.

So: is this a feasible design? My two chief concerns are if it's stable enough given that the legs are less wide than the motherboard (wouldn't mount a heavy GPU on this, I suppose, though using the leg mount beneath the GPU might help with that) and that one of the standoff holes is quite close to one of the mounting notches for the legs, which might be a structurally weak point.

I haven't actually submitted it for a quote to Ponoko yet, so I don't know if it fits within their <$20 limit, but I thought it was a neat idea, especially if it's free (except for shipping, I suppose)! Of course, feel free to steal, copy, reuse, modify or whatever you might feel like doing with the design, and let me know if you want a vector version of it for easier iteration

 

[el01]

While tooling around looking for material and production options for the HTPC case I'm working on designing, I signed up for laser-cutting service Ponoko. Turns out they have a sign-up option where you get your first product for free if you order within ten days of signing up and the production+material costs are below $20. That's not much, but why not try to take advantage?

They have 181x181mm sheets of 6.7mm thick bamboo plywood which both look nice and ought to be quite strong. The size, as most of you've probably realized, is reasonably close to an ITX motherboard. So why not see if I can get a free DIY test bench out of this? I have a bunch of motherboard standoffs lying around, so why not.

This is my design:

As noted on the image, the "bench" has two wide legs, which mount (friction fit? One can hope!) to the outer edges. I made mounting notches on all sides so that they can be mounted on whichever axis is more stable. The base is slightly larger than the motherboard, but of course the legs have to be narrower than this to be cut from a single sheet of wood. One of the legs (2) has a hole for a C6 AC power receptacle and mounting holes for the side screws of a Mean Well RPS-200-12-C, with a small support plate that slots into the bottom of the leg and lies underneath the PSU. I'm guessing I'll have to epoxy in the standoffs, but if I could find some sort of threaded insert to hammer in instead (or similar), I'd take that. If friction fitting the legs doesn't work, it should be possible to either screw or glue them together. The bottom cutout is made large for easy access to CPU backplates and rear-mounted SSDs. I forgot to add this before exporting the image, but the first leg (1) should have a hole for mounting a 16mm momentary power switch.

So: is this a feasible design? My two chief concerns are if it's stable enough given that the legs are less wide than the motherboard (wouldn't mount a heavy GPU on this, I suppose, though using the leg mount beneath the GPU might help with that) and that one of the standoff holes is quite close to one of the mounting notches for the legs, which might be a structurally weak point.

I haven't actually submitted it for a quote to Ponoko yet, so I don't know if it fits within their <$20 limit, but I thought it was a neat idea, especially if it's free (except for shipping, I suppose)! Of course, feel free to steal, copy, reuse, modify or whatever you might feel like doing with the design, and let me know if you want a vector version of it for easier iteration

The durability is pretty good, but stability may be a bit difficult if the power supply is lighter than the top hardware, and if the GPU makes system off balance.

Considering that it's bamboo and 6.7mm thick, it will be durable. My main suggestion would be to figure out how to add a base or some supplementary feet if you can chop off some of the size.

Friction fit will be a bit difficult considering that the bamboo plywood will not have very very good tolerancec, but in 90% of cases, a bit of sanding or some wood filler will to the trick.

I would suggest making the design more refined and essentially widening the internal area available. Think of it as a picture frame, then with some tabs reaching in to "intercept" the standoffs on the motherboard.

 

[Valantar]

The durability is pretty good, but stability may be a bit difficult if the power supply is lighter than the top hardware, and if the GPU makes system off balance.

Considering that it's bamboo and 6.7mm thick, it will be durable. My main suggestion would be to figure out how to add a base or some supplementary feet if you can chop off some of the size.

Friction fit will be a bit difficult considering that the bamboo plywood will not have very very good tolerancec, but in 90% of cases, a bit of sanding or some wood filler will to the trick.

I would suggest making the design more refined and essentially widening the internal area available. Think of it as a picture frame, then with some tabs reaching in to "intercept" the standoffs on the motherboard.

Thanks for the feedback

I agree that stability is the main concern here. I've tried to alleviate that somewhat by mounting the feet on the outer edges, which should help - but it won't help if I were to attach a tall, heavy GPU more or less directly above (or even slightly outside of) one of the legs. The PSU mount is also notched to mount opposite of the GPU, which would bring the center of mass lower down and towards the middle - but its 300g weight likely wouldn't make it that stable. I could try shifting the motherboard mount towards the "top" (opposite the PCIe slot) side of the board to move the center of mass if a GPU is mounted/move the bottom leg further out past the PCIe slot, but that would mean mounting at least one standoff on the mounting tabs for the legs up top. That shouldn't be a problem given that this would be supported by the leg below it, but it's still not ideal: the material around the standoff mount would be 3-4 mm, which is not a lot - especially considering that the hole size for the standoffs are pure eyeball measurements. It would make it impossible to use any kind of threaded insert for that standoff, at least.

