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  1. #41
    Member ChrisD314's Avatar
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    Default Re: My First CNC Build

    Quote Originally Posted by mactec54 View Post
    Looks good for your first build, you will see by this build where you need to improve it. depending on the spindle you choose, the performance will only be able to match the power of the spindle.
    Im using the Bosch 1617 router



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    Default Re: My First CNC Build

    Quote Originally Posted by ChrisD314 View Post
    Peter, are you referring to me as Dean? My name is Chris, but no worries. Yeah guys, I'm far from done, i understand its not a perfect design but like Peter said its not my last machine and I'm not going to push it too hard. Throwing another piece of 3/4 wood on top of the gantry beam is a good idea to even square things up even better than they are.

    Can you guys give me some advice on picking the rest of my parts. Stepper motors, how can I calculate how much torque I need to move each axis? I will need two motors for my y axis, and just 1 for the other 2 axis'. I've seen a couple of ideas and equations but I want to know what you guys think. Also how do I determine how big my drag chain should be? Thanks
    There has been a lot of discussion with regards to motors and controllers and this combination has come up a lot as an excellent choice.

    https://www.omc-stepperonline.com/ne...m-4-wires.html

    https://www.omc-stepperonline.com/st...or-dm860t.html

    Without going into the long discussions, the stepper motor has low inductance that results in higher torque at higher speeds, and can handle higher acceleration rates.

    The controller is very affordable for its performance. You want to feed the controller at least 60 VDC for the motor above. The controller supports a max input of 110 VDC! And you can also feed it with 80VAC straight off of a transformer.

    This combination of motor and controller can far out perform your current build, and can be pulled from your first build for the second and even third. Basically, until you are ready to upgrade to servos, this combination should serve you very well.

    The reference to Dean was in response to another member with regards to their critique mentioning racking in the design having the linear bearing trucks close together on the sides.

    I second the need for some strengthening ribs on the vertical sides, plus along the entire back of the gantry. Box that in top, bottom, plus a few vertical ribs to tie the top, bottom, and face together. Make the bottom brace wider than the top, perhaps 6-8", then the top just wide enough to support a drag chain. The side profile would be triangular in shape. The bottom rail on the gantry is going to have the most force applied to it while machining, the top, much less.

    For your drag chain, it needs to be large enough for all of your cables to fit, and if you are using a spindle instead of a router or dremel, you need some separation between the spindle cable and your z axis stepper wires and especially your limit switches. Clean wiring goes a long way towards reducing troubleshooting wiring issues in the future.

    I hope that this helps.

    John Z

    Sent from my SM-G991U using Tapatalk

    Last edited by JohnZ; 01-16-2022 at 12:21 PM. Reason: Fixed links


  3. #43
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    Default Re: My First CNC Build

    Quote Originally Posted by JohnZ View Post
    There has been a lot of discussion with regards to motors and controllers and this combination has come up a lot as an excellent choice.

    https://www.omc-stepperonline....5-0...m-4-wires.html

    https://www.omc-stepperonline....-fo...or-dm860t.html

    Without going into the long discussions, the stepper motor has low inductance that results in higher torque at higher speeds, and can handle higher acceleration rates.

    The controller is very affordable for its performance. You want to feed the controller at least 60 VDC for the motor above. The controller supports a max input of 110 VDC! And you can also feed it with 80VAC straight off of a transformer.

    This combination of motor and controller can far out perform your current build, and can be pulled from your first build for the second and even third. Basically, until you are ready to upgrade to servos, this combination should serve you very well.

    The reference to Dean was in response to another member with regards to their critique mentioning racking in the design having the linear bearing trucks close together on the sides.

    I second the need for some strengthening ribs on the vertical sides, plus along the entire back of the gantry. Box that in top, bottom, plus a few vertical ribs to tie the top, bottom, and face together. Make the bottom brace wider than the top, perhaps 6-8", then the top just wide enough to support a drag chain. The side profile would be triangular in shape. The bottom rail on the gantry is going to have the most force applied to it while machining, the top, much less.

    For your drag chain, it needs to be large enough for all of your cables to fit, and if you are using a spindle instead of a router or dremel, you need some separation between the spindle cable and your z axis stepper wires and especially your limit switches. Clean wiring goes a long way towards reducing troubleshooting wiring issues in the future.

    I hope that this helps.

    John Z

    Sent from my SM-G991U using Tapatalk

    Can you supply those links again, the link doesnt seem to be working. Can you or anyone show me an example of a build that is similar to mine but with the proper boxed and rib support? Im using a router, but why does there need to be separation between the spindle wire and other, some type of interference happens? Im in the automotive business and I do a lot of clean, hidden wires, so I will for sure make it look nice and it will function well.



