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  1. #61
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    I spoke with masterbond and west system yesterday in regards to another aluminum project that I have. Here are the highlights.

    Masterbond has a $700 minimum order and they advised that I look elsewhere.

    West System was next on my list since I already use their 105 system. They told me that the 105 system has a holding power of 1100 psi over sanded aluminum. The number goes up to 1300 psi if you wet sand both sides of the joint with the epoxy in place (80-100 wet dry sandpaper). The epoxy serves as an oxygen shield. They said that they are suggesting the wet sand technique over the use of the 860 surface prep. I asked why and was told that the psi results are nearly identical and that they are having trouble meeting environmental requirements with the 860 so they cant sell it to every state.

    The conversation shifted to their G flex epoxy. They said that wet sanded joints are resulting in a 2800psi joint. The product has a shelf life of years. They said that they have a test batch that is 9 years old and is still working like new. All of this resulted in an order of a 2 quart kit for $100 delivered from one of their online retailers. The tech suggested that I use the 655 Gflex which is thickened. The reason is more to do with the viscosity than the need for a filler in the joint. He said it can stay put even on vertical surfaces while the 610 would be impossible to control.

    this does not really answer the question, but I hope that the information is helpful



  2. #62
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    Where did you find the 2 quart kit of the G Flex?

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  3. #63
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    I called my local distributers and then gave up and used Jamestown Distributers. I wave ordered various products from them over the years.

    G/flex Thickened Epoxy Adhesive Resin and Hardener Kit

    EDIT: If I was not going to be impulsive I would have called West System again and asked what thickener they use in the thickened Gflex. I would probably have ordered the regular Gflex and the thickener. My fear is that the thickened stuff might be too thick for all of my applications. I will report back one I have some experience with it



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    Sapele, Thanks for pointing out the dimension--I didn't look at the drawing carefully enough.
    - Yes, it's the total outside dimension of the tube that is most important.
    - Any of those widths would be fine for cutting wood. If you want to cut alum, I'd recommend as deep a cross-section as you're willing. I usually find the stiffness and 'efficiency' are best when the cross-section is roughly a square.
    - Attached are a few more runs (#40-#43) comparing the effect of a 1/4" back panel and more xsection depth. The 1/4" back does lose some efficiency, but not much and it's a good place to save cost and weight.
    - Then I tried a 3/8" wall thickness all around (#44) and with a 1/4" back panel (#45). With a 6.5" section depth, both of those performed very well.
    - So, #40, 41, 42, or 45 would all be great for cutting wood. For cutting alum, I'd go wtih #43-44 or bigger yet.
    Thanks also for the lead on the G flex.

    Gerry, thanks for the info.

    Today I checked some of our alum extrusion stock for straightness of the side faces, vs our 5' precision straight edge (rated at 0.0011 edge flatness).
    - 1/2 x 2: for one side, a 0.005" feeler gauge fit. The other side, 0.004" fit.
    - 1/2 x 3: for one side, 0.002" fit. Other side, 0.005"
    - 3/4 x 4: one side, 0.002" did *not* fit. Other side, 0.003" did fit.
    - 1 x 4: one side, 0.002" fit. Other side was way off at one end--probably it was dropped.
    So, there's good potential an alum extrusion side face would be straight enough to mount rails right on, or, to mount tooling plate of uniform thickness and mount to that, or, to use for a router sled. Or, as a starting point for some easy scraping to true up to 0.001". Since there is variation, I'd bring a good long straightedge to the metal store. And the wider the extrusion, the straighter it is likely to be.

    Attached Files Attached Files
    David Malicky


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    I just wanted to follow up with a bit more information on the G-flex. I used it to face glue two boards for an outdoor piece of furniture. I like it. The thickened epoxy wetted out the wood well and the resulting joint was just as I had hoped.

    The thickener in the G-Flex 655 is the 406 silica incase anyone wants to buy the regular stuff and thicken it themselves. This might also answer dmalickys earlier question.

