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  1. #1
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    Input on my DIY CNC design

    My inspiration was Jeremy Young’s design along with some modifications to reflect materials availability in my area. I decided to use alum extrusions since I wanted to re-use as many materials as possible from my Openbuilds machine. My goal is to cut hardwood (80% of the time) and aluminium (20%).

    The X rails & extrusions are 565mm long and Y are 700mm long. I will be using 20mm linear on the X and 15mm on the Y. The two X extrusions will be braced together with a backer alum plate 5/8” thick. 1605 ball screws all around. The Z axis will be modified latter on.

    Please use the following link to access the 3D model. Thanks in advance for your comments.


    https://a360.co/2IvxfcJ

  2. #2
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    Re: Input on my DIY CNC design

    If you can make a way to flip your X axis frame so that the exposed ball screw mechanism will be at the back, it will save you tons of problems on the machine getting stuck or offset due to the dust debris from the wood, or the metal chips getting eaten by the ball screws and eventually will get stuck. as much as possible cover your ball screws from the direct exposure to saw dust or metal chips, if possible place your Y axis on top and the X axis flipped, I saw some commercial machines set-up this way, the guys that built those machines really knows how important it is to hide the ball screws from the dust debris, that makes their machines rock solid stable even on a thousand program loops


  3. #3
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    Re: Input on my DIY CNC design

    Khouj, thanks for your input. I plan on covering the front of the X- Axis with a flex dust cover similar to the one offered here:
    https://www.aliexpress.com/item/200-...999.262.bZK0KL

    Thanks

  4. #4
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    Re: Input on my DIY CNC design

    I think that will do as long as it`s covered, our CNC machines in the shop does`nt have covers on the ball screws, and im like a security guard holding an air blow gun waiting on the CNC machines operating 8 hours a day, making sure the ball screws are free from dust debris, im also the one that overhauls the ball screw when one of our machines gets errors due to stuck ball screws, it`s a tedious job when it gets stuck. ohh well

  5. #5
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    Re: Input on my DIY CNC design

    Quote Originally Posted by Phil_Par View Post
    My inspiration was Jeremy Young’s design...
    OK, sorry for my ignorance but I have no idea who he is. Anyway, some comments about the model you posted.

    In my opinion it would be better to make the Y the longer one and the X the shorter one, but I would twist the whole thing 90 degrees so that the actual gantry with the Z is the X and the gantry moves along the Y. My understanding is that in your design the Z moves on the longer Y axis and the gantry moves on the shorter X. Your machine will be more rigid if you modify it and at the same time the gantry will be lighter due to less material. Rigidity is important, especially if you plan to use it for aluminium and hardwood.

    What are your plans for the extrusion dimension? You are only giving us the length, so I don't know.

  6. #6
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    Re: Input on my DIY CNC design

    Jeremy goes by JermNZ in this forum. The whole idea of making the x axis longer than the y is to give me the opportunity to carve wider boards while overhanging of my table if it comes to that. 700mm is still short compared to other machines using the same beam design I used. The extrusions are the V-slot from OpenBuilds. I plan on using their signature C-beam for all axis (4080) and the base cross members are 4040.

  7. #7
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    Re: Input on my DIY CNC design

    This thread highlights how confusing it is to chose arbitrary assignments to X,Y & Z on these machines!!!!

    In any event, lets look at your needs where you indicated about 20% usage in aluminum. You didn't get into specifics of what that means but having a long gantry axis works against you when it comes to getting good results. Think about it in this manner, you will want about ten times the stiffness to machine aluminum the way you machine wood. You are already starting out with questionable extrusions so that is a factor that makes using them in a long span even more questionable. While plastering a plate on the back of the extrusions will add some stiffness it isn't a huge win.

    As I see it, in many cases the gantry ends up be the weakest link in the DIY machines out there. I suspect this is the case here also as the extrusions simply look thin in your rendering. That and you are almost always better off using box sections to hold the gantry its self up instead of plain plates. If you really think that the long gantry will work better for you consider an upgraded beam of larger extrusions or ideally a steel beam. Support the gantry properly. The rest of the machine looks pretty good though I would throw in at least a few gusset plates at each corner of the base frame; also make sure the "ladder rungs", at least the ones on the end, are the same dimensions as the legs of the ladder frame.

