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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Large router table capable of being dismantled and fit through a standard doorway
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  1. #1
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    Apr 2018
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    Large router table capable of being dismantled and fit through a standard doorway

    Greetings, :wave:

    I have come to humbly prostrate myself before the gods of DIY CNC with what I'm hoping is not a stupid idea. :banana:

    So basically I live in a rental and want to build a giant CNC router table which at this stage looks like it will have a cutting area of 2500x1300x120 / 7.56'x4.27'x4.72". I plan to make the table out of two sub tables with self leveling feet which I can *hopefully* align with the space between being spanned by sections which bolt onto either table. Each sub table will measure 1380x1000x650 / 4.53'x3.28'x2.13' (715 / 2.35' with leveling feet installed) and weigh approximately 50kg / 110lb which means two people should stand a chance at a) moving the bloody thing and b) fitting it through a standard doorway (am I asking too much?). The top spanning section weighs in at 15kg / 33lb.

    75x50x2 / 2.95"x1.97"x5/64" RHS is used for the main structure with 65x35x2 / 2.56"x1.38"x5/64" RHS for the centre spans and 50x25x2 / 1.97"x0.98"x5/64" ribbing for the table surface. I will clad each section in plywood and then attach an MDF wasteboard to the top later..

    I want to use 2800 / 9.19' long 8080 sections resting on 18x brackets cut from 75x75x5 / 2.95"x2.95"x13/64" equal angle section which will bolt to the side of the table *hopefully* allowing me to finely adjust the straightness of the 8080 section in both the Z axis and parallelism in X and Y.

    After speaking with the owner of a local steel merchant he supported the idea of cutting the angle section into brackets so that when I'm trying to get the 8080 level I won't be fighting the angle section itself. Yes there are a million holes to drill but I'm a patient man. (Last year I built a 3m / 9.84' tall 6m / 19.68' diameter 4v geodesic dome with 3D printed hubs and 250 lengths of PVC conduit cut using various jigs, ended up having to use a heat gun to flare the ends of most of the pipes to fit on my hubs as we all know the ID of PVC conduit is not a spec'd dimension @#$@#! haha)

    Compared to a lot of the builds I've seen, mine certainly seems to be on the light weight side of things but I've tried to optimise the usage of the RHS steel sections to give it strength where it needs it / reduce the length of spanning sections etc. The local steel guy who built his own CNC plasma table pointed out that you're paying for metal by the tonne more or less and so RHS with narrow top is ideal for spans where square section is just wasting metal etc.

    I've conducted a gazzilion stress/strain simulations and the ones pictured show the table itself loaded with 300kg (2943N) along with an additional 200kg (1962N) load held by the side brackets (100kg per side) with only one foot fixed on the floor and the rest of the feet on a friction-less sliding surface. Max simulated deflection is a little over 0.1mm / 0.004" and my gantry assembly at this stage will be around 45kg / 100lb including spindle etc so as far as I can tell this will be well and truly strong enough for a wood router.

    It's easy enough to add gussets later down the track if rigidity proves to be insufficient.

    The 8080 will support HGR20 w/ HGW20CC blocks for the gantry which will be a section of 80160 - driven by a moving omega drive using 25mm / ~1" AT5/ATL5 belt but I'll post more about that later as my primary focus at the moment is on the table itself.

    I'm a humble electronic tech / tinkerer who's welding is good enough to join @#$# together but by building in the adjustment I hope to save myself from disaster down the track.

    Normally I'm pretty shy / lurker but this has been a dream of mine for a long time and I have a patron who is paying for more or less everything to make it happen so it's time to make this dream a reality!

    I really appreciate the opportunity to engage with all of you lot so let the constructive criticism begin! (flame2)

  2. #2
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    If you look at other welded frames and component videos and forums out there you will see that welding distorts a lot and this has to be corrected via machining or grinding. I suggest you design all bolted joints (to allow adjustment) or you braze the connections not weld them. Brazing doe not distort as no metal melted. Channel of suitable size is just as stiff as RHS in bending yet it allows you to bolt up surfaces properly. Channel is not as stiff in torsion but then your bench is not going to be twisted so matters little. Do a channel vs RHS simulation and see what you think. Regards Peter S

  3. #3
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Thanks for the feedback Peter!

    What you are saying regarding channel vs RHS makes a lot of sense. I'll do another design with channel and see how it goes, when I was designing I figured that two walls of 2mm thickness supported top and bottom in the RHS would be stiffer than say 4mm thick channel but of course if the bolts are too tight they would tend to distort the RHS. I'll run the numbers on a channel based table and see how it goes.

