4x8 (plus a bit) heavy duty router build


Page 1 of 2 12 LastLast
Results 1 to 20 of 36

Thread: 4x8 (plus a bit) heavy duty router build

  1. #1
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default 4x8 (plus a bit) heavy duty router build

    This project is a group effort. One of our group wants a big router and is willing to buy the materials. Others are engineers who like to build stuff.

    Design and build are going on somewhat in parallel. Probably not the smartest approach, but it gets boring just looking at the computer.

    We are frugal (aka cheap), so we are in many cases designing around materials that we have or can get cheap. For example, we got lucky at HGR surplus with the X rails. Two SHS35 rails 3000mm (9'10") long, plus one car on each rail, for $100. Got a couple more cars on ebay. So the X axis is going to be SHS35. Overkill for a router, but the price was right.

    I hate frames that twist and flex, so I decided that a truss would be the way to go. We have lots of pipe, including some 2" and 2-1/2" schedule 40. Square tube is easier to mount things to, but very expensive. So we're using the pipe that we already have.

    I used the 15-day free trial of Skyciv engineering software to analyze the base. It is going to be very rigid - deflections under 0.001" for forces of 200 lbs or more anywhere on base.

    The design is happening in OnShape, which is quickly becoming my favorite 3D software. There are still a lot of loose ends, for example right now the gantry is floating in space, not connected to the X carriages yet. We're probably going to flip around the X carriage angle iron to provide a horizontal surface for the gantry to bolt to.

    4x8 (plus a bit) heavy duty router build-router-overview-png

    The base consists of a core truss and an outer truss. The core truss is the bottom frame plus the center longitudinal tube that supports the center of the table. It is sufficiently stiff that it can serve as a skeleton for assembly and alignment of the outer truss, which is made up of the tubes that carry the X rails and the diagonals running vertically and horizontally from them to the core truss.

    Last weekend we completed the core truss. The base and the top center rail are 2" pipe. The rest of the truss members are 3/4". The base needs to handle mid-span loads if the machine is picked up by forklift or pallet jack, and the center rail has supports for the wooden cutting surface that are between the truss nodes, so both needed to be stiff in bending. 2" is a bit of overkill for the base; the analysis said that 1-1/2" or even 1-1/4" would work. But we had a few pieces of 2" laying around the shop. There are 3/4"-10 coupling nuts welded into the base tubes at the four corners. Currently we have some 4" long 3/4" bolts in there as leveling feet. Might wind up buying the high-class leveling feet with swiveling pads later.
    4x8 (plus a bit) heavy duty router build-20220424_015807-jpg

    Currently we are preparing the tubes (2-1/2" schedule 40 pipe) that carry the X rails. We know that a weldment like this is going to wind up all kinds of crooked. "If you can't make it precise, make it adjustable" is the mantra here. The SHS35 rails are attached to the tubes using mounts that can be tweaked. There are 10 mounts on each side, 320mm (just over 12") apart. Since the rails are so big, we can get away with supporting them at every fourth mounting hole.
    4x8 (plus a bit) heavy duty router build-rail-mounts-png4x8 (plus a bit) heavy duty router build-rail-mounts-real-jpg

    The light blue channels are welded to the tubes. The green part is a 5/16" thick "shim" that can be removed and either milled or surface ground thinner to precisely move the rail toward the tube. The darker blue part below the shim is called the "shelf". It too can be removed. Grinding or milling the part that bears on the light blue will raise the rail, while removing material from the outer part that touches the shim and the rail itself will lower the rail. Each shim and shelf has a number stamped on it so they can be removed, machined, and then replaced in the proper location. We're planning to use a taut wire (or kevlar string) along with a precision machinist level as a straightness reference for the first rail. The second rail will be aligned parallel to the first one using a combination of taut wire, precision levels, and a temporary "gantry" beam with a dial indicator on the far end.

    This evening I welded the rail mounts to one of the tubes. I hope to have the second tube prepared by this weekend. Not sure if we'll attach the tubes to the core truss this weekend or if that will happen next week. The diagonals supporting the tubes will be 1/2" pipe, but the truss should make it very stiff at the nodes where everything comes together. The 2-1/2" pipe is stiff enough to span between the nodes and support both the linear rails and the wooden cutting surface.

    Does anyone have any experience with DIY stress relief of weldments? We're thinking of heating it up evenly as much as possible with a weed burner or two and letting ti cool slowly. That would happen before we get out the taut wire and start adjusting the shims and shelves.