    Quote Originally Posted by Phil_Par View Post
    Jeremy goes by JermNZ in this forum. The whole idea of making the x axis longer than the y is to give me the opportunity to carve wider boards while overhanging of my table if it comes to that. 700mm is still short compared to other machines using the same beam design I used.
    The 700mm is relatively short but you are indicating usage in aluminum. Now that means different things to different people but it also means that you need a stiffer machine than one dedicated to wood working. Also just because you see that somebody else has done something similar it doesn't mean it will be good enough to meet your expectations.

    On the net it is hard to understand what your expectations are. However if you are using minimalist materials such as Openbuilds extrusions you likely are already limiting machine capability. As somebody has already mentioned we don't know what the cross sectional sizes are here. So we can only infer from the rendering what the actual parts are. If we better understand your expectations we might be able to better comment. Otherwise we are forced to comment in general terms and those comments reflect what we think you mean by 20% usage in aluminum.
    The extrusions are the V-slot from OpenBuilds. I plan on using their signature C-beam for all axis (4080) and the base cross members are 4040.
    There are a couple of problems here.

    First the cross members, in the base, should be the same dimension as the axis members at least at the ends but ideally across all members. While you may see the cross members as a base for the table and waste board they also have a significant impact on the rigidity of the axis extrusions. With suitable fastening methods and plenty of gussets you can end up with a very rigid base.

    The second issue here is that the only exposure I've had to the Openbuild hardware is what I've seen on line and frankly I'm not impressed. I'm not impressed with the idea of V rollers of any type running on aluminum extrusions for one. The second issue is that the extrusions appear to be very light weight. Beyond that you are implementing smaller sized extrusions for the cross members which has its own issue

    Now about that light weight, a few months ago somebody put on line a picture of some square extrusions he apparently got salvage rights to. Now this was small square extrusions all of the same outside dimension but clearly different "inside". Now the small square tubing has limited machine building usages to begin with but in this case two of the extrusions where extremely light weight, one having hollow sections. I could easily imagine breaking that extrusion just like I will be breaking branches in my back yard i will be picking up in a hour or so. The point is not all extrusion are the same so you need to know the specifics of the items in question. Even the likes of Misumi sells extrusions with varying design elements including the wall thickness of the cross section.

    I'm a bit long winded here. I can't say if the OpenBuilds hardware is suitable for your needs. However a bit of attention to design can make for far better performance from what ever materials you use which is the important point.

  8. #8
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    Re: Input on my DIY CNC design

    Quote Originally Posted by wizard View Post
    This thread highlights how confusing it is to chose arbitrary assignments to X,Y & Z on these machines!!!!

    In any event, lets look at your needs where you indicated about 20% usage in aluminum. You didn't get into specifics of what that means but having a long gantry axis works against you when it comes to getting good results. Think about it in this manner, you will want about ten times the stiffness to machine aluminum the way you machine wood. You are already starting out with questionable extrusions so that is a factor that makes using them in a long span even more questionable. While plastering a plate on the back of the extrusions will add some stiffness it isn't a huge win.

    As I see it, in many cases the gantry ends up be the weakest link in the DIY machines out there. I suspect this is the case here also as the extrusions simply look thin in your rendering. That and you are almost always better off using box sections to hold the gantry its self up instead of plain plates. If you really think that the long gantry will work better for you consider an upgraded beam of larger extrusions or ideally a steel beam. Support the gantry properly. The rest of the machine looks pretty good though I would throw in at least a few gusset plates at each corner of the base frame; also make sure the "ladder rungs", at least the ones on the end, are the same dimensions as the legs of the ladder frame.


    The 700mm is relatively short but you are indicating usage in aluminum. Now that means different things to different people but it also means that you need a stiffer machine than one dedicated to wood working. Also just because you see that somebody else has done something similar it doesn't mean it will be good enough to meet your expectations.

