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IndustryArena Forum > GENERAL MANUFACTURING PROCESSES > CHUCKING and MEASURING > 3D Probe - Tri-balls type accuracy & DIY
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  1. #21
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    To attach the balls, apply the solder past to the pads on the PCB, place the parts, then preheat the balls to just above the reflow temperature of the solder paste. Place the balls on the pads. They should melt the solder. Then put the whole thing in the oven and let the rest of the solder reflow.

    Heh heh heh...
    Now try doing that with case-hardened steel balls. Without disintegrating the PCB in the process.
    It is much easier if you can get some gold-plated steel balls - finding them and paying for them might be more difficult though.

    I used gold-plated rods in place of the 6 balls, and gold-plated ball-ends in place of the 3 rods, for some of my creations. But I happened to have such parts left over from other R&D work (not from my budget!).

    On the other hand, you could try the jewellery channels:
    https://www.ebay.com/itm/3Pair-Set-G...4AAOSwZQRYc9X3
    But a caution here: the gold 'plating' on all these jewellery bits is extremely thin and when you try to solder to it the gold 'plating' just melts off the steel surface. You would have to go for a mechanical connection, which can be a bit unreliable, or spot-weld to the shaft. They are stainless steel, not case-hardened, but with low forces they can work.

    Your next problem will be the stability of the PCB material. That is only medium. It can be subject to slow creep during use. Using a ceramic replacement material is more stable, but you have to find the ceramic and be able to machine it (and pay for it). Macor, which is a machinable glass, is a possibility here IF you have the budget. But it is really NOT cheap!

    Sad experience shows (me) that one spends more time realigning the probe tip (every time) than actually using it.On the other hand, one can make a Z-axis probe with micron resolution quite easily, and one can equally make a single axis single-direction sideways probe without too much hassle.

    Does all this mean I (and many others) have spent ages experimenting with making 3D probes? How did you guess? Fwiiw, I have 3 - 4 3D probes of various sizes and several Z probes and Z-touch plates on the shelf (and more bits too). They work, very well too, but they are also too much bother in practice.

    Cheers
    Roger

  2. #22
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    U need to have balls and contactor gold plated , for best acuracy , u can achive verry easy 2 um with golden components .

  3. #23

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Hey Roger. Appreciate all the advice, very cool of you. At the moment I am prototyping with pure copper which is sufficient, at this initial stage anyway. I'm yet to call it a permanent measuring tool but if I end up doing so (i.e. success/accuracy), I might just find my way to those plated gold balls you and @Andreiir recommended. Or I might just keep the copper balls and air-seal the probe tip with a silicon boot - undecided yet. Reasons for the copper selection is obviously ultra-fast switching and ease on the soldering process (they immediately stick to my low temp solder like super glue). The PCB mat I'm using is FR-4. Glass epoxy essentially, so I know for a fact I'll be okay on that part.

    Stick around with me mate, I'll document my findings of what I'm using so we can dial this tool and make use of it. I'm actually quite anxious to get that data...
    Attached Thumbnails Attached Thumbnails CopperBalls.jpg  

  4. #24

    Re: 3D Probe - Tri-balls type accuracy & DIY

    Copper will tarnish in no time and gold plating won't last long at all. If you spend a bit of time looking at how the established probes are constructed you may save yourself a lot of time and frustration. You'll also note that professional probes are sealed and filled with a special oil....

    You don't need to get the balls dead level. If you think about it, it's really not critical with 6 balls / 3 points of contact, which is why they went that way.

    If you manage to achieve 1um repeatability with this set up, be sure to write to Renishaw and let them know - it's taken them decades to get there. You can follow Cliff Hall's ITTP development story to get an idea what is involved getting to around 10um https://hallmarkdesign.co.nz/probe

  5. #25

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by Muzzer View Post
    If you manage to achieve 1um repeatability with this set up, be sure to write to Renishaw and let them know - it's taken them decades to get there.
    Hey, if I can point cloud scan those 9 parts I need-so-desperately this autumn within a huge max of 0.02mm, and for a super duper 25 bucks worth of material and 8-10hrs of machining/assembly work, I swear I'm out spending BIG on one of the finest champagne btl the very next day - and dance it all! Renishaw can join in the party to stare at their $5895 quote they sent me not long ago

    PS: will be hard to divorce me from my Haimer 3D sensor (got the digital one, 2.000mm)... as for what wcs/offsets and in-machine process goes anyway.

