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Author Topic: Working router table, options to increase travel speed ?  (Read 14085 times)
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fabhund
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« on: November 02, 2014, 12:22:59 AM »

Dear All.
I guess you could call this a luxury problem.

I have a functioning router table, of a gantry type. It's all driven by 3-phase steppers 3.1Nm
The gantry (Y-axis) is driven by 2 motors one for each "leg" and the linkage is 5mm pitch ballscrews.

So, the Y travel speed max. out at approx 4500-5000 mm/min (~180~200 IPM) where one of the steppers loose the steps and comes to a halt.
Currently i run it at max. 4000 (~160 IPM) to be on the safe side.

I guess that around the motor speed of 1000 RPM (5000 mm/min / 5mm pitch = 1000 RPM) the stepper greatly is reduced in torque.

Options to increase speed:
1) Looking into AC Servos. I'm a bit scared of them, never used, setup, tuned or what so ever with a motor and drive. Still I think this could be fun.
Any recomendation for an "easy to install" kind of thing. Is there any preferred brand to look for, do I need software or can I get a turnkey preset system  Undecided

2) Change ballscrews, this would be rather "cheap", as I can get a 10mm pitch ballscrew, that fits directly into my current setup. No modification at all to the table, or electronics.  Undecided

3) Hybrid steppers, a stepmotor with a feedback encoder. But how can that be faster if it simply max. out and looses steps like the regular stepper  Huh

4) Shut up,be Happy, go to the garage, grab a beer, get those chips flying  Smiley

Best Regards, Bo Andersen
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stirling
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« Reply #1 on: November 02, 2014, 04:08:54 AM »

1) Go to servos if you want to. Just don't blame the steppers. It's not their fault you've mis-spec'ed the ballscrews.  Smiley
2) Yes. 5mm lead ballscrews on a router wouldn't be my choice. 10mm is much more like it - I use 20mm.
3) Pointless (IMO).
4) Works for me. Wink
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ger21
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« Reply #2 on: November 02, 2014, 06:13:02 AM »

While #1 would give you more speed, it could cause other issues. Keep in mind that using faster spinning motors (AC servos) would probably result in the current screws whipping from spinning too fast. INdustrial machines with AC servos typically use ballscrews with a pitch between 32-50mm


#2 is the probably the best and cheapest course of action.
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Gerry

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garyhlucas
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« Reply #3 on: November 02, 2014, 06:51:14 PM »

You don't say what voltage power supply you have, and what the drivers are rated for. It is the back EMF from the steppers that limit their torque.  If you can raise the drive voltage it makes a big difference. My steppers run on 68vdc powered by 80 volt rated drives. I can easily get 300 ipm with 5mm ball screws.
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fabhund
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« Reply #4 on: November 03, 2014, 10:34:07 AM »

Hi All.
Thanks for your feedback.

Not blaming anybody/anything other than my ignorance in all the diy stuff that I do.
I just figured that a 5mm pitch would work, and i does. But now it seems 10-40 mm would be even better :-)

The voltage is 48V, and my drivers can go up to 60V. I can try to crank up the voltage, but it's only fine tuning so i guess it can only be 50-52V perhaps.

Best regards, Bo Andersen.
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Brian K
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« Reply #5 on: December 17, 2016, 05:42:02 PM »

If you have followed the progress of industrial routers you would have noticed a change several years ago as speed increased.  Indexing speeds are up I use one machine that indexes at 3100 ipm and cuts 3/4 plywood at 1200 ipm all day long.  That's not the fastest machine out there either. In getting to these speeds the manufactures found that the screw would whip and we are talking about 50mm screws, their answer was to hold the screw stationary and turn the nut. But before you get there I think you will run into issues getting enough pulses from a PC controller.  A Windows PC spends a lot of clock cycles doing house work, you do not notice these small inturuptions but they are there and the faster you go the more pulses you need in a given time.
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ger21
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« Reply #6 on: December 17, 2016, 05:47:38 PM »

Quote
In getting to these speeds the manufactures found that the screw would whip and we are talking about 50mm screws, their answer was to hold the screw stationary and turn the nut

We bought a Masterwood machine in 1997 that had a spinning nut on the X axis. It's nothing new.

Quote
But before you get there I think you will run into issues getting enough pulses from a PC controller.  A Windows PC spends a lot of clock cycles doing house work, you do not notice these small inturuptions but they are there and the faster you go the more pulses you need in a given time.

Mach3 can use a variety of external motion controllers which can generate pulse rates of up to 4Mhz.
Mach and any of it's competitors have no trouble generating pulse rates as fast as you need them, if you spend the $100-$150 for the hardware.
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Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
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