Strength and stability of new extruded aluminum electronics workbench - Page 1
Forum section: electronics / projects

author: jrowberg
author_rank: Contributor
timestamp: December 21, 2021, 07:51:03 pm
content: Hi all,I'm working on replacing my dual rectangular white IKEA desks with a custom design that has a higher work surface and made out of 4545L extruded aluminum with T-slots. I fumbled my way around the Bosch Rexroth MTpro design software until I figured out how to put together a basic design, and now have something that I think should work. It's about 10.5 feet (3.2m) across, and 32 inches (0.8m) deep. I've included a set of photos that show the structure as I have it now. The main surface will be two 3/4" thick cuts of melamine, and the three shelves on the right will be the same material, just smaller cuts.The longest unsupported spans are the two in the front, which are slightly under 63 inches (1.6m) each. My goal is to have a rock-solid bench that doesn't wobble or flex--hence all the diagonal cross braces. I used 45x90 oriented vertically for the main support beams, and 45x45 for the verticals and the anti-flex braces. I don't have a lot of heavy equipment, e.g. what goes on the shelves on the right will not weigh more than 50-60 lbs at most (22-27 kg). Anything slightly heavy will be positioned near stronger supports and not on the hanging edges, or the front middle of the 1.6m spans of the main work surface.The big open space on the left above the main surface fits around a large TV that I use for a monitor + viewport for an HDMI inspection camera, in case anyone is wondering why I did the shelving the way I did. I would otherwise have extended the shelves all the way across with vertical supports at the three obvious points.Now, the fun part: I'm looking at the 45x45L/45x90L profile from tnutz.com, here:https://www.tnutz.com/product/exm-4545l/All else being equal, I'd go for the non-lite profile just to be safe. But Tnutz has a significant sale on that particular profile right now, making it significantly cheaper than anything else. It is for this reason that I used the over-braced + 45x90-vertical arrangement shown in the photos. On the 80/20 website that has a calculator for estimated flexing of any given design, it looks like the 45x90L profile with a max 1.6m span supported on both ends has basically zero flex, as in a tiny fraction of an inch at worst if you put a 50kg object right in the middle. This seems sturdy enough to me; it's just an electronics workbench, not intended for massive industrial equipment.Does this design look reasonable to all of you? Or, more appropriately, *unreasonable* to any of you?Thanks!

author: H.O
author_rank: Frequent Contributor
timestamp: December 21, 2021, 08:27:58 pm
content: That thing looks sturdy as heck to me, I don't think you'll have anything to worry about - EXCEPT possibly for the front left corner of the shelves which doesn't "look" quite on par with the rest so to speak.I'd TRY it as it is but be prepared to add vertical supports (or angled supports to the back) if needed.Edit: Can't you make the 45x90s go all the way from left to right side and have them rest on top of the center legs instead?

author: rdl
author_rank: Super Contributor
timestamp: December 21, 2021, 09:31:57 pm
content: If the shelves can't be any wider, I'd at least add some angle braces on the left side. Similar to those you have on the back side.

author: strawberry
author_rank: Super Contributor
timestamp: December 21, 2021, 09:35:36 pm
content: against warping ~25mm high density plywood top surface will do

author: Benta
author_rank: Super Contributor
timestamp: December 21, 2021, 10:42:52 pm
content: Looks over-designed to me.There's no need for double 45 braces at the rear, also not for the top.Concerning the top: Melamin is not a very good choice. At least not the standard type. It's not really resistant to scratches and heat.I'd suggest Formica laminate as the top surface, bonded to multilayer 40...45 mm hardwood plywood. Such tops can be found made to size (glueing Formica on such a large surface is not really DIY).But has it's cost, of course.My own workbench is appr. 3 m wide by 0.9 m deep and sits on standard aluminium profiles, the cross carriers are 100 x 50 x 5 mm L-profiles. The three front legs are 80 x 30 x 3 mm U-profiles bolted on.But this is not really comparable to your project, as the rear of my bench is carried by the workshop wall, and thus has much more forward/rear/side stability.The top is standard 40 mm coated chipboard plate originally intended for kitchen use. I have no cross supports under it, but it carries a 130 kg lathe and a 90 kg mill without problems. It's rock steady!In hindsight, I'd rather have had the multilayer plywood top plus Formica, simply because the surface is so much more rugged.But back then I didn't have the money:(EDIT: it doesn't have to be "Formica", that's just the term in my mind. The generic term is "High Pressure Laminate".