    Questions, comments, and suggestions are much appreciated.

    Still making decisions about things like the spindle. Considering the pros and cons of air- vs water-cooled.

    John

    Similar Threads:


  2. #2
    Member awerby's Avatar
    Join Date
    Apr 2004
    Posts
    5728
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    I like your table; people rarely put as much time and effort into them. I'd suggest putting more attention into the attachment between the gantry uprights and the linear rails. It looks like it's just perching on the edge, but it really needs a solid and much wider connection there. The stability of any machine is no better than its weakest link.

    [FONT=Verdana]Andrew Werby[/FONT]
    [URL="http://www.computersculpture.com/"]Website[/URL]


  3. #3
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by jmkasunich View Post
    This project is a group effort. One of our group wants a big router and is willing to buy the materials. Others are engineers who like to build stuff.

    Design and build are going on somewhat in parallel. Probably not the smartest approach, but it gets boring just looking at the computer.

    We are frugal (aka cheap), so we are in many cases designing around materials that we have or can get cheap. For example, we got lucky at HGR surplus with the X rails. Two SHS35 rails 3000mm (9'10") long, plus one car on each rail, for $100. Got a couple more cars on ebay. So the X axis is going to be SHS35. Overkill for a router, but the price was right.

    I hate frames that twist and flex, so I decided that a truss would be the way to go. We have lots of pipe, including some 2" and 2-1/2" schedule 40. Square tube is easier to mount things to, but very expensive. So we're using the pipe that we already have.

    I used the 15-day free trial of Skyciv engineering software to analyze the base. It is going to be very rigid - deflections under 0.001" for forces of 200 lbs or more anywhere on base.

    The design is happening in OnShape, which is quickly becoming my favorite 3D software. There are still a lot of loose ends, for example right now the gantry is floating in space, not connected to the X carriages yet. We're probably going to flip around the X carriage angle iron to provide a horizontal surface for the gantry to bolt to.

    4x8 (plus a bit) heavy duty router build-router-overview-png

    The base consists of a core truss and an outer truss. The core truss is the bottom frame plus the center longitudinal tube that supports the center of the table. It is sufficiently stiff that it can serve as a skeleton for assembly and alignment of the outer truss, which is made up of the tubes that carry the X rails and the diagonals running vertically and horizontally from them to the core truss.

    Last weekend we completed the core truss. The base and the top center rail are 2" pipe. The rest of the truss members are 3/4". The base needs to handle mid-span loads if the machine is picked up by forklift or pallet jack, and the center rail has supports for the wooden cutting surface that are between the truss nodes, so both needed to be stiff in bending. 2" is a bit of overkill for the base; the analysis said that 1-1/2" or even 1-1/4" would work. But we had a few pieces of 2" laying around the shop. There are 3/4"-10 coupling nuts welded into the base tubes at the four corners. Currently we have some 4" long 3/4" bolts in there as leveling feet. Might wind up buying the high-class leveling feet with swiveling pads later.
    4x8 (plus a bit) heavy duty router build-20220424_015807-jpg

    Currently we are preparing the tubes (2-1/2" schedule 40 pipe) that carry the X rails. We know that a weldment like this is going to wind up all kinds of crooked. "If you can't make it precise, make it adjustable" is the mantra here. The SHS35 rails are attached to the tubes using mounts that can be tweaked. There are 10 mounts on each side, 320mm (just over 12") apart. Since the rails are so big, we can get away with supporting them at every fourth mounting hole.
    4x8 (plus a bit) heavy duty router build-rail-mounts-png4x8 (plus a bit) heavy duty router build-rail-mounts-real-jpg

    The light blue channels are welded to the tubes. The green part is a 5/16" thick "shim" that can be removed and either milled or surface ground thinner to precisely move the rail toward the tube. The darker blue part below the shim is called the "shelf". It too can be removed. Grinding or milling the part that bears on the light blue will raise the rail, while removing material from the outer part that touches the shim and the rail itself will lower the rail. Each shim and shelf has a number stamped on it so they can be removed, machined, and then replaced in the proper location. We're planning to use a taut wire (or kevlar string) along with a precision machinist level as a straightness reference for the first rail. The second rail will be aligned parallel to the first one using a combination of taut wire, precision levels, and a temporary "gantry" beam with a dial indicator on the far end.