  6. #26
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by Mecanix View Post
    I was hoping you'd noticed the blink at the far end of my sentence

    Yea, I know about that TP6... received a quote 2 or 3 weeks ago from the local re-seller here and nearly had a heart-attack while falling off my chair. Still traumatized today... so so so much money for something so dumb that will eventually(most likely) smash in the side wall of your vise.

    Wait! we'll do the Tri-Compact model in the OD24.5mm with a 16bits 'something' not long after the one I'm prototyping now (I'm in the mood LOL)
    There is nothing wrong with being in the mood, a lot of amazing things can be made, I say go to it keep it flowing :cheers:

    Did you look on Ebay there you will find a TP6 starting at $325 with the probe, you can find some great deals for precision measuring instrument's if you have a need, .02 is a long way from 1um but a good starting point if that is all you need

    Tooling only gets smashed into something if you don't know what you are doing, I have some probes that have been used daily for 20 years and are still as good as the day they where manufactured
    Mactec54

  7. #27

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by mactec54 View Post
    There is nothing wrong with being in the mood, a lot of amazing things can be made, I say go to it keep it flowing :cheers:

    Did you look on Ebay there you will find a TP6 starting at $325 with the probe, you can find some great deals for precision measuring instrument's if you have a need, .02 is a long way from 1um but a good starting point if that is all you need

    Tooling only gets smashed into something if you don't know what you are doing, I have some probes that have been used daily for 20 years and are still as good as the day they where manufactured
    :cheers:

    Yea, .02 and we roll here! Just need to keep it real, it'd be an epic fail interfacing a 1~2um precision tool onto a machine doing 0.01mm (max) on a good day. I bet many gets realed-in those high cost deals none the less lol. (ps. good for cmm only really... not for a vmc).

    I feel ya, although experienced or not, hard to keep a straight mind under pressure... a 'displaced vise or stock' happens quick. Keep it up! Cheers to U2 mate

  8. #28
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by RCaffin View Post
    To attach the balls, apply the solder past to the pads on the PCB, place the parts, then preheat the balls to just above the reflow temperature of the solder paste. Place the balls on the pads. They should melt the solder. Then put the whole thing in the oven and let the rest of the solder reflow.

    Heh heh heh...
    Now try doing that with case-hardened steel balls. Without disintegrating the PCB in the process.
    It is much easier if you can get some gold-plated steel balls - finding them and paying for them might be more difficult though.

    I used gold-plated rods in place of the 6 balls, and gold-plated ball-ends in place of the 3 rods, for some of my creations. But I happened to have such parts left over from other R&D work (not from my budget!).

    On the other hand, you could try the jewellery channels:
    https://www.ebay.com/itm/3Pair-Set-G...4AAOSwZQRYc9X3
    But a caution here: the gold 'plating' on all these jewellery bits is extremely thin and when you try to solder to it the gold 'plating' just melts off the steel surface. You would have to go for a mechanical connection, which can be a bit unreliable, or spot-weld to the shaft. They are stainless steel, not case-hardened, but with low forces they can work.

    Your next problem will be the stability of the PCB material. That is only medium. It can be subject to slow creep during use. Using a ceramic replacement material is more stable, but you have to find the ceramic and be able to machine it (and pay for it). Macor, which is a machinable glass, is a possibility here IF you have the budget. But it is really NOT cheap!

    Sad experience shows (me) that one spends more time realigning the probe tip (every time) than actually using it.On the other hand, one can make a Z-axis probe with micron resolution quite easily, and one can equally make a single axis single-direction sideways probe without too much hassle.

