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Configuring PC speed, motor speed, etc.
« on: June 23, 2007, 09:36:58 PM »
Hi all,

New here and evaluating Mach3 for the past 2 days, with a CNC mill I purchased (converted by someone else).  Currently I'm running it on a laptop, but want to know what's the best/minimum PC size for MY configuration.  Here's the way I see it...
The mill/controller is *currently* setup for half-step, with 1.8-deg per step motors, and 40 motor revs per inch. Max reliable speed seems to be ~20 IPM.  So that requires (360/1.8 ) x 2 x 40 x 20 = 320,000 pulses per min = 5333Hz.

Somewhere I read (in the manual IIRC) that a 1Ghz CPU ==> 25000 Hz output.  But do I have to multiply the 5333 by 3 axes???  5333Hz x 3 = 16,000Hz) which will require me to get a faster PC?

But I also want to change to at least 8, but preferably 16 microsteps.  16usteps ==> ~43khz output (per axi)s.  Again, is this fixed for all 3 axes or do I need to triple this value?

Later I'd like to up the traverse speed to about 60 IPM, which means 128khz output (at 16 usteps).  This somewhat implies that Mach 3 can't run it that fast (IIRC there is a 45kHz limit) -- am I wrong here?  Is the limit really 45Khz, or is my math wrong? Or...???

If I do need to change PC's, I was looking at very small form-factor motherboards that I can fit into a small enclosure.  Mini-ITX boards are really nice at approx 7" x 7", but they are usually lower-performing than other form factor PC's at the same processor speeds.  Micro ATX (approx 9.6" x 7.2") are also workable and I'm looking at this... http://www.newegg.com/Product/Product.aspx?Item=N82E16813138047 . Add RAM, HD and and small PS and I can run it headless.  I'd activate Mach3 remotely from my Laptop.  But there's another issue -- so far I've noticed that if I connect to the network with my laptop, Mach3 will bog down a lot and work "choppy" -- runs for a second, then pauses for a second, etc.  Response to key- or mouse- clicks is very slow.  Not sure if that's my laptop being too underpowered, or if Mach is not supposed to run with a network connection.

Thoughts appreciated.
-Neil.

Hood

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Re: Configuring PC speed, motor speed, etc.
« Reply #1 on: June 24, 2007, 03:06:21 AM »
First off its 45KHz per axis (up to 6), secondly its not Mach that sets this limit it is the parallel port. You could go with a G Rex or NCpod and get more, think the pod is 75KHz and the Rex is 4Meg. I think 8microstepping will be enough as I seem to remember mariss from Gecko saying much above that is a waste of time, but best check up on that as I may be dreaming as usual ;)
 Your slow down problems with a network are not normal , I have my mill and lathe hooked up with a desktop computer and dont suffer any problems. One thing though is I remember Brett (Chaoticone) having problems when he used a wireless network, so if yours is wireless that could be the problem.
 Micro ATX should work OK but sometimes having onboard graphics can cause issues although personally I have used a few mobos with it and not had problems.
Hood

Offline jimpinder

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Re: Configuring PC speed, motor speed, etc.
« Reply #2 on: June 24, 2007, 03:49:34 AM »
One thing you might try (which is a lot cheaper than changing computers) is additional memory.
This has worked very well in the virtual theatre organ forum that I am in, where speed is sometimes a bit of a problem. If you think about sorting letters without enough pidgeon holes, you'll get the idea. Doubling you memory certainly has quite an effect. (And if you sell the computer, you can always take it out and use it elsewhere.)

Jim.
Not me driving the engine - I'm better looking.
Re: Configuring PC speed, motor speed, etc.
« Reply #3 on: June 24, 2007, 10:47:11 AM »
Laptop currently has 327MB.  An additional 256MB for this older machine is ~$70, which I'll need to take it to 512MB (max).  But a new mobo, CPU, cooler and 512MB RAM is ~$105.  I have HD's and PS's floating around here somewhere, so a new mobo seems like the way to go.  I'd probably just do 1GB while I'm at it for an additional $25.