    I had tried to minimise welding in the design, restricting it to only the table corners and the ribs up top.. I was hoping to counteract any bananas for edges with those angle brackets - a few mm here and there in the XY plane can be accommodated for when the 8080 extrusions are mounted and also if the table itself isn't perfectly flat the angle brackets can be moved up and down in the Z axis to get the 8080 extrusions level.

    As part of my CAM process I'm tempted to use data from a height probe mounted next to my spindle to adjust the gcode to track the wasteboard / material as is done in 3D printing for very accurate first layers (my delta achieves flatness in probe tests to within std deviation of +/-0.025mm after automated calibration routines) however of course I would like to end up with a table that is physically as flat as possible to begin with.

    The big question is whether I can manage to build each sub table relatively flat - I plan to use a huge welding corner clamp to weld the uprights w/ the levelling feet installed onto the short edges of the table, then I can level the table sides to each other with the longer spans clamped in place before tacking and stitching..

    Regards,

    David B.

  4. #4
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    I realise also I'll need to shim the brackets on the edges in order to take any roll out from a table edge that isn't vertical..

  5. #5
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Hi David - Any welding done in the "hope" of straightening it after is hopeless. Better to have bolted joints then you can adjust. Brazing is very good, I do this alot (steel and aluminium no distortion) if you have an oxy or propane set. Peter

  6. #6
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Thanks again Peter, I had a quick sticky beak at your post about brevis - I love the minimalism - less is more as they say. I'm in Townsville so you're quite close in the grand scheme of things..

    You've really got my gears turning about brazing now, I can't afford an oxy / acetylene setup even thought I would absolutely love to have it - I have fond memories of using my grandfather's set - perhaps a propane torch or the like from Bunnings will get me across the line but I will admit complete ignorance to the world of brazing. I saw him do it on numerous occasions but have never investigated it myself.

    I remember being paid a few dollars pocket money as a kid to oil a steel tubular fuselage my grandfather welded together for an ultralight aircraft (Sonerai II) and he seemed to have great success keeping the frame very straight of course with clever order of operations / jigs / clamps and whatnot. The angle brackets were not intended to stretch the table back out afterwards but merely act as a shelf to support the straight aluminum profiles - oversize holes in the brackets + shims if required in order to make up for my lack of a decent welding / fixture table but the more I think about it I definitely agree and will make a jig to make all the table ribs that bolt into place.


    (Yes, it flew)

  7. #7
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    You can Tig braze or even mig braze as well, that's how I do it just use pure Argon. I don't have a torch and for me it's easier to do it with the welder anyway. Just remember that the joints don't give any warning when they fail and really shouldn't be used for anything structural and I know that some will disagree with this statement. If you're good at brazing you can achieve a strong joint, but it's not a easy process if you haven't done it before. Bolts will be easier in my opinion and there's not going to be a concern with them failing as long as you use grade 8. I'm with the other poster on a bolted assembly since you have adjustment, unless you can jig everything up and you're a good Tig welder. It's funny that I am yet to see one router frame that was Tig welded on this forum or on a production industrial machine. I guess it's because you still need to have all the mounting surfaces machined anyway and mig welding is faster and easier. A good Tig welder which I am not, can jig up and weld a frame with zero distortion. I see it done all the time in the off road industry. Example welding up rear end housings that have machined parts welded to them that can't have any distortion or it will blow up the rear end due to bearing failure or improper gear meshing. Anyway that's my personal opinion for what it's worth, just design a good bolt together design and eliminate the potential for a bunch of headaches if something is out of alignment.

    Dan

  8. #8
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    I've TIG, MIG and stick welded and it all distorts to some degree. Gas welded thin stuff and brazed it still distorts a little. If you have a good Jig it really helps or If you have enough built in adjustments it may not matter. One way is like Dan suggests above just bolt it together, and my suggestion is when you finally get to a forever home, do some limited tack welding... say on the corners.

    Plan B, CNCRP (see above) makes Pro grade bolt together Aluminum extrusion kits that are very good.
    Retired Master Electrician, HVAC/R Commercial. FLA Saturn 2 4x4 CNC Router Mach4 Kimber 1911 45ACP

  9. #9
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    A few things that should be pointed out. Applying a significant amount of heat to metal will distort it. You do not even need to get to brazing temperatures. If you don’t believe this there are good videos on this online. Kieth Fenner has some great demos of straightening steelshafts with heat. Someplace on the net there was a video of steel workers forming a large tube with the heat shrink method.