    I will glue some aluminum in the coming days.



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    I have been working on the design of the machine by reading and searching the forum. I have run into a few questions which are stopping me from refining the rest of the design.

    The first has to do with my Y axis drive mechanism. I had planned on rack and pinion from the start but I have noticed some machines out there that use ballscrews for the Y and Z and use rack and pinion for the longer x axis (If I have read this right ballscrew whip rules out ballscrews for the longest axis.). I am not sure how to make this decision? It seems that ballscrews are more cost effective than I had thought when measured against a rack and gearbox setup.

    The second has to do with my need to make the machine as narrow as possible. Researching the x-axis has resulted in me considering gearboxes as an upgrade to the belt driven CNC router parts mounting plates for the the NEMA 34 motors. Boy those stick out! I found myself researching right angle gear boxes which would be great if they were not so expensive. I found one machine that was still in the design phase that placed the gearbox and motor on the bottom of the x axis beam. I reworked my base to accommodate this plan and I am liking the results. Is this possible? It occurs to me that the rack gets pretty far away from the Hiwin blocks which can amplify any issues with flex. Is there another way to set the machine up to minimize the envelope of the machine?

    CNC Router for Hardwoods: Evaluation and Questions-cnc-q1-jpg

    Once I know if I can pursue this design i will continue to refine the base, which is adding steel and being designed for end welding to reduce stress.

    CNC Router for Hardwoods: Evaluation and Questions-cnc-q2-jpg

    the design that I am getting away from. Ditching the 80/20 and I would love to find an alternative to the motor placement for the x axis

    CNC Router for Hardwoods: Evaluation and Questions-cnc-q3-jpg

    thanks so much, any thoughts would be appreciated



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    Quote Originally Posted by Sapele View Post
    I have been working on the design of the machine by reading and searching the forum. I have run into a few questions which are stopping me from refining the rest of the design.

    The first has to do with my Y axis drive mechanism. I had planned on rack and pinion from the start but I have noticed some machines out there that use ballscrews for the Y and Z and use rack and pinion for the longer x axis (If I have read this right ballscrew whip rules out ballscrews for the longest axis.). I am not sure how to make this decision? It seems that ballscrews are more cost effective than I had thought when measured against a rack and gearbox setup.
    Zero backlash gear boxes can be very expensive in and of themselves. Then you need a zero backlash rack and pinion solution so yeah it can be expensive. The biggest problem I see with ball screws on a wood router is that they pick up dust and may get cruded up. That is something that can be dealt with maintenance wise though.
    The second has to do with my need to make the machine as narrow as possible. Researching the x-axis has resulted in me considering gearboxes as an upgrade to the belt driven CNC router parts mounting plates for the the NEMA 34 motors.
    Why gearboxes over belt drives?

    You can always consider a centrally mounted motor with a drive shaft going to either side of the gantry. Now people might object due to twist in the shaft. This is a real possibility but there are options here too. I've seen gantry systems that address the twist issue via the use of a large steel tube instead of a small diameter shaft. Large here being about 2" in diameter. Of course this introduces coupling issues but those issues can be over comes.
    Boy those stick out!
    You only have two options that I can see if this is an issue. One is to go underneath the table which probably isn't an option in a long table either. The other is to go above the table. In each case you would use a centrally located drive motor with a stiff shaft in between the left and right supports. Or you can accept some stick out as described below.
    I found myself researching right angle gear boxes which would be great if they were not so expensive.
    Much less zero backlash.
    I found one machine that was still in the design phase that placed the gearbox and motor on the bottom of the x axis beam. I reworked my base to accommodate this plan and I am liking the results. Is this possible? It occurs to me that the rack gets pretty far away from the Hiwin blocks which can amplify any issues with flex. Is there another way to set the machine up to minimize the envelope of the machine?
    Use ball screws. Solve the whip problem by lowering rotational speed by using a ball screw with a high lead. You could always try a belt drive solution but over long distance they have problems of their own. In the end you don't have a lot of options.

