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Thread: junkbox 18x7x7

  1. #1
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    Post junkbox 18x7x7

    Well finally sat down and came up with a plan for some combo linear slides / screws I had floating around.

    The long axis is a true ball screw but the smaller plates are acme with some sort of plastic nut (but with adjustable tension).
    Both are 0.2" per rev

    Also dug up a old Parker automation 081-6641 for my 4th axis

    For motors I have a set of 4 compumotor ZETA drives and 125oz-in 23 steppers (need to dig up 1 coupler for the 4th axis still)
    Also have a bunch of cable race track and position sensors left over from other projects.

    Trying to build this out of what I have on hand (spent way too much on Xmas).
    Other than a the 1.5x1.5 steel square tube, some 3/8" bar, and the 1.9" alu round tube all the materials are from my junk pile (treadmills are a great source for steel tube if your willing to grind some paint off). I also picked up a ER-20 collet chuck and a 650W brush-less RC motor and ESC (going to set it up on a PID controller) With my current set of collets I can go from 1/2" down to 1/32 if needed. (don't use most of them today on my other mill. But a set was almost the same price as just buying the 5 I use on a normal basis.)
    Bearings I am starting out with some 6004-2RS/C3 should be good up to 18,000RPM on grease and at $5 a pop worth the risk. If all goes together well I can upgrade to some 7s or 9s at a later date if needed.

    Sketchup color codes
    gray / blue is aluminum (note light gray area of the table is the working window)
    light olive is steel
    any white parts are NOT finished yet. (need for my ER-20 collet chuck to arrive so I can get the final dimensions)
    red holes are tapped
    "blue glass" is where the slides would be when fully extended in each direction. (Keeps me from putting support posts in the way)

    The "spindle torque block" is not going to be on the first version but I wanted to make sure all the holes are there in case it is needed. Due to the thin wall size of the aluminum tube after I mount the bearings I can only get 2-56 screws in there. Just afraid that if a bearing ceases the might get sheared off. In theory that will never happen but past experience tells me it's easier to add the holes now and build the block later if needed.

    Current plan is to weld up the frame as square as I can get it. I know things will warp some in the process. the 3/8 bars stock on all the mounting surfaces is to help with this. Once it is all welded up I am going to have my buddy mount it up on the Haas and skim cut those surfaces. Also will have him drill the 4 pin holes. That should get the slides flat and square to each other.

    Have not decided yet but may also add some cross braces to the rear tower to keep it from swaying when milling. (once I get the frame welded up I will have a better idea on how much it moves if at all) The base will get bolted down to a MDF / steel frame to give it some more support from flexing (also the drives and PC will be mounted inside)

    1st end goal is to route PCBs. Prices for small proto runs have been going up quite a bit lately so want something I can bang out one to test with before submitting the full order to a board house. Also want to do some general engraving on it in alu / brass.

    Feel free to leave comments / suggestions / ideas.

    Tomorrow going to start cutting the steel stock and milling the ends flat while I wait for the chuck to come in.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0010-jpg   junkbox 18x7x7-img_0012-jpg   junkbox 18x7x7-mill29dec10-jpg  
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  2. #2
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    Got a bunch of the steel tube cut and milled flat.

    If all goes well I should have all the steel tube cut tomorrow (unless we start partying early).

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-picture-001-jpg   junkbox 18x7x7-picture-002-jpg  


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    Well got all the steel cut other than the vertical tubes (need my collet to set that distance. Still not here yet...)

    Will start welding up the upper frame tomorrow.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0015-jpg   junkbox 18x7x7-img_0016-jpg  


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    Well got all the parts welded up other than the uprights (spindle is still not here today)

    Laid out the base and everything seems to fit / line up so far.

    Tomorrow I am going to head over to a buddies and see if I can get the aluminum plates cut down and machined.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0023-jpg   junkbox 18x7x7-img_0028-jpg   junkbox 18x7x7-img_0027-jpg  


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    Well for today's update I got the 1/2" aluminum plate cut down. Those with keen eyes will not a lot of extra holes in that plate... I found a new shop hazard today EXPLODING motor start / run capacitors. Sounded like a shotgun going off. Had I been standing 1 foot to the left I think I might have been in the ER. Guessing it was the start cap since the motor kept going even after the boom. (First reaction was duck and cover. Second was find the EPO) Was just drilling a 1/8" hole not overloading or anything else weird...