    So the idea that brazing doesn’t distort is misleading, it may distort less butthat doesn’t mean zero. Beyond that good brazing requires good fit up. If the same effort is put into welding fit up you will have lessdistortion in that weldment. Skin a nut shell you will have distortionbut how bad it will be is unknown because there are many factors. There are however many ways to address the distortion problemso distortion should stop you but you do need a plan to address it. Frankly every build approach has its challenges when it comes to final alignment, nothing wil bolt up perfectly.

    The second thing to address is your machine length. In the US anyways the standard size for sheet goods is 4x8 feet. Your machine comes up just a bit short for that type of sheet goods. Not knowing your standard sizes I’d make sure that the long axis is a few inches longer than the standard sheet size.

    The third idea surrounds the idea of a machine that can be broken down to move through doors. There is nothing wrong with the idea at all. Your challenges are in weight control and suitable rigidity. The rigidity issue is two fold, one being suitably rigid sub frames and a rigid method of joining the two together. The welded up frames are easy but you will need significantly robust plates on the frames to bolt the seconds together with. These methods are fairly common in automation ad the frames also need to fit through doors and bolt up subsections. The plates welded to the frames need to be very robust not to distort and to support keying methods like dowel pins.

    I would also consider which orientation of the frame makes sense when moving it through doors. ThAt is rolling the frame on its side might make more sense than trying to move it upright. In any even design in the method of moving. For example wheels at one end and handles at the other for wheel barrel type transport or center mounted wheels with out rigger casters. You will likely want these to be removable. The frames will likely end up heavier than desired or imagined so building in features for easy movement is smart.

    Generally solutions for easy movement don’t cost a lot. You are basically talking brackets and wheels. But there are other options. You can for example make sure the design makes it easy to move with a pallet jack. Pallets jacks are relatively cheap these days but suck across uneve terrain. There are other options like carts that are better acroos rough surfaces. In any event I’m trying to get across the idea of designing in ways to move the frames.

    As for the 8080 extrusion I have to wonder why? Everything else is steel why not stay the course! Here is the thing from my perspective, extrusions are not perfectly straight to begin with (most are pretty good though) but here you will be bolting them to brackets that are likely to distort the beam some. shiming and adjustments will hAAppen so any straightness advantage evaporates. You might as well put a steel beam in there. In either case I would beef up the brackets. I’d probably also consider adding features (“leveling screws) to help with beam adjustment. The focus on adjustability comes in part from the fact that the machine will be broken down at some time in the future. Reassembling it to exactly the same conditions will be a challenge so you might as well add helpful features. Mounting this beam is a real challenge was generally you want it to be a very rigid part of the frame, you might want to completely rethink this approach. This is where you have to consider the trade offs between easy portability and good mechanical design.

    Another possibility is a one piece table design that rolls onto its side for transport. You keep the fixed legs short to allow easy movement through standard door widths and use extensions in the operating orientation to raise it to the right hight. Of course we are now twice as heavy but centered mounted wheels can reallly help here. What will work obviously comes down to what you need to negotiate when moving.

    In any even lots of potential ideas here.

  10. #10
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Thanks wizard! I don't know what happened but I made a mistake converting 2500mm to moon units, it should be 8.2' x 4.26' cutting area as I had full sheet cutting in mind (here in Australia everything is 2400x1200, occasionally 2440x1220 etc).

    Also I appreciate everyone's warning that steel expands / contracts as it is welded. The trick outside of clamping everything to within an inch of it's life I've seen used is clever placement of tacks and weld/stitching order so that one tack pulls it one way, the other tack pulls it back etc then of course the pros who leave a gap judged from their many many years of experience welding so that as they run the length of the join it pulls itself together straight which is a beautiful thing to watch but definitely out of my league.

    I would love to do without the aluminum extrusion to be honest - it does seem a bit ridiculous to have this big steel frame and then fix the HGR20 rail to relatively thinwalled aluminum extrusion which is also expensive as hell. I'm not really that keen to do the epoxy leveling thing on 2.8m lengths of steel and don't have a budget to get 2x 2800mm long pieces of channel Blanchard ground haha.

    I thought that if I try to mount the two HGR20 rails on two pieces of hot rolled channel that parallelism won't be that great and I might have issues with binding etc

    I guess I could mount the HGR20 horizontally on top of the steel channel rather than vertically on the sides so the rails can be parallel to each other and then any deviation in the steel will turn up as +/- Z axis which is probably less important.