BTW, the mill I bought came with the stepper drivers/PS in a nice large machined aluminum box with cooling fins all over.  Looks like it was re-used from some industrial-quality product or better.  It's also heavy!  I was originally thinking I'd chop it in 2 as only 1/3 of it is used for the drivers/PS, but I can fit a micro ATX mobo in the remaining space for a nice all-in-one package... http://www.narwani.net/neil/mech/cnc_enclosure_open.jpg .  There's a machined aluminum bottom-plate that covers it.  The big open area is about 10" x 11" and adjacent to that is about 7" x 4.5".  Should be plenty enough for a Micro ATX board, HD, PS, etc.  I'd just need to cut vent holes for cooling.  BTW, the stepper drivers in there are IM805's, which can do up to 5A RMS, 7A peak, 75V.

My network is wireless (Verizon cellular broadband).  If Mach3 will work properly with a local network then it seems like I can get this idea to work -- I'll setup the new mobo headless and disable the on-board video.  Then I'll use a regular crossover cable to connect it to my laptop or perhaps run the cable to the router and remotely access/control it from the laptop.  This frees up the new mobo to be only a CNC controller.  BTW, I'm using Win2k as I've found this to be the most stable version of Windows to date.

I just looked up the G rex and ncPod.  Nice.  So this eliminates the need for the parallel port right?  Actually, I also heard that 8 microsteps are enough as well, but I was thinking I'd go more if possible.  I forgot to mention something ... the motors are only 276 oz-in currently (small for this HF geared-head mill) and thus geared (belted actually) 4:1.  When it's time for the speed increase, I will change to 500 oz-in (highest torque I can find for Nema23's) and re-gear it 2:1, so that drops the frequency to 64kHz/axis for 16ustep at 60IPM.  At 8ustep that's 32kHz/axis.

Thanks,
-Neil.

Hood

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Re: Configuring PC speed, motor speed, etc.
« Reply #4 on: June 25, 2007, 01:12:59 PM »
Yes the ncPod is USB and the Rex is ethernet, also there is the Galil, not sure how far the compatibility is with Mach as of now but a couple of people are using it.
Hood
Re: Configuring PC speed, motor speed, etc.
« Reply #5 on: June 26, 2007, 07:51:21 PM »
Thought of something else here... rather than be limited to 45khz, why not use a PCI parallel-port card that (allegedly) goes to more than 45khz?  I'm sure I've seen these somewhere.  I'll go google now...

Hood

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Re: Configuring PC speed, motor speed, etc.
« Reply #6 on: June 27, 2007, 02:18:00 AM »
not sure if you get them but I dont think it will work in any case as you have only the three kHz options in Mach when using a parallel port.
Hood
Re: Configuring PC speed, motor speed, etc.
« Reply #7 on: June 27, 2007, 12:39:30 PM »
Saw that now, thanks.  This is all confusing me, so I am still running some experiments to help my understanding of things.  I'll be back...
Re: Configuring PC speed, motor speed, etc.
« Reply #8 on: June 27, 2007, 03:25:16 PM »
But do I have to multiply the 5333 by 3 axes???  5333Hz x 3 = 16,000Hz)
No you don't need to multipy it per axis as the paralell port is a (by the name) paralell interface and not a seriell.
It sends out all 8 bits at the same time through the 8 pins.

Remote desktop or VNC has never worked well with interacrive apps that redraws a lot (updates graphics). It also takes a lot of CPU and network to make it work ok. If you use TightVNC make sure you select fast compression. It would be a lot safer to just use a normal monitor, keyboard and mouse.
And as Hood said, yous an external videocard. Even if it's an ATI Rage 3D (it works fairly good despite it's age and has the benefit that it's practicly free if you can find it in a scrapbin)