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  1. #41
    Member hanermo's Avatar
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    Default Re: New DIY build - design suggestions/ideas welcome

    I fully agree with Your list.
    My dual-column machine is a portal mill with a moving table.
    Spindle is ISO30 with auto toolchanger.


    The biggest benefit of a portal design with moving table is huge rigidity vs a C-frame like common VMCs.
    Both ends are anchored.
    So the free length is halved, vs a C-frame.
    This makes it, at a minimum, 8x more rigid.

    In practice, because it is a fixed-fixed system, it is about 10x more rigid.
    Preloading the frame, easy and cheap to do with tensioning bolts, makes it even more rigid.

    --
    Big machine.

    Table is 1600 mm wide, yes over 5 feet.
    Portal external size, or total width, is 2500 mm, a bit over 8 feet wide.
    About 1.6 m tall.


    Quote Originally Posted by wizard View Post
    If somebody is building a small machine I see a moving table design as a hands down winner. There are lots of reasons some of which might be debatable some not so much. I might add to your list the following possible advantages:
    1. More mass can be put into non moving parts of the machine thus damping vibration and possibly addit to rigidity.
    2. That mass can be added by filling tubeular steel with anything from lead to epoxy concrete.
    3. There are fewer electrical lines that need to move and flex. This can be huge in that it allows cost reductuion through elminated or downgraded parts. You only have one axis that needs its wiring running thorugh a drag chain or something similar.
    4. It is farily easy to enclose such machines. This can help greatly with chip control and coolant control.
    5. You end up able to acheive a higher degree of precision in machine alighment which can be huge for a small machine. You mention this in your response but i think people under estimate how much of a postibve this can be. You can literally achive milling machine like results given a good stiff gantry design. Certianly good enough to do prcision milling on aluminum and possibly other materials with lower speed spindles.
    6. The gantry. base and other parts of the mahcine not in motion can be braced in any manner you want leading to very stiff mechanical designs. This can lead to machine that are easy to move about and set up with minmal effort. If I wanted a portable machine, say somehtign ot take to a job site, a moving gantry machine would be high on the list of acceptalbe designs.
    7. The biggest problem with moving table designs is that some parts of the table might be unreachable which some will see as wasted space. Howver if you look at the very common knee mill, many bed mills and so forth you can see that this isn't uncommon in the mahcining world. The machinist just needs to be able to adapt to the hardware and use it to his advantage when creating fixturing and so forth.
    8. This probalby applies to small machines more gnerally but a small frame can be easily mounted in a milling machine of a size that is ocmmon in many shops around the country. This means that mouning pads for bearigns or the gantry can be machined to a high precision with relative ease. In other words it doesn't have to cost an arm and leg to get your frame machined in a machine shop. Obviously lhis applies to moving gantry machines also but you still have issues with keepign the gantry square in operation on a moving gantry design.
    9. From the human factors standpoint it is easier to keep track of what is going on at the cutter if the cutter is moving only on one axis.
    10. Less money spent on "plumbing". This is ismialr ot the issues of elexctrical wiring in drag chains. Most of your plumbing can be with permanent hard plumbing instead of hose that wears out. hoses are subject to the same failures in drag chains as electrical wiring so being albe to minimiz how much hose ahs to go through such flexing saves you money in the long run.
    11. Speaking of hose, your larger hoses such as vacuum hoses for dust collection, can be dropped from the ceiling down to the Z axis on the gantry. Since the gantry doesn't move and the Y axis stroke is mimimal the hose can be easily hung in such a way that the movements are easily handled even from a relativley low ceiling. In other words a moving table design mimimizes the horrors of handling the vacuum hose for chip collection. Many appaorches are viable that might not work well on a large moving table machine.




  2. #42
    Member mactec54's Avatar
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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by datac View Post
    Perhaps you misunderstood me. Sure, the gantry clearance is whatever you want to make it. In his design, TOOLING will infringe on that space.

