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  1. #37
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    My initial thoughts when I came up with this mid range machine thread, was to have a machine that was similar to the K2 CNC machine. In particular I liked that fact that it was all metal. I figured once I built that it would be the machine I would keep. I also figured I would use the homebuilt machine to cut the parts for the K2 clone. The 3925 machine is $3250, so that would be the price to beat!

    However, having said that, I realize that any design that is all metal, whether steel or aluminum, is going to be worth keeping.

    Izzle is doing a wonderful job with the angle iron design so far. I'm looking forward to seeing more.

    Mike...



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    i realy like the k2 machine
    has it has been mentioned that the hardware store design cnc should machine aluminium i think that this should be included in the choice of available machining options

    guess the hard part would be the machining on the non alloy parts used for the runners
    although i think that if the machining on non alloy parts is drilling (and maybe tapping ) then it could be posible to supply gcode that could mark out thease parts

    may be worth looking at a place like http://www.metalsontheweb.co.uk/ for the metal , ok so thats a uk site but i suspect there will be simalar sites in the us and elseware

    problem in cutting aluminium on a MDF design is coolant
    well not so much of a problem but it would creep into the mdf making it soggy

    unfortuanatly i can see there beeing 2 designs here , one machined from aluminium like the k2 and another from angle iron

    personaly i would be doing more aluminium work on it than MDF etc so it makes sence to have metal framed design than a MDF one as i dont want to find i got a pile of mushy mdf once the coolant has been soaked up by it

    Dave



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    Any more progress on your design Carl?

    Mike...



  4. #40
    Registered anoel's Avatar
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    I still contend that a Midrange design should have the following requirements...

    Rigidity
    Durability
    Speed
    Work envelope.


    In that order of priority.

    MDF ain't going to cut it for rigidity... so it's got to be a metal frame.
    Unsupported rails is not going to work for rigidity, gotta be supported rails with real bearings of some type. Delrin or UHMW bearings won't work unless it's an IGUS solution, where the composite is encased in a metal housing to retard deformation and where the "Stick - Slip" factor is minimal.

    Durability... Again MDF ain't going to cut it again, gotta be metal to handle messy material and coolant.

    Speed, I'd think that 80 - 150 ipm is a good target for rapids.

    Work envelope is subjective... I think a 2'x3'x5" is a great all around size for most applications and is bigger than the average knee mill. And will keep the cost to a minimum for the metal framing. I have a one car garage as my shop and much bigger and it gets very big very quick. Perhaps a modified version or two can be done to accomodate different envelope needs.

    Nathan


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    Mike, I've been grinding away on the design, I'll post some pics in a day or so when I'm ready for criticism. -Carl



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    Anoel,

    I agree with most of your requirements but I do think a few may not work. 1st we are, at the moment, planning on skate bearings or another ebay bearing, maybe bigger. The speed you mention 80-150 ipm, I am no expert on steppers but I really don't know if these numbers can be reached with any torque left in the motor to do the cutting. Servos would have no problem with the numbers but the cost would put us into the high end design. Now to the size. As the old saying goes "It's easy to take some off but it's hard to put it back on." This definately applies to CNC as well. If we design this machine to be a 3'x4' work area it is simple to downsize to any size you want, with no loss in rigidity. Now concerning rigidity I fully agree no MDF here. We can go steel, aluminum, 80/20 or whatever the group decides. At the moment I am liking Carls rail design. It should be a vast improvment over other, more expensive, designs I have seen on so called mid range machines.

    So I hope no one is offended but no MDF in this thread please. Lets also try to come up with some new and inovative ideas that can cut cost and improve quality!

    Thanks Jimmy



  7. #43
    Community Moderator ger21's Avatar
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    Quote Originally Posted by Jimmy Southern
    The speed you mention 80-150 ipm, I am no expert on steppers but I really don't know if these numbers can be reached with any torque left in the motor to do the cutting.
    Use 2-4 turns per inch screws (multiple start acme) and you should have no problem. Taus uses Nema23 steppers on his K2 and gets ~120 ipm. See post #84. http://www.cnczone.com/forums/showth...7&page=3&pp=40

    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)


  8. #44
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    3'x4' is managable... as well. I just want to make a point that "midrange" doesn't mean a "bigger" hardware store machine.