    I was going to order the steel today but you've got me thinking about it all again..

    Very relevant:

    https://www.youtube.com/watch?v=w-wbWGwZ7_k

  11. #11
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    NTL - brazing is an excellent structural connection when done correctly. Especially for fatigue. There are lots of custom motorbike frames made this way and the Italians are particularly good at TIG brazing. But gas brazing held together many early aircraft and billions of bicycles and cars before TIG/MIG became viable. If you have an aluminium radiator in your car its brazed together. DB for the purposes of a router you could soft solder or silver solder as well the connection requirements in routers are stiffness not strength dominant, that's the reason not to use bolts as brazed/welded connections are 100% efficient structurally. Heat requirement is much less if you want to have a play with this sort of connection. I put these out there as alternate solutions to the usual as they are viable and suit the backyarder. I have worked as a TIG welder (steel, al and titanium, let's build a Ti router!! ) and as robotic MIG programmer, I have worked as a welding trainer, I did my thesis on fatigue of aluminium welds and I've done a considerable amount of welding analysis in the last 30 years. So I consider I put forward a viable view here. To step forward even further you could glue the connections together these days, lots of structural adhesives out there that are for welding replacement. There are even tapes out there called Very High Bond tapes that are sold for welding replacement in sheet metal structures. Takes a bit of a rethink to get your head around it but the wings of most new aircraft are glued together these days. More alternatives. Regards Peter S

  12. #12
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Quote Originally Posted by peteeng View Post
    NTL - brazing is an excellent structural connection when done correctly. Especially for fatigue. There are lots of custom motorbike frames made this way and the Italians are particularly good at TIG brazing. But gas brazing held together many early aircraft and billions of bicycles and cars before TIG/MIG became viable. If you have an aluminium radiator in your car its brazed together. DB for the purposes of a router you could soft solder or silver solder as well the connection requirements in routers are stiffness not strength dominant, that's the reason not to use bolts as brazed/welded connections are 100% efficient structurally. Heat requirement is much less if you want to have a play with this sort of connection. I put these out there as alternate solutions to the usual as they are viable and suit the backyarder. I have worked as a TIG welder (steel, al and titanium, let's build a Ti router!! ) and as robotic MIG programmer, I have worked as a welding trainer, I did my thesis on fatigue of aluminium welds and I've done a considerable amount of welding analysis in the last 30 years. So I consider I put forward a viable view here. To step forward even further you could glue the connections together these days, lots of structural adhesives out there that are for welding replacement. There are even tapes out there called Very High Bond tapes that are sold for welding replacement in sheet metal structures. Takes a bit of a rethink to get your head around it but the wings of most new aircraft are glued together these days. More alternatives. Regards Peter S
    Years ago I had a 3m adhisives engineer meet with me about exactly what you're talking about. We replaced welding on a aluminum product with 4611 VHB tape since we were having problems with the welds cracking. He showed me a airport with a glass ceiling that was held on with 2x tape. He also show me different Jets that use VHB instead of rivets, I've been using it for close to 20 years. I've also used the liquid weld that they make the green stuff, works awesome as well. But man all that stuff is expensive. The crazy part of the tape is it's low tac intitaly and gets stronger over time. If you ever had to get the parts apart you had to use a air chisle with a attachment they use to make that looks like a paint scraper but super thin. And then use the pinstripe erasers they sell to get the adhesive off, or Scotchbright pads with a grinder.

    As for the Tig brazing I was just saying that it shouldn't be used for anything structural because it won't pass inspection from what I've heard, not because it's not strong. I'm well aware that a lot of bicycle frames are brazed, first I've heard of any motorcycle manufacturer brazing frames. Learn something new everyday.

    Dan

  13. #13
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Hi Dan - Here's a shot of some magic tig brazing. Much better then I ever did. Its a motorcycle steering head in CrMo tubing. Some years ago I was involved in a bicycle frame project selling into europe and we had to met European fatigue rules. The TIG steel frames could not met the cycles and load required, the brazed steel frames did. The aluminium tig frames just did and the carbon fibre frames we could not fail. If you do an image search for tig brazing there's quite a bit out there and there are videos as well. Peter