    This is important for the OP to stop and think about because he is coming from his old machine, where he has always been able to fully retract his tooling from the gantry clearance, making that distance always 100% guaranteed. The new design will no longer allow that and very likely will already require an increase in his current clearance, unless of course, he changes his Z axis again to allow the lowest part of the z axis plate to rise higher than the gantry clearance by the dimension of his longest intended tooling.

    If the goal is to cut nothing but PC boards.... well, then this is a non-issue.

    A usable Z axis design must work hand in hand with available gantry clearance, or, the longest bit will quickly minimize the maximum height of an object that can be machined, and/or, the shortest bit will not even reach the table plane when in full down Z location.

    And, I use "tooling" loosely.... these days, one can venture into things far beyond cutting tools, from hot foil work, hot foam cutting, liquid dispensing, pick and place, stamping, metal punching/forming...... the list goes on. Design must target intention, but should also include at least a little headroom for other potential.

    Regards one method being Superior over the other ? I disagree...... EACH has its own advantages and disadvantages, and which to use really comes down to actual end goals, and also why OEM machines continue use each design rather effectively. That said, I have built far more machines with the moving rails than bearings, but take all things into consideration, especially that of "under tooling clearance".

    Yes I see what you mean, that could be a problem, I used it for 5 years and never had a clearance problem, if he leaves the Bearings where he has them in the currant drawing there would not be a problem, but if he moves the bearing down to the bottom of the housing as I suggested this could cause what you are saying, his tooling won't clear the bottom of the Z axes main Housing, that would depend on what type of work he is going to be doing in reference to gantry clearance

    I don't use either of these designs now, I have a new design where you get the best of both of these designs, plus with more rigidity

    The moving Rail is Superior because of the added rigidity you get, the only trade off is what you posted that you may not get enough tool clearance when all the way up

    Mactec54


  3. #43
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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by mactec54 View Post
    In theory and calculation's that is correct, let's see it in practice, on these small machines, and then stop once it reached the12mm move at 8000mm/min ( 315" /min ) with a stepper
    That's not just theoretical calculation, that is measurable and measured facts. What do you mean by that? After 12mm the axis reaches a speed of 8000mm/min and can keep that speed until it reaches the deceleration point, which is 12mm before the end of move. At constant velocity it can keep on moving until the turn it makes is too sharp for the speed.

    Quote Originally Posted by mactec54 View Post
    Servos are for any size machine

    The only difference is if you want to pay the extra for them, there is no disadvantage what so ever having a quality servo for a small machine, just lots of Pluses
    Yes and no. It is pretty pointless to pay for servos unless you have use for them. So it's not always about money. I have no problems spending more money but I have to see the point and see some REAL benefit I get for my money. The bragging value is pretty low for me and just to be able to say that "Look, I have a servo based system" no benefit to me at all.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


  4. #44
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    Default Re: New DIY build - design suggestions/ideas welcome

    Yes, and no.
    As you said at 12 mm travel you get to max speed in your example.

    If one is making traditional parts, blockish, with some corners, and some little chamfers, this will make relatively-little difference, in steel, if the top speed in cutting is limited for some reason like tool length, machine rigidity, power, etc.

    But..
    A servo system gets to the same top speed in approx 0.5 mm of travel.
    About 24 times faster.

    IF one is doing contouring in 2d, or 3d, or shapes of any kind, the moves are usually 0.01 mm - 0.1 mm.
    Very short moves, lots of them.
    The servo system will be == 20x faster, and leave better finishes.

    I used to use the "best" stepper drives, geckos 203V, at 68V DC.
    With the "best" hw pulse system at the time, a centipede (smoothstepper, pokeys, others).
    Driving a very good gantry, on linear rails (low friction, low stiction),

    A stepper based system takes about 1 sec to get to top speed, if I want high speed.
    (I don´t, so far, in 12 years. Top speed is irrelevant.)
    Because of the torque curve.
    At better settings, about 0.3 secs to top speed, around the 12 mm travel you mentioned (5-10 mm).
    But..
    my current system with same-size cheap nema 23 sized ac brushless servos, does the same speed in approx 5x less time.
    In about 1 mm of travel.
    And it could do so at 20x less time, if I wanted to, but I don´t, because it is too fast and wears things out.

