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    Default Need help with design and screw pitch

    Hey guys, last year I went to a guys house whose ad I found on Craigslist for cutting CNC parts. I had him cut some complicated shapes which I was happy about, but on my drive back I pulled over on the side of the highway and started researching. Yup, that day I won a gecko g540 on ebay! Talk about diving in.

    I have wood working experience but not metal, I hope to someday. 8020 was a natural choice for me. Or so I thought, for what I spent a reputable welding shop would have gladly done this and it would be stiffer.

    I think my big problem is that I didn't spend enough time researching really. haha tends to be my issue. I found a design I knew I could build to get my feet wet. Here is what I was going for:

    Need help with design and screw pitch-machine-png

    Here is where I am today, I'm finally playing with two axis. There is my question. What do I put into mach3 for the 1605 chinese screws for microsteps. I left mach 3 in mm. I can't seem to figure this out. I'm extremely proud of this mockup.

    I'm using gecko g540, mach3, wantai 200step motor, 1605 screws (which i think means diameter 16mm and the pitch is 5mm)



    I'm starting to realize the errors in my design where I will lose stiffness, but I think i will be able to use this machine to make itself stiffer.

    Honestly, any input is welcome!

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    Default Re: Need help with design and screw pitch

    Hi

    in mach3 you have to enter 400 for step



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    Quote Originally Posted by mattcnc123 View Post
    Hi

    in mach3 you have to enter 400 for step
    Thank you, I will try that and measure. Any inputs on design?



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    Default Re: Need help with design and screw pitch

    Your design is good for first machine



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    Default Re: Need help with design and screw pitch

    Quote Originally Posted by bgymr View Post
    Thank you, I will try that and measure. Any inputs on design?
    As Matt stated it isn't bad for your first machine! Using the current machine to build a stiffer machine is pretty common. When you get around to your X axis make sure you have a good spread on the linear bearings upon which the gantry supports ride.

    By the way, yes Extruded T-Slotted aluminum is expensive, especially when purchased new. This is why I tend to steer people away from it in preference for steel. There is often a machining requirement for steel structures but even that can be done economically in many locations.



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    Default Re: Need help with design and screw pitch

    Hmm 400 doesn't work either. I must be missing something. Am I correct that on the mach 3 screen, when I move my y axis from 10.000 to 11.000, I should measure 1cm movement on teh y axis?

    Thanks for the kind words guys. Yes, for the spread I just bought a starret 10 inch rod and I have 6" calipers. I plan on measuring exactly the distance between them, and then ordering 1530 profile (probably 3 of them) to put between the 3030. This will definetly stiffen the machine and give me further options to bolt down the spoil board.

    One question that I can think of now. The rails I have didnt fit my m6 screws. So I bored them out a bit to fit. But now the plastic pieces that go into the hole to keep debris out won't fit. I researched and read that some people use clay. Is that ok? Do I need anything in there?

    Thank you.



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    Default Re: Need help with design and screw pitch

    No, it should move 1mm from 10 to 11.

    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: Need help with design and screw pitch

    I've seen that suggestion of clay before and I'm not sure that it makes sense. Clay is finely ground rock or dirt with traces of metal oxides. I don't think I'd want that anywhere near my linear rails. Every time the carriage seal passed over them it could collect a few particles, and before long your lubrication is actually a lapping paste. High spots could also damage your bearing carriage end seals such that you lose lubrication faster. If you read literature about linear rails you'll soon find information about expected lifetime and lubrication. A reasonable estimate to take away from that is that an un-lubricated linear rail system has about 5% of the lifetime of a lubricated one.

    I'm not sure what plasticene is made from, but that might be a better option than real clay - it depends on whether it's softer than the bearings and rails. I'd still be concerned about the seals.

    Another option that might work - candle wax. Chemical compatibility with the lubrication is important and would need to be tested. It is easily shaped and smoothed and sets quickly, and you know that it's soft enough to not damage anything when it rubs.

    Whichever of these you might choose, cover the bolt head first with some fibrous material that is easy to remove - a small piece of balled denim or cotton that prevents the bolt head from being filled.

    I think that boring the rails was a choice that you should try to avoid in the future. Linear rails are precision ground extrusions and usually hardened for wear. The heat from drilling could generate stress in the rail that reduces that precision. I hope that you kept it flood cooled.

    Another choice could have been to make custom nuts for your 8020 drilled and tapped to the correct size (likely 4 or 5mm depending on rail size). You could start with a two hole nut and use the space between the two holes. I bet the drilling would be easier - the black oxide finish is likely the limit of their hardness.



    Sent from my SAMSUNG-SM-G900A using Tapatalk



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    Default Re: Need help with design and screw pitch

    Quote Originally Posted by bgymr View Post
    Hmm 400 doesn't work either. I must be missing something. Am I correct that on the mach 3 screen, when I move my y axis from 10.000 to 11.000, I should measure 1cm movement on teh y axis?
    That should be millimeters. In other words 1.000 mm.
    Thanks for the kind words guys. Yes, for the spread I just bought a starret 10 inch rod and I have 6" calipers. I plan on measuring exactly the distance between them, and then ordering 1530 profile (probably 3 of them) to put between the 3030. This will definetly stiffen the machine and give me further options to bolt down the spoil board.

    One question that I can think of now. The rails I have didnt fit my m6 screws. So I bored them out a bit to fit. But now the plastic pieces that go into the hole to keep debris out won't fit. I researched and read that some people use clay. Is that ok? Do I need anything in there?

    Thank you.
    No, don't use clay as others have said the results won't be what you are hoping for. Personally I'd look for a strong RTV type sealant .

    As a side note imagine yourself working for a lathe manufacture as a field engineer and getting sent on a service call to fix a machine. In this case the fix involves filling the heads of every socketed screw on the machine. The reason being the user is machining materials that are explosive and doesn't want the highly flammable material collecting anywhere. Is it a gravy job or does the work around something that might blow up give you second thoughts about field service.



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    Default Re: Need help with design and screw pitch

    Any suggestion on RTV? I have some for car gaskets, i could give it a try.

    I guess these machines have a lot of applications. I heard that a cake shop in my town uses a cnc machine to put the icing on. Go figure. I bet you wouldn't mind working on that one!



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    Default Re: Need help with design and screw pitch

    Well, last night was awesome. Finally got my machine to do something for me! i gotta say that the first time you see your machine do something with Gcode is probably something that will be remembered. I've spent a lot of time getting to this point, and can't wait to keep going. Below is the video. I have no idea what I'm doing with the software yet, and that will be fun to learn. I just wrote that in "easel" and imported into Mach3.





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    Default Re: Need help with design and screw pitch

    Quote Originally Posted by bgymr View Post
    Any suggestion on RTV? I have some for car gaskets, i could give it a try.

    I guess these machines have a lot of applications. I heard that a cake shop in my town uses a cnc machine to put the icing on. Go figure. I bet you wouldn't mind working on that one!
    Just about any bog standard RTV silicone should work in most environments. Make sure your holes are clean (degreased), and that your bolt heads are covered with a small wad of cloth to stop them plugging up. Removing old silicone is a thankless task.

    I'm trying out a non-drying plastilene "clay". Apparently it's made from vegetable matter, not rock, so any particles should be softer than the bearing surfaces and balls. I left it just below the plane of the rail surface so hopefully the wipers won't catch it.

    Sent from my SAMSUNG-SM-G900A using Tapatalk



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