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Thread: Some advices for my CNC router build = Appreciating!

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    Default Re: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by ger21 View Post
    That dual beam gantry is not going to be very rigid. Try to make the extrusions bigger, and put a thick solid plate on the back of them, maybe 10mm thick?
    well , the backplate i just made a quick 2mm extruding of my first sketch and not decided the thickness yet . I really like the pattern of polygons , very pleasing my eyes for the moment ! I really like the twin beam that will house the motion components in between them . I could maybe use lower 80x80 beam and 40x80 on top to keep a solid squared gantry but my extrusion supplier really knows the behavior of the available profiles , got 4-5 different types of every dimensions . He was suggesting me a single 8080 beam.



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    Default Re: Some advices for my CNC router build = Appreciating!

    Those motors are the best choice for 5mm pitch ballscrews. 100lbs is not a problem

    Holding torque is the torque when the motors are NOT spinning. The faster they spin, the less torque they have.

    I am also still wondering if a 2.5kW ATC
    JGL-100/2.5R24
    spindle kit Jian-Ken (1900usd with water pump , VFD and shipment fees) would be very okay for my wood and Aluminum needs or a 4.2kW
    JGL-110/4.2R24
    kit from Jian-Ken (2115$ shipped, would be almost double power for only 10% price increase ) if it would be usefull or never need it at all ?
    If you don't know, then you probably don't need the bigger one.

    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: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by ger21 View Post
    Those motors are the best choice for 5mm pitch ballscrews. 100lbs is not a problem

    Holding torque is the torque when the motors are NOT spinning. The faster they spin, the less torque they have.



    If you don't know, then you probably don't need the bigger one.

    Allright , very nice , ordering the 465s 6A today !

    Allright ,so wont go too forward in the spindle kWatts and this review is really showing good points compared to the cheap chinese ones , especially the noise!! and probably a chinese cheapo telling 2.2kW is not giving it for real ...




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    Default Re: Some advices for my CNC router build = Appreciating!

    Now still wondering which type of gantry i would need ... high rails and short gantry plates or rails lower or even flat height with the surface .... , my aim is aluminum machining soooo , pros and cons of the different rails heights ? I also added a Z-axis CAD i found on GrabCad this is usefull!!

    Some advices for my CNC router build = Appreciating!-cnc-table-design2-jpg

    Attached Thumbnails Attached Thumbnails Some advices for my CNC router build = Appreciating!-cnc-table-design2-jpg  


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    Default Re: Some advices for my CNC router build = Appreciating!

    my aim is aluminum machining soooo
    You really need one BIG gantry beam. The bigger the better. Steel would be even better.

    What you have will flex easily with very light finger pressure at the collet.

    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: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by Letomoto View Post
    Now still wondering which type of gantry i would need ... high rails and short gantry plates or rails lower or even flat height with the surface .... , my aim is aluminum machining soooo
    Too some extent what you need depends upon what you mean by “aluminum machining” but I gave to ageee with ger21 the bee depicted here is flimsy. Beyond the mechanical issues you should also consider other needs Aluminum has. You will need good spindlecontrol and a form of coolant supply. Coolant and even aluminum swarf is messy town enclosed machine is nice.

    I strongly suggest reading the stickies as one of the threads there goes into beam design in depth. It might be over simplifying things but bigger in cross section is better. Of course detail is manner and the beam needs to be properly supported. The goal is to minimize deflection and twist which can be very high in long thin beams. Allied with this is having enough width to allow suitable separation of the ganytry saddle(Y axis saddle) so that they can handle the twisting forces from the Z axis. Again the wider the spread the better but you can’t be increasing beam size forever so you need to find the happy point.


    , pros and cons of the different rails heights ?
    For easy access, especially on larger machines with heavy parts, you will want a flush table top. This is a human factors thing to make loading the table easier. Even if you have mechanical help, with a job crane for example, you still want to avoid pinch points. In my opinion you have massively more options on a small machine handling light parts and I don’t see one design being spectacularly better than the other.

    This actually brings up a point, human factors are important in machine design and implementation. Any design that compromises the person working on the machine should be excluded. Even placing a ten pound object can be a problem if that puts a person in an unnatural position.
    I also added a Z-axis CAD i found on GrabCad this is usefull!!

    Some advices for my CNC router build = Appreciating!-cnc-table-design2-jpg
    I don’t like anything at all about that gantry beam design.

    You are free to do what you want but you also may want to consider the issues others have with light weight machines trying to machine aluminum. At a minimal you will want a machine that is 10 times stiffer than a machine that can do quality work in wood. There is even a recent example of somebody trying to use a flimsy wood router in aluminum.

    Depending on the alloy, the temper, phases of the moon and other unknowns, aluminum can actually be tricky to machine. Chip welding is a real problem that will break cutters real fast on a CNC machine. A good surface finish demands a stiff machine. In a nut shells well built machine frees you from another parameter that may be causing you trouble in Aluminum.