As for widening the central cutout - I could try doing that, at least a bit. Currently, the distance between the central cutout and the edges of the upper mounting notches is around 9mm. I don't really have a clue about how strong this material is (although bamboo should be very strong, and cross-laminated bamboo plywood possibly even more so), but I don't feel comfortable going narrower than the thickness of the material for anything that would be unsupported and load-bearing (such as the area around a standoff without a leg directly beneath it). Still, that would mean I could widen the legs a bit. The main limitation for this is the spacing of the motherboard mounting standoffs, which I sadly can't change Of course I can make notches in the legs/whatever they should interfere with, but it wouldn't be ideal. Not much point in making the legs wider if they have to be trimmed afterwards.

I also tried finding somewhere to cut out a cross-brace or similar to tie the legs together, but there simply isn't enough material for this without moving up to the next board size, pushing me well past the $20 limit of the promotion, or moving the legs inward, which would make the whole thing less stable.

What would possibly be a better solution than a cross-brace would be to notch the bottom of the leg without the PSU mount (the one that would go beneath the GPU) for 2-3 small "nubs" that would mount similar to the GPU plate on the other leg, but pointing outwards, forming a wider and more stable base for the GPU. They shouldn't need to stick out more than an inch or so to significantly decrease the chance of a heavy GPU tipping over the whole build. This would make the assembly take up more desk space, but only marginally so.

 

[Valantar]

Here's rev. 2 of the design.

Updates:

• Expanded base plate size to maximum possible (inner edge of orange bounding box)
• Shifted motherboard standoff mounts up and to the right
• Shifted right-side leg mount to match
• Made "extensions" (4) for the leg under the GPU with screw holes for security. They will extend ~40mm from the leg, further than the thickness of most GPUs, so they should provide adequate support to make the platform stable with a reasonably heavy GPU.
• Widened the legs as much as possible without affecting structural strength

All in all, this should make for a more stable platform, but at the cost of some structural strength. I don't consider the top left standoff mount a problem as it would be supported by the leg if the top+bottom mounts are used (and using the left+right mounts means you're not using a GPU (or doing it wrong), so less stress overall). I'm more apprehensive about the bottom right mount, but I think that's close enough to the bottom leg to not be an issue if a GPU is installed. Still, I would probably want to be careful not to push down too hard when inserting said GPU.

Even without a GPU installed, this revision should be more stable, as the right-shifted design would stand up better to heavy display cables and dongles hanging off the I/O on the left, and the base overall is a couple of mm wider in each direction.

 

[el01]

Here's rev. 2 of the design.

Updates:

• Expanded base plate size to maximum possible (inner edge of orange bounding box)
• Shifted motherboard standoff mounts up and to the right
• Shifted right-side leg mount to match
• Made "extensions" (4) for the leg under the GPU with screw holes for security. They will extend ~40mm from the leg, further than the thickness of most GPUs, so they should provide adequate support to make the platform stable with a reasonably heavy GPU.
• Widened the legs as much as possible without affecting structural strength

All in all, this should make for a more stable platform, but at the cost of some structural strength. I don't consider the top left standoff mount a problem as it would be supported by the leg if the top+bottom mounts are used (and using the left+right mounts means you're not using a GPU (or doing it wrong), so less stress overall). I'm more apprehensive about the bottom right mount, but I think that's close enough to the bottom leg to not be an issue if a GPU is installed. Still, I would probably want to be careful not to push down too hard when inserting said GPU.

Even without a GPU installed, this revision should be more stable, as the right-shifted design would stand up better to heavy display cables and dongles hanging off the I/O on the left, and the base overall is a couple of mm wider in each direction.

nice...if all else fails, ask users to nail it to their desk

 

[Valantar]

nice...if all else fails, ask users to nail it to their desk

While that would kind of defeat the "as few tools as possible" design of this, it's definitely an option

I've tweaked the design ever so slightly, moving the motherboard mounts slightly back down and to the left again (but nowhere near as far as the first revision). This let me expand the mounting holes to 5mm, which should let me fit these m3-threaded knurled nuts. I'll have to be careful hammering them in, but it ought to work, and would make mounting the standoffs and motherboard far better.

I'll be ordering this in the next couple of days to make use of that sign-up coupon. Shipping to Norway still won't be cheap, but the price is below our import VAT limit, so it's bearable even for an experiment like this. I'll be sure to post some photos once I have it in-hand Now I kind of wish I had a spare ITX motherboard to test out on it!