    Once I know if I can pursue this design i will continue to refine the base, which is adding steel and being designed for end welding to reduce stress.
    I wouldn't weld anything until you are sure which way you are going.

    the design that I am getting away from. Ditching the 80/20 and I would love to find an alternative to the motor placement for the x axis
    You can always mount the motors vertically to save a bit of space. Lay the rack on its side and you have the potential to compact things significantly. In this case the motors stand vertically with the gear pointing down. It is a workable solution. Further the arrangement of the rack and pinion is such that major fouling should fall off.

    thanks so much, any thoughts would be appreciated
    You have already thrown out some interesting designs. The design you want to throw away though can easily morph into a more compact design. The big trick is being able to locate all components with reasonable clearances. Fitting it altogether is sometimes a big challenge when it comes to implementing a good idea.



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    Thanks for the comments Wizard
    Why gearboxes over belt drives?
    I am not sure? I have kind of gotten all turned around with the research that I have been doing. I thought I had read that gearboxes like these 10:1 keiling were a good choice when compared to the plate with belts.

    CNC Gear Head | CNC Gear Box

    Use ball screws. Solve the whip problem by lowering rotational speed by using a ball screw with a high lead. You could always try a belt drive solution but over long distance they have problems of their own. In the end you don't have a lot of options.
    I had given up on the idea of ballscrews for the x-axis. If I were to resurrect the idea what kind of pith would qualify as "high lead"? I had been looking on ebay for ballscrews and I had found a 3000mm 5 mm pitch screw 25mm in diameter. Does that qualify? I do like the way ballscrews attach to the x - axis and could see them at the heart of a narrower design.

    Ballscrew 2505 3000mm Diameter 25mm Pitch 5mm L 3000mm ballnut BK BF17 | eBay

    I wouldn't weld anything until you are sure which way you are going.
    I always knew that this would be a slow build. The way its shaping up I am happy to take even more time! I keep learning and trying to improve the design.

    You can always mount the motors vertically to save a bit of space. Lay the rack on its side and you have the potential to compact things significantly. In this case the motors stand vertically with the gear pointing down. It is a workable solution. Further the arrangement of the rack and pinion is such that major fouling should fall off.
    So the design with the rack on the bottom of the x-axis is not possible? If that is the case I will take your suggestion and try to orient the motors vertically. That sure does solve the problem with the rack being far away from the linear bearings!



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    You'd want a 10mm lead ballscrew.
    Many eBay vendors will do custom lengths.
    Many people here have bought from linearmotionearings2008 (Chai) and I've found him good in a few transactions.
    There are whip calculators online. Max rpm from most strippers I'd about 1200rpm but that top speed is only useful for rapids as steppers torque falls with increasing rpms.



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    Actually, for a really long screw, you'd want a pitch between 20 and 50mm. You can use a belt reduction to increase resolution while keeping the screw spinning slower, where it won't whip. Unfortunately, screws like that are not easily found at low prices, unless you can snag one or two on Ebay.

    Back to the Rack. A 10:1 reduction is probably too high for steppers, and would work better with servos. There's nothing wrong with belt reductions, though. About 99% of home built r&p machines use them

    Gerry

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    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    I am not sure? I have kind of gotten all turned around with the research that I have been doing. I thought I had read that gearboxes like these 10:1 keiling were a good choice when compared to the plate with belts.
    10:1 might be OK depending on the size of your pinion. Realize however that these gearboxes have a rated backlash rating; the high precision gearboxes (<3 arc-min) are VERY expensive...