    This evening I welded the rail mounts to one of the tubes. I hope to have the second tube prepared by this weekend. Not sure if we'll attach the tubes to the core truss this weekend or if that will happen next week. The diagonals supporting the tubes will be 1/2" pipe, but the truss should make it very stiff at the nodes where everything comes together. The 2-1/2" pipe is stiff enough to span between the nodes and support both the linear rails and the wooden cutting surface.

    Does anyone have any experience with DIY stress relief of weldments? We're thinking of heating it up evenly as much as possible with a weed burner or two and letting ti cool slowly. That would happen before we get out the taut wire and start adjusting the shims and shelves.

    Questions, comments, and suggestions are much appreciated.

    Still making decisions about things like the spindle. Considering the pros and cons of air- vs water-cooled.

    John
    The part you call the shim what material is it, the shim would have to be fastened to the Chanel and then machined in place, it would not be removable, or the accuracy would be messed up if removed, the frame will work but does not have to be built like you have it, simple is better, the distortion of fabricating this type of base frame would be high, which you don't want for any type of machine building, the Rail mounting on the shim piece would need to have a shoulder when machined for the Rail to be pushed against with the clamps on the other side, this will keep the rail in position and straight, without the shoulder the rail will not be straight, there is no such thing as tweaking a 35mm Linear rail, you need to rethink this mounting, look at how the linear rail manufacturer mounts there rails there is no exceptions

    You can't stress relieve a frame like you have with a torch, the whole thing would have to go in an oven, to stress relieve it

    Mactec54


  4. #4
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by awerby View Post
    I'd suggest putting more attention into the attachment between the gantry uprights and the linear rails. It looks like it's just perching on the edge, but it really needs a solid and much wider connection there. The stability of any machine is no better than its weakest link.
    Yeah, that hasn't been properly modeled yet, but we have a plan. The X-axis carriages will be mounted to the 5" leg of a 12" long chunk of 5" x 3" x 3/8" angle. The 5" leg will be oriented vertically, with the 3" leg on top sticking out horizontally away from the table. The gantry uprights will be bolted to the 3" leg. I'll probably weld a couple 3" x 5" triangular gussets in the angle just because I can. Both the carriage mounting surface and the gantry mounting surface will be skim-cut on a Bridgeport (after all welding is complete) to make sure those surfaces are flat and perpendicular.



  5. #5
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by mactec54 View Post
    The part you call the shim what material is it, the shim would have to be fastened to the Chanel and then machined in place, it would not be removable, or the accuracy would be messed up if removed, the frame will work but does not have to be built like you have it, simple is better, the distortion of fabricating this type of base frame would be high, which you don't want for any type of machine building, the Rail mounting on the shim piece would need to have a shoulder when machined for the Rail to be pushed against with the clamps on the other side, this will keep the rail in position and straight, without the shoulder the rail will not be straight, there is no such thing as tweaking a 35mm Linear rail, you need to rethink this mounting, look at how the linear rail manufacturer mounts there rails there is no exceptions

    You can't stress relieve a frame like you have with a torch, the whole thing would have to go in an oven, to stress relieve it
    The shim (green in the drawing), the shelf (dark blue), and the clamp (orangeish red) are all steel.

    The whole point of having those parts is so that they can be removed for machining. We don't have access to a machine that can cut a 10 foot long rail seat on the completed frame, let alone two of them almost 4 feet apart and facing in opposite directions.

    The plan is to finish all the welding, do whatever primitive half-assed stress relief we feel that we can manage, then mount the rails with all the shims at their original thickness and all the "shelves" flat on their top surface, so that the bottom edge of the rail is flush with the bottoms of the channel pieces. The rails will not be straight. Then we will carefully measure the deviation from straight and determine how much needs to be taken off of each shim and each shelf. The rails will come back off, and the shims and shelves will pay a visit to the mill or the surface grinder (probably the grinder). Once they have been modified, everything goes back together and we check for straightness again. If necessary, the rails can come off again and the shims/shelves get adjusted until they are right.

    It will be finicky and time-consuming, but I'm OK with that. This is a one-off machine, not a product.

    I'm fairly confident that we will make it work. I may be wrong, time will tell.



  6. #6
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by jmkasunich View Post
    The shim (green in the drawing), the shelf (dark blue), and the clamp (orangeish red) are all steel.

    The whole point of having those parts is so that they can be removed for machining. We don't have access to a machine that can cut a 10 foot long rail seat on the completed frame, let alone two of them almost 4 feet apart and facing in opposite directions.