    Speed... I get reliable rapids of 60ipm on my current MDF machine with unsupported drill rod rails and a 1/2"-10 2 start lead screw... Acetal anti-backlash nuts and 120oz steppers... I'm sure that with 200oz steppers I could squeeze that up to 80ipm or more wth no trouble. My axis are not frictionless by any means either, they are much tighter than they should be but it works and I'm not screwing with it. I did a test axis that moved very freely and with the same steppers and lead screws I could get around 100ipm. So I don't think that the speed numers I posted are out of line at all. 80ipm for steppers and 150ipm for Servos... (I should have mentioned that though)

    I guess that my vision of "high" end machine is like that of a Techno-Isel or other manufactured machine with highspeed spindles and run 600ipm rapids and automatic tool changers.

    Nathan


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    Hey Guys,

    I could not remember seeing a stepper design exceed 80 ipm, so thanks for the clear up. I just want to avoid having too high of expectations and people loosing interest. I am really looking forward to seeing the design come together!

    Keep the Ideas coming!
    Jimmy



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    Community Moderator ger21's Avatar
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    I've heard of 300+ ipm rapids with 150oz motors and rack and pinion drive.

    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)


  11. #47
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    another long rant but,

    i tend to agree with most points
    speed of the machine though well ok 150 ipm well thats going to be determined by the steppers / servos used and the lead screws used
    think this is best left to builders choice , its posable to upgraded to bigger steppers and different lead screws but as the builder may not have funds i think the best option is to provide a standard stepper mounting ,
    theres nothing stopping it having a stepper mounting drilled to accept a couple of sizes of steppers , and well the lead screw , well again that should be builders chioce, the mountings for it tend to be the same for 2mm per turn as for 10mm per turn (for metric ones )

    and yes no MDF , if the main use is going to be woodworking then the bed from ply or mdf maybe (it should be made easy to replace )

    i also like the idea of carl's rails , but i can see a problem that may be troublesome
    that tends to put me off
    if the rails are made from aluminium they are going to wear fast , also aluminium in that configuration is going to deform quickly where most working pressure is applied causing kinks in the rails
    making them from steel well the running surface is going to be prone to rust that will make the surface uneven after a year or so
    and unfortunatly stainless steel is not readily avalable in angle section
    i don't fancy having to strip down the machine and sand down the rails every 12 months or keep having to replace them because they wear, should do the job right and with the right materials so this machine should last a long time

    maybe using flat 1/2" by 1 1/2" section stainless steel or whatever size is best suited bolted to the frame for the x&y axis and another method for the z , bar or square section may be better in the long term for wear and environmental reasons
    grease is only going to get squashed out of the way by the bearings , and add to the friction

    skate bearings well ok there readily available and cheep ( but dose not mean there any good )
    we could look for a bearing that is as widely available and used in a comman everyday item like a bike or car (of the right size that is ) if skate bearings don't look like there going to do the job

    Dave



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    Quote Originally Posted by achiestdragon
    another long rant but,

    i also like the idea of carl's rails , but i can see a problem that may be troublesome
    that tends to put me off
    if the rails are made from aluminium they are going to wear fast , also aluminium in that configuration is going to deform quickly where most working pressure is applied causing kinks in the rails
    making them from steel well the running surface is going to be prone to rust that will make the surface uneven after a year or so
    and unfortunatly stainless steel is not readily avalable in angle section
    i don't fancy having to strip down the machine and sand down the rails every 12 months or keep having to replace them because they wear, should do the job right and with the right materials so this machine should last a long time

    maybe using flat 1/2" by 1 1/2" section stainless steel or whatever size is best suited bolted to the frame for the x&y axis and another method for the z , bar or square section may be better in the long term for wear and environmental reasons
    grease is only going to get squashed out of the way by the bearings , and add to the friction

    skate bearings well ok there readily available and cheep ( but dose not mean there any good )
    we could look for a bearing that is as widely available and used in a comman everyday item like a bike or car (of the right size that is ) if skate bearings don't look like there going to do the job

    Dave
    Using aluminum for the rails would be unacceptable, for the exact reasons that you say. In fact that thought never occured to me, I have been planning on using angle iron. As for the rust, It might be a problem, but it should be negligible, perhaps by keeping the tracks oiled? I'll post some pics tonight. -Carl



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