    On the net it is hard to understand what your expectations are. However if you are using minimalist materials such as Openbuilds extrusions you likely are already limiting machine capability. As somebody has already mentioned we don't know what the cross sectional sizes are here. So we can only infer from the rendering what the actual parts are. If we better understand your expectations we might be able to better comment. Otherwise we are forced to comment in general terms and those comments reflect what we think you mean by 20% usage in aluminum.


    There are a couple of problems here.

    First the cross members, in the base, should be the same dimension as the axis members at least at the ends but ideally across all members. While you may see the cross members as a base for the table and waste board they also have a significant impact on the rigidity of the axis extrusions. With suitable fastening methods and plenty of gussets you can end up with a very rigid base.

    The second issue here is that the only exposure I've had to the Openbuild hardware is what I've seen on line and frankly I'm not impressed. I'm not impressed with the idea of V rollers of any type running on aluminum extrusions for one. The second issue is that the extrusions appear to be very light weight. Beyond that you are implementing smaller sized extrusions for the cross members which has its own issue

    Now about that light weight, a few months ago somebody put on line a picture of some square extrusions he apparently got salvage rights to. Now this was small square extrusions all of the same outside dimension but clearly different "inside". Now the small square tubing has limited machine building usages to begin with but in this case two of the extrusions where extremely light weight, one having hollow sections. I could easily imagine breaking that extrusion just like I will be breaking branches in my back yard i will be picking up in a hour or so. The point is not all extrusion are the same so you need to know the specifics of the items in question. Even the likes of Misumi sells extrusions with varying design elements including the wall thickness of the cross section.

    I'm a bit long winded here. I can't say if the OpenBuilds hardware is suitable for your needs. However a bit of attention to design can make for far better performance from what ever materials you use which is the important point.
    Thanks for the thorough review. The extrusions Pointed out on my design are very thin as you suspected. I guess I overlook the thickness of my extrusions and wanted to get away with easily available extrusions. I need to source beefier extrusions just like the ones used on the routerparts cnc benchtop pro. Any recommended suppliers?

    I decided to stay away from steel since it involves welding. I dont have a welder and dont trust someone to weld for me with the same precision as cnc'd plates and extrusions.


    Sent from my iPhone using Tapatalk

  9. #9
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    Quote Originally Posted by Phil_Par View Post
    Thanks for the thorough review. The extrusions Pointed out on my design are very thin as you suspected. I guess I overlook the thickness of my extrusions and wanted to get away with easily available extrusions. I need to source beefier extrusions just like the ones used on the routerparts cnc benchtop pro. Any recommended suppliers?
    Misumi might be a good source for the gantry beam.

    Note that if you already have extrusions, the base frame will not suffer as much from lighter materials. This due to gusseting and the cross members working together to stiffen everything up.
    I decided to stay away from steel since it involves welding.
    For some parts of the machine steel does involve welding but you can easily implement steel into some parts fairly easy without welding. The gantry beam is one area where almost zero effort is involved. You can use two T-Slotted extrusions as part of the beam supports and bolt directky to the tapped T-Slots. No welding required.

    I dont have a welder and dont trust someone to weld for me with the same precision as cnc'd plates and extrusions.


    Sent from my iPhone using Tapatalk
    Wiith welding comes distortion and the need post process the weldments in some manner. However unless you buy a kit your extrusions will need processing also, for example cut to length. If you dont have the ability to cut to length critical parts to the right length and squareness then you need to have them machined to length and squarenees. If you need to hire a thrird party to do this costs can become a wash between the two materials.

    This is where extrusion kits are often a sound investment even if the price of materials is inflatted. The machining costs are built in to the kits price and thus a tool poor user doesnt have to invest in machine tools or source a local machine shop.

    On another note do consider leveling feet at each corner of the frame. If you use faily heavy gusset plates for the four corners the leveling feet can be mounted in holes in the plates. By the way not every gusset plate need to be precisioned machined on a CNC.

  10. #10
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    Re: Input on my DIY CNC design

    Quote Originally Posted by wizard View Post
    Misumi might be a good source for the gantry beam.

    Note that if you already have extrusions, the base frame will not suffer as much from lighter materials. This due to gusseting and the cross members working together to stiffen everything up.