    Hi David and others - The issue of connections is an interesting one. If you decide to bolt you need flanges or thick material. Both take up real estate in your design and need access for spanners. If you weld you need to deal with the fit's and the distortion. You can't use chewing gum yet but maybe down the track. If you use adhesives you still need a flange or you may try fillets but still need some room, same room as a bolt I'd expect. Welding/brazing/hard solder/soft solder allow you to butt join objects. No real estate required just the thickness of the material. This is the attraction of these methods. For a router the connections need to be as stiff as their mating components to maintain structural intent. I suspect that soft solders (like used for soldering wires) maybe OK David to have a play with. These melt at 200-300deg C so the metal does not even change colour. Your frypan gets to 250deg to cook an egg...A simple propane torch and good cleanliness and flux will get you there with the sort of thicknesses you are talking about. Looking at the table attached the mid range solders are 50MPa strength which is quite good in a large surface. The silver solders are near 100Mpa. Take a 50x50x2mm square tube it would take over 980kgf, a tonne to pull it apart which is unlikely to be seen in the router. If it was a column say or at the end of a gantry. If you used 100x100 tube SHS it would be 2 tonnes etc. This is also easy to pull apart if you needed to. Definitely would not distort as far as this router is concerned. I'll have a play next time I get the torch out... keep Making

  14. #14
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    Re: Large router table capable of being dismantled and fit through a standard doorway

    Hi Dave from another Dave;

    A few clarifications.

    First; with respect to extrusions there seems to be this idea that they are perfectly straight and flat structural materials. They aren’t but often are good enough for a router in question. Some extrusion vendors, such as Misumi, actually offer grinding services to better flattentheir extrusions for CNC usage.

    Second; steel tubing comes from a variety and of manufactures, some with much tighter controls on dimensions and flatness. So how much remediation is required varies considerably. Sometimes surface cupping can be dealt with buy cold rolled steel flats bounded with an epoxy filler. This isn’t leveling per say by rather just a way to deal with a cupped surface on square tubing that isn’t flat. The point here is that there are many ways to deal with the problem of less than perfect steel tubing.

    Third; what I was trying to get at is that the brackets you imagined holding up that extrusion will be very difficult to get exactly in line acroos two different frames. The thought was the combination of jack screws and epoxy grouting at the pads (brackets) may be needed or at least helpful in alignment after a move and set up. Actually you likely could get by without the grout.

    Forth; the idea of making the machine deferrently that is a full sized table and separate leg frames or cola psi level legs may be a better approach. If the table can be kept as one piece a lot of your mechanical issues go away. Thus the mention of a built in method of attaching wheels and the ability to turn the table on its side for transport. This of course will only work if an 8’ long table can negotiate all the turns involved. In any event the idea here is to avoid the mechanical issues trying to join two tables together will produce.

    Fifth; This might be obvious but steel frames get heavy fast. I learned this from piecing a steel bench together from an old machine frame. Every time I welded something on it the thing got heavier, imagine that!!! In any event weight is an issue with any machine designed to be transportable. So put emphasis on weight projections during your design and ways to handle the weight.

    Sixth; Extreme precision for the entire table top frame may not be a good investment in effort. The only thing that needs to be precise are the mechanical motion components. What is inbetween isnt as demsnding, that is a spoil board or a subboard for the spoil board down need to be precisely aligned with the axis. The common practice is to mount such boards and then flatten them with the machine. The better the alignment the less waste of course. So what you need is to have the two outside frame members in plane, this is where a lot of people use epoxy leveling, not so much for “level” but rather to obtain a flat surface that is one plane to mount linear rails to.

    Seven; one critical aspect to limit distortion in welding is to precisely fit up parts. That combined with a flat surface to mount the components to prior to welding is very helpful. Of course you run into a problem of access to tooling but it is common in the automation industry to machine steel tubing to length and squareness in a horizontal mill. The better the parts fit before welding the less built in stress you will have and you will get reduced distortion.

    In any event I’m hoping this clarifies things a bit. There are likely dozens of ways to solve this transportability issue. You just need to figure out what makes sense for you.

    A little P.S. here;

    Someone mentioned above the use of adhesives above. This might not be a bad idea, if you have every dealt with shafting assembled with Loctite you will understand how well this stuff holds. Today there are many more options that the traditional loctite bonders. The problem as I see it is the need to manufacture close fitting brackets and the like (sort of like joist hangers) to glue everything together with. This makes me wonder if anybody is actually manufacturing such brackets in volume, I’m surprised that there isn’t a supplier of such for steel tubing. These brackets are often called lugs in bicycle building. Frankly they could allow for brazing too. However let’s not kid ourselves brazing will distort metal to some extent also.

    In any event I just wanted to point out that there are many potential options out there. If you are willing to experiment and understand the limitations it might be worth pursuing one of these ideas.

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