HERCUS Mill Retrofit

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martyscncgarage
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Re: HERCUS Mill Retrofit

Post by martyscncgarage »

If you go with steppers, consider hybrid closed loop steppers with encoders and drives. Leadshine makes them, but there are a number of them on eBay. Lucky guy to have a friend like that. Be sure to post pictures of that build and video of it running.

Marty
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Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

First chips... all be it wood chips lol. I have no work holding stuff at home so found a scrap of timber and jammed it in the slot.

The spindle motor is rather weak as expected being about half the power of the original one but I was surprised at how well it handled being smashed into the block with relatively high feed.
6B857004-E564-481E-ACB9-7EFE2DBE6F49.jpeg
martyscncgarage
Posts: 9912
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Re: HERCUS Mill Retrofit

Post by martyscncgarage »

Congratulations!
Post a video of it running, including the control panel.
Pics of your handy work too!
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
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Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

I have posted about this on the Facebook page but decided to post here to document my troubleshooting.

After re-reading my posts it looks like i was having servo speed issues before i even had the spindle drive installed in the cabinet so i may not be my main problem. i picked up some shielded VFD cable to try reduce any noise produced by that anyway.

I also reread the manuals for the leadshine drives and they recommend having the + and - wires for the pulse and direction twisted together and also state that any unused wires be connected to the shield and grounded out. this makes it a bit tricky since the acorn doesn't supply the 5v and it comes from a separate power supply so im not sure the best way to set out the cabling.

I was watching this video from Franco: https://www.youtube.com/watch?v=KKSvwbldObY were he talks about pulse width and how you change it by the parameter in CNC12 and how his drives had a requirement of a pulse duration being longer than 10μs. The manual for my drives have a requirement of pulse duration being longer than 0.85μs. according to his video the pulse duration the acorn outputs at 400,000 pps is 1.25μs. this would indicate to me that the pulse duration should not be an issue.

i will keep experimenting and update what i discover.
Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

After watching a DMM servo video and hearing about them discuss a gear ratio of something i went back to the leadshine manual for some more reading and discovered this feature in the tuning software. There is a field where i can set an electronic gear which will change the actual ppr of the servo. I think this will achieve what people were suggesting on Fb about lowering the ppr. i have closed up the shed for the night so i will do some more playing with this at a later date but the DMM video said the settings in cnc12 need to be adjust also. So if i set CAM-denominator to 2 my ppr becomes 5000 and i set this in the acorn parameters i should be able in theory to double the rapid to 6000mm/min but the acorn will be outputting the same frequency step signal.
Attachments
electronic gear.PNG
Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

Update: I changed gear ratio in servo drive to 4 for a 2500ppr servo. It then works well now and no more missed steps. I also have the larger spindle motor fitted and tried rigid tapping. I had to upgrade to cnc12 4.12 to get it to work but first hole in ally it tapped fine. I also tweaked the backlash settings now that the machine has bed in and have gotten the circular pockets pretty nice. 3d tool paths are a little dodgy as the z axis backlash is not set properly. I am having some issues with the new servo drive and it not holding real tight, definitely not like the older existing servo drives I have. They are super tight and won’t let u move the pulley at all. The new servo I can twist quite easily and it doesn’t fight back like the other ones. There is also slop in the jack screw mechanism so i plan on disassembling it and machining up some shims to take out the play. I’m also thinking of changing the pulley sizes to speed up the z axis as it’s currently about 0.5mm per revolution. The other axis are around 2.29mm/rev. I’m pretty confident that with the z axis sorted this old machine will do some awesome 3d ball finishes.

I can’t seem to upload a pic from my phone so I’ll have to do it from the pc later.
Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

As requested by Keith on FB, see attached report.

every thing is working well after upgrading to 4.12 however it still does seem to bog down a bit with the non engagement feeds. i dropped the feedrate down to 3000mm/min and it still has a noticable pause.

see attached report.
Attachments
report_B0D5CC847FFD-1130170301_2018-12-31_21-00-00.zip
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martyscncgarage
Posts: 9912
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Re: HERCUS Mill Retrofit

Post by martyscncgarage »

Commotion wrote: Mon Dec 31, 2018 4:12 pm As requested by Keith on FB, see attached report.

every thing is working well after upgrading to 4.12 however it still does seem to bog down a bit with the non engagement feeds. i dropped the feedrate down to 3000mm/min and it still has a noticable pause.

see attached report.
What do you mean by NON engagement feeds? The machines rapid movements?
Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
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Commotion
Posts: 83
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Re: HERCUS Mill Retrofit

Post by Commotion »

It may be a fusion 360 term. In fusion360 u set the non engagement feed rate. When it makes a move from one cutting pass to another down inside the work envelope of the material it runs at a different feed rate to the cutting feedrate to reduce cycle time. I can also set high speed move commands to be hi feed g1/g2 commands instead of true rapids (g0) to avoid dogleg movements. The acorn may not have dogleg rapid issues I’m no sure it depends how it commands servo moves with g0

A lot of industrial vmc’s quote a max rapid (g0) and max feed rate (g1,g2,g3). On our mazak vtc20b it has a max feed of 5000mm/min but rapids of 24,000mm/min. Regardless of what u program feed for g1 it won’t exceed 5000 so all my programs have non engagement feedrate of 5000. I tried a program with the non engagement feedrate dropped to 3000 but it still not noticable pausing as it processed the g2/g3 lines.

Industrial vmc’s have parameters for tolerance which can be changed by g or m codes to set how closely the servo move commands follow the arcs of the g2/g3. The tolerances can be loosened for roughing passes and tightened up for finishing passes. I’m not sure if the acorn or cnc12 does this decomposition and if there are any way of adjusting its behaviour.
Commotion
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Re: HERCUS Mill Retrofit

Post by Commotion »

I just had a thought. I think all axis acceleration values are default. Maybe those values are too low and it’s actually them which is making it appear to bog down by limiting how fast the axis can accelerate? From memory those arc move commands are very small.

If that is the case, what’s to best practise to setting those acceleration values. Set jog to max rapid and jog back and forth increasing the acceleration until the drives have a position error and then reduce by a certain percentage to account for variation on mass on the table?
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