Opti BF46 Build

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    Default Opti BF46 Build

    I will be using this thread to document and discuss the CNC converion of an Optimum BF46 mill I just received. I think this may be the first such conversion in North America, since Optimum machines are pretty scarce over here. I started my research on RF45 class machines in February, and placed my order back in May. It was a long time coming, so you'd think I'd be ready for it...but you'd be wrong.

    It's currently on the floor in my shop, but now that summer is winding down, my efforts to renovate my work shop and get the mill converted should accelerate. Realistically, it will probably be at least Christmas before it makes it's first CNC move.


    So, here are my plans and specs.

    Mill: Optimum BF46tc w/ 40 taper. Came set up for ISO40, but I'm making a new drawbar and taking it to CAT40. That seems to be the most available spec for reasonable dollars in the US.

    Servos: DMM 750 W AC motors and drives on all three axes via 2:1 belt.

    Ball screws: Hiwin 25 mm dia with 5 mm lead (already in hand).

    Motion control: Kflop + Kanalog. Not sure whether I'll run KmotionCNC or Mach 3 yet, but I plan to play with both. I also plan to run dual loop control, provided the Sinpo DRO kit I just ordered has a way to get at the quadrature signal off the scales.

    I just ordered a pile of tooling and a Glacern 6" vice today, with hopes to make some chips as a manual mill pretty soon. Lastly, here are some pics of the machine.
    Opti BF46 Build-mill-overall-02-jpgOpti BF46 Build-mill-overall-04-jpgOpti BF46 Build-mill-overall-06-jpgOpti BF46 Build-spindle-1-jpgOpti BF46 Build-table-iso40-jacobs-taper-jpg

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    Default Re: Opti BF46 Build

    I received the DRO kit I bought off eBay yesterday, and unfortunately, all three scales arrived with broken glass. The plan is to get the mill running as a capable manual machine first, and then use it to make the bracketry for mounting the servos. Once that is done, I intend to splice into the quadrature signal off the scales and feed it to KFLOP to implement dual loop control.

    The seller says he will stand behind the kit and get me replacement scales. Until then, I'll withhold any names
    Opti BF46 Build-overall1-jpgOpti BF46 Build-be91475-2-jpgOpti BF46 Build-bd32852-1-jpgOpti BF46 Build-bd32852-3-jpg

    I've done a bit of steel machining with the mill sitting on 2x4s on the floor, as I don't have a stand built yet. The project was a shorter spindle drive dog, as the switch from ISO to CAT requires one shorter dog.
    Opti BF46 Build-img_20140926_191130_710-jpg

    And here's the temporary drawbar I cobbled together to get me by until the nice, heat treated part arrives from All Machine Parts. Yes, that's a 5/8" grade 8 bolt mated to the factory draw bar. I made 2" of 7/16" UNF thread engagement to join them, along with red loctite. So far, it's holding up well. If anything, I expect the threads will pull out of the factory side of the bar, as it only tested at 20 HRC when I checked it.
    Opti BF46 Build-img_20140926_083506_024-jpg


    -Steve



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    Default Re: Opti BF46 Build

    Where did you buy the mill from?

    I'll be watching with interest.

    Thanks
    Dan



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    Default Re: Opti BF46 Build

    Nice question the Travel in x and y is really how Long ? 400 mm x 200 ?


    Gesendet von iPad mit Tapatalk



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    Default Re: Opti BF46 Build

    Travel in X, Y and Z is claimed by Optimum to be 520 mm, 260 mm, and 541 mm. I have verified travels to 510 X, 252 Y and 500 Z. You can probably get to Optimum's advertised travels, but for X, you will need to move the table enough to expose 30-40 mm of dovetail, as well as adjust the mechanical table stops. To get advertised Y and Z, I think you would need to remove the Z way chip guard (it gets crushed at the limits of Y toward the column and the same with Z all the way down.

    I purchased the mill directly from the factory in China in a deal brokered by a person state side, in what was a sort of trial run. I'm waiting for a reply from that person to see if he is ready to have his info shared and start bringing more machines in. FYI, future exports will be private labeled, but still come from the same factory. Incidentally, that factory is owned and operated by an American.

    -Steve



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    Member Tkamsker's Avatar
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    Default Re: Opti BF46 Build

    Hmm that is wired
    i thought optimum is run by germans like Optimum Machines: About us

    i am doing now similar thing like you are but european built machine(s)
    thomas



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    Default Re: Opti BF46 Build

    I thought the same too, but it seems Optimum subcontracts some of their machines to other factories in China. Regardless, they still seem to maintain high quality. My machine came with a four page inspection report showing Optimum's acceptable limits as well as the actual measured values. Measured parameters include things such as spindle run-out, spindle perpendicularity in X-Z and Y-Z over travels, table flatness, t-slot squareness to the spindle in X-Y, just to name a few.

