First CNC build - ESS, Mach4, Ballscrews - velocity vs. feed rate + misc

[spandadk]

Got my new CNC (hobby) build up and running and have successfully connected to all axis (X, Y, Z) and for now, things seem to move and work. So far, only setup things with "standard/default" settings

I am new to Mach4 (and in generel new to the CNC world) and was hoping for some input on the below:

My setup:
1x1 meter (mainly for hardwood)

- 4x Ball screws SFU1605
-> 16mm > pitch : 5mm
1 x 5 Axis Breakout Board4 x Nema23 3.1Nm Stepper Motors
-> Dip switch settings > 4.3 Amps > 1/10th Microstep

4 x CWD556 Microstepping Drivers
1 x 400Watt PSU 36Volts
1 x Ethernet Smoothstepper (USB) (plugin frequency: 40 hZ)


1. G-code > Fusion feed rate vs. Mach 4 velocity
I exported g-code from Fusion 360 (done this many times) for a simple contour. Cutting feed rate was set to 2500 mm/min. However executing the g-code movement is VERY slow. On the machine i've run similar on, 2500 mm/min was moving O K fast.

My Mach 4 motor tuning settings: (Metric)
Counts pr. unit
40.0478

Velocity Units/minute
24703

Acceleration Units
988.13

How come it is moving so slow? I guess if "velocity" needs to be compared with the "feed rate", I have my answer there, but would that then mean I need to update my tool library and all feed rates calculated towards the very high velocity number?

ps. The current velocity seems to reflect pretty close to the 2500 feed rate I've tried on another machine, but unsure why I need to set it so high to get any decent movement speed.

2. Mach 4 > Traverse or Feed ?
Can anyone shed some light on what to choose here? I'm not entirely sure what it means



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[ger21]

Can you actually jog the machine at 24,000mm/min?? I would expect it would stall.

What is the feedrate in your g-code?

2500mm/min is only 100ipm, which isn't really that fast?

[spandadk]

Can you actually jog the machine at 24,000mm/min?? I would expect it would stall.

What is the feedrate in your g-code?

2500mm/min is only 100ipm, which isn't really that fast?

Yea, that speed doesnt Seem like any issue (atleast yet)

But it “only” seems to be moving like 100-200 ipm, so im clueless as to why i need to define such a high number to get any decent speed?

[wizard]

I will try to answer one of your questions about feed rate vs rapid(traverse). I'm not sure if Mach 4 is in fact using the term "Traverse" to mean rapids but lets assume that is the case. Rapids are the absolute mac speeds the various axis on you machine. Generally it is considerably faster than a feed rate move and is likely to be limited due to physics of the machine.

Feed rate moves are designed to set up the proper cutting action for the given materiel. More specifically the combo of a feed rate and a load per tooth. In an ideal world anyways you set your feed rate to cut off the optimal amount of material per tooth, per rev.

In any event in this situation you believe your feed rate is too slow. You best bet it to go back though any and all calculations to see where you might have messed up. Calculate both ways to help locate the error. By both ways I mean:
1. Start a desired feed say 500 IPM and run though the steps to determine steps required per second to get that feed rate.
2. Calculate from the other direction (counts per inch) and work out how fast you need to turn the leadscrew. YOUR results should be similar if not exact!

The idea here is that you should get very close results, if not mistakes have been made. In other words if you want to make 500IPM you should be able to calculate the steps per minute to get there. The opposite is also true, if you know how many steps is required to move an inch you should be able to calculate steps per minute to get to 500IPM.

Now if you do this calculation for 500 ipm that doesn't mean your machine will run at that speed. What we want to do here is to establish that you are putting the right values into your CNC controller.

I hope I'm not confusing things here as it has been one long work day. But your CNC control software should be asking you for a few parameters for each axis. How Mach 4 works is up to you and your documentation, but at the very least it will be asking someplace for a value that tells the controller how many steps are required to move a specific distance. There should also be a parameter that sets max feed rate, it could be a value in IPM or mm/min or some raw figure like counts per minute.

[joeavaerage]

Hi,

1 x Ethernet Smoothstepper (USB) (plugin frequency: 40 hZ)

To my knowledge the USB connected SmoothStepper does not have a Mach4 plugin. The Ethernet connected SmoothStepper
does.

Can you clarify what SmoothStepper you are using?

Craig

[joeavaerage]

Hi,
on the Configure/Control/General page there is a setting 'Traverse Mode'. It can be set to Rapids or Feed.

Traverse mode is a G0 move. The rate at which the machine moves can be selected as the same as the Rapids or max velocity set in the
motor tuning pages, ie normal Mach operation, or you can set it to move at the prevailing feedrate, that is the F word.

The usual setting is Rapids.

Note however that jog speed may not necessarily be the same. Usually the jog rate is some percentage of the Traverse Rate. Thus when testing the capability
of your machine you should use MDI instructions not jogging.

To test the Traverse speed enter a G0 move in the MDI panel.
To test a feed move enter a G1 move including the desired F value in the MDI panel.

Craig

[spandadk]

Hi,



To my knowledge the USB connected SmoothStepper does not have a Mach4 plugin. The Ethernet connected SmoothStepper
does.

Can you clarify what SmoothStepper you are using?

Craig

My bad, i did ofcourse mean Ethernet connected smoothstepper- Got it setup with the working plugin

[spandadk]

Guys - thanks for the input on the subject of traverse - i'll just read it through and digest those parts before returning with a response. FYI, I have calibrated my X Y Z steps and they seem to be more or less spot on at the moment.

I decided to do a simple pen test for a simple 50mm diameter circle.
-> I exported the .tap file (mach3 mill post processor) and ran it in Mach4.

Result: The circle drawn with the pen came out as 5mm and not 50mm.

Could this have something to do with the stepper drivers being set to 1/10th Microstep? (recommended setting from the provider for my Nema motors).
If so, how do I "normalize" this?

[skrubol]

You've done your calibration wrong. Starting point of steps per unit should be (for a standard 200 step/rev stepper,) 200 (steps/rev) / pitch (5mm/rev) * microstep (10), so should be 400 steps/mm. 10x microstepping is a reasonable value, but with an ESS you could go higher if you needed to try to get rid of vibration or something (stick with 10x for now though.)