    The plan is to finish all the welding, do whatever primitive half-assed stress relief we feel that we can manage, then mount the rails with all the shims at their original thickness and all the "shelves" flat on their top surface, so that the bottom edge of the rail is flush with the bottoms of the channel pieces. The rails will not be straight. Then we will carefully measure the deviation from straight and determine how much needs to be taken off of each shim and each shelf. The rails will come back off, and the shims and shelves will pay a visit to the mill or the surface grinder (probably the grinder). Once they have been modified, everything goes back together and we check for straightness again. If necessary, the rails can come off again and the shims/shelves get adjusted until they are right.

    It will be finicky and time-consuming, but I'm OK with that. This is a one-off machine, not a product.

    I'm fairly confident that we will make it work. I may be wrong, time will tell.
    You have nothing to reference from, to align the Rails, you would need a straight edge Cast iron or Granite to setup the rails, they need to be within .0002" in both planes or the Linear Bearing will bind

    The heat treating you are going to try will only make it worse, as whenever you heat a localized area, that area will shrink, and pull it further out of alignment

    Mactec54


  7. #7
    Member mactec54's Avatar
    Join Date
    Jan 2005
    Location
    USA
    Posts
    15362
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Here is a series video's you can watch on Linear Rail Mounting and the Tolerance for the different Grades of Rails and Bearings



    Mactec54


  8. #8
    Member routalot's Avatar
    Join Date
    Dec 2003
    Posts
    1206
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    It seems weird to have such a superbly braced and triangulated base and such a tall,skinny gantry with little support.As it has been described as a work in progress,the same amount of attention ought to lead to a good machine.Getting the rails at precisely the same height to ensure that they are co-planar could be an interesting challenge.



  9. #9
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by routalot View Post
    It seems weird to have such a superbly braced and triangulated base and such a tall,skinny gantry with little support.As it has been described as a work in progress,the same amount of attention ought to lead to a good machine.
    Agreed. The desire to see things taking shape has led to work on the frame build before the rest of the design is fully fleshed out. Hopefully that won't bite us in the ass. The gantry uprights in particular are definitely just placeholders. Hoping to make some progress in that area of the design this week.

    Another thing driving the iterative design is that since we are trying to do things very well but also on the cheap, we are designing around materials that we get good deals on, like the X axis linear rails. As another example, we got a 48-1/2" long chunk of 4 x 8 x 3/16" rectangular steel tube at a very good price for the main gantry beam. Do I wish it was longer? Yes. Are we going to have to futz around to make it work? Yes. Are we open to redesign if we find a better piece of steel? Yes again.

    Quote Originally Posted by routalot View Post
    Getting the rails at precisely the same height to ensure that they are co-planar could be an interesting challenge.
    Yes. One of us (me) is a metrology geek and has some ideas in that direction. Also as a metrology geek I have more precision measuring stuff that most folks. Four foot long granite straight edge, for example. And a 27" long cast-iron scraped level with 0.00025" per foot resolution. And an auto-collimator (which I normally use to check my surface plates). I have some experience at hand-scraping, have taken Richard King's scraping class, and have a Biax scraper. Although steel is harder to scrape than cast iron, I'm not above applying some of the machine alignment and adjustment techniques that rebuilders use to this woodworking machine.



  10. #10
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Friday progress photos:

    Although I hope to use the shims and shelves to adjust the rails in Y and Z respectively, we also need to address twist around the roll axis (X). On Friday I tackled this for the left rail tube (which will be the master rail). Set it up in v-blocks on the bench, and use an arm bolted to one of the table surface mounting pads with a screw to adjust it in roll. (See green oval below).

    4x8 (plus a bit) heavy duty router build-20220430_042315e-jpg

    I used a precision level to measure the roll angle of each rail mounting pad (red ovals above), then rotated the rail to the best overall angle and started working on the outliers. I marked the area that the shim will sit on (red rectangle below) and relieved the rest a couple thou with an angle grinder to make sure it doesn't interfere with measurements. The I used a combination of levels, a small reference flat, and marking blue to identify the high spots on each pad and work them in. I didn't try to get them all co-planar, that will happen after the tube is attached to the frame. I just wanted to remove any pad-to-pad twist around the axis of the tube while the part was still easy to work on.

    4x8 (plus a bit) heavy duty router build-20220430_042258e-jpg

    Last edited by jmkasunich; 05-01-2022 at 02:16 PM.


  11. #11
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Saturday progress photos:

    We mounted the left rail tube to the core truss...

