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  1. #141
    Hi Zeeflyboy,

    You are building almost exactly what I am thinking of building. I was wondering if you had a working drawing and a material list. Great job!

    Thanks Dale

  2. #142
    Quote Originally Posted by Zeeflyboy View Post
    Cheers, though its a toy compared to some of the beasts on here (looking at you chaz!). Don't have any drawings, what are you after specifically?

    Rob - ta!

    I noticed today that I've had a bit of a design snafu. My motor mount model was mislabelled - the model is a mb10-c and what I have are mb12-c.

    Thankfully I caught it before I made the x or z parts, but it means my ball screws are 3mm too low at the motor end as the mb12-c is a little taller.

    So options are:

    - Buy 2x MB10-C (bad... about £60 each and it isn't great for consistency)

    - Re-machine a new front face plate with the ball screw bearings moved down by 3mm (I'll have to order more aluminium... not great but cheaper than two new motor mounts). Will also require a small design tweak to the ballnut mounts.

    - skim the motor mount plates down by 3mm. Downside is they were only 10mm to start with so would be getting a bit skinny.

    I'm leaning towards option 2. Really annoying - good lesson to verify all models are correctly labelled before using them! Could be worse, at least I caught it before it caused problems on all the axis.
    Feel for you, I almost made a similar mistake I just assumed all my Hiwin's were HGH carriages but some were HGL which are 4mm shorter. I almost missed it it's only because I put all my Hiwin's together that I noticed there was a height difference and so actually checked with a steel ruler and discovered the recovered Hiwin's were HGL.

    Really shows that measuring everything in the real world to make sure you cad models are correct and the right ones is just a good idea.

    Can you get tooling plate locally? Where I am there are a few suppliers doing tooling plate they are more expensive than aluminium warehouse but cheaper on small orders because there's no delivery charge.
    Last edited by Desertboy; 22-07-2017 at 07:52 AM.
    http://www.mycncuk.com/threads/10880...60cm-work-area My first CNC build WIP 120cm*80cm

    If you didn't buy it from China the company you bought it from did ;)

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  4. #143
    Not aware of any sadly, but never mind - can order some more stuff next week from alu warehouse.

    So given some doubts raised about the accuracy of the shoulder bolts as a way of aligning the mounting plates, I thought I had better check what I was getting. Given the gantry arms will sit on a saddle plate, these mounting plates do dictate the squareness of the Z to the Y axis, so the closer they are to perfect the easier time I will have making sure the gantry is squared up.

    I figured this was a good method of checking - in theory if the mounting plate is perfectly level then the reading on the indicator should stay at zero as the plate moves from front to back (indicator is metric, 0.000mm)







    Magically, this side was 0.000mm both at front and back, the middle showed -0.006mm which I would guess is due to non-straightness in my current machine's X-axis gantry meaning that there is a slight bow in the top of the plate, but 0.006mm is only slightly larger than the some bacterium is long so I'll forgive it that!

    Sadly, my joy at that stunning level of alignment was short lived - the other side showed one end about 0.072mm out between front and back. Not that bad over a 200mm or so span, but not really at the level of what I'm after.

    So two options - either I just skim down one of the shoulder bolts and surgically tap the mount into alignment, or I make life difficult for myself and add a shoulder for the carriages.

    I decided to try the shoulder method, since i can easily change back and forth between either method then depending on the results of my experiments. The only catch is that since my current machine isn't exactly perfectly accurate, I was largely relying on the flatness of the eco-cast plate to give the required alignment and tolerances... that means machining a pocket to then give the carriages a shoulder to rest on is not ideal as I've then lost the flatness of the plate and am back to relying on my machine's tolerances.

    I decided to try machining a slot, then making a counterpart to go in there which would provide an alignment rail whilst still having the carriage mount to the ground surface of the plate.

    This is the design:




    Doing it retrospectively, I would have machined the whole thing back side first, then flipped over for pocketing the heads of the screws... that would have ensured the absolute best possible alignment between slot and mount plate. Seeing as that option is no longer possible, I used some 6mm H7 dowel pins and pre drilled a pattern into the bed so that the plates are aligned as best as I can manage to the machine.






    Then machined the inserts:






    They fit very snugly, can't feel any play even without the screws in place.







    I then re-ran my indicator test, and while an improvement over the poorer side of 0.072mm, when compared to the perfect side it got significantly worse - it is approximately 0.020mm higher at the back than the front. It is fairly easy to knock it into shape to within around 0.004mm between front and back by loosening the bolts a touch and giving a little tap. I may try just using a little shim material to give a more precise fit. I think aiming for anything more precise than that really is just chasing my own tail since the first test showed the surface isn't flat to more than 0.006mm anyway.

  5. #144
    Quote Originally Posted by Desertboy View Post
    Really shows that measuring everything in the real world to make sure you cad models are correct and the right ones is just a good idea.
    Thats some realy good and important advice ^^.
    Always make sure the real world is up to spec and the reverse :p

    Made that error many times myself.