  4. #44
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    Default Re: My First CNC Build

    Let's try the links again, since they did not copy over right last time.

    https://www.omc-stepperonline.com/ne...m-4-wires.html

    https://www.omc-stepperonline.com/st...or-dm860t.html

    Spindles generate a lot of electrical noise, and can introduce phantom issues in other wires nearby. Proper grounding, shielded wire etc. is needed, as well as separation between low voltage wires and the spindles power cable.

    Thanks, John Z

    Sent from my SM-G991U using Tapatalk



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    Default Re: My First CNC Build

    Quote Originally Posted by ChrisD314 View Post
    Can you supply those links again, the link doesnt seem to be working. Can you or anyone show me an example of a build that is similar to mine but with the proper boxed and rib support? Im using a router, but why does there need to be separation between the spindle wire and other, some type of interference happens? Im in the automotive business and I do a lot of clean, hidden wires, so I will for sure make it look nice and it will function well.
    For inspiration, read through Jerry's Big Bamboo build thread.

    https://www.cnczone.com/forums/cnc-w...st1629984.html

    Similar design to what you are building, but exceptionally thought out and refined. The gantry is boxed in and I think that he even filled some voids with epoxy granite, but not 100% certain if I recall that detail correct. His build uses bamboo plywood and I'd say the most successful plywood build I've seen. More than half of the build thread is projects built with that machine once it was completed. His YouTube channel shows experiments machining brass and steel even. Nothing like a vmc, but for a plywood based router, very impressive.

    (I just realized that I referenced the Big Bamboo thread earlier. I guess that I'm repeating myself. My First CNC Build)

    Thanks, John Z

    Sent from my SM-G991U using Tapatalk

    Last edited by JohnZ; 01-16-2022 at 03:00 PM.


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    Default Re: My First CNC Build

    Hi Chris - To clarify the spindle interference. This is mainly from high freq AC spindles. DC spindles and your Bosch will not create interference if earthed correctly. I have run 240V 50htz routers using single multicore wire alongside the motor and control signals with no issues. I usually run a 12 or 16 core flexible cable rated at 750V for the main loom. Good earthing for all components is a must. Peter



  7. #47
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    Default Re: My First CNC Build

    Okay thank you for the clarification, good to know for the future.

    So back to stepper motors, the ones you linked to me seem like a great choice. But my question is, the y and x axis will need a motor with this power and torque at accelerated speeds, but what about the z axis, Its moving the weight of the router up and down and of course it needs the power to carve into the project, but is that too much power for the z axis? Should you have the same motors on every axis in a build?



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    Default Re: My First CNC Build

    Hi Chris - 1) Did you get 5mm pitch screws? 2) you need to size the motors for each axis for what they need to do. Its common to have all the same as its easier and if there is a problem they can be swapped 3) what is the estimated weight of your Z axis assembly ie the weight the motor has to lift? 4) what is the estimated weight of the gantry in total? 5) what is the weight of the saddle plus Z axis ie the weight of the parts sliding along the gantry?

    The size of the motor is mainly driven by the acceleration you want to achieve. A large N23 (114mm) will provide 3Nm at stall. A medium N23 76mm long) will provide 1.9Nm at stall. A 5mm pitch screw at 3Nm will push 340kgf so at slow speeds (so keep your fingers clear) I expect your going to have lots of grunt to move things around. The medium size will be say half that.

    medium motor $26 long motor $34 (stepperonline) so in the scheme of things the cost delta is not much so most people just buy the big one. Unless space is an issue or you want to use a smaller cheaper driver. But then a low amp driver is $16 and the higher one is $22 so again pick the higher rated driver....

    Now acceleration is usually 60% of the torque consumption if you want to go fast. I expect your parts are light and a N23 or N24 will move them quite fast if needed..... Peter

    If $$$ are tight look at Nema17's they are much cheaper and will cut timber and plastic really easy especially if you use a 5mm pitch screw.... I use them on my small belt machines and they work fine...



  9. #49
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    Default Re: My First CNC Build

    Quote Originally Posted by peteeng View Post
    Hi Chris - 1) Did you get 5mm pitch screws? 2) you need to size the motors for each axis for what they need to do. Its common to have all the same as its easier and if there is a problem they can be swapped 3) what is the estimated weight of your Z axis assembly ie the weight the motor has to lift? 4) what is the estimated weight of the gantry in total? 5) what is the weight of the saddle plus Z axis ie the weight of the parts sliding along the gantry?

    The size of the motor is mainly driven by the acceleration you want to achieve. A large N23 (114mm) will provide 3Nm at stall. A medium N23 76mm long) will provide 1.9Nm at stall. A 5mm pitch screw at 3Nm will push 340kgf so at slow speeds (so keep your fingers clear) I expect your going to have lots of grunt to move things around. The medium size will be say half that.

    medium motor $26 long motor $34 (stepperonline) so in the scheme of things the cost delta is not much so most people just buy the big one. Unless space is an issue or you want to use a smaller cheaper driver. But then a low amp driver is $16 and the higher one is $22 so again pick the higher rated driver....

