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  1. #1
    Carries on from here

    http://www.mycncuk.com/forums/diy-cn...al-please.html


    Right here's version 3 with the Z axis moved up into position

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    Quote Originally Posted by silyavski View Post
    I assume your gantry will be 160mm high, that means for the 600mm travel you will use something like 1m of 160x12mm plate which weights 15kg. For example 1m 160x60x4mm steel profile weights 9 kg and would be stronger than your combined plate+aluminum profile.
    I said I might add the plate. Are you talking about steel box section ? if you are the problem is it doesn't enclose the ball screw like the C shape.
    Last edited by EddyCurrent; 13-09-2013 at 11:34 PM.

  2. #2
    Bearings till look too close together on Z axis.?

    I'd also re-think having the profile for gantry bearing plates it's just not flat enough or strong enough. Profiled linear bearings won't tolerate much error so these areas are important, the profile will bend and impart twist on the bearings making them bind. To give an idea of how little just the thickness of piece of paper can be the difference between binding and smooth running much more and easily locked up.!!
    Last edited by JAZZCNC; 13-09-2013 at 11:46 PM.

  3. #3
    Quote Originally Posted by JAZZCNC View Post
    Bearings till look too close together on Z axis.?
    Bearings now 150mm spacing, drawings show Z axis at extremes of travel.

    Click image for larger version. 

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    Quote Originally Posted by JAZZCNC View Post
    I'd also re-think having the profile for gantry bearing plates it's just not flat enough or strong enough. Profiled linear bearings won't tolerate much error so these areas are important, the profile will bend and impart twist on the bearings making them bind. To give an idea of how little just the thickness of piece of paper can be the difference between binding and smooth running much more and easily locked up.!!
    Gantry rails are not on a profile it is steel box section to be bolted onto a base so it can be shimmed level. I've also read all about the epoxy leveling idea.

    Listening to what silyavski is saying I've done an alternative for the Y rails, one pic shows the original position, the other shows the rail moved forward but is mounted over the inside vertical edge of the middle 80x40 extrusion instead of down the centre of it. I'm thinking the original is strongest.

    Click image for larger version. 

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    Questions
    1. I mentioned earlier that due to the standard ball nut I need 4mm shims under 15mm bearing carriages on Z axis so should I fit 20mm bearings instead without shims?
    2. Steel or aluminium for gantry ?
    3. Anything else to amend ?

    One I get the gantry finalised I can try to estimated the centre of gravity and get the X axis bearings better placed.
    Last edited by EddyCurrent; 14-09-2013 at 12:45 PM.

  4. #4
    Quote Originally Posted by EddyCurrent View Post
    Gantry rails are not on a profile it is steel box section to be bolted onto a base so it can be shimmed level. I've also read all about the epoxy leveling idea.
    Not talking about rails I'm talking about the profile you show the gantry sitting on, or should say sat on top of the X axis bearings.

    Regards the rail position on the profile.? You are showing or presuming the profile is flat and smooth across it's surface but most i've used have some recess down the centre or between slots so you may find they interfere with plans.
    Also if your using 15mm rail then you'll find the slots are wide with chamfered edges, this means the rail sits awkward and can cock when fastened down.

    Q1: First are you sure you only need 4mm shims.? When I make Z axis even with 20mm profiled rails I need to machine approx 6-7mm channel down centre of both plates to give clearance for nut and bearings.?

    Q2: Either.!!. . . . Steel is cheaper and strong but it resonates more so ideally needs filling . Profile is OK but not has strong and often not flat has folks realise and can make rail setup/alignment harder not easier like folks think.

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  6. #5
    Spot on, I think there's enough info here and in the other current build logs to embark so I'm going to start ordering some stuff. Rather than add to this in dribs & drabs I'll update at strategic points in the build.
    Hopefully I won't have to ask many more questions.

  7. #6
    On the other hand, went back to basics for a rethink, used spreadsheet and this set up should be very strong with not too much metal bashing.

    Gantry width 1000mm, 80x80x3 steel box section
    Gantry sides 120x80x5 steel box section with top open end plated.
    All other plate 20mm aluminium
    Rails mounted on front to remove need to have extra brackets if they were placed top and bottom.
    150mm travel on Z axis.
    Front could have thin slotted plate for chip protection or the whole front could have bellows fitted to cover rails as well.

    Rail are spaced at 170mm centres and Z carriages are same spacing vertically
    Y rails, not shown, mount directly under plate at bottom of gantry sides.
    Hole for Y ballscrew to exit at one end (not shown) may require double plating around it for strength.

