Jake's 4x8 CNC Build


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    Default Jake's 4x8 CNC Build

    Greeting from the Olde North State, and welcome to my first CNC router build. This will be an all steel welded table with a 5hp ATC spindle (hopefully), Clearpath's or servos, linear rails, and rack and pinions . The plan right now is to have the gantry and frame machined at a shop (TBD). This will be a machine for cutting out cabinet parts primarily. I have been learning Fusion 360 for the design, and decided to start with the Z-axis and build out from there. I'm planning to buy the motion parts from Automation Overstock, but I am open to suggestions for everything. I'm looking for good value readily available components that could be upgraded later if possible.

    Some details on the Z:
    BLH 20mm guides
    20mm x 500mm rolled ballscrew (5mm start)
    245mm of travel
    Z is 200mm wide
    Gantry beam 6" x 10" x 3/8"

    Questions:
    Is a 20mm ballscrew enough to handle 100 lbs. ? (spindle, plate,rails,srcew)
    Micro switches vs proximity switches? Proximity switches seem to be problematic.



    Jake's 4x8 CNC Build-z-axis-jpg

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    Community Moderator ger21's Avatar
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    Default Re: Jake's 4x8 CNC Build

    Yes, a 20mm screw is plenty.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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


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    Default Re: Jake's 4x8 CNC Build

    Thanks Gerry. I was planning on a 5mm pitch screw, but I read an old post where you recommended 10mm or 20mm. Will I be able to lift the Z with spindle with a 10mm pitch ball-screw? On the same note, I'm designing right now around using NEMA 34 motors and was wondering if I will be able to find drives powerful enough in that frame size?

    When I tried to mount the z to the gantry beam I realized it was getting pretty narrow. I redesigned it using 10" wide 1/2" thick plate. I am planning to use the same plate for the gantry beam and weld up my own rectangle tube. Seems like that is what Onsrud has moved to.

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    Community Moderator ger21's Avatar
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    Default Re: Jake's 4x8 CNC Build

    A lot of people use 5mm pitch screws on the Z axis.

    It just depends on the performance you're looking for.
    10mm should work too. There are formulas to determine how much torque you need to lift a given amount of weight at a given acceleration.

    If you're worried, stay with the 5mm.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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


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    Default Re: Jake's 4x8 CNC Build

    Ripped the band aid off yesterday and ordered all the steel for the base and gantry. My design has changed once again and I'm going with an open base. Space is at a premium for all of us and the thought of all that dead space underneath bothered me. Pretty much 3/8" thick everywhere except the gantry, it will be 1/2". The table under the spoil board will be 1/4". Howard Steel is going to shear all the leg plates for me and break down the 20 footers into manageable lengths. I have been on the Oriental Motor website trying to use their motor sizing guides and it seems like I will have enough room in the legs to drive the gantry. I'm still not sure what travel speed I should shoot for with a DIY machine. 1500 ipm? I saw some of the professional machines are 2000 standard. Anyways, everything should be ready for pick up on Tuesday and I still have a lot of details to fill in before I start welding.

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    Default Re: Jake's 4x8 CNC Build

    Hi Jake - I don't think the stiffness of your Z axis plate matches the capability of the machine, especially when its down. The rest looks very good. It needs to be quite a bit thicker. Look up the Maximus thread I spend a lot of time looking at the Z axis stiffness in that. Do you have someone to machine the gantry after you weld it? It will change shape quite a bit with those long welds.

    If you send me the step model of the columns, bearings (or zip it and publish here) , gantry and z axis I'll run it in an FE program to see how stiff it is. Put it in the max down position, with Z in the midway gantry position....Do you want to cut aluminium ? Peter

    Last edited by peteeng; 05-15-2019 at 08:25 PM.


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    Default Re: Jake's 4x8 CNC Build

    Are you planning on direct driving the pinions? You really want to use gearboxes.

    With a 5HP spindle, your cutting speed will probably be limited to 500ipm or so. And acceleration is more important than top speed. 1500IPM would be useless, if it takes a while to get there.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

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

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


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    Activation process peteeng's Avatar
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    Default Re: Jake's 4x8 CNC Build

    Hi Jake - Can I ask where did you get the dimensions for the drivescrew components? Nut, nut housing, coupling and support bearings? been digging around trying to find them, no luck yet. Peter



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    Default Re: Jake's 4x8 CNC Build

    Quote Originally Posted by ger21 View Post
    Are you planning on direct driving the pinions? You really want to use gearboxes.

