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Author Topic: Need some advice on new CNC  (Read 1875 times)

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Offline Hylan

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Need some advice on new CNC
« on: June 19, 2014, 04:37:12 PM »
Greetings, I've got a couple questions about Mach3 for my new CNC.  I build a CNC in 2007 and it works pretty well but I'm almost done building a new one.  On the old CNC I was using KCam and it worked okay but I could never get the machine up and running really quick, mainly on the Z axis.  Now my new machine appears to have the same malady with the Z axis.
So, I'm looking to switch everything to Mach3 and I want to understand what I'm getting into.
So my new machine is running nema 34 motors.  I'm running dual 960 oz/in motors on the X axis with 444 steps/in with rack and pinion gears.  Y axis is a single 960 with same rack and pinion setup.  Z axis is a 640 oz/in motor driving a 10 TPI Acme thread with 20000 steps/in.
I've got a new (refurbished) Win7 pro desktop computer with a 2.7 dual core Pentium processor & 4 gig ram.  Currently I'm feeding the signal to a Max32 (Kcam stepper controller) that is feeding 4 G203V Gecko Drives (one for each motor, X axis motors spinning in opposite to each other).
So I've got 2 questions.
First, can Mach3 put out enough steps to get me 20"/min on the Z axis?  Basically I'd like to move 1" in about 3 seconds.
Second, I figure if I make the switch, I'll have to pull the Max32 board and go with something else so I'd like some suggestions.  I was looking at this board on Amazon which says it'll work with Mach3. http://www.amazon.com/dp/B00CY42VM0/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=VO2MNMCY8AQ9&coliid=I3LBQ7XFX3TY3B

Any help is appreciated.
Thank you,
Hylan

Offline ger21

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Re: Need some advice on new CNC
« Reply #1 on: June 19, 2014, 10:06:19 PM »
How much weight are you lifting with the Z axis? My Z axis uses 1/2-10 acme, and I can get about 70ipm with a 250oz motor.

Depending on the weight your  lifting, you'd probably be better off with a much smaller motor, or a 5 start screw. Larger stepper motors don't spin as fast as smaller ones, and 1/2-10 acme requires high rpm's to get good speeds.

Are you direct driving your pinions? Your machine would probably be much smoother, and have more power if you used a belt reduction.
Gerry

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

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

Offline Hylan

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Re: Need some advice on new CNC
« Reply #2 on: June 19, 2014, 10:30:01 PM »
Gerry,

With my current configuration I was finally able to get the Z up to a decent speed but I have to lie to it and it's not really usable.  I set my max Z speed to 2000"/min and at which point it would move smoothly and quickly around 35"/min.  Which is good but it creates a problem in that I don't currently have independent control over my travel, cut and jog speeds per axis.  (This is using Kcam).

My X and Y are direct drive and I debated during the build whether to go belt or direct.  The direct is working smoothly and I'm happy with it.

So I was just watching the initial training video on the set up of Mach3 and correct me if I'm wrong.  But I saw that you can set up different ramps and velocities for each axis.  But can I also set different cut, jog and travel speeds per axis?  I guess that could potentially cause problems in 3D cutting but I'm not sure.

Thank you,
Hylan

Offline ger21

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Re: Need some advice on new CNC
« Reply #3 on: June 19, 2014, 10:44:10 PM »
Cutting speeds are controlled by the feedrate in your g-code. You don't really set axis cut speeds.  Each axis moves at whatever rate is necessary for the movement to be at the commanded feedrate.

Jogging speeds are usually a percentage of the motors velocity in motor tuning. If the axis have different velocity settings, then their jog speeds will be different. (I think).
When you say travel, speed, do you mean rapid speed? The rapid speed in the velocity set in motor tuning.
Gerry

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

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

Offline Hylan

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Re: Need some advice on new CNC
« Reply #4 on: June 21, 2014, 05:18:14 PM »
Gerry, yes I'm speaking in terms of how Kcam handles things so it's a little apples to oranges.  In that system, you can import a dxf file and it generates the G code using preset cut speeds.  Then you also set up in the machine configuration what your travel and jog speeds are.  I think it is like having Lazy Cam built into the program.
What I can tell so far is that Mach has a lot more flexibility and so I'm going to chop up a serial cable and wire it in on at least an axis or two and give it a whirl.