author: jpanhalt
author_rank: Super Contributor
timestamp: December 21, 2021, 11:09:32 pm
content: Quote from: jrowberg on December 21, 2021, 07:51:03 pmGood. It looks plenty strong enough for SMD electronics but not for welding ship bulkheads. Which are you doing?

author: jrowberg
author_rank: Contributor
timestamp: December 22, 2021, 02:52:38 am
content: Quote from: H.O on December 21, 2021, 08:27:58 pmYes, in a perfect world that TV would be in a different spot relative to the desk and I'd pull the shelves all the way to the middle, or even the far left side of the workbench. But there's not really a convenient way around it, so I figured I would gamble with the above approach and add more structure if absolutely necessary.Quote from: H.O on December 21, 2021, 08:27:58 pmStructurally yes, but if I can keep all pieces below a certain length (about 2.4m), then I save a lot on shipping because I can use a common carrier like UPS instead of a freight service. This also allows the bench to be built in a slightly more modular fashion, i.e. if I want to shorten one section, lengthen it, or add another later, I can do so pretty easily. I don't anticipate this, but it did occur to me.Quote from: Benta on December 21, 2021, 10:42:52 pmGreat. I'll take them out. The angled pieces are the most complex part due to the mitered cuts and special end drilling necessary.Quote from: Benta on December 21, 2021, 10:42:52 pmAgreed, but I also plan to cover the whole thing with a cut-to-size high-quality antistatic mat. Would that take care of the damage risk? I'm not opposed to the Formica/etc. approach, but I figure why go the extra mile if I plan to cover it anyway?Quote from: jpanhalt on December 21, 2021, 11:09:32 pmHa! SMD/PTH electronics assembly, troubleshooting, testing, prototyping, etc. Occasional retro gaming on the big TV on the wall. No ship bulkheads. The heaviest and riskiest thing I have (which I actually have yet to use) is a 12x10 solder pot bought in anticipation of still-pending design that has about 500 PTH header joints on the bottom. Not sure I want to do that on the workbench anyway...probably in front of the window with the fans running outward on high.

author: elekorsi
author_rank: Regular Contributor
timestamp: December 22, 2021, 08:15:43 am
content: Last year, i did something similar and i am very pleased with it. It's made from 45x45 profiles, shelves from 30x30. You can see it here:https://www.eevblog.com/forum/chat/whats-your-work-benchlab-look-like-post-some-pictures-of-your-lab/msg3444924/#msg3444924Work surface is made from 30mm plywood (2k lacquered), which really ads to the rigidity of the bench. Top shelves from 22mm MDF.It is rigid more than enough, if i put 120kg on the middle it doesn't flex more than 2-3mm...Looking at your pictures, i would say that you over engineered this one. On the bench1_edited.png i marked you with red what is for my opinion just a waste of material and money. Also the blue ones will not be necessary if you will use a work surface that is rigid enough. Consider adding the green one and putting another shallow shelf under the table, as you can see at mine bench.On the picture bench2_edited.png, those with red are also unnecessary...I see that you used 90x45 profile for the connections between the legs. Keep in mind that this will be very "fat" together with the top surface and if you have long legs, you will keep banging with knees into it, when seated. That is also why i don't like drawers under the bench...For this reason i even moved the profiles a little further towards the back, as you can see on the picture attached. Also the front legs are placed 200mm from the front edge.