    Does all this mean I (and many others) have spent ages experimenting with making 3D probes? How did you guess? Fwiiw, I have 3 - 4 3D probes of various sizes and several Z probes and Z-touch plates on the shelf (and more bits too). They work, very well too, but they are also too much bother in practice.

    Cheers
    Roger
    Hardened steel ball bearings soldered to the PCB using the procedure outlined. The solder is mostly tin. Tin will stick to steel. Lead not so much. No need to "disintegrate the PCB" by over heating it, choose your solder past carefully and make sure you have clean surfaces.



  9. #29

    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by mactec54 View Post
    Did you look on Ebay there you will find a TP6 starting at $325 with the probe, you can find some great deals for precision measuring instrument's if you have a need, .02 is a long way from 1um but a good starting point if that is all you need
    I got a Renishaw MP1S for £150 / $180 on ebay, removed the inductive coupling interface to reveal a 5 pin DIN connector and hard wired that to my controller - job done. You can buy replacement ruby styli for $30 or so - if you don't have a spare, I expect you can count on a breakage when it causes most inconvenience.

    No point kidding yourself you need or will attain microscopic repeatability if you are using a hobby machine. My machine is probably "only" good for (gasp) 10-20um accuracy on finished parts, so this probe exceeds its capability, which is the right way round.

  10. #30
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    I am suspicious you may get better results with a gold plated pcb than a hot-air solder leveled one (i.e, when ordering it, be sure to select the ENIG option, not the HASL one). My experience with HASL is that although it's fine for electrical connections to chips and whatnot; it's a bit uneven... and I'm suspicious that will translate into unevenness with the balls.

    On the other hand... I've never actually built one of these; so what do I know?

  11. #31
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Copper will tarnish in no time and gold plating won't last long at all.
    True about copper, although how much tarnish varies. But copper is soft and will deform over time.

    False about gold plating, unless you are talking about really really thin flashes of gold, when moisture can get underneath. That is very cheap and nasty 'jewellery'. Respectable gold plating ... find a small country church in Europe and look at the gold-plated stuff on the alter there. Several hundred years old. Or look at the gold-plated stuff in any high-catholic church in UK or USA. Ditto for age.

    Tin will stick to steel. Lead not so much.
    Interesting - I did not know that. Thank you very much!
    (Actually, I SHOULD have known that, because the tinkers of hundreds of years ago used to tin-plate their steel wares using quite mild heat. See how knowledge gets lost!)
    I suppose that means getting tin-plate (or gold plate) finish rather than solder reflow on the PCB too.



    Cheers
    Roger

  12. #32

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by __Britt View Post
    I am suspicious you may get better results with a gold plated pcb than a hot-air solder leveled one (i.e, when ordering it, be sure to select the ENIG option, not the HASL one). My experience with HASL is that although it's fine for electrical connections to chips and whatnot; it's a bit uneven... and I'm suspicious that will translate into unevenness with the balls.

    On the other hand... I've never actually built one of these; so what do I know?
    Thanks for the advice Britt. I've sent them the gerber 24 hrs ago, so tin it will be for this first round. In all honesty my hope is in that hole pattern accuracy, the tin will melt when I'll reflow and the balls will sit/settle on that FR-4 as opposed to the tin - that's the plan/idea anyway. To the best of my knowledge their drill router is belt driven therefore 'no backlash' and from previous experience their hole patterns have always been spot-on so those balls should line-up quite nicely (certainly well within or less than my 0.01 max req for sure).

    If all this goes well I'll have them do a final version of this PCB with enig. I'll report back when all starts to take shape!

    PS: I've never actually built one of these, also lol. That's why I'm taking baby steps and remaining on the low cost side for the initial prototype. All I'm after right now is data, i.e. sort of validating the data from that non-linear analysis I've ran prior. If this validates I'll go full speed on a final built, anodize the kit and go gold-gaga!