  6. #145
    Hi Zeeflyboy
    The check you doing at the top of post 143 doesn't guarantee that the side plates are parallel to the bed. They might be pointing up or down hill. As you are measuring at one point you won't see this.
    So repeat but this time keep the side plate fixed and slide the mag base instead. If that is also ~0 then the two parts are parallel.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  8. #146
    Indeed, it doesn't guarantee alignment to the bed, but to the rail/carriages... which are aligned separately to the bed. If the plate was at an angle to the rail/carriages the readings would change as it moves past - I can actually demonstrate that by inducing an angle.

    If measuring to the bed then yes, it needs another point of reference... but moving the indicator is enough to induce a small change just when it comes down into contact with a different part of the plate so that's not quite so easily done. I figure it's easiest for me to align the rails to the bed, then align the side mounts to the rails.
    Last edited by Zeeflyboy; 30-07-2017 at 01:48 PM.

  9. #147
    Quote Originally Posted by Zeeflyboy View Post
    Indeed, it doesn't guarantee alignment to the bed, but to the rail/carriages... which are aligned separately to the bed. If the plate was at an angle to the rail/carriages the readings would change as it moves past - I can actually demonstrate that by inducing an angle.

    If measuring to the bed then yes, it needs another point of reference... but moving the indicator is enough to induce a small change just when it comes down into contact with a different part of the plate so that's not quite so easily done. I figure it's easiest for me to align the rails to the bed, then align the side mounts to the rails.
    Understood -carry on !
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  11. #148
    Just interested in some thoughts of this slightly different approach to mounting the rails in reference to the eco-cast bed. One of the rails in particular has a very slight bend it seems (not unusual apparently from my research), and the method I used of clamping the carriage with a spacer isn't working quite as well as hoped due to what I assume is the steel rail bending down the 20mm bed surface rather than being pulled up during the clamping.

    I designed this little spacer which would be screwed into the extrusion and has some up/down movement on the screw slots and are slim enough to pass under the carriage. The idea would be to drill the extrusion to take 6 of these along the length of the Y-axis. they could be butted up against the bed plate and then screwed down into place, then the rail can be clamped against them while fastening. Basically ending up similar to having a machined lip for the rail to butt up against.



    The plan for making these would be to align them on the machine in such a way that the important dimension (height) would all be cut on the same part of the ballscrew to minimise any potential variation.



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  13. #149
    I'm waiting for some new end mills and some motivation to re-cut the front plate after my motor mount boo boo, but in the mean time I made a start on a low profile machine vice I designed. Haven't been very happy with the low profile vice I already have and want something much stronger and hopefully more accurate.

    This is the overall design, today I made the fixed end:



    Basically it uses a bolt pattern on the bed for alignment dowels and bolting down, but gives access right down to bed level (or below with a cut out I suppose!) which will be useful when trying to machine or drill taller pieces. I have since tweaked the design slightly to allow the travelling end to be bolted down as well if required for extra rigidity.

    Missed taking a photo of the first bits, but basically vertically it is made up of 2 pieces of plate as I don't have any tools long enough to cut the whole thing in one pass and it allows me a bit more flexibility in how it is made.

    After machining the two pieces and bolting them together, I popped them into the machine again and faced them down by 0.2mm on each of the main faces to give a nice flat and square face.






    And after a quick tickle with some 1500 grit wet and dry:






    Once I invest in some anodising equipment the plan will be to give this a nice black anodised finish... assuming the thing works as expected.
    Last edited by Zeeflyboy; 08-08-2017 at 10:00 PM.

  14. #150
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 2 Weeks Ago Has been a member for 9-10 years. Has a total post count of 1,600. Received thanks 110 times, giving thanks to others 69 times.
    Quote Originally Posted by Zeeflyboy View Post
    I'm waiting for some new end mills and some motivation to re-cut the front plate after my motor mount boo boo, but in the mean time I made a start on a low profile machine vice I designed. Haven't been very happy with the low profile vice I already have and want something much stronger and hopefully more accurate.

    This is the overall design, today I made the fixed end:



    Basically it uses a bolt pattern on the bed for alignment dowels and bolting down, but gives access right down to bed level (or below with a cut out I suppose!) which will be useful when trying to machine or drill taller pieces. I have since tweaked the design slightly to allow the travelling end to be bolted down as well if required for extra rigidity.

    Missed taking a photo of the first bits, but basically vertically it is made up of 2 pieces of plate as I don't have any tools long enough to cut the whole thing in one pass and it allows me a bit more flexibility in how it is made.

    After machining the two pieces and bolting them together, I popped them into the machine again and faced them down by 0.2mm on each of the main faces to give a nice flat and square face.






    And after a quick tickle with some 1500 grit wet and dry:






    Once I invest in some anodising equipment the plan will be to give this a nice black anodised finish... assuming the thing works as expected.
    Nice work as always.

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