    In any event there is a common problem in DIY machines and that is a weak gantry beam assembly. The larger the span the greater this issue. There are lots of reasons for why this happens, budget is often the biggest factor. However not understanding the mechanical issues is also a big one. I tend to push towards a robust gantry especially if the builder has high expectations. Building a machine that is expected to process aluminum as it’s only work load puts you into the high expectation category.

    Yeah I know we can easily break a budget here. However a machine that doesn’t work as intended really blows the budget. In any event high expectations usually translates into high prices.



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    Default Re: Some advices for my CNC router build = Appreciating!

    That gantry beam is about as rigid as a soggy lettuce leaf.There is absolutely nothing to stop the weight of that humungous Z axis and huge spindle just pulling it several degrees out of line.We haven't even mentioned what the cutting forces are likely to do.A big steel box section with ends that are triangulated to well spaced sliders would have more of a chance and steel isn't that expensive compared to that brute of a spindle.



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    Default Re: Some advices for my CNC router build = Appreciating!

    Quote Originally Posted by ger21 View Post
    You've already made a big mistake by using 1605 screws. They require high rpm to get high speeds, which is difficult with steppers. And the larger the stepper, the slower they'll be. You'll probably get the best performance from 1605 screws with small Nema 34 motors, ~450oz-in, with a rating of ±6 amps.



    1605 will give you plenty of precision. Geared steppers are not a good choice, as they have a lot of backlash. Driving the screw with a belt is a much better option. IF anything, you want to gear it so you have less resolution, and more speed, by spinning the screw faster, and the motor slower.





    1) The purpose of a controller like this is to eliminate the need for the PC. Many people see this as a benefit, even though it is much more limiting Imo.
    2) No, it's a standalone control, no PC. If you need the features a PC provides, then there's no reason to use a control like this.

    3) Choice of control software is a matter of personal preference, and feature requirements. The only way to know which you prefer is to try them. Unfortunately, you can't try most without purchasing them.
    Mach3 can only use controllers specifically designed for Mach3. The ESS is one of the best for Mach3, and is by far the most popular.

    I'm not so sure I agree with this as an absolute. You can drive a 1605 with nema 23 440oz/in direct drive and get 2000 mm/m if you don't belt/gear reduce and rather direct drive them. This speed is going to put a heck of a load on your cutter and machine. The grain of sale i'd give the advice from ger21 here is that the motors and drivers may not be the weakest link in your machine. in my case i'm using DRV8825 drivers ( these are better suited for 3d printers) putting out about 2A (with cooling) and there is more than enough power to highlight the rigidity issues of my machine. I have drivers that will output more power but I can't really utilize them since my machine is running plenty fast for my skill level and making super fast rapids introduces many risks to your tools! I make enough mistakes that slower rapids are better for me. I broke a cutter the other day just taking a part out of the workholding!

    That said ger21 knows his stuff and I'm sure if you followed all of his advice you'd have a very capable machine!

    I am amazed at how well my machine works based on the many flaws it does have. It is better to have something that works and you can get some experiences with than seeking the perfect machine/design.

    my final .02 is that the frame is maybe the hardest part when building for a large cutting area. Flat is hard, square is hard, parallel is hard and it only gets harder as you make your parts bigger!



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    Default Re: Some advices for my CNC router build = Appreciating!

    Thanks guys for the opinions , it is my first build design . I thought my beam would not be super stiff but i do no have experience on builds like this , maybe would have been stiff enough so i wouldnt overkill it for nothing and costing more . I really appreciate your thoughts , it helps me following a direction!! I havent found many aluminum router builds on the web but the ones i found were pretty insanely nice and looked a bit overkill . Some i seen were wood working routers doing some aluminum milling tests but nobody shows up the differences of the surfaces finish in between the machines so it was hard to really know the direction of my build !

    So i will check out for my gantry beam design and make it stiffer .The gantry offsetting the beam to center the center mass over the linear bearings would work but not cancel the twisting in between the spindle and beam itself, i didnt thought about this yet .

    The beam lenght would be just 20" longer than the Y-axis , i am not really scared by this but will hunt for better stiffness , steel tube wouldnt be easily twistable so i will orient there. My doubt with steel was to have trouble welding anything and keep everything square and flat without bringing this to machine shops to shave/leveling straight

    What i am imaging in my head right now is that i could use 2 steel tubes like 1/8" thick , probably 1.5"x6" and lay them on eachother and weld them together and it would bring internal structure in all directions instead of an empty bigger tube who would also be more heavy. I have almost 20 square tubes 8 feet long of 2"x2" steel but they are about 80 pounds each and they feel flex a bit when the two ends supported and stepping in the center .

    Or maybe could use a heavy aluminum H beam and bolt it down on thick gantry plates with gussets 45deg to stabilise . Not sure of the price of this kind of beam but the ones ive seen in a distributor wharehouse looked pretty flat and straight.

    Thanks alot guys for your knowledge support , i am appreciating a lot !!!

    And ...........


    HAPPY NEW YEEAARRR!!!



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Some advices for my CNC router build = Appreciating!

Some advices for my CNC router build = Appreciating!