    Examples:
    A best-system stepper setup took about 3 secs to drive the stepper to 12.000 rpm no load.
    0.5 secs "good" load, to 1000 rpm.
    Suitably inertia-matched.

    The servo goes to 3000 rpm in 20 ms.
    To 1000 rpm in 10 ms.
    0.1 secs "good" load, to 1000 rpm.
    Would do 0.05 secs, but this is bad for the mechanicals.

    The same-motor-sized servo system of *same or similar cost*,
    is 10x faster in the real world for work done, and
    5x more accurate in the real world.

    Running the roadrunner on my small-step size machines, goes about 5x faster with the servo systems.

    You spend about the same money, but get 500% better results, and 500% more accurate results.
    All my stuff is about accuracy, I have never cared about speed.

    I use about 1/3 top acceleration,and 1/3 top speed, in sw settings, to reduce risks and costs in errors.

    Example:
    A cheap nema 23 ac brushless servo system = 290 €, EU, taxes paid 22% VAT.
    400W, 60V, 5000 counts, 3000 rpm, motor, drive, industrial cables.
    I will sell one to anyone, if they need, as I buy them in boxes of 10.

    A gecko 203V + nema 23/34 motor will cost about the same, maybe 250€ with cables (with 22% VAT).

    The servo system will run 3000 rpm vs 800 rpm,
    at 2.3 Nm cont. torque at 3000 rpm vs .5 Nm at 800 rpm (stepper, typical), 5:1
    20 ms to 3000 rpm vs 100 ms to 2000 rpm, 5:1
    2/5000 accuracy in positioning vs 1/400 accuracy, 6:1

    Lathe runs 7.5 m/min or 7500 mm/min.
    But at 0.25 microns step size, or 4000 steps/mm.
    And a single step 1/10.000 x 1:2 belt drive has 10 Nm x 2 ==> 2000 kgf push force to make it position.
    Error readout on the servo drive led indicators is always 0.


    Quote Originally Posted by A_Camera View Post
    That's not just theoretical calculation, that is measurable and measured facts. What do you mean by that?
    After 12mm the axis reaches a speed of 8000mm/min and can keep that speed until it reaches the deceleration point, which is 12mm before the end of move. At constant velocity it can keep on moving until the turn it makes is too sharp for the speed.

    Yes and no. It is pretty pointless to pay for servos unless you have use for them. So it's not always about money. I have no problems spending more money but I have to see the point and see some REAL benefit I get for my money. The bragging value is pretty low for me and just to be able to say that "Look, I have a servo based system" no benefit to me at all.




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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by hanermo View Post
    Yes, and no.
    As you said at 12 mm travel you get to max speed in your example.

    If one is making traditional parts, blockish, with some corners, and some little chamfers, this will make relatively-little difference, in steel, if the top speed in cutting is limited for some reason like tool length, machine rigidity, power, etc.

    But..
    A servo system gets to the same top speed in approx 0.5 mm of travel.
    About 24 times faster.

    IF one is doing contouring in 2d, or 3d, or shapes of any kind, the moves are usually 0.01 mm - 0.1 mm.
    Very short moves, lots of them.
    The servo system will be == 20x faster, and leave better finishes.

    I used to use the "best" stepper drives, geckos 203V, at 68V DC.
    With the "best" hw pulse system at the time, a centipede (smoothstepper, pokeys, others).
    Driving a very good gantry, on linear rails (low friction, low stiction),

    A stepper based system takes about 1 sec to get to top speed, if I want high speed.
    (I don´t, so far, in 12 years. Top speed is irrelevant.)
    Because of the torque curve.
    At better settings, about 0.3 secs to top speed, around the 12 mm travel you mentioned (5-10 mm).
    But..
    my current system with same-size cheap nema 23 sized ac brushless servos, does the same speed in approx 5x less time.
    In about 1 mm of travel.
    And it could do so at 20x less time, if I wanted to, but I don´t, because it is too fast and wears things out.

