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  1. #21
    Thank you very much! I will digest this information tomorrow...hopefully get let out of Jury Service early!

    Dave

  2. #22
    Quote Originally Posted by JAZZCNC View Post
    Yep 6 + 3.!!
    Doesn't matter if the recess or slot is wider than the carriages. What matters is the slot has a Machined reference edge which the Carriage Reference edge sits and registers too. Again look at the picture of the Gantry uprights (bits8) the long slot with 4 holes is for the Carriages and the top edge registers against the carriage Ref edge but the slot is 1mm wider than the carriages. Having the slot a tight fit would make no difference other than making it harder to fit.!!
    If I have read this correct, the top edge "registers" with the carriage (i.e. points it in the right direction?) but does not actually have a close/touch fit with the carriage?

    Another question regarding clearances... I am in the process of adding milled out sections in the end plates to locate the extrusions. Should I allow an additional margin (say 0.5mm??) for the extrusion? Or should I design an 80x80 slot with 4mm radius corners as per the extrusion?

    Thanks,

    Dave

  3. #23
    Little update... It doesnt look like much has changed but I've added a lot of minor details. Currently ALL aluminium plate is 20mm thick. Does anyone think this is overkill for the plate which attaches to the X axis carriages (on top of gantry) and the plate which attaches the motor mount to the Z axis?

    My useable bed dimension is now 343mm x 434mm. I think that's fairly reasonable for what I will be cutting.


    Click image for larger version. 

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    Dave

  4. #24
    JAZZCNC's Avatar
    Lives in wakefield, United Kingdom. Last Activity: 16 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 5,859. Received thanks 910 times, giving thanks to others 37 times.
    Quote Originally Posted by biketrialsdave View Post
    If I have read this correct, the top edge "registers" with the carriage (i.e. points it in the right direction?) but does not actually have a close/touch fit with the carriage?
    Yes the top edge sits directly on the carriages, the edge acts has the register. If you have them already look at the carriages and at least one edge will be machined, this the the reference edge.
    The rails will also have a Machined Ref edge, exactly the same applies with the rails regards Referencing against an edge thou in your case using profile you will only be able to do this if you machine the profile or have a separate plate machined which bolts to the profile.

    Quote Originally Posted by biketrialsdave View Post
    Another question regarding clearances... I am in the process of adding milled out sections in the end plates to locate the extrusions. Should I allow an additional margin (say 0.5mm??) for the extrusion? Or should I design an 80x80 slot with 4mm radius corners as per the extrusion?
    The only sure way is to measure the profile your using then machine to light interference fit. Wouldn't suggest you have them machined without the profile first if your wanting close fit.
    Same goes for anything you want machined really, don't trust Cad or dimensional drawings where fit is important has there is always some slight difference waiting to bite you. Can't beat having the part in your hands and I won't machine anything were tight or close tolerance is important without parts in hand.

    Quote Originally Posted by biketrialsdave View Post
    Currently ALL aluminium plate is 20mm thick. Does anyone think this is overkill for the plate which attaches to the X axis carriages (on top of gantry) and the plate which attaches the motor mount to the Z axis?
    Nope it's perfect and will help reduce resonance. . . .Certainly wouldn't go below 15-16mm.

    Can I suggest you change the position of the BK/BF bearing blocks and put them on the outsides of the gantry and End plates, or at least the motor side bearing.?
    The way you have them on the inside will mean they are trapped between the gantry side and end plates which will make fitting very awkward and inflexible, will also mean they need to be done at the same time has bolting profile together.

    Put them on the outside at the motor end and you can insert the screw thru the ends/sides after building frame. Notice you have the motor mounts has closed blocks like this Click image for larger version. 

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ID:	7970 so just machine the inside to clear the bearing block and fitting will be much easier and very neat, The bearing will also be protected from crap inside the motor mount so that's another plus.!!

  5. #25
    Quick question, do end mills tend to come in 'standard' lengths? I am still struggling to calculate my Z axis height. I only have 90mm of travel to play with on the KR33 so it's fairly critical.

    On a side note, I have fairly drastically reduced the size of the plate which attaches the motor mount to the KR33. The idea being that the motor mount is almost exactly centralised on the two KR33 carriages to reduce canter-levering effects. Good idea?


    Dave

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  6. #26
    Bump

  7. #27
    JAZZCNC's Avatar
    Lives in wakefield, United Kingdom. Last Activity: 16 Hours Ago Forum Superstar, has done so much to help others, they deserve a medal. Has been a member for 5-6 years. Has a total post count of 5,859. Received thanks 910 times, giving thanks to others 37 times.
    BUMP BUMP.!!

    Thought I'd replyed to this question.?? Obviously not but did mean too.!


    Look more towards drills has they tend to be the longest things you'll put in the spindle.
    Endmills can be various lengths depending on flute length. Common 6mm typical standard endmill will have a flute length around 12-15mm and stick out around 18-20mm. Overall length roughly 55mm.

  8. #28
    Thanks JAZZ, I will do some calculations.

    There is one thing that has been bugging me for a long time regarding setting up material to be cut. Here goes!....

    1. Lets say I have placed an aluminium billet roughly in the centre of my bed and I want to cut a simple motor mount out of it. Lets assume that the billet is slightly bigger than the size of the motor mount. How do I align the router up so that the flute is in the right place to start cutting?! I assume that if the billet is larger than the part then you would manually put it in the corner somewhere?

    2. Now here comes the real question. Lets assume I have finished milling one side of the mount and I need to turn it over and mill the other side. How do I ensure that the mount is in exactly the same place once flipped?! Or would you put it in a new position and somewhere align the cutter in exactly the right place to start cutting?



    I hope I am not missing something obvious here! :)

    Cheers,

    Dave

  9. #29
    1. if the billet is oversize, just touch of roughly from the relevant sides. Touching of can be as simple as with the cutter spinning, just jogging up until the cutter marks the material, then hitting the relevant zero button (or entering size if not working of zero)

    2. Depends on tools at hand, and how many you'll be doing.
    For any more than a few, you really need to make up some kind of jig capable of accurate mounting.
    However for one offs, you really need some kind of additional tool. For cnc, a touch probe is the best suited, however there's nothing stopping you from using old manual techniques, such as edgefinders, dial gauges, bit of paper stuck on, and jogging up to where you need to be.

  10. #30
    Thank you, that confirms what I suspected!

    On a slightly different topic, where is a good place to buy a set of end mills? Just after standard metric sizes...if such a thing exists! It will also help me work out my Z axis height.

    Cheers,

    Dave

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