  13. #33

    Re: 3D Probe - Tri-balls type accuracy & DIY

    PCB platings such as ENIG, silver and nickel are only used to prevent tarnishing of the copper between PCB manufacture and PCBA soldering. Then they are soldered. The actual plating thickness is absolutely miniscule, so won't make the slightest difference to any of this. Gold plating for use as connector contacts is much thicker and thus obviously costs a lot more. Moreover, gold is seriously soft....

    You clearly haven't grasped the concept behind the 6 balls. They could all be randomly out by half a mm or so in X, Y or Z and the three legs would still sit on them consistently. So all this talk about getting the PCB flat and within 10um accuracy is barking up the wrong tree. Save your thoughts and energies for how to minimise flex and movement within the assembly. Getting rid of the PCB might be a good start.

    There's plenty of information out there telling you how these things are constructed - and good reasons why they are that way.

  14. #34

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    You are right, Muzzer. Regardless of how high/low those balls sits on, that assembly will find its way down to contact. The part you've missed, however, is how much (more) force is required to disengage a set when that assembly is uneven and 'binding'. Hence the paramount importance to get them as true as possible from the start, and the reason many have reported not getting the same accuracy between X & Y, for instance. Spotted this behavior when I've carried out both the linear and non-linear analysis (sims).

    The PCB remains as planed! It is a OD26mm PCB with a thickness of 1.6mm. Not sure if you are familiar with glass epoxy (fr4); at that size/ratio a great deal of force will be required to flex it i.e. the ceramic probe shank will snap way long before a flex from that PCB. I'm also bringing independence to each ball sets in a micro controller and therefore can compensate/offset switching timings via code (aka calibration). And hey... there is a fancy LED also LOL

    Off to the lathe this weekend (!!!), working on the CAM toolpaths as I type. Lucky me the weather forecast is pretty crappy this weekend so great time to get the home shop de-dusted!

    Final prototype assembly attached. PCB should arrive in 72hrs (more or less, perhaps, dunno lets see)
    (size: OD30mmX80mm (collet to probe tip), pretty small... wish me luck!)

  15. #35
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Muzzer - The point of ENIG in this context is to avoid the hot-air solder sprayed on the board; not because of the gold itself. FWIW, jlcpcb.com adds $16 to their base price of $2 for five each prototype boards.

    I do get the point of the 6 balls contact; but I get the intuitive feeling that it will work better if they are sitting flush right off the bat, so to speak. But - that's just my intuition; I could be just plain wrong about that!

    Anyway... as he's already sent the boards out for manufacturing; we'll all find out when they get back...

    Mecanix - probably obvious, but I'll mention it anyway... assuming that there's no components mounted there; for maximum stiffness, I would epoxy the entirety of the PCB's lower surface down to the lower housing with a high-stiffness glass or silica filled epoxy (and obviously, you'd want to keep the epoxy layer as thin as possible).

  16. #36

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Quote Originally Posted by __Britt View Post
    Mecanix - probably obvious, but I'll mention it anyway... assuming that there's no components mounted there; for maximum stiffness, I would epoxy the entirety of the PCB's lower surface down to the lower housing with a high-stiffness glass or silica filled epoxy (and obviously, you'd want to keep the epoxy layer as thin as possible).
    You smart Britt, I'd work with folks like yourself all day long man. Well spotted, and yes the plan was to have it part of the body for added rigidity. Nothing should move was also the feeling I was getting so I did planned a relief groove of little more than half the thickness of that pcb to ensure the 'spit' gets trapped in and not over-flow; solidifying the edge of the pcb to the body as a bonus. Let's see.

    Wasn't a huge fan of screwing this to the body (causing unwanted flexing).

    Good call man. Thanks!
    Attached Thumbnails Attached Thumbnails 3DProbe_V1.01__relief.jpg  

  17. #37
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Mecanix, i have been looking at your design. Very nice.
    I have a couple questions if you don't mind.
    Do you have a mechanism to keep the center hub from rotating off the balls? With the components on the top of the pcb, would anything be damaged of one were to rotate the hub to the point where the pins came to rest on the components instead of on the balls?
    Also, it looks like TP3 thru TP6 is for programming. Correct? Will you use the same connector as the Tormach probe?