    For some parts of the machine steel does involve welding but you can easily implement steel into some parts fairly easy without welding. The gantry beam is one area where almost zero effort is involved. You can use two T-Slotted extrusions as part of the beam supports and bolt directky to the tapped T-Slots. No welding required.


    Wiith welding comes distortion and the need post process the weldments in some manner. However unless you buy a kit your extrusions will need processing also, for example cut to length. If you dont have the ability to cut to length critical parts to the right length and squareness then you need to have them machined to length and squarenees. If you need to hire a thrird party to do this costs can become a wash between the two materials.

    This is where extrusion kits are often a sound investment even if the price of materials is inflatted. The machining costs are built in to the kits price and thus a tool poor user doesnt have to invest in machine tools or source a local machine shop.

    On another note do consider leveling feet at each corner of the frame. If you use faily heavy gusset plates for the four corners the leveling feet can be mounted in holes in the plates. By the way not every gusset plate need to be precisioned machined on a CNC.
    I will add more gussets to the base as suggested and that would narrow the concerns to the gantry.
    What if I change the alum backer plate joining the two extrusions for a steel plate or even a c section?
    Based on the discussion above, the two extrusions on the gantry would then become mounts for the rails and NOT an structural member, therefore relying on the steel member for stiffness.



    Sent from my iPhone using Tapatalk

  11. #11

    Re: Input on my DIY CNC design

    Hello,
    It looks like you have two c-beams stacked? Based on the fact that your x-axis is so short, I think you'll be plenty rigid for hardwood and some light aluminum work. If I were you though, I would use steel rectangular tube as an x axis material, perhaps 2"x4" and use hardened steel v-track and bearings. In the long run you'll be much happier. I have a single c-beam machine now that I'm trying to make more rigid. You can see my trials and tribulations here. I'll post a video shortly on adding steel channel into the c-beam pockets to see how that effects rigidity and torsion. If I were to start from scratch, I'd use steel to build the Z-beam and frame and build an X/Y table style, the nature of the design is inherently more rigid and hence why metal mills are designed this way. If you won't be carving up large pieces of wood, you don't have to worry about the movement of the table. I may end up going that route eventually, but I'm already down the path, so to speak. It looks like you're going with v-track anyway and not poly wheels, that's a good move. Oh, I just realized this is from 2 years ago. What did you end up building?
    https://youtu.be/2QTZa2Ge9A0
    Cheers,
    Tyler

  12. #12
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    Re: Input on my DIY CNC design

    Quote Originally Posted by Phil_Par View Post
    I will add more gussets to the base as suggested and that would narrow the concerns to the gantry.
    What if I change the alum backer plate joining the two extrusions for a steel plate or even a c section? If you watch Youtube "This Old Tony" did a gantry beam out of C channel and even after having it machined by 0.030" ( I believe that is what he quoted) it still wasn't completely flat. Steel tubing seems to fair better in my estimation but even then often needs correction in some manner.
    You still have to bolt everything together. On top of that C sections and steel plate are notorious for not being extremely flat. Beyond that C Sections are not extremely twist resistant. Now your gantry (if I understand your first post ) isn't extremely long at a little over a half meter, so given a large enough C-section it may do. However I'm confused, if you have a supplier for C sections you should be able to source steel tubing.

    In any event once you have a piece of steel why add the aluminum to it? Instead bolt the rails directly to the steel section.
    Based on the discussion above, the two extrusions on the gantry would then become mounts for the rails and NOT an structural member, therefore relying on the steel member for stiffness.
    An arbitrary steel section will not be necessarily stiffer than an aluminum section. It all depends upon the size and form of the section.

    To better understand what I'm trying to say here i will offer this up. Adding a backer plate to lightweight extrusions will not offer a lot to the over all systems rigidity. Depending upon how thick the plate is it might end up being the stiffest member in the design, this is almost a certainty for vertical deflection even for a thin plate. It is likely that the extrusions will improve plate deflection in the horizontal range but those extrusions can also be a disadvantage in over all rigidity. On the flip side they can offer a design advantage in creating a channel for the lead screw.