    4x8 (plus a bit) heavy duty router build-20220501_012342e-jpg4x8 (plus a bit) heavy duty router build-20220501_011841e-jpg

    This involved a lot of fixturing and measurement. The rail was supported from the core truss by a set of struts which include turnbuckles (red ovals below). Two vertical at each end to control Z, two horizontal at each end to control Y, and a couple diagonals to control Z.

    4x8 (plus a bit) heavy duty router build-20220430_225857e-jpg

    For alignment, the reference points are the two "table surface support pads" (aka "wood pads") at the ends of the center tube of the core truss. Those points are aligned with the second rail mount from each end of the rail tube. The photo below shows the back end setup. I made two test pieces exactly the same length, long enough for one end to rest on the rail mount shelf and the other end to stick up above the rail tube's wood pad by the thickness of a parallel laying flat. See below. Then the level spans between the center rail reference pad (with the parallel) and the top of the test piece. This lets us adjust the vertical (using a vertical turnbuckle that you can't see in this photo). For horizontal, we used a length gage made from a piece of all-thread with a coupling nut and lock-nut. The exact distance isn't critical, only the matching between the two ends. We used the length gage like an inside mic, gaging between the inside surface of the test piece and the side of the center rail wood pad. The yellow strap in the photo is to provide some preload to the horizontal turnbuckle; gravity does that for the vertical ones.

    4x8 (plus a bit) heavy duty router build-20220430_225908e-jpg

    The image below shows the setup for roll around the X axis, and for alignment along X (which is pretty non-critical at this point). The level sitting on a wood pad is the reference for roll. The unistrut in the foreground is bolted to another wood pad, and there are shims and a clamp at the far right end (off screen) to adjust the roll. For alignment along X, the framing square is bolted to two wood pads on the central tube with the corner aligned with the end of the farther pad. Then the end of the corresponding pad on the rail tube is aligned with the arm of the square (not visible, hidden by the level).

    4x8 (plus a bit) heavy duty router build-20220430_225904e-jpg

    Finally the front end. Just like the back, there is a test piece bolted to the rail mount, and a level spans between it and the reference pad on the center tube. We checked the horizontal using the length gage mentioned above, that doesn't show in the photo. The blue strap preloads the horizontal turnbuckle.

    This pic also gives a good look at how the truss diagonals are attached to the rail tube (green circle). Since the structure is a truss, the diagonals see only compression and tension. We used a "tab and slot" method of attachment for a couple of reasons. First, it allows us to adjust things easily, the tab just slides in the slot as we mess with the turnbuckles. Second, it keeps the welding heat away from the rail tube. We know things will move when we weld, but this limits the effect. Finally, the tab prevents the weld or the diagonal member from introducing any bending moment into the rail tube.

    4x8 (plus a bit) heavy duty router build-20220430_225901e-jpg



  12. #12
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    6248
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Hi JMK - such an ambitious project. I like it. So many things that will bit you in the bum, but your team will solve those niggles. Keep us informed, where here to help and giggle. Peter

    edit - I'll comment on the last sentence. The only way a connection can "prevent" transferring a moment is if its a ball joint (spherical) or a bearing in the plane of the truss. Your welded tab connection can transfer considerable moments. But a machine frame like this is under very little strain and the moments at connections will be tiny tiny. The main issue is max stiffness and the triangulated truss is well along the way to achieving globally a very stiff frame. The design has lots of small brackets and these are not stiff locally so all of these compliances add up to some deflection somehow. But continue, solve the issues along the way and we look forward to seeing some sawdust soonest...

    Last edited by peteeng; 05-01-2022 at 06:07 PM.


  13. #13
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by peteeng View Post
    The only way a connection can "prevent" transferring a moment is if its a ball joint (spherical) or a bearing in the plane of the truss. Your welded tab connection can transfer considerable moments. But a machine frame like this is under very little strain and the moments at connections will be tiny tiny.
    As I was writing "prevents the weld or the diagonal member from introducing any bending moment into the rail tube" the little voice in my head said "any" is the wrong word. Of course you are right and the tab can transmit some moment. But the tab is only about 1/8" thick, and in the plane of the truss it acts like a hinge. Especially compared to the much stiffer diagonal tube and the much much stiffer rail mounting tube.

    The tab is fairly stiff for moments trying to rotate the rail mounting tube around it's own axis, by design. That is the only thing that controls roll of the rails.