    I had given up on the idea of ballscrews for the x-axis. If I were to resurrect the idea what kind of pith would qualify as "high lead"? I had been looking on ebay for ballscrews and I had found a 3000mm 5 mm pitch screw 25mm in diameter. Does that qualify? I do like the way ballscrews attach to the x - axis and could see them at the heart of a narrower design.
    You might want to consider placing the motor and reducer within the gantry itself, similar to this: (one of the nicest DIY designs IMO)





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    Quote Originally Posted by Sapele View Post
    Thanks for the comments Wizard


    I am not sure? I have kind of gotten all turned around with the research that I have been doing. I thought I had read that gearboxes like these 10:1 keiling were a good choice when compared to the plate with belts.
    I only ask because decent gear boxes are expensive both to install and replace. I've seen gear boxes go bad before the timing belts they are driving wear out.

    As to belts they can be a very good choice for economical motion control. As long as your reduction ratios are reasonable all you need is two pulleys. This assuming of course that you have the motor shaft and lead screw shaft to attach them to.



    I had given up on the idea of ballscrews for the x-axis. If I were to resurrect the idea what kind of pith would qualify as "high lead"? I had been looking on ebay for ballscrews and I had found a 3000mm 5 mm pitch screw 25mm in diameter. Does that qualify?
    nope
    I do like the way ballscrews attach to the x - axis and could see them at the heart of a narrower design.
    Everything works together here, your top motor speeds any gear reduction and then the screw lead impact machine velocities. Your best bet is to go to some of the ball screw suppliers and study the engineering documentation. Whip can be a problem but often I think people go overboard when dissing lead screws. I've seen some very high precision work done on machine with the lead screw only supported at one end. You can't do that on a router but the point is whip is a problem when certain parameters are exceeded. Keep your rotational velocity down and lead screws can work on a longish router table.

    Now I'm not saying you should go with lead screws, just that it is best not to dismiss them for the issue of whip if you can work around it.

    I always knew that this would be a slow build. The way its shaping up I am happy to take even more time! I keep learning and trying to improve the design.
    Better to take you time. Look at it this way classic machines like a HArdinge HLV did not happen over night and are rather the result of many generations of machine to come before them.


    So the design with the rack on the bottom of the x-axis is not possible?
    I'm not sure what you mean by that question. What I'm suggesting is that the rack teeth instead of pointing up be rotated over 90° so that a vertically mounted motor can engage the teeth with a motor mounted pinion.

    If that is the case I will take your suggestion and try to orient the motors vertically. That sure does solve the problem with the rack being far away from the linear bearings!
    The biggest problem with the arrangement suggested is that the surface you mount the rack and the linear bearings on needs to be fairly wide for suitable clearance all around. Remember you need to clear the linear bearings not the rail those bearings ride on.

    The choice of going with a lead screw or rack and pinion is up to you. Either way you loose a bit of space, either on the sides or at the ends of the machine. For my money I'd probably go with lead screws. I say probably because it isn't written in stone but managing backlash in a rack and pinion system bothers me.



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    Quote Originally Posted by ger21 View Post
    Actually, for a really long screw, you'd want a pitch between 20 and 50mm. You can use a belt reduction to increase resolution while keeping the screw spinning slower, where it won't whip. Unfortunately, screws like that are not easily found at low prices, unless you can snag one or two on Ebay.

    Back to the Rack. A 10:1 reduction is probably too high for steppers, and would work better with servos. There's nothing wrong with belt reductions, though. About 99% of home built r&p machines use them
    Gerry, I specified 10mm lead because the Chinese screws are commonly available in that. Unfortunately higher lead ball screws are, as you say, not easily found

    Nook have a whip calculator: http://www.nookindustries.com/Engine...cCriticalSpeed

    3 metres is certainly pushing it for a 25mm screw. 336rpm critical speed with one end fixed, other end radially supported (standard mounting)

    I'm looking at 1250mm screws. 20mm screws whip over 1528rpm, 25mm screws at 1934rpm (note I just chucked in nominal screw size for the root diameter field which I'd probably incorrect. I'd say it should be the minor diameter used)



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    Thanks everyone! Many of the articles and resources that I had bookmarked now make more sense to me.

    I am going to pursue two options at the same time.