    Now acceleration is usually 60% of the torque consumption if you want to go fast. I expect your parts are light and a N23 or N24 will move them quite fast if needed..... Peter

    If $$$ are tight look at Nema17's they are much cheaper and will cut timber and plastic really easy especially if you use a 5mm pitch screw.... I use them on my small belt machines and they work fine...


    Yes all my ballscrews are 1605. The Z axis weight would be no more than 15 pounds between the wood, bosch router, and hardware. The total weight of the gantry is heavy, probably 30-50 pounds after everything is on there. I want the machine to move as fast as possible but also as safe as possible for the longevity of the machine. I think the ones John linked will be good. I was going to go with a nema 23 3.0Nm, but id rather have more than less. I really want to do this right the first time when it comes to the electronics.



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    Default Re: My First CNC Build

    Hi Chris - 50lbs 25kg is not "heavy" compared to others. N23 tops out at 3Nm and on many of my machines which are much heavier I run them at less then full amps as a safeguard so you won't go wrong there. Peter



  11. #51
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    Default Re: My First CNC Build

    Quote Originally Posted by peteeng View Post
    Hi Chris - 50lbs 25kg is not "heavy" compared to others. N23 tops out at 3Nm and on many of my machines which are much heavier I run them at less then full amps as a safeguard so you won't go wrong there. Peter
    Okay thats good to hear, maybe ill stick with my original selection. Thanks Peter



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    Default Re: My First CNC Build

    Chris just some food for thought... the Z axis is only ever moving the Z axis, it generally is only moving the Z axis very small increments, unless it is doing a full retract and even then it is likely only to be moving 100-200mm. The Y axis (or X depending on country and machine layout) is moving both the Y axis and the Z axis, so it is moving the combined weight of both. The X axis of course is moving the weight of all three.

    So really you don't need to get crazy on the Z axis motor, one of the smaller / shorter N23 motors would suffice. For the Y axis I would recommend the larger of the N23 motors as it needs to do more work. For the X axis you need to step up to two N23 motors or a single N34. ALL of these motors are overkill for what you have currently built, as you won't be able to max them out due to stability issues in your CNC.

    But it is nice to not have to re-buy them if you make improvements in the future. I have been using N23's on my CNC since the beginning and I am currently in the process of stepping up to N34, but we have very different CNCs.

    You asked about how many motors on the X axis, you will probably need two, but here is a link to my conversion to one.



    Last edited by Bad Wolf; 01-16-2022 at 10:26 PM.
    If my post is missing the n't you might have to mentally add it yourself.


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    Default Re: My First CNC Build

    I agree with the comments about converting the gantry beam to a box.As mentioned earlier,it will provide a surface for a drag chain and help a lot with stiffness.It will be easier at this stage of the build than leaving it to a later point when the cables will be present and may need to be removed.A generous supply of access holes would still allow reaching bolts or cable connectors.For my own amusement I created a very rough approximation of the gantry to see where the weak points are-it's about the limit of my ability with FEM.If I managed to attach the screenshot,you will see that the leverage from the Z axis is likely to deflect the bottom of the gantry beam.

    Attached Thumbnails Attached Thumbnails My First CNC Build-gantry-deflection-png  


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    Default Re: My First CNC Build

    Quote Originally Posted by routalot View Post
    I agree with the comments about converting the gantry beam to a box.As mentioned earlier,it will provide a surface for a drag chain and help a lot with stiffness.It will be easier at this stage of the build than leaving it to a later point when the cables will be present and may need to be removed.A generous supply of access holes would still allow reaching bolts or cable connectors.For my own amusement I created a very rough approximation of the gantry to see where the weak points are-it's about the limit of my ability with FEM.If I managed to attach the screenshot,you will see that the leverage from the Z axis is likely to deflect the bottom of the gantry beam.
    It took me a while staring at the screenshot before I realized that the view was looking up from the bottom in order to see the back plate of the gantry design is deflecting under load.

    Great input and quick analysis.

    Thanks, John Z

    Sent from my SM-G991U using Tapatalk



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    Default Re: My First CNC Build

    Hi Chris and others - Regarding timber machine construction. With metals we build hollow sections to take advantage of its geometric inertia to weight ratio to keep weight down. With timber say plywood its density is very low ~650kg/m3 vs AL at 2700kg/m3 and steel at 7800kg/m3. Thin hollow structures can change shape due to local shear forces. Thin is a relative term, 10mm steel sections can still be regarded thin if they lozenge under shear loads.