    Quote Originally Posted by peteeng View Post
    The main issue is max stiffness and the triangulated truss is well along the way to achieving globally a very stiff frame. The design has lots of small brackets and these are not stiff locally so all of these compliances add up to some deflection somehow. But continue, solve the issues along the way and we look forward to seeing some sawdust soonest...
    Yeah, I wish the web on the rail mount channel was a bit thicker.



  14. #14
    Member
    Join Date
    Aug 2014
    Posts
    232
    Downloads
    4
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    I love the trussed design, but have noticed that commercial designs don't often use it. My thoughts are that they are trying to keep temperature related expansion and contraction in-line with the linear rails by avoiding triangulation. I could be wrong, let's hope so.



  15. #15
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    6248
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Hi Zorbit - I don't think triangles are inherently poor with temperature delta. The Ingersol octahedral hexapod is entirely triangles. I'm thinking about taking Milli down this path.... Peter

    Attached Files Attached Files


  16. #16
    Member
    Join Date
    Aug 2014
    Posts
    232
    Downloads
    4
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by peteeng View Post
    Hi Zorbit - I don't think triangles are inherently poor with temperature delta. The Ingersol octahedral hexapod is entirely triangles. I'm thinking about taking Milli down this path.... Peter
    That's a very different case though. I'm not an engineer, so open to education, but in the case of the triangulated truss sides of the router above, the diagonals are longer than the horizontals and meet at a common point. If the structure expands by X%, will there be a tendency for the horizontals carrying the linear rails to bend ?

    Genuine question.

    This type would seem much easier to predict;IMG_0746.jpg (1600Ă—976) (bp.blogspot.com)

    Last edited by Zorbit; 05-04-2022 at 09:23 AM.


  17. #17
    Member
    Join Date
    Feb 2007
    Location
    usa
    Posts
    54
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Regarding thermal expansion: if the temperature change is uniform (whole machine heats up or cools down) and the material is uniform (not half steel and half aluminum), it doesn't matter what the shape is. The whole thing will get uniformly bigger or smaller as the temperature changes. A good example of this is comparing a solid disk to a ring. Start with two disks 1" in diameter and 1/8" thick. Drill a 3/4" hole in the center of one of them, so it looks like a 1/8" x 1/8" square rod bent into a circle. Heat them both up and measure the OD of both with a micrometer. They will grow the exact same amount.

    Where you get in trouble is from non-uniform heating. For example if the top bed of the machine heats up in the sun but the bottom is in the shade, the top will expand more than the bottom and it will tend to hump up in the middle.

    I think the reason you don't see trusses in commercial machines is that for the same stiffness a truss uses less material but a lot more labor. In the commercial world, steel is cheaper than labor. So they use a rectangular structure and throw more steel at it. For this project, labor is cheaper than steel. Also, I have wanted to build a truss structure machine for a while and this is my opportunity

    A truss has lots of complicated angles at the joints. A welded structure (truss or rectangular) bulky and expensive to ship. A bolted truss would require complex (expensive) parts at the joints so that things could bolt together, and lots more assembly work. But a bolted rectangular frame is easy to fabricate, easy to ship (disassembled), and easy for the end user to assemble.



  18. #18
    Member
    Join Date
    Aug 2014
    Posts
    232
    Downloads
    4
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Quote Originally Posted by jmkasunich View Post
    Regarding thermal expansion:
    Thanks for that explanation, it makes sense now I think about it.



  19. #19
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    6248
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Hi JMK - good explanation. Thermal differences is the key issue in thermal management. Trying to get everything stable is a big deal with high precision machines. I've made a lot of frames and trusses over time (automotive and yacht industries) and every time I start thinking about a trussed machine frame I get excited but then get the heeby geebies on the complexity and effort its going to take....I see the commercial guys going Hmmm nah too hard...Peter



  20. #20
    Member peteeng's Avatar
    Join Date
    Jul 2018
    Location
    dum dum
    Posts
    6248
    Downloads
    0
    Uploads
    0

    Default Re: 4x8 (plus a bit) heavy duty router build

    Hi - Here's a machine VMC measure at 169N/um.

    https://www.mdpi.com/2076-3417/8/1/15/htm Peter



Page 1 of 2 12 LastLast

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


About CNCzone.com

    We are the largest and most active discussion forum for manufacturing industry. The site is 100% free to join and use, so join today!

Follow us on


Our Brands

4x8 (plus a bit) heavy duty router build

4x8 (plus a bit) heavy duty router build