    Examples:
    A best-system stepper setup took about 3 secs to drive the stepper to 12.000 rpm no load.
    0.5 secs "good" load, to 1000 rpm.
    Suitably inertia-matched.

    The servo goes to 3000 rpm in 20 ms.
    To 1000 rpm in 10 ms.
    0.1 secs "good" load, to 1000 rpm.
    Would do 0.05 secs, but this is bad for the mechanicals.

    The same-motor-sized servo system of *same or similar cost*,
    is 10x faster in the real world for work done, and
    5x more accurate in the real world.

    Running the roadrunner on my small-step size machines, goes about 5x faster with the servo systems.

    You spend about the same money, but get 500% better results, and 500% more accurate results.
    All my stuff is about accuracy, I have never cared about speed.

    I use about 1/3 top acceleration,and 1/3 top speed, in sw settings, to reduce risks and costs in errors.

    Example:
    A cheap nema 23 ac brushless servo system = 290 €, EU, taxes paid 22% VAT.
    400W, 60V, 5000 counts, 3000 rpm, motor, drive, industrial cables.
    I will sell one to anyone, if they need, as I buy them in boxes of 10.

    A gecko 203V + nema 23/34 motor will cost about the same, maybe 250€ with cables (with 22% VAT).

    The servo system will run 3000 rpm vs 800 rpm,
    at 2.3 Nm cont. torque at 3000 rpm vs .5 Nm at 800 rpm (stepper, typical), 5:1
    20 ms to 3000 rpm vs 100 ms to 2000 rpm, 5:1
    2/5000 accuracy in positioning vs 1/400 accuracy, 6:1

    Lathe runs 7.5 m/min or 7500 mm/min.
    But at 0.25 microns step size, or 4000 steps/mm.
    And a single step 1/10.000 x 1:2 belt drive has 10 Nm x 2 ==> 2000 kgf push force to make it position.
    Error readout on the servo drive led indicators is always 0.
    Perhaps you didn't read my previous posts so here is a short summary:

    I have nothing against servos, I know about their advantages but FOR ME not worth the trouble and FOR ME not worth spending the money on them. FOR ME AND MY NEEDS the steppers I have are good enough. I don't need to be convinced that there are benefits, but FOR ME AND MY NEEDS the benefits are not enough to motivate the spending.

    I hope that's clear now.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by A_Camera View Post
    Perhaps you didn't read my previous posts so here is a short summary:

    I have nothing against servos, I know about their advantages but FOR ME not worth the trouble and FOR ME not worth spending the money on them. FOR ME AND MY NEEDS the steppers I have are good enough. I don't need to be convinced that there are benefits, but FOR ME AND MY NEEDS the benefits are not enough to motivate the spending.

    I hope that's clear now.
    No one cares what your preference is, this is not about you, and your self righteousness, any new build no matter how small should always look at all the options

    Mactec54


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    Default Re: New DIY build - design suggestions/ideas welcome

    I'm currently using leadshine "easy servo" which is effectively just a stepper with an encoder.... but in practise they are much smoother and faster than the steppers I had before.

    I would actually consider servos at 290 a pop just as it's be something new to play with, but I already have the leadshines so for now it's not really necessary.

    Datac - Interesting point, thanks for bringing it up. I can't say I have ever needed to deal with particularly long tooling yet but that's definitely worth thinking about. I have shunted the carriages down 45mm (not quite to the bottom but closer to it), and raised the tram plate and spindle mount by 45mm. That gives me about 5mm clearance between the bottom of the Z-axis and the spindle chuck, and with the z axis fully retracted about 60mm tool clearance from the gantry bottom to the spindle chuck.

    That should be sufficient for my needs, it would allow a 100mm long tool to be retracted so that the bottom was 120mm from the bed surface.

    Mactec - any links to your z-axis design that you are talking about?