    Any thoughts on this ? especially best way to engineer the various butt joints at end of each box section.

    Click image for larger version. 

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    Last edited by EddyCurrent; 15-09-2013 at 09:06 PM.

  8. #7
    Quote Originally Posted by EddyCurrent View Post
    I said I might add the plate. Are you talking about steel box section ? if you are the problem is it doesn't enclose the ball screw like the C shape.
    Yes, i get it. I was suggesting a steel box section profile and 2x 30x30 or similar aluminum profiles fixed on one face so you can imitate your first design. Best would be your design made from steel box.

    Looking at the design, what i see is that you try to make flat the z but at the same time the whole Z assembly seriously overhangs on the linear bearings. So making it same but from steel, you could fix the rails further in front up to the near end of the steel box, which you could not do with aluminum.

    I have redrawn million times this and until now i couldn't find a real way to diminish overhang without placing the ball screw behind the gantry. For a better understanding is better to draw the spindle mount brackets, the spindle itself and the bit. On the 3d warehouse there is 2.2kw spindle with mounts. So you will have better picture what you gain and at what price and compare actual bit position.

    -using flat wide rails 15 size on the Z will gain you 15mm versus 20 size square rails
    Last edited by Boyan Silyavski; 14-09-2013 at 12:19 AM.

  9. #8
    Quote Originally Posted by silyavski View Post
    Yes, i get it. I was suggesting a steel box section profile and 2x 30x30 or similar aluminum profiles fixed on one face so you can imitate your first design. Best would be your design made from steel box.

    Looking at the design, what i see is that you try to make flat the z but at the same time the whole Z assembly seriously overhangs on the linear bearings. So making it same but from steel, you could fix the rails further in front up to the near end of the steel box, which you could not do with aluminum.

    I have redrawn million times this and until now i couldn't find a real way to diminish overhang without placing the ball screw behind the gantry. For a better understanding is better to draw the spindle mount brackets, the spindle itself and the bit. On the 3d warehouse there is 2.2kw spindle with mounts. So you will have better picture what you gain and at what price and compare actual bit position.

    -using flat wide rails 15 size on the Z will gain you 15mm versus 20 size square rails
    I'll make a drawing to see what this is like, also estimate the weights. I've had a good play with the spreadsheet but it can't do the aluminium extrusion however there is another calculator for that.

  10. #9
    How many people build the control panel first ? Just got it finished today, I decided I would wire the spindle cable directly to the Inverter later on without going through a set of terminals.
    The door interlocked isolator is in a position I would not normally use but layout and segregation of components dictated the design.
    I'll also install a cooling fan at the bottom blowing air into the enclosure via a replaceable filter and an outlet at the top. It's better to blow air in, than suck it out, this maintains a positive pressure inside the enclosure keeping crap out, the only access point being through the filter.

    Click image for larger version. 

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    I came across these handy automotive fuse holders, ideal to individually supply and protect each stepper driver from your power supply. While sold as 12volt I decided they would be perfectly fine for the 60 volts I am using but you should decide yourself if you think about using them.

    2/4/6/8/10/12 WAY + HEAVY DUTY AUTO FUSE BOX/HOLDER 12V VOLT STANDARD BLADE | eBay
    Last edited by EddyCurrent; 12-11-2013 at 09:25 PM.

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  12. #10
    Quote Originally Posted by EddyCurrent View Post
    How many people build the control panel first ? Just got it finished today, I decided I would wire the spindle cable directly to the Inverter later on without going through a set of terminals.
    Wow eddy, that's a great looking control panel! I am especially interested as I am in the process of boxing up all of my hardware (currently all screwed to a bit of old mdf that has seen better days!).

    I would love to know a bit more:-

    • Quote Originally Posted by EddyCurrent View Post
      I decided I would wire the spindle cable directly to the Inverter later on without going through a set of terminals.
      Do you mean rather than going INVERTER -> Through the conduit -> DIN mounted terminal -> panel mounted connector, you will be skipping the conduit/DIN terminal and wire straight to the panel connector? Is this to reduce the chance of noise/interference?

    • Do you have any wiring diagrams you would care to share? I can identify some of the components in your pic and guess how some connect but a bit more detail would be great.

    • Where are you planning to mount the various connectors? I guess the bottom panel?
    • I see you have an EStop on the front but do you have any other provision for machine mounted estops/limit switches/home switches?
    • Are those grey jobbies at the bottom din mounted terminal blocks?

    • Can you recommend a supplier for the various parts (DIN rail, cable conduit etc)?

    Sorry for all the questions, just very interested!
    Thanks again for sharing the pics Eddy!

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