    Anyway after the excitement I swapped out motors but must have bumped something in my setup because the next set of holes I dropped in were off by about ~.12" GRRRRRR. So just decided to flip the plate 180 and start over.

    Also found out one of my dimensions on my slides was off by 1" for the upper mounting holes. (I know exactly what I did... Forgot to subtract 1" since I had to use a tape to get those hole spacings) So just moved the entire Y table over 1" and drilled and tapped a extra set of holes in the top rail of the X slide. (Plate was already cut down so SOL otherwise)

    And I recently bought one of those tap jigs (supposed to hold the tap strait to the surface the base rests one). Yea right just looking at it you can easily see how out of round it is.

    So just NOT my day today.

    Good news is I have the Y mounted on the X and it seems to be all square to each other

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0035-jpg   junkbox 18x7x7-img_0043-jpg   junkbox 18x7x7-img_0045-jpg   junkbox 18x7x7-img_0054-jpg  

    junkbox 18x7x7-img_0055-jpg  


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    No real progress today other than I got my motor in the mail and the Gcode for the table holes done (going to have my buddy run the plate on his CNC vs me screwing it up on my manual mill. Just too many holes...)

    Here are some photos of the motor and controller...
    Comments so far:
    Dam it's small
    Throttle input is touchy

    Tried it out and off a 12V battery I can get it to run from ~1750 to ~14000RPM and seems quite stable. Supposedly this is a 650W motor (0.9HP) not quite sure I believe that yet... Good news my spindle plans are WAY overkill so if this motor does not pan out my backup is belt drive off a rotozip or a router Controller is based off a ATMEL mega so there will be some hardware hacking in the future if the motor pans out.

    Still waiting on my collet chuck. Funny thing is it was ordered and shipped before the motor and both came from China. Hopefully this means it will show up soon.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0058-jpg   junkbox 18x7x7-img_0059-jpg   junkbox 18x7x7-img_0060-jpg   junkbox 18x7x7-img_0061-jpg  



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    Got some time on the Haas today and got my tooling plate all drilled and tapped. Still no collet chuck hopefully it will show up next week else I am going to have to try and find some tracking info.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0069-jpg   junkbox 18x7x7-img_0068-jpg   junkbox 18x7x7-img_0073-jpg   junkbox 18x7x7-img_0081-jpg  

    junkbox 18x7x7-img_0084-jpg   junkbox 18x7x7-img_0085-jpg  


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    Look what finally showed up in the mail
    Off to finish my Z height in sketchup then on to finishing the frame.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-img_0088-jpg  


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    Got my depth set and will pick up the last of my steel tomorrow. (hopefully they have the standard unplated 1.5" tube back in stock else going to have to do a lot of grinding to get the plating off.)


    Well all said and done I will have 5.6" max clearance between the Z support and the table. My rotary table is a little over 5" tall so that works out well for cutting gears.

    With the head all the way down I will have ~0.48" between the end of the collet and the top of the table. My 1/32" end mills min stick out is 0.35 so a slice of sacrificial plexy and that is about dead on.

    Running the head all the way up will give me 7.9" of cutter clearance (can't think of any reason I would ever need that much but that is the way it is.)

    Going to figure out my stock situation then start work on a base for this thing. May end up using 80/20 or steel just a matter of cost at this point.

    Attached Thumbnails Attached Thumbnails junkbox 18x7x7-mill_overview-jpg  


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    That's a nice looking build for something you called "junk".

    Are you going to add any triangulation within that large box column that makes up the rear of the machine? It may not flex much but if machining something hard (like aluminium) the column may act a bit like a tuning fork. Can your CAD program tell you what the resonant frequency of the uprights will be? It might be worth checking.



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    Currently running under a wait and see for the diagonal braces. I expect I will need to add something just not sure what or how yet. Soon as I get the upright built I can start playing with it and see how much flex I get out of it.

    Not fully sure what I am going to use on the software side yet. I am a few months away from needing that part yet.



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    Got the last 4 pieces of steel cut and trimmed. Welded up one half of the frame. Hopefully will get back to the other half yet this week but may not be till next weekend. Supposed to be really cold and snowing all week.

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    junkbox 18x7x7-img_0094-jpg   junkbox 18x7x7-img_0095-jpg  


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