  18. #38
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Hmm... just occurred to me... as you have a microcontroller in there... making it wireless wouldn’t be difficult. All you would have to do is add some IR LEDs, and have a few 38khz IR receiver modules mounted to the enclosure of your mill. Have the micro output a 38khz squarewave to the LEDs as long as the probe is not in contact, and then switch the signal off as soon as contact is detected (this way it’s fail-safe - if the connection gets interrupted the mill will stop, rather than plowing into your part and snapping the probe shank).

    I don’t know what kind of mill you have, but if you have an ATC, then the probe could have a tool number allocated for it and you could use it in regular programs, too. By putting a switch on the bottom of the body of the probe, it could turn on the microcontroller whenever it’s out of the tool carousel, so that the battery doesn’t go flat while it’s not in use.

  19. #39
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    Re: 3D Probe - Tri-balls type accuracy & DIY

    Hi Mechanix

    So far so good. It looks nice.
    But I am having trouble seeing how the 4 set screws at the top do the alignment. Details?

    I put the set screws on mine underneath so they tilted the PCB support, and the body stayed solidly attached to the collet shaft. I also put a fat soft O-ring at the exit hole at the bottom to provide some sealing and some cushioning. It also stopped the tripod from rotating loosely and becoming misaligned with the balls. Internal columns also served this purpose.

    Now, gold balls. Obviously you can buy them on the web. But for developmental purposes, you can also play around with, of all things, banana plugs! They have a good gold plating on them, although the base metal is usually just brass. Hard brass imhe. If you have a lathe, then the possibilities are (almost) endless, for very few pennies.
    And before you invest in special ceramics, you can have a lot of fun with some very hard plastics. They have the extra advantage, apart from ease of machining, in being insulating.
    Attachment 425930
    A typical eBay ad for gold-plated banana plugs: note the nicely rounded tips and the solid cylindrical shafts.

    Attachment 425932
    This shows banana plugs bits and hard acetal plastic for the base. The 'balls' being the ends of the gold-plated banana plugs, were press fits into the plastic. Not hugely stable, but very very cheap for experiments.

    Attachment 425936
    This shows banana plugs bits and internal alignment columns. The pairs of rods were held in place with E6000 adhesive. The single balls were press fits into the spider.

    Cheers
    Roger

  20. #40

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    Re: 3D Probe - Tri-balls type accuracy & DIY

    @Max - see *_ztravel.jpg attachment where I'm demonstrating how I was planning to solve this issue. Basically limiting the Z travel of the probe down to a hair-less-the-distance it takes for the a pole to disengage from the balls. The disadvantage of this system is, well, accidental over travel (e.g. drunk at the MPG?) and having that probe's shank shattering in pieces. I plan on using a commercially available renishaw 50mm tip so... let's hope this doesn't happen one too many time lol Those testpoint pads on the pcb are indeed the MOSI/MISO/SCK/RST programming interface for the MCU.

    @Britt - let's leave it as-is (simple) for the prototype. If this ends up to work as planned (and it should!), let's work out the final version one and I promise I'll bring your idea in the design for connectivity. Let's see how we can get around fitting a rechargeable 3.3v button cell/batt in the assembly, shouldn't be a problem. Again, brilliant idea from ya mate (thanks!)

    @RCaffin - I've put up a visual for you (*_adjustment.jpg) to understand how this adj works out. I haven't invented this but more or less copied the concept from my German-made Haimer. I bet there are several ways/mechanisms to adjust those, I've just settle on one that I am already familiar and comfortable with - having had to adjust my other probe more than +10 times during the last 5 years I had it. Could do it again eyes closed, works well! Connector-wise; and at this stage, I plan on running a OD3mm/3wires out of the probe to the bob. I still haven't given too much thoughts on a micro connector although thought about using that audio jack and a micro usb. Banana sounds better though

    By the way, thanks for the visuals (Roger, &all), looks as if you've gone that path more than once. Looks damn good man!

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