    -Steve



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    Default Re: Opti BF46 Build

    I was finally able to string together a few free hours and got my mill stand designed, and roughed out a model of the mill. The stand is complete overkill at 650 lbs, but I don't see a down side to a heavy, very stiff stand. The tubes are steel 3x3 0.25" wall, and the top is 1" plate. The two lateral stiffening plates are 1/4". Eventually I want to build an enclosure, and this stand should have plenty of places to attach that to.

    My intent is to fabricate the top level of the frame, and then fly cut the 1" plate to ensure flatness. Hopefully it doesn't pull at all when doing the rest of the welding.

    Attached Thumbnails Attached Thumbnails Opti BF46 Build-uploadfromtaptalk1412856134638-jpg  


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    Default Re: Opti BF46 Build

    More beautiful parts arrived today. Guess my work is cut out for me. Opti BF46 Build

    Attached Thumbnails Attached Thumbnails Opti BF46 Build-uploadfromtaptalk1413224936992-jpg  


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    Default Re: Opti BF46 Build

    It has been some time since I've updated my build thread, and progress has been slow. I was able to get the mill stand fabricated, and after all the welding, I put it on a big horizontal mill and face milled the top plate back flat. Between flame cutting the 1" thick plate and the welding, it pulled up 0.050" in the middle. Now it is back within 0.0015" in any direction across the plate, as measured with a long straight edge and feeler gauges.

    I leveled the stand in it's temporary location in my shop, and then put the mill on it. As expected, the 700 lb stand didn't move very much. On the edges of the top plate that stick out beyond the machine's base, I could not measure any increased deflection. I then re-leveled the machine and stand to the mill's table using a ridiculously sensitive machinist level I bought on eBay (0.02 mm/m graduations!!).

    Unfortunately, and not unexpectedly, the column is not as square as I'd like (or as square as the inspection report that came with the mill stated), so now I'm fiddling with shims under the base to get the column back to as close to perfectly square as I can. Just sitting free on the stand, the mill was about perfect in X-Z, but was out about 0.0007 inch per inch of Z in Y-Z. I'd like to see that closer to 1 tenth per inch of Z, but I'm not sure if that is realistic or not on this class of machine.

    Right now I got Y-Z down to 2 tenths per inch, but then X-Z gained some and is sitting at 3 tenths per inch. I should probably be satisfied with that, but I still feel the need to try to make it better. What does everyone else think? Am I trying for too much perfection?

    In any case, here are some pictures of what I've been working on.

    Opti BF46 Build-img_20141122_204142_718-1-jpg
    Opti BF46 Build-img_20141123_122119_406-1-jpg
    Opti BF46 Build-img_20141123_135145_000-1-jpg
    Opti BF46 Build-img_20141123_210525_735-1-jpg



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    Default Re: Opti BF46 Build

    Quote Originally Posted by Windscreen View Post
    I thought the same too, but it seems Optimum subcontracts some of their machines to other factories in China. Regardless, they still seem to maintain high quality. My machine came with a four page inspection report showing Optimum's acceptable limits as well as the actual measured values. Measured parameters include things such as spindle run-out, spindle perpendicularity in X-Z and Y-Z over travels, table flatness, t-slot squareness to the spindle in X-Y, just to name a few.

    -Steve
    I have a smaller Optimum and I have to say the build construction and tolerances are absolutely top class. I couldn't be happier with it and the machining results. I think a lot of the "made in China" stamp doesn't always mean what it used to in a lot of increasing cases.

    I spent ages investigating larger mills when buying and the only reason I didn't go a bigger Optimum as well, was because I wanted a larger knee mill.

    cheers, Ian

    It's a state of mind!


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    Default Re: Opti BF46 Build

    It's been almost 8 months since my last update, and unfortunately, I don't have much to report on the subject of the CNC conversion. About the only progress I made was to get my glass scales and DRO mounted, and source an inch sized, heat treated drawbar to convert to CAT 40 tooling. Instead, I put all my time and money into building a proper shop to house the machinery. It will probably be late October before I have time to get back to working on the CNC conversion.

    Until then, here are a couple pictures of the shop I built.Opti BF46 Build-imag0856-jpgOpti BF46 Build-imag0859-jpg



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    Default Re: Opti BF46 Build

    Time for another update.

    I have nearly all the mechanical design done for the servo and ball screw supports.



