TTC Kinematic Mount Design
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- เผยแพร่เมื่อ 30 ก.ย. 2024
- Part 1 video describing the design approach for a removable tool setter mount I built for my X7 borrowing from a Maxwell Criterion kinematic mounting scheme.
Part 2 video showing operation and repeatability testing to follow!
No affiliation, just great information: practicalpreci...
Love the design Chuck. I really like the recess to keep chips away. I knew my design wasn’t that great but we do what we can in the time that we’re given. I have machined a lot of things but I certainly am no design expert. But what you have done here is exactly why we do what we do. You took it to greatness. Great work!
Thanks Jesse. I'd probably still be chewing on the decision to pursue the cnc world at all if it weren't for your online academy to help make it accessible and I'd certainly still be chewing on this particular application if it weren't for your video, so thank you guys for the inspiration. It has changed my life. I'm not a design expert either - there's always room for improvement on anything (including this) but if you approach each situation with humility and a curious mind you never stop learning. At least that's what I try to do. It's hard to argue with the repeatability you were able to achieve with your design though!
Very nice!
Thanks Steve!
Hello, where can I get the modeling of the rotary table? I would appreciate it very much.
If you go over to the Syil Cnc Users facebook group it is located there in the files section. PTD125 model
Very cool, I too work with high precision optics and metrology and really scratched my head at Titans 4 v groove design. My biggest concern is the magnetic hold strength vs hardened ball bearings on unhardened base material. Magnets have to be strong enough to firmly hold it in place while not so strong that it makes the assembly snap together so hard as to plastically deform the mating faces with the balls.
Great comment. Your concern is well-placed because that's exactly the problem I am dealing with now due to what are now some pretty obvious oversights on my part.
Initially I selected magnets that were rated at 10 lbs of pull each. What I neglected to account for was that the hold down strength for each magnet nearly triples when you position them in between two steel plates, I guess due to how the field is influenced / focused. What I thought should have been 30 lbs of total preload force wound up being almost 75 lbs which made it an absolute bear to remove. It was also enough load to produce sufficient (enormous) contact stresses at the joint and it deformed the mating surface of the v-groove after repeated installations / removals due to the mismatch in material hardness (HRC60 ball bearings vs. HRC10 4140).
As a proof of concept it worked pretty well (at least initially) but to fix this I think I am going to machine the baseplate out to accept some hardened inserts with the V-grooves machined into them that I can press in place. This allows me to experiment with different materials or replace them as needed due to wear without having to replace the whole baseplate and/or get it heat treated after machining. Right now I'm leaning towards hardened A2 tool steel for the inserts - on paper it should be close in hardness to the ball bearing but if you have any other suggestions I'm happy to hear them. They make carbide v-groove inserts for this purpose but I can't seem to find any in the size I need.
I've also changed my magnet selection and machined the pockets for them deeper to cut the preload down to around 40 lbs which is very reasonable. I'm hoping between that and the material change the problem will be resolved. Also potted the magnets in epoxy to keep chips away from them.
I'll be talking through these things in the next video once I work through this solution. Thanks for the comment
@@cskovach i ran into that exact problem in some kinematic optics stages I designed a while ago. I first considered using a heat treated high carbon steel / tool steel but it would be an uber pain in the @$$ to grind all the complex faces in after heat treat. (I’m pretty sure my machinist team thought I was insane for suggesting that option lol). I ended up using pairs of heat treated pins that were either epoxied in or press fit in depending on the design. McMaster sells HRC60 dowels from 1/64” to 3/4” with tolerances as tight at +1 to +3 tenths. Regarding the magnetic strength, depending on the material permeability and the arrangement of the magnet poles you can really some interesting field intensities. Best recommendation to avoid those issues as best you can without breaking out ansys to sim the field is to make sure all magnets have the same polar orientation eg all have north side down. Also remember magnetic attractive force is proportional to 1/(r^2) so if you had a 0.025” gap last time, doubling the gap to 0.50” will reduce the force to 1/4 the previous value.
@@andrewh2341 I have a concept worked up and I think it will be simple enough to machine, but we'll see how it works out once I get there. Obviously grinding them in would be best practice but I'm going to try it and see what kind of repeatability I can get out of it from just hard milling them. I made a clearance slot pass straight through the part to allow me to hit the chamfered edges with some precision ground flatstones to try and get rid of any high spots. Repeatability testing will reveal if any subsequent processing is necessary.
Exact Engineering does pretty much exactly what you suggest with the dowels. It was an intentional choice of mine not to copy their design so I sought out other ways to obtain the same functional performance while trying to keep machining on the baseplate simpler. I have a 4th axis that I could use to do that but haven't had a whole lot of seat time on it yet.
Thanks for the info.
Chuck, awesome setup!
I appreciate the thought and time you invested into your setup.
I’m also looking to maximize my work holding on my x7 within the envelope. What did you use for your 96mm base plate? Can you post a link? Looking forward to your next video.
Hey Jeff, sorry for the delayed response. Been extremely busy lately. The baseplate is from SilverCnc which they now have listed on their website, at the time of my ordering they did not. SC96-S410 is the part number. www.silvercnc.com/product/multi-position-base-plate-and-pneumatic-plate/
@@cskovach thank you! I ended up going with a 5th axis base plate, two GMT 6” precision vises, SilverCNC ER40 collet, and 3 jaw chuck. I’m about to buy their 4th axis SC-C170, SOMP40 infrared probe, single zero point plate and self center vise … what are your thoughts on those?