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Author Topic: How fast?  (Read 2783 times)

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How fast?
« on: January 11, 2014, 11:31:06 PM »
I've had my CNC mill running for about 6 months and tuned the motors for 100 ipm rapids.  It has 18 inches of travel on all three axis. However I got wondering about how quick it might actually be able to run.  So today I played a little with motor tuning.  My axis are all driven by 20 mm x 5 mm pitch ball screws and the ways are THK recirculating ball type.  I have a Xilufeng USB breakout board driving Leadshine 80 volt steppers with a 68vdc power supply.  The motors are Nema 34 860in/oz holding torque.  Z axis mass is about 50 lbs, Y axis is 40 lbs and X axis is 85 lbs with a stationary 205 lb table.

I was able to tune it to work well with all axis running at 320 steps/mm, 8700mm/min and acceleration set at 2200.  That's a stepper motor speed of 1740 rpm, and 342 in/min rapids.  Its a little scary watching it move at those speeds!  Is this a good rate or are some you running much faster?  I tuned it back down because I have my grandson working with me and I don't see actually cutting at those speeds.

Offline Hood

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Re: How fast?
« Reply #1 on: January 12, 2014, 03:57:43 AM »
Quote
Is this a good rate or are some you running much faster?

All my machines are servos so not really a good comparison, the big lathe I have set to 10m/min, the small one I think is 5m/min, the Beaver mill is 8m/min, the Chiron is 20m/min. All could be run faster with the exception of the Chiron as that is the motors Max RPM (4000).
I would say the correct velocity is what you feel comfortable with.

Hood

Offline RICH

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Re: How fast?
« Reply #2 on: January 12, 2014, 05:29:30 AM »
As Hood said, run at what you feel confortable with..... safety the number one consideration. I will add as long as the machine is buit for it,is relaible, and speeds are appropriate for the task at hand.

Non of my machines will run reliably faster than 120 ipm.

The engraving machine is limited to 5 ipm and and run it at say 3 ipm.  ::)

RICH
Re: How fast?
« Reply #3 on: January 12, 2014, 01:52:28 PM »
The only reason I might have for moving fast is that I am mounting an extruder head on the machine for 3D printing. From what I a have seen on the 3D printer forums they are mostly low mass moving fast.  So I will probably have what is a relatively slow but very accurate 3D printer.  We will know soon as I plan on installing the extruder shortly.

Offline simpson36

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Re: How fast?
« Reply #4 on: January 21, 2014, 12:31:05 PM »
The only reason I might have for moving fast is that I am mounting an extruder head on the machine for 3D printing.

Wow! Can you elaborate on this. I did not that one could buy an extruder head to mount on a CNC mill. Info please? Links?

Offline RICH

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Re: How fast?
« Reply #5 on: January 21, 2014, 05:11:58 PM »
You could always make an extruder head....think my friend just used a block of Al / small cal rod for heating/ temp probe to measure with feedback for controlling temp / along with similar to an oil burner nozzle for a die w 0.012" dia hole in it. Not personaly into the 3d printing stuff, but, it is impressive what you can.

To think all we had was an erector set and none of the dads would give us a wrench, then came one with a motor and man that was uptown!

RICH
Re: How fast?
« Reply #6 on: January 21, 2014, 07:53:50 PM »
The only reason I might have for moving fast is that I am mounting an extruder head on the machine for 3D printing.

Wow! Can you elaborate on this. I did not that one could buy an extruder head to mount on a CNC mill. Info please? Links?
Join the RepRap forum.  Lots of people building their own machines. A 3d printer is basicly a very lightly built CNC that moves very fast if possible. When I look at pictures of most of them my brain just screams "IT"S NOT STIFF!!!" and then I read the tales of woe about ripples in the print etc.  I am anxious to see what my machine, which has a build envelope of about 12" x 12" x 18" high and is made from very stiff and accurate THK rails can do.

A few guys with machines running Mach 3, you use the spindle stepper output to drive the stepper motor on the extruder.  I bought an extruder kit from QU'BD and that was a mistake.  It looks very nice, but it has so many flaws you have to conclude it was designed by someone that has never seen a 3D printer!  As a result I haven't gotten mine working yet because I am making some new parts for it.  Fortunately I have a CNC not a 3d printer with an extruder that doesn't work. There are some good ones out there and it pays to ask those who are actually using them.

I also bought a temperature controller and a silicone heater for the build platform as I am interested in doing materials that need the heated bed or they warp. A word of warning, the parts sold for 3D printers are often poorly designed and even more poorly made! "Oh! you want mounting holes on that circuit board? Do they have to line up?" What a circus! However I am trying to join so who am I to complain?

Offline simpson36

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Re: How fast?
« Reply #7 on: January 22, 2014, 05:29:15 AM »
Excellent, thanks.

Fast is no problem. Last year I built a first prototype mill using the frame castings from a new IH bench mill (largest available bench mill) to showcase and do testing on my new BT30 spindle and ATC. Here is a video of the 150lb table running at 500 IPS:

https://www.youtube.com/watch?v=_sH8nBUxIV8

The above mill was built for a customer, but I am about to start work on the new prototype mill for my own use. It will not use any 'recycled' mill parts except a 300lb Bridgeport table. The rest is all new including the frame castings. Bigger motors, bigger screws and ball slides on all axis. It will run all day at 500 IPS.

The new machine already can accommodate three different spindles, but maybe I can squeeze in an extruder head somewhere.

Very exciting stuff. Thanks very much for the info!