author: jrowberg
author_rank: Contributor
timestamp: December 22, 2021, 05:31:50 pm
content: Quote from: elekorsi on December 22, 2021, 08:15:43 amDo you know off-hand (or can you check) whether you used the standard profile, or the "lite" profile, or even something extra-thick?Quote from: elekorsi on December 22, 2021, 08:15:43 amI'd do this under different circumstances, but I currently have three large sets of drawers that are filled (and organized) full of tools, devkits, spare parts, cables, etc. which I intend to keep. One of them will fill half the space on the left section, leaving half of the remaining space for feet/legs. The other two drawer sets will fill the right half completely. I anticipate actually standing to make use of that space, if I need to. (I'm already standing to use it, just hunched way over, which is annoying.) So, for the moment, I'll omit the lower forward crossbeams and under-desk shelves. I can always add them later if I decide to get rid of the drawer sets.You have a good point also about a rigid desktop eliminating the need to square up the top sections, since obviously nice thick wood isn't going to magically turn into a parallelogram.Quote from: elekorsi on December 22, 2021, 08:15:43 amUnderstood, but I'm dealing with this. Maybe I could use a 45x45 just for the front left cross section that I will actually sit at, then if flex is a problem, swap it out for a 45x90.

author: elekorsi
author_rank: Regular Contributor
timestamp: December 23, 2021, 01:49:28 pm
content: It's a "lite" one, as you can see on the picture. Rigid enough... You can go with the "standard" one if you are worried, but i don't think it is necessary...

author: wizard69
author_rank: Super Contributor
timestamp: December 25, 2021, 04:24:28 am
content: This looks to be massively over built leading to excessive cost for what amounts to a work bench for electronics.Quote from: jrowberg on December 21, 2021, 07:51:03 pmFor straight electronics work you don't need more than one layer of hardwood plywood. Place Formica on both sides to keep it stable.By the way you mention 3 different brands of extrusions in this post. Stick with one as they are not all compatible and sometimes in ways that create gotchas. I don't which is better is hard to say as we probably have a dozen different brands at work, thus how I know about compatibility. Personally I have a couple of Bosch tools I made up to make using that brand easier. If you make a few drilling guide blocks your construction job becomes 100% easier.QuoteThat is all well and good but it makes little sense to go overboard. For example the top, once bolted in place will add structurally. Gussets are required in my mind so I'm not going to dismiss them but the diagonal braces are a waste. to be perfectly honest I would mot make the bench any longer than the length of the plywood that would make up the top can be had. If that is 8 ft then design for an 8 foot long bench with no center support legs as they just get in the way. Frankly the longer span would better justify the 45x90 extrusion.QuoteNote my comment about using one brand and sticking with it.QuoteIt might actually be too stiff. By the way if you want to add a vice or other metal working equipment, of size, you will be better off having a second heavy duty bench. Backing up a bit, the legs at the front are the weak areas on benches like these, it is advisable to use gussets to better support those legs but that does move your usable sitting space in on each side. This is another reason to get rid of the center leg. Also a foot rest type runner can help support the legs better.In any event back to the idea that another bench might make sense, that is build two different benches. The Problem with electronics work benches is that you need more depth than a common desk. Obviously this depends upon your interests but if you take some wild ass number, lets say 18 inches, for the front to back length of many common bench instruments, you end up having the work area on a 36 inch deep work bench. An 18" deep work area is not ideal for many interests. In other words an electronics work bench takes up a lot of space in a given room, I wouldn't make it any wider than required, at the same time I'm not convinced that a depth of 32 inches is enough.Put your other tools and so forths on benches or counter tops that are not so deep. The savings in floor space will pay off down the road. I actually like kitchen cabinets (assuming better quality here) as they are designed to support a counter top, and create instant storage beneath.Now kitchen cabinets can be seen as permanent but there are no rules against mounting them on a frame and wheels. I only mention them because being prefabed there is not a lot of custom wood working involved. In any event the idea here is to suggest alternatives.QuoteWell it is over built in some ways. Is it unreasonable, that isn't for me to say. However I've pointed out what MIGHT be issues for you. The bench is very long for example but at the same time I'm not sure it is deep enough. How deep is very very dependent upon what your interests are. If you want to work on rack mounted equipment and have common bench electronics it probably will be tight. If the goal is to work on Raspberry PI's it is likely fine. I would not however make it much wider than 8 feet. There are lots of reasons behind managing size one is simply the effort required to move the bench.This brings up one other really important item - wheels. Wheels can really make your life much easier, especially as you get older. Even if they are only used once every 5 years. So make sure you design in wheels or an easy way to put casters under the bench when you need to move it. You can buy temporary casters and jack a bench like this up and do so easily if you plan ahead. The obvious need is for a place to put the jack. The fact is this will be a heavy bench and you may not believe you will need to move it but crap happens.By the way there is another option for a supplemental bench to the main electronics bench. That is to go to your local home center and buy the lower half of a roll around tool box. Put a layer or two of plywood on top and you have an instant roll around bench with oodles of storage. Considering how much aluminum costs these days that might actually be cheaper and you will not knock the storage. If you can make sure that the heights end up compatible. these are great for mounting a small drill press, CNC or a bench grinder.