    With a 5HP spindle, your cutting speed will probably be limited to 500ipm or so. And acceleration is more important than top speed. 1500IPM would be useless, if it takes a while to get there.
    I am open to ANY motor option at this point. Geared or direct, I just want to make sure I leave enough space for them. The gantry is weighing in at close to 800lbs. On the IPM, I got those numbers from Onsrud. How do they (or anyone) calculate that speed? In one direction or two, three? With the bit in the material?

    Quote Originally Posted by peteeng View Post
    Hi Jake - I don't think the stiffness of your Z axis plate matches the capability of the machine, especially when its down. The rest looks very good. It needs to be quite a bit thicker. Look up the Maximus thread I spend a lot of time looking at the Z axis stiffness in that. Do you have someone to machine the gantry after you weld it? It will change shape quite a bit with those long welds.

    If you send me the step model of the columns, bearings (or zip it and publish here) , gantry and z axis I'll run it in an FE program to see how stiff it is. Put it in the max down position, with Z in the midway gantry position....Do you want to cut aluminium ? Peter
    I too think that plate is too long and thin. The Z design has been pretty frustrating for me. If you look at the first picture in this tread I had the rails on the Z "sled" for stiffness. I changed this to blocks on the Z sled in some sort of attempt in faster management. I was trying to avoid using flange style carriages to keep rails as far apart as possible. At a minimum I plan to add side and maybe middle stiffeners to the Z sled. Steel comes in 20 foot lengths and the plan is to use the leftover drops from the gantry (10" x 1/2") for the Z plate and gantry legs (top and bottom).

    This will machine will cut plywood and melamine only. I have found a machine shop 45 minutes away with a big bridge mill but I have not been able to find anyone to do the street relief as of now. I will download the .stp file and send it your way. Thanks!


    Quote Originally Posted by peteeng View Post
    Hi Jake - Can I ask where did you get the dimensions for the drivescrew components? Nut, nut housing, coupling and support bearings? been digging around trying to find them, no luck yet. Peter
    On a side note, how do I upload pictures that will display as a thumbnail until clicked? Just trying to keep things tidy.

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    Default Re: Jake's 4x8 CNC Build

    Hi...i really like your design, looking forward to see this develop



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    Default Re: Jake's 4x8 CNC Build

    This is a very interesting design and looks like a lot of thought has gone into it.

    The one thing that bothers me a bit is that you apparently intend to use 3 rails on the gantry beam with one mounted 90° out from the other two. This can be an assembly issue as you now have two planes to contend with. Having the gantry machined in a good machine shop will help. However I’d seriously consider simplification, a larger beam for a two rail system with a wider distance between rails might be a better path. I’m sure you will get different opinions but I’d most certainly discuss this with the machine shop you I tend to have do the fabrication.



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    Default Re: Jake's 4x8 CNC Build

    Jake which Charlotte are we talking about here. There are shops in the Buffalo NY area that can stress relieve just about anything.


    Quote Originally Posted by JakeInCharlotte View Post
    I am open to ANY motor option at this point. Geared or direct, I just want to make sure I leave enough space for them. The gantry is weighing in at close to 800lbs. On the IPM, I got those numbers from Onsrud. How do they (or anyone) calculate that speed? In one direction or two, three? With the bit in the material?
    It is the linear speed of the cutter on the path it is following.


    I too think that plate is too long and thin. The Z design has been pretty frustrating for me. If you look at the first picture in this tread I had the rails on the Z "sled" for stiffness. I changed this to blocks on the Z sled in some sort of attempt in faster management. I was trying to avoid using flange style carriages to keep rails as far apart as possible. At a minimum I plan to add side and maybe middle stiffeners to the Z sled. Steel comes in 20 foot lengths and the plan is to use the leftover drops from the gantry (10" x 1/2") for the Z plate and gantry legs (top and bottom).
    Don’t make the Z any higher than required for the intended usage plus a bit of clearance for usability. If the goal is to machine sheet goods having 20” of S capability just leads to an expensive machine. Given that there is no perfect value for Z axis capability.
    This will machine will cut plywood and melamine only. I have found a machine shop 45 minutes away with a big bridge mill but I have not been able to find anyone to do the street relief as of now. I will download the .stp file and send it your way. Thanks!
    If plywood is the goal then excessive Z stroke isn't required. You do need to avoid too little also. By the way I’d also suggest keeping the linear motion bearings on the Y axis saddle. This way the rails are always supported as near to the working end of the tool as possible.


    On a side note, how do I upload pictures that will display as a thumbnail until clicked? Just trying to keep things tidy.




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