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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by mactec54 View Post
    No one cares what your preference is, this is not about you, and your self righteousness, any new build no matter how small should always look at all the options
    Of course people should look at all the options, evaluate and come to THEIR own conclusions, not yours... I am not trying to convince anyone, as opposed to you, and you are wrong, my preference is just as valid as yours.

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by zeeflyboy View Post

    That should be sufficient for my needs, it would allow a 100mm long tool to be retracted so that the bottom was 120mm from the bed surface.
    What about fixture? Is 20mm enough for that?

    https://www.youtube.com/c/AdaptingCamera/videos
    https://adapting-camera.blogspot.com


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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by zeeflyboy View Post
    I'm currently using leadshine "easy servo" which is effectively just a stepper with an encoder.... but in practise they are much smoother and faster than the steppers I had before.

    I would actually consider servos at 290 a pop just as it's be something new to play with, but I already have the leadshines so for now it's not really necessary.

    Datac - Interesting point, thanks for bringing it up. I can't say I have ever needed to deal with particularly long tooling yet but that's definitely worth thinking about. I have shunted the carriages down 45mm (not quite to the bottom but closer to it), and raised the tram plate and spindle mount by 45mm. That gives me about 5mm clearance between the bottom of the Z-axis and the spindle chuck, and with the z axis fully retracted about 60mm tool clearance from the gantry bottom to the spindle chuck.

    That should be sufficient for my needs, it would allow a 100mm long tool to be retracted so that the bottom was 120mm from the bed surface.

    Mactec - any links to your z-axis design that you are talking about?
    I'm not showing the new Design here yet, it would also be to hard for the hobby guy to make unless he was an expert machinist, a hint the Spindle become part of the Z axes, and the rails are no longer at 180 degrees to the moving axes, as most are now

    Mactec54


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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by zeeflyboy View Post
    Datac - Interesting point, thanks for bringing it up.
    No problem. Easier to deal with now than get a surprise. It stood out as a good point to make because I myself on my first machine, never thought I would be asked to do any deep work, and then when I needed to, I had to raise the gantry with blocks. Well, too, the fact that you had the other design on your first machine.

    One can build a moving rail axis that will pull the spindle and tooling up and clear of the gantry clearance, but it does generally require that the z axis plate itself ends up much thicker as the bearings they will slide thru must end up mounted substantially higher and no where near the bottom (top) of the clearance area. This also means that for screw driven Z axis machines, a much, much higher overall profile as well.

    I have a general use CNC Router at work with 2 feet of z axis travel. To keep 2 feet of axis from bending under pressure, you can imagine how "thick" that moving portion had to be made... But then you are forced into excessive distances away from the next set of rails carrying it, to which has to be managed with larger linear rail systems.

    Your machine looks good though... Keep at it and look long and hard before you commit.

    Chris L


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    Default Re: New DIY build - design suggestions/ideas welcome

    Cheers for the comments.

    So taking on board the comment the the thickness of the gantry could be a weak point in the design, I have been tweaking things a bit.

    Firstly, I've changed the profile up to 40x200mm as suggested. Secondly, since I was needing to make 20mm spacer blocks to give clearance to the ballscrew mount I figured I may as well make that 20mm part of the gantry structure instead and space the rails from behind... to that end I've designed a 20mm plate which will have the middle machined for motor mount and ball screw clearance, and will screw into the slots of the profile section. I've also bumped the rear plate up to 12mm... I doubt it will help too much but I've also bumped the horizontal trim pieces up to 4x120mm plate and will screw them into the profile top and bottom slot with countersunk screws and then top with a 1mm trim piece.


    So in total the gantry section is now 20mm steel rails, 20mm alu plate, 40mm heavy ITM profile, 12mm back plate.

    Should be rigid enough for the relatively short span of 550mm?




    I had a quote back for the motion components... it's only actually a couple hundred more dollars total to go for c3 ground vs c5 ground. Is it worth just ponying up a couple hundred bucks more to get the c3 grade?