author: Renate
author_rank: Super Contributor
timestamp: December 25, 2021, 08:25:55 pm
content: DIY Formica rocks!. It's not rocket science. Just make sure that the glue is "dry" to touch. Use lots of dowels as spacers to make sure that it doesn't stick prematurely. Lot of pressure, lots of rolling. Good carbide tools for trimming.

author: jrowberg
author_rank: Contributor
timestamp: December 28, 2021, 12:47:37 am
content: Quote from: wizard69 on December 25, 2021, 04:24:28 amI suppose that general feedback is better than if you'd said terribly underbuilt.Quote from: wizard69 on December 25, 2021, 04:24:28 amWith the number of recommendations for this, I'll definitely look into it. I hadn't even considered it before.Quote from: wizard69 on December 25, 2021, 04:24:28 amThe software I'm using is from Bosch-Rexroth, but my intent is to get everything from Tnutz.com if I can, unless there are a couple of special accessories that I can't get there. All of the framing and basic fastener sets will come from there, and they do cutting and drilling as requested. Very few pieces of aluminum need drilling at all since I'm using the angle brackets for attaching the pieces together; it's really just the 45-degree gussets. Everything else is just a standard straight/perpendicular cut.Quote from: wizard69 on December 25, 2021, 04:24:28 amI'm trying to stay within cheaper freight requirements, but also building this to improve a system that already works pretty well for me (2x desks put together with 3/4 of the under-desk space allocated to a storage drawer system). To get rid of the drawers and put all of that stuff somewhere else--sufficiently organized--would be pretty drastic in my existing office space. I have plenty of sitting space at large corner desk elsewhere in the room. I'd happily go with the foot rest/runner approach, except for all of the aforementioned drawers.Quote from: wizard69 on December 25, 2021, 04:24:28 amAlternative suggestions are great; I never would have thought of kitchen cabinets, for instance. However, in this case, the three large drawer sets that I have beneath the desk serve the same purpose on my end, and they're already on wheels.For heavier-duty tools and projects, I have a workbench in the garage with a vice on it and things like saws, etc. I intentionally keep that kind of work away from my office since it tends to be messy in ways that are hard to clean up and possibly dangerous to tiny electronics. So, in one sense, I already have two different benches; they're just in different parts of the house.In the past, I had exactly one bench tool that was ridiculously deep, temporarily borrowed from the company I work for and returned some time ago. Everything else I have is either handheld or much shallower (100 MHz DSO, Saleae Logic, Joulescope, etc.). I don't either intend or desire to collect a set of equipment like what I've seen showcased on some forums here--very impressive, but not ideal for the kind of work I do. My tasks fall more in the area of RasPis, firmware design, etc. with occasional need for spot repairs or troubleshooting with a debugger and logic analyzer attached.I may opt to add a couple of inches of depth, as the room could accommodate that almost without noticing. Concerning the need to accommodate moving the desk: this is actually one reason I went with a dual-section design with each section under 6 feet. The upstairs office has a set of stairs towards the middle, and that's the only way to get stuff in and out. There is zero chance an assembled 8-foot-wide workbench would make it through in either direction. If/when we have to move, I fully expect to take these things down into basic planar sections. I have other equipment up here already (PnP machine on a table) that will require the same effort. I'm willing to gamble on my predicted health and longevity for now (I'm only 36).I will think about all of your suggestions though, and simplify/alter where possible, helpful, or necessary.