Thread: Smiler's Build

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  1. #1
    Thanks to Zapp and Kip for the information.

    I've machined the ballscrew as per KIps drawing and fitted the BK BF as Zapp's instruction and all is well. In fact all is so well that I went on a building binge last week and especially the weekend and almost finished the mechanicals. X,Y and Z axes are near as dammit complete so look out for some piccies soon. I say almost finished because Marchant-Dice still haven't delivered my Rack and Pinions after three weeks, they now say TNT lost them and they are having the manufacturer send them direct, I thought MD WERE the manufacturer! Only the second time I've dealt with them and never again. I only went with them because Zapp don't do rack (hint, hint).

    Anyway.....

    I had originally intended to buld the gantry from heavy PVC plate but I think I was heading down a dead end street. I couldn't see how I would get the stiffness I needed given the forces invloved. I therefore decided as I work in the local forge (as they call it here), I should make the base frame and gantry from steel box section. The gantry ends are still PVC as are the Y and Z tables and it has worked out better than I could have imagined. The marriage of the two materials has worked really well. The Z is driven by one of Zapp's ready made 16mm ballscrews and the Y by a 25mm ballscrew (machined by me, first time ever on a lathe YAY!!!). The X is driven by rack and pinion, both sides (if it ever gets here).

    Cutting area is 1250mm x 800mm x 120mm in the Z (I intend installing a 4th axis as soon as funds allow).

    I'll post some pictures later for your critical gaze....

    regards to all
    Nothing is foolproof......to a sufficiently talented fool!

  2. #2
    Hi everyone,

    Ok, here goes. This is what I've achieved in the last week of manic building. Originally it was going to be an all wood design as per the Solsylva plans but it was easy to substitute steel in its place which is handy since that is my area of expertise :)

    The base frame is not quite finished yet as I still need to add supports for the work surface. I'm thinking this should be removable so I can add a fourth axis which could then rotate odd shaped items (Queen Anne legs etc.) below the normal bed height.

    Any questions, criticisms, free beer, please feel free to send them my way.

    Please excuse the mess in my shop ;)


    By the way, Marchant Dice have let me down AGAIN, promised to email me with an explanation for why it's taken so long for the rack to appear but nothing in my inbox tonight. Looks like I'm going to have to get the CC company to get my money back.
    Last edited by Smiler; 28-12-2009 at 05:35 PM.
    Nothing is foolproof......to a sufficiently talented fool!

  3. #3
    HI Kip,

    The box sections are 50 x 50 x 3 steel box section, welded to 6mm thick endplates. The frame is bolted to the rigid PVC endplates. I can't detect any flex at all in that. My only concern is the rails (20mm) and the ballscrew(25mm) are in effect taking the torsional load but whether it will be a problem only time will tell. I've seen larger machines than mine where the rails are also the gantry frame (i.e. no box section )and they don't report problems with them.

    On reflection, maybe I should have gone for a supported rail like on my X axis but it was an impulse buy from EBay so I'm stuck. Still there is nothing to stop me adding supports and open bearings later or even flat rails and trucks mounted face on to the box section.

    Thanks for the input, any ideas for removing any flex?
    Nothing is foolproof......to a sufficiently talented fool!

  4. #4
    I also see a possible problem with the rails bowing slightly, and this will also put presure on the ball screw.
    May be a good idea to either use some profile rail along the top of the 50X50 box section, or upgrade the top rail to 25 or 30mm.
    Also how are you driving the gantry along X axis you mention rack, but are you looking at driving it from one side or both? if you are driving from one side, you may encounder some crabbing?
    Looks very good overall though.

    Quote Originally Posted by Smiler View Post
    HI Kip,

    The box sections are 50 x 50 x 3 steel box section, welded to 6mm thick endplates. The frame is bolted to the rigid PVC endplates. I can't detect any flex at all in that. My only concern is the rails (20mm) and the ballscrew(25mm) are in effect taking the torsional load but whether it will be a problem only time will tell. I've seen larger machines than mine where the rails are also the gantry frame (i.e. no box section )and they don't report problems with them.

    On reflection, maybe I should have gone for a supported rail like on my X axis but it was an impulse buy from EBay so I'm stuck. Still there is nothing to stop me adding supports and open bearings later or even flat rails and trucks mounted face on to the box section.

    Thanks for the input, any ideas for removing any flex?