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    Default Re: New DIY build - design suggestions/ideas welcome

    Quote Originally Posted by zeeflyboy View Post
    Cheers for the comments.

    So taking on board the comment the the thickness of the gantry could be a weak point in the design, I have been tweaking things a bit.

    Firstly, I've changed the profile up to 40x200mm as suggested. Secondly, since I was needing to make 20mm spacer blocks to give clearance to the ballscrew mount I figured I may as well make that 20mm part of the gantry structure instead and space the rails from behind... to that end I've designed a 20mm plate which will have the middle machined for motor mount and ball screw clearance, and will screw into the slots of the profile section. I've also bumped the rear plate up to 12mm... I doubt it will help too much but I've also bumped the horizontal trim pieces up to 4x120mm plate and will screw them into the profile top and bottom slot with countersunk screws and then top with a 1mm trim piece.


    So in total the gantry section is now 20mm steel rails, 20mm alu plate, 40mm heavy ITM profile, 12mm back plate.

    Should be rigid enough for the relatively short span of 550mm?




    I had a quote back for the motion components... it's only actually a couple hundred more dollars total to go for C3 ground vs C5 ground. Is it worth just ponying up a couple hundred bucks more to get the c3 grade?
    Most machining centers are only using C5 Ballscrews, if your machine was larger then if you wanted very precise measurements over a long distance, then use C3, my Bridgeport has C3 Ballscrews and can cut /hold parts within .0001"

    Even though you are doing a good job of your design a C5 would be good enough for your machine, if you want the C3 and the extra cost is not a problem, go for it, just make sure you have the Ballscrew support AC Bearings, with a good enough housing and mounting, as the benefits of a C3 or a C5 Ballscrew could be lost as to how it is mounted

    Mactec54


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    Default Re: New DIY build - design suggestions/ideas welcome

    Yeah it's all quoted with proper angular contact FK12 setup mounted directly to MBA12-C mounts, so should be good on the mounting front.

    I had planned to go with c5 ground, but basically for the linear motion stuff the quote I've had is only just under $200 more if I go for c3... seems daft to spend that much and not just go the little extra for c3 really. I know my machine isn't particularly large at 395x750mm travel, but I do like precision!



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    Default Re: New DIY build - design suggestions/ideas welcome

    So just to keep up to date, here's a few bits of progress...

    First of all I re-designed the bed section around using Misumi Milled profile and thorlabs angle brackets... For the main Y-axis extrusions I used 100x50 GFS high rigidity (6.7kg/m) and the
    cross braces are using 50x50 HFS. The milled extrusion provides a better mounting surface for the rails and helps improve the precision of the build overall.

    I've also taken the opportunity to change to a HGR25 rail and HGR25HA carriages on the Y-axis since there is more space now.





    Bottom screw nut mounting plate will probably become a single piece once I have a machine large enough to make it.






    Gantry fore/aft tramming adjustment (both sides)... undecided whether to go this way or just rely on shimming for this bit. Thoughts on that?





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    Default Re: New DIY build - design suggestions/ideas welcome

    So I've just got my hands on the extrusions...





    Packaging looked okay but alas they weren't quite as well protected as one might hope - upon inspection one of the large extrusions has clearly suffered a drop on one corner.




    Cleaned up with a file and it shouldn't have any impact on the final result.




    To do a quick and easy check of comparative length I placed the extrusions on a piece of alucast plate and put them side by side. Given that a fingertip can detect features in the 10 micron range through dynamic touch (i.e. dragging your finger across a feature) this is actually a surprisingly accurate method of determining if there is any difference in length.






    The good news is that they seem to be completely flush and more-over standing them side by side you can't even see a hint of daylight between the two, so they must be nice and straight as well.

    Did the same for the smaller cross-extrusions where it's arguably much more important that they are of consistent length and the initial check seems good too. As these are shorter than the main extrusions they should be within my ability to measure using the CNC machine and a touch probe, so should be able to get some more scientific results!