    Mind you this is my point of view but if you upgrade your materials to steel you really should take advantage of that material to mount your rails. You do this gantry beam right and it will remain good even if you decide to upgrade the rest of the machine later.



    Sent from my iPhone using Tapatalk
    Oh one more thing, my preference for steel might be a regional issue but right now steel is very economical compared to aluminum for a DIY machine. If you already have the majority of the parts that is another issue. One the other hand if you are about to buy materials I'd think long and hard about the long term and overall costs.

  13. #13

    Re: Input on my DIY CNC design

    Yes, if you watch my video, you'll see that we may be barking up the wrong tree trying to make this c-beam mill metal. In the next few days I'll post another video showing how my CNC performs after adding a stainless steel channel to the 750mm X-axis. This will be the last attempt at a stop-gap solution. After this I move to a steel X-axis with hardened steel V-track and wheels. Good luck!

  14. #14
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    Re: Input on my DIY CNC design

    Quote Originally Posted by wizard View Post
    You still have to bolt everything together. On top of that C sections and steel plate are notorious for not being extremely flat. Beyond that C Sections are not extremely twist resistant. Now your gantry (if I understand your first post ) isn't extremely long at a little over a half meter, so given a large enough C-section it may do. However I'm confused, if you have a supplier for C sections you should be able to source steel tubing.

    In any event once you have a piece of steel why add the aluminum to it? Instead bolt the rails directly to the steel section.

    An arbitrary steel section will not be necessarily stiffer than an aluminum section. It all depends upon the size and form of the section.

    To better understand what I'm trying to say here i will offer this up. Adding a backer plate to lightweight extrusions will not offer a lot to the over all systems rigidity. Depending upon how thick the plate is it might end up being the stiffest member in the design, this is almost a certainty for vertical deflection even for a thin plate. It is likely that the extrusions will improve plate deflection in the horizontal range but those extrusions can also be a disadvantage in over all rigidity. On the flip side they can offer a design advantage in creating a channel for the lead screw.

    Mind you this is my point of view but if you upgrade your materials to steel you really should take advantage of that material to mount your rails. You do this gantry beam right and it will remain good even if you decide to upgrade the rest of the machine later.



    Oh one more thing, my preference for steel might be a regional issue but right now steel is very economical compared to aluminum for a DIY machine. If you already have the majority of the parts that is another issue. One the other hand if you are about to buy materials I'd think long and hard about the long term and overall costs.
    Do you know of steel gantry build that you may recommend for reference?

    Base on the feedback I am no longer considering CBeam extrusions. I am now contemplating between a heavier alum extrusion with milled surfaces or steel sections for the gantry.

    The base will be alum extrusion with a milled face for the linear rail and filled with an engine filler for additional weight and strength. Staying away from a welded steel base.


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  15. #15
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    Re: Input on my DIY CNC design

    Quote Originally Posted by wiremonkey View Post
    Hello,
    It looks like you have two c-beams stacked? Based on the fact that your x-axis is so short, I think you'll be plenty rigid for hardwood and some light aluminum work. If I were you though, I would use steel rectangular tube as an x axis material, perhaps 2"x4" and use hardened steel v-track and bearings. In the long run you'll be much happier. I have a single c-beam machine now that I'm trying to make more rigid. You can see my trials and tribulations here. I'll post a video shortly on adding steel channel into the c-beam pockets to see how that effects rigidity and torsion. If I were to start from scratch, I'd use steel to build the Z-beam and frame and build an X/Y table style, the nature of the design is inherently more rigid and hence why metal mills are designed this way. If you won't be carving up large pieces of wood, you don't have to worry about the movement of the table. I may end up going that route eventually, but I'm already down the path, so to speak. It looks like you're going with v-track anyway and not poly wheels, that's a good move. Oh, I just realized this is from 2 years ago. What did you end up building?
    https://youtu.be/2QTZa2Ge9A0
    Cheers,
    Tyler
    This thread is less than a month old. I haven't picked a final design yet. However, I am staying away from openbuilds extrusions due to the light weight.
    Subscribed to your video series. Curious to see the outcome of your upgrades




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