    This is a common problem in machine elements. Machine beams are short and shear effects can be dominant vs long beam (global ) effects. So with timber its often better to use solid sections not hollow. The total weight gain is not much and solids have excellent local and global shear stiffness properties. So Chris to improve the stiffness of the gantry ( if found to be needed) just double/triple up its thickness. Architecture is embracing timber construction at the moment as a sustainable and effective material. They call it mass timber and cross laminated timber (or lumber). Large timber beams outperform steel beams in stiffness, weight and fire resistance. Our machines don't need to do well in fires though hopefully they never see a flame.

    If weight is an issue then the internal laminates can be drilled out a bit but effectively keep it a solid.. Peter



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    Default Re: My First CNC Build

    Quote Originally Posted by peteeng View Post
    Hi Chris and others - Regarding timber machine construction. With metals we build hollow sections to take advantage of its geometric inertia to weight ratio to keep weight down. With timber say plywood its density is very low ~650kg/m3 vs AL at 2700kg/m3 and steel at 7800kg/m3. Thin hollow structures can change shape due to local shear forces. Thin is a relative term, 10mm steel sections can still be regarded thin if they lozenge under shear loads.

    This is a common problem in machine elements. Machine beams are short and shear effects can be dominant vs long beam (global ) effects. So with timber its often better to use solid sections not hollow. The total weight gain is not much and solids have excellent local and global shear stiffness properties. So Chris to improve the stiffness of the gantry ( if found to be needed) just double/triple up its thickness. Architecture is embracing timber construction at the moment as a sustainable and effective material. They call it mass timber and cross laminated timber (or lumber). Large timber beams outperform steel beams in stiffness, weight and fire resistance. Our machines don't need to do well in fires though hopefully they never see a flame.

    If weight is an issue then the internal laminates can be drilled out a bit but effectively keep it a solid.. Peter
    Hey Peter,

    While increasing the thickness is one way to tackle the problem it is not necessarily the best way to tackle the problem. I did a quick demonstration for my wife the other day to demonstrate the strength of boxing a section. I showed her how easy it was to twist a remote control (not wanting to break it) but to demonstrate how flat materials are easily twisted with little pressure. Then I showed her trying to twist an empty tissue box made out of thin cardboard. The empty tissue box because of it's boxed construction held up to twist forces significantly better than the remote control, even though it was only made out of thin cardboard.

    If we are going to add weight to a gantry, I think we should add it in a way that we get maximum anti twist benefit from it. One of my major bug bears with that design is that the lack of boxing in it allows the gantry to twist in multiple directions. Making it prone to cutting errors. Motors moving and changing directions can cause all sorts of deflection issues.

    If my post is missing the n't you might have to mentally add it yourself.


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    Default Re: My First CNC Build

    Hi Bad Wolf - I am fully aware of the box vs the solid. But a timber box can have poor local shear stiffness. Unless you do the math/engineering on each option its difficult to make an off the cuff suggestion. I spend a lot of time in other threads looking at gantry sections lozenging, sections bending and how the shear centre of hollows work. I would generally recommend a square section as this has equal stiffness for plunging and cutting transverse to the gantry ie bending the gantry and torsion of the gantry. Designs are rarely not stiff enough in the along the gantry direction. The proof is in the cutting and Chris will figure these out as he goes depending on his cutting requirements. Its an easy design to reinforce as he goes with metal or plywood. Peter



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    Default Re: My First CNC Build

    Agree the last thing you want is the Y axis bending through a lack shear stiffness. But even that can still be pseudo boxed by creating an LVL(Laminated Veneer Lumber) with holes. You can get 4 plys for the weight price of 3. That extra width is going to improve both sheer and torsional twist.

    .My First CNC Build-lvl-jpg

    Attached Thumbnails Attached Thumbnails My First CNC Build-lvl-jpg  
    If my post is missing the n't you might have to mentally add it yourself.


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    Default Re: My First CNC Build

    Hi BW - That's what I had in mind in #55. Nice you didn't have co-linear holes, Very good Peter



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    Default Re: My First CNC Build

    Quote Originally Posted by peteeng View Post
    Hi BW - That's what I had in mind in #55. Nice you didn't have co-linear holes, Very good Peter
    Where you are looking sheer as well as torsional in wood I would go that way. But where I am looking for predominantly torsional like the frame or deck I would go box.

    I learned a lot about frame building from the guy who told me how to build mine (I still did all the work), as well as some tips on how to stop frame twist into the bargain.

    If I was to re do mine I would use lighter wall steel but bigger box section for the main bed area, not that I have the slightest hint of twist, but once he explained how the larger box section gets its strength it made perfect sense.

    If my post is missing the n't you might have to mentally add it yourself.


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