    Interesting to see the difference between the milled sides and the un-molested sides - you can see the gaps between the non-milled edges where they aren't flush (the edge that runs horizontal left-right in the pic)




    Quick layout to see the size:




    Next month's budget will go on some alu plate and some thorlabs precision corner brackets (well, and a big bbq for a new built in project I'm doing in the garden!) , and then the build of the y-axis can properly begin, hopefully with the motion components arriving some time next month too. Apart from the unfortunate corner ding, I'm very impressed with the quality. They are some seriously chunky and solid feeling hunks of alu too which is reassuring.

    - - - Updated - - -

    So as promised, something more scientific....

    I used my touch probe to measure the length of the cross braces. Fairly impressive cutting tolerance really I suppose, the nominal length was 344mm and the longest was 344.34mm while the shortest was 344.28mm so they are within 0.06mm of each other. Would have been even more impressed if they were all 0.3mm shorter layful:








    So my options are to use some shim material to make them all up to an effective 344.34mm or I can try to nip them all down to 344mm on the CNC... Shimming is probably the least risk route.

    - - - Updated - - -

    Got home today to find FedEx had left me a nice treat:




    My linear motion stuff arrived, and initial inspections it all arrived intact. HG25 rails and carriages could probably be used for seal clubbing if one were so inclined... didn't realise quite how beasty those are.

    Quality of the TBI ballscrews looks to be fantastic - finish is excellent, as is the end machining and they are as straight as an arrow with absolutely no discernible slop or play on the ballnut. I intend to do some tests with the glass scales just to see what that tells me but from a visual inspection stand point they seem top-dolla!

    some linear motion porn (NSFW?)













    Had a bit of an order snafu with Thorlabs - got an order receipt and they reserved funds on my bank account but the order didn't get processed. I have spoken to them and re-ordered so those should be arriving shortly. Other than that I'm just waiting on an order from motedis for various extrusion related fixings and then I should have most of what I need for the bottom frame build.

    - - - Updated - - -

    Did a little machining today... found some nice little extrusion connectors at motedis which will work nicely at pulling the two side extrusions together:




    There is a rather pricey drill bit and jig that you can buy to put the hole in the extrusion at the right spot, but I figured it was just as easy and much cheaper to use the CNC instead. I just 3D printed some little work alignment jigs so that I didn't have to re-zero between each setup:

    setting up:




    Milling using a fairly long 8mm bit to a depth of 36mm






    Fits nicely:






    Oh and Thorlabs brackets arrived last week - I've just gone for the front ones at the moment given that they are certainly not cheap. Will wait to see whether I think the rear ones are a good idea or not.





  17. #57
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    Default Re: New DIY build - design suggestions/ideas welcome

    Nice. Watching with interest.

    Your CNC machine may be the error rather than the misumi cuts...

    25mm rails are overkill. Unlikely to hurt though.



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    Default Re: New DIY build - design suggestions/ideas welcome

    Do you mind sharing how much the alu profiles (with machining) cost?



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    Default Re: New DIY build - design suggestions/ideas welcome

    The error shouldn't be on the CNC, on a macro level it's been calibrated using 5 micron resolution glass scales so I'm confident that the .3mm extra length is real... as for the .06mm variation it was all measured along the same part of the screw so should be fairly reliable as a relative measurement, and the probe is completely repeatable to 0.01mm but granted, once down into the 10's of microns level it becomes less assured as to with whom the error lies.

    25mm rails are definitely overkill, but I had the space on that axis and they actually made my life a little bit easier regarding mounting so thought might as well.

    The total cost of those extrusions was £213.70 ($268), the HFSP8-5050 50x50 milled extrusion (so actually 50x49) was about £49 ($61) per meter and the larger GFSP8-10050 100x50 (actual 100x49) was just over £70 ($88) per meter.



  20. #60

    Default Re: New DIY build - design suggestions/ideas welcome

    Wow...can't wait to see the rest of the build!



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New DIY build - design suggestions/ideas welcome

New DIY build - design suggestions/ideas welcome