    Arriving at this bearing arrangement was a bit of a contrived process. I pulled one of the existing Optimum mounts off, which they tell you to re-use with their ball screw kit (which is all 25 mm, 5 mm pitch Hiwin screws; very happy with those). Their thrust bearing arrangement on X and Y is crappy at best - a pair of Chinese 6004 ball bearings with the outer rings separated by a spacer, and the inner ring preload simply set by squeezing them together with a jam nut arrangement (no positive stop). Yuck!

    I came across automation4less.com and decided to use their flanged ball screw supports. The thought process being they were real AC bearings, and using an axially piloted bore would make them easy to remove later on for inspection and re-greasing. They showed up with some Japanese brand bearing I'd never heard of, KYK, which I figured was better than some Chinese brand bearing I'd never heard of.

    After a bunch more forum reading, I convinced myself to further upgrade these supports by putting some side shield NTN 6204ZZ bearings on the floating end, and a pair of the much vaunted NSK TAC bearings on the fixed end (20TAC47CSUHPN7C). I think I found a pretty good deal on them for $57 ea on eBay. The outer rings are 1 mm wider than the bearings the supports came with, so I will need to surface grind ~2mm off the end cap's projecting boss to get the outer ring preload set back correctly.


    After all that, it would have made more sense to just modify the Optimum bearing housings, but I already own all the parts, so I'll solider on with the original (now modified) plan.

    For belts and pulleys, I'm going with a 5 mm pitch, 15 mm wide, Gates PowerGrip GT profile. 34 tooth on the servo, 68 tooth on the ball screw. The large diameter is to keep the running belt loads and installed tension reasonable, and to stay within the servo's max shaft load spec. DMM says 300 N max radial load for the 880-DST servos I'm using. My installed belt tension will be just about 150 N, which takes the servo radial load right up to 300 N, max, under any operating condition.

    Popular think on the Zone, right now, is to use CarbonGT belts, as they are very stiff and don't stretch much after break-in. I'm pretty sure Gates doesn't actually make a 5 mm CarbonGT belt. I found one catalog that showed part numbers for 5 mm carbon belts, however if you look up those part numbers on Gates PartView, the specs say Aramid fiber, not carbon, and calls them PolyChain GT. If you spec PolyChain GT in Gates design software, it says the minimum installed tension for a 15 mm wide is 174 N, which would have been well over my servo's design limit. So, I recommend to anyone considering the PolyChain to download Gate's Design iQ software, and check their system design before going down that path.


    The pulley diameter choice was also driven by the small side pulley diameter. I wanted to use tapered bushings to mount all pulleys to their shafts, and the servos have a rather large 19 mm shaft. 19 mm, plus room for the bushing, then the pulley over that limits your minimum diameter. Why not just use set screws and keys, you ask? As a mechanical engineer, I abhor using keys and/or set screws for power transmission; even more so in a system with precision control requirements. Leave the keys and set screws to lawn mowers!

    I ordered my pulleys from cmtco.com, as I really like their tapered bushing hub design. They are able to package their tapered hub inside the small 34 tooth pulley and still fit in a 19 mm bore. Also, they offered pulley sizes I wanted in aluminum. The big 68 tooth pulley would have had an unmanageable inertia in steel. The inertia issue was something I never considered, which this forum led me to the light on (thanks, mactec54, and others!). The only downside to these timing pulleys is their rather extravagant cost ($235 per axis!).

    With three days off next week, I'm trying to get all the parts gathered up that I can, with hopes to push this thing to near completion next week. The biggest remaining unknown is the electrical enclosure. I need to get that laid out tomorrow in CAD and get an enclosure ordered. I wish I could find a how-to guide for dummies on wiring CNC controls. I've got some ideas on the right way to get from the outlet on my wall and out to the servos, but I'm sure I'll trip over a few things like where I should be putting in contactors or relays to let the motion control board to control stuff, and the right way to do the e-stop cascade. At least with wires, changes are easy, unlike aluminum channel that you've already made a bunch of chips on.

    -Steve

    Attached Thumbnails Attached Thumbnails Opti BF46 Build-x-axis-ball-mount-screw-2-jpg   Opti BF46 Build-x-axis-ball-mount-screw-1-jpg   Opti BF46 Build-bf46-mill-assembly-2-jpg   Opti BF46 Build-bf46-mill-assembly-1-jpg  

    Opti BF46 Build-polychain-warning-jpg   Opti BF46 Build-img_20160318_205104-jpg  
    Last edited by Windscreen; 03-19-2016 at 02:22 PM.


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    Default Re: Opti BF46 Build

    nice to see. I am currently going through the same process



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