Fusion360 Postprozessor für LinuxCNC 5 Achsen

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10 Jun 2019 13:12 - 10 Jun 2019 21:00 #136467 by plopes9000
Yes the post will handle 5 simultaneous axis just fine as will the machine. But I do have issues with the toolpaths generated by Fusion360 ... they are not clean - nothing to do with the post processor or machine. In the last video - part 5, the curved section is actually a Flow op so 5 axis simultaneous - I even made the remark that the toolpath is not clean. Also the op before the last of the same video - part 5 - is a simultaneous 5 axis op.
Last edit: 10 Jun 2019 21:00 by plopes9000.

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10 Jun 2019 13:13 #136468 by plopes9000
Thanks Andy - quite happy. Yes the FHA are like a perfect fit for 4th and 5th Axis.

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12 Jun 2019 12:55 #136718 by andypugh
I keep imagining a mirror-image rotary on the other end of my table and some cunning differential mechanism to convert the positions of the two actuators in to AC motions on an unpowered trunnion.
But I can't really think of anything to do the job without backlash.

I don't think I have the headroom to swing an FHA under the tool.

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12 Jun 2019 14:25 - 12 Jun 2019 14:26 #136732 by plopes9000
Yes the C FHA25 eats up around 180mm Z travel so it can be swung. The versions with a motor break would consume another 20mm. My A FHA32 does have a break, the C FHA25 does not.

An alternative design that requires somewhat less headroom is the one often seen on Chinese 4/5th axis with a trunnion table where the C axis motor is placed on the opposite side of the A axis and drives the C axis with a belt. I think this would work well with a standard harmonic drive as C Axis driven by that belt. Any backlash caused by the belt would be greatly reduced by the HD reduction ratio.

I do have a standard (HFUC32 without motor, without through-hole) HD and considered that design as well, but due to the overall diameter of the HD, added to the need for coupling it with the belt - additional shaft on bearings with pulley, the actual height reduction is not that significant - the FHA are already quite compact.

There are some HD which are extremely compact, I also bothered to get a 32 size one in the hope I could use if for the C axis, but those only provide rotational reduction without dealing with any axial or radial load ....

All in all, HD gear, radial and axial load bearings, servo motor + encoder, I find the FHA are pretty compact as they are.
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Last edit: 12 Jun 2019 14:26 by plopes9000.

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22 Jun 2019 16:21 #137600 by pl7i92
the Harmonic drives are the best to go
but suuuuuper expensive against a wormgear pricice and a standard 4Nm stepper

SOMEONE GOT A TURBO VENT PART to test on 5Axis Postprocessors
about 150mm Diameter

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22 Jun 2019 18:09 #137608 by 3D-Master
Harmonic drives are nice and have almost no backlash, but really are expensive. Then there are Hypocycloidal gears, which may be more rigid but also cheaper and also have almost no backlash (afaik)

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22 Jun 2019 18:52 #137610 by plopes9000
I read or heard somewhere that Hypocycloidal gears are not that resistant to crashes ... no idea, but it turned me off a bit. For a long time I considered Hypocycloidal gears as well, one advantage is that they are capable of faster rotation. For example the Mazak Intergrex uses a hypocycloidal gear on the spindle - see
.

Now, I could never find a Hypocycloidal on eBay for a good price and in a good format to make a 4/5 axis - can you?

HDs appear now and again on eBay/Ebaykleinanzeige for a good price. It takes months, even years to get a break - I got lucky a few times, twice for FHAs and on top of that of an ideal size for my mill work envelope.

Then of course there is the servo drive issue if one has to also get a HD configured Drive - I didn’t.

But yes it’s a long shot by any measure.

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22 Jun 2019 19:04 - 22 Jun 2019 19:14 #137611 by plopes9000
There is an older version FHA-b on eBay for Europe buyers rover.ebay.com/rover/0/0/0?mpre=https%3A...2Fitm%2F143022312188 .
Last edit: 22 Jun 2019 19:14 by plopes9000.

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22 Jun 2019 19:29 #137612 by plopes9000
I got mixed up above, I was referring to roller cam gears and not hypocycloidal gears - the Mazak uses roller cam gears.

Wish I could get a drop in roller cam gear.

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22 Jun 2019 21:48 #137614 by andypugh

plopes9000 wrote: There is an older version FHA-b on eBay for Europe buyers rover.ebay.com/rover/0/0/0?mpre=https%3A...2Fitm%2F143022312188 .


The FHA-B is easier to drive than an FHA-xx-C as it uses Hall sensors and incremental encoder.

They work very nicely with an STMBL.

I did, for fun, design my own sort-of-cycloidal reducer a while ago. It's something I am pretty sure I could make.

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