    1- Ballscrews for the x-axis. Especially now that I understand pitch. I had been picturing TPI. Now I understand that a higher number is a coarser pitch. I understand that this approach will hinge on finding the right screws at an affordable price.

    2- Rack and pinion for the x-axis. I had fallen into the upgrade trap and thought that gearboxes were an upgrade. Now I understand that I can pursue belt reduction which will reduce the width of my machine (I am picturing these kits PRO Rack and Pinion Drive, Nema 34 | CNCRouterParts)

    I am still hoping to reduce the protrusion of the stepper/servos. I also realize that ending up with an oddball solution that saves an inch or two of width is not worth it.

    speaking of which here is a close up of my space saving idea (I don't think that I had described this well in an earlier post)
    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-4-jpg

    I will work up Wizard's suggestion of top mounting the drive assembly. I dragged a few components onto a 1530 extrusion
    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-5-jpg

    I don't think I can implement the in gantry solution that Louieatienza posted. I really enjoyed seeing it. Thanks!



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    Quote Originally Posted by Sapele View Post
    Thanks everyone! Many of the articles and resources that I had bookmarked now make more sense to me.

    I am going to pursue two options at the same time.

    1- Ballscrews for the x-axis. Especially now that I understand pitch. I had been picturing TPI. Now I understand that a higher number is a coarser pitch. I understand that this approach will hinge on finding the right screws at an affordable price.
    Or just accept slower rapids.
    2- Rack and pinion for the x-axis. I had fallen into the upgrade trap and thought that gearboxes were an upgrade.
    It depends upon what you need and how compact you need to make it. The real problem with gear boxes is the expense of the gear box, sometimes it is worth the expense, sometimes not. Personally I'd try to work out a suitable solution using belt drives first. If that does not give you the right gear ratios in the allotted space then consider a gear box and a ballooning budget.
    Now I understand that I can pursue belt reduction which will reduce the width of my machine (I am picturing these kits PRO Rack and Pinion Drive, Nema 34 | CNCRouterParts)
    If you go with leadscrews and stepper motors it probably will make sense to direct couple those steppers to the leadscrews and avoid any gearing. At least on some of your axis.
    I am still hoping to reduce the protrusion of the stepper/servos. I also realize that ending up with an oddball solution that saves an inch or two of width is not worth it.
    Honestly you need a clear space around the machine anyways unless you goals are to have one side up against a wall. Even then with your designs you need clearance. The best arraignment would be for one end of the machine against a wall. Yes it sticks out but you get access to both sides of the machine for load/unloading and system maintenance.
    speaking of which here is a close up of my space saving idea (I don't think that I had described this well in an earlier post)
    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-4-jpg
    Now I understand! Question though, how is that floating beam supported? There is one advantage here in that the rack is protected from stuff falling directly on it.
    I will work up Wizard's suggestion of top mounting the drive assembly. I dragged a few components onto a 1530 extrusion
    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-5-jpg
    That is what I was thinking though on steel tubing. The nice thing here is that getting the rack parallel to the X axis linear bearing is easy.
    I don't think I can implement the in gantry solution that Louieatienza posted. I really enjoyed seeing it. Thanks!
    All of us run into tooling limitations. That is why so much effort goes into making simple solutions that are good enough for the task at hand. Which brings us back to those gearboxes, sometimes a gearbox is the simple solution. This especially the case if you have limited ability to machine parts for this router.



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    I have emailed Linearmotionbearings2008 asking if he has any options with a coarser pitch.

    Wizard- The "floating" beam would be supported with legs welded at the end and a middle leg that is bolted on the inside. Here is a top view and a side view. My concern is that the rack is 6" away from the linear bearings. I have read that closer is better. No?

    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-1-jpg

    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-2-jpg

    The router will be placed in the middle of my wood shop. With partial access from all sides. Reducing the protrusion will allow for much better flow in the aisles and a slightly wider machine.

