CNC router axis running slowly

[barrica]

Hello guys,

I have recently purchased a new CNC router "kit" and am at the stage of getting the stepper motors to run.

I have them setup in MACH3, but when I try and jog the axis around using the keyboard the motors move but pretty slowly.

I've tried tweaking all sorts of settings in the motor tuning config, but cant seem to get the axis to pyhsically move past around 1m/min - even though the output screen on MACH3 says they should be up to 4m/min!

The only description I have of the stepper motors are "425oz", which doesn't mean a lot to me.
My breakout board is this>>>

https://www.ebay.co.uk/itm/Mach3-5-A...72.m2749.l2649

Stepper motor drivers are >>>

http://www.ebay.co.uk/itm/Stepper-Mo...72.m2749.l2649

Can anyone help???

Thanks

[cropwell]

In Mach3 hit the 'tab' key and the MPG mode will pop-up. If the slow jog rate is less than 100% put it back up to 100%. Hit the tab key when you have done.

[johngoodrich]

it would help if you told us your motor settings in mach 3 and what microstep settings you have the drivers set to

[Clive S]

Hi Welcome to the forum barrica. If you need help you have to help yourself by giving good info so that people have a chance to help you.

I have recently purchased a new CNC router "kit" and am at the stage of getting the stepper motors to run.

I have them setup in MACH3, but when I try and jog the axis around using the keyboard the motors move but pretty slowly.

A link to the kit would help also what voltage are you using on the drivers.

I've tried tweaking all sorts of settings in the motor tuning config, but cant seem to get the axis to pyhsically move past around 1m/min -

That is no help at all without what you actually have tweaked with numbers etc. Crystal ball has broke.

[cropwell]

I understood (maybe wrongly) that the OP had the motors running at good speed, but using the keyboard they only crawled. Certainly would be good to have the motor settings and microstepping settings on the drivers and also screw pitches. Pick an axis and give us a screen shot of the motor tuning.

Here is some bedtime reading http://www.machsupport.com/wp-conten...all_Config.pdf. http://www.machsupport.com/wp-conten...3Mill_1.84.pdf

[JAZZCNC]

Hi Barrica,

Like the guys say we need more info to be able to identify the problem exactly. however, let me explain how and give an example what you have to set for it to work correctly.

The first thing to do is select Micro-step setting on the drive. Now if you're using the parallel port then better to select lower setting as you are limited to the number of pulses the PP provides. So lets go middle of the road and select 800ms.

Next you need to set "Steps per" in motor tuning. Steps per relates to how many pulses are required to move 1mm or 1inch if using imperial.
But first, we need to know the Pitch of ball screws or lead screws so can do little calculation.
So let's work in Metric and say your using 5mm pitch ball screw with no gearing ratios applied. If any gear ratios applied the ratio will have to factored into the equation.

Steps Per = MicrosSteps / Pitch. Giving 800 / 5 = 160 steps per. This # is what you enter into Steps per in mach3 so will give the correct travel distance.

Next setting is Velocity and Acceleration.
How these are set will depend on several factors and why the guys are asking for info like voltage etc. Voltage plays a large part in how fast stepper motor will spin. So if low voltage you'll get lower rpm.
Other factors are things like ballscrew Pitch, type of linear rails ie: Friction, Mass ie: Gantry weight etc. All these play part in how fast the machine can move.

So again let's work low settings to start with then you can increase from there.
Velocity -1500
Acceleration = 400
This will get you moving at 1500mm/min with a steady ramp up to full RPM. This is good first setup speed based on the parameters used above. If your ball screws are lower pitch ie: 2.5mm then these settings will be on the high side and will be best lowered for testing.

Now when you are happy to go faster then Only change ONE of these parameters at a time per Axis and test before changing the others.
What your looking to do is increase until the motors Stall then back off 25% Ie: if reach 8000 then set at 6000. This will give you good safety margin for when cutting and load increases.

Just be aware that you cannot have high velocity and High acceleration. You choose which is most important to you. But must lower one to get the other.

This should get you moving at a reasonable rate. If it doesn't then like Cropwell says check Jog speed isn't set low. If still slow then will need more info and pictures of drives, wiring, Mach3 settings etc

[barrica]

Hi guys,

Thanks for the responses, I have taken the advice and changed the microsteps to 800m/s on the driver card, this is using dipswitches 5,7 and 8 ON. This has made the axis much quicker but still very jerky and growly.

The kit im using is actually chain driven, heres the link

http://sheetcnc.co.uk/

This means im struggling with the steps per value, as there is no leadscrew to figure out the calcs.

For some reason I can't attach a screenshot of my motor tuning, but its set to

steps per = 200
velocity = 3000 mm/min
accelration = 16.66mm/min

step pulse = 0
dir pulse = 0

Still very noisy and jerky.

Appreciate all the help

Thanks

[JAZZCNC]

Ok then here's another way to set the steps per.

Go to the Settings Tab. Just above the Reset, there is a button which says "Set steps Per unit".
This will open a box where you select the axis to calibrate. It will then ask you to enter a Distance to move. Be careful here because if you enter a high number and your steps per is wrong then could travel into end of machine. So enter low munber first say 20mm.
The machine will move then it will ask you how far it moved. So measure the distance it actually moved It will then calculate the steps Per for you.

So mark each axis before doing this so can easily measure how far it moved. After done it ounce with a low number then do it again over a larger distance this gives you more accurate setting.
Obviously, you'll need to measure accurately else could be off. If your just fraction of a millimeter off then will have a big effect on the accuracy of the machine when cutting.

Also, change the acceleration to 300. 16.66 is way too low.

Edit: Also got to say this which you won't probably like hearing. The design of this machine is always going to struggle. The linear bearing setup and Chain drive are not ideal for CNC. You'll spend lot of time chasing issues with this machine.

[m_c]

Chain calculations are the same as rack and pinion.

Multiply the number of teeth on the sprocket, by the chain pitch, and it gives you distance per revolution of the sprocket.
Then dived the number of steps it takes to spin the sprocket one revolution, which for direct drive with a standard stepper motor is 200 times the microstep setting, by the distance.

So if you've got a 10t sprocket with a 1/2" pitch chain, it'll move 5" or 127mm per rev.
Paired to a standard stepper motor with 8 microstep setting, gives 1600 steps needed per rev.
So 1600/127 gives 12.594 steps per mm.

[Neale]

So if you've got a 10t sprocket with a 1/2" pitch chain, it'll move 3" or 76.2mm per rev.

Should that be 5"?