  5. #5
    hi Zapp,

    Quote Originally Posted by zappautomation View Post
    I also see a possible problem with the rails bowing slightly, and this will also put presure on the ball screw.
    May be a good idea to either use some profile rail along the top of the 50X50 box section, or upgrade the top rail to 25 or 30mm.
    Also how are you driving the gantry along X axis you mention rack, but are you looking at driving it from one side or both? if you are driving from one side, you may encounder some crabbing?
    Looks very good overall though.
    I'm driving both sides of the gantry with rack and pinion from a stepper through a 3:1 reduction using pulleys and belt. The Solsylva plans were very specific about driving both sides and the problems you can encounter if you don't. Can't recommend the 4x2 plans enough, even if all you want is ideas for a machine.

    For the rails I'm thinking of using profiles as you suggested on the top at least as this will require the least modification. I'll do a bit of deep thinking on that one :)

    Just heard my Rack is on it's way (I have a tracking number!) so hopefully that's an end to that little episode.

    Thanks for the comments, they really do help.
    Nothing is foolproof......to a sufficiently talented fool!

  6. #6
    Hi everyone,

    Well, the Holy Rack of Marchant-Dice finally arrived and got fitted today so that is the mechanical side pretty much complete. I'll take pics tomorrow, and get them posted.

    Now, a question. I'm using a timing belt (15mm) to drive the X axis on the rack. Most belt systems I've seen use a small idler but I have just tensioned the belt by making the stepper mount adjustable. Should I put an idler in there? The only reason other than tension I can see for one is to wrap the belt around the pulleys more, is that the case?

    On to the limit switches next. I'm using some microswitches from DIY-CNC (roller type) but may upgrade to optical switches later on depending how they perform.

    Take care all and have a good weekend!
    Nothing is foolproof......to a sufficiently talented fool!

  7. #7
    Quote Originally Posted by Kip View Post
    If you're running high torque it may be worth the "spreading" of the load.....I haven't bothered :D
    Good enough for me, I'll leave it alone :D


    Ok, I have a question......

    What cable should I get to drive the steppers? I have bought some 8 core shielded from Zapp Automation but It is probably too small for driving the motors. Zapp have some 4 core on their site but that looks too big, more like mains cable. Anyone have a link to some 4 core to do the job?

    Also, the Stepper drivers are rated 4.2A peak, what size fuses should I use?

    As you can tell, electrics are not my strong point ;)
    Nothing is foolproof......to a sufficiently talented fool!

  8. #8
    The 4 core cable we have will be fine, i only supply one type of 4 core, so it can be used on all the motors we sell (All the way up to the FL86)
    The 8 core cable is signal cable and should not be used for the motor phases.
    If the cable is not man enough and burns and goes open circuit, it will damage the driver, and going larger than needed will not cause any problems.
    The fuse rating depends on the current setting of the driver, but if you use a fuse about one amp higher than the rated current that should be fine.
    Put this on the DC going to each driver.

    Quote Originally Posted by Smiler View Post
    Good enough for me, I'll leave it alone :D


    Ok, I have a question......

    What cable should I get to drive the steppers? I have bought some 8 core shielded from Zapp Automation but It is probably too small for driving the motors. Zapp have some 4 core on their site but that looks too big, more like mains cable. Anyone have a link to some 4 core to do the job?

    Also, the Stepper drivers are rated 4.2A peak, what size fuses should I use?

    As you can tell, electrics are not my strong point ;)

  9. #9
    Hi Gary,

    Thanks for that. I'll order some cable later in the week. The fuses I plan on using are car blade type, will they be ok do you think?

    Also,

    Lubricating the ballnuts, what should I use? I have some Lithium High Melting Point (costs a fortune) grease which I use on the tractor, would that be good enough or is there some specific grease I should use.
    Nothing is foolproof......to a sufficiently talented fool!

  10. #10
    Hi Everyone,

    Well, the mechanical part of the router is almost there. The router is now mounted and I've done a few sneaky test cuts which were very successfull considering I don't have proper mills yet, only router cutters.


    I still need to buy and fit my energy chain to keep the pesky cables under control as you can see. The yellow and white colied wires are my touch probe for setting X,Y and Z and for centre finding. Works really well.



    I got lucky with my choice of router. I was going to use one of my Triton routers but they are such an odd shape so I thought about dismantling my Makita 3612 which is in the same HP league as the Tritons (3 1/4). It turns out that the plunge slides are exactly 20mm diameter, the same as the precision rail I bought from Zapp and so all I needed to do was to fit two 20mm mounting blocks to my Z axis plate, fit two offcut 20mm rails into them and drop the router on. Tighten up the plunge locking screw and the router is solid, the whole thing works a treat. One massive bonus is that I can remove the router in ten seconds, and have it back on its plunge base in another ten minutes.

    I'll post more photos as and when I get my Energy chain.
    Nothing is foolproof......to a sufficiently talented fool!

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