    CNC Router for Hardwoods: Evaluation and Questions-sixorwindow-jpg



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    1- Ballscrews for the x-axis. Especially now that I understand pitch. I had been picturing TPI. Now I understand that a higher number is a coarser pitch. I understand that this approach will hinge on finding the right screws at an affordable price.
    If you can find precision ground ballscrews, they typically have higher RPM ratings than a rolled screw of the same lead and diameter. The good thing is that many people gravitate toward the finer pitched ground ballscrews, making the coarser pitched screws more available (and cheaper) if and when you can find them on eBay.

    2- Rack and pinion for the x-axis. I had fallen into the upgrade trap and thought that gearboxes were an upgrade. Now I understand that I can pursue belt reduction which will reduce the width of my machine (I am picturing these kits
    Some gearboxes are definitely an upgrade, if you can afford them or are fortunate enough to find good surplus or NOS ones. If you familiarize yourself with some of the major brands of planetary reducers (Parker, Wittenstein/Alpha, Thomson, Apex) and their part numbers it becomes easy to identify the base size, reduction ratio, the accuracy and whether they are stepper or servo grade. Sometimes the accuracy is implied in the model name (i.e. DuraTrue, UltraTrue). A servo grade reducer won't necessarily work with steppers since the bores on the coupler are usually larger metric sizes and the pilots (the round protrusion at the motor base) are usually larger as well. Also some reducers are meant to be oriented in one configuration only and it helps to know that as well (though this usually is the case with right-angle gearboxes.) 10:1 may be fine for stepper use, though it would depend on your pinion size. I would say the smaller the pinion, the lower the gear reduction you could use but going too low would give you decreased resolution. A larger pinion might offer more tooth engagement and quiter operation.

    Atlanta Drives also makes integral tracks that work with major linear bearing manufacturers. This can also help save space as well as eliminate the alignment of rack to linear rail, as they are both integral. It would complicate things a bit, but I can't see why you couldn't have the drive motors mounted vertically in the gantry tube complete with whatever reduction you use, and drive the pinion via a jack shaft, though this would require being able to move the entire drive assembly as one unit for adjsutment. Or have the motors mounted horizontally within the gantry tube and use timing belts to drive the pinions, with the integral rack/linear rail mounted on the sides.

    =======================

    The nice thing with belt drives, aside from ease of use, is you're not limited to the stock reduction ratios that gearboxes offer, so it's easier to fine-tune the ratio that gives you the best performance just by changing pulleys and belts.



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    With your idea of hiding the rack on the bottom of the x axis beams: be aware that you will have to have a rigid and beefy mounting between the gantry and the drive components. If this connection is not rigid you'll get problems. It looks like you've modeled a C channel?



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    It looks like you've modeled a C channel?
    Sort of. I was just beginning to think of materials, thickness and how to reinforce that part of the x-carriage when I started to doubt the whole design because of the distance between the linear bearings and the rack. If the consensus is that this design is feasible I will continue to develop it by trying to make that part of the carriage as stiff as possible.



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    Quote Originally Posted by Sapele View Post
    I have emailed Linearmotionbearings2008 asking if he has any options with a coarser pitch.

    Wizard- The "floating" beam would be supported with legs welded at the end and a middle leg that is bolted on the inside. Here is a top view and a side view. My concern is that the rack is 6" away from the linear bearings. I have read that closer is better. No?
    I'd be more worried about the unsupported length of the beam than anything else. That is easy to deal with though. If I remember correctly this is a long machine which is probably why you are considering rack drive. In any event a long beam will be subject to vibration and deflection if not supported properly.

    The router will be placed in the middle of my wood shop. With partial access from all sides. Reducing the protrusion will allow for much better flow in the aisles and a slightly wider machine.
    If that is the case I would think a leadscrew drive would save you the most space. However creative engineering can do wonders.



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CNC Router for Hardwoods: Evaluation and Questions

CNC Router for Hardwoods: Evaluation and Questions