Hello All!
Hope everyone has a great Holiday and New Years!

I had a lot of time to work on my OX, and have working home switch including the Z (kind of jury rigged, but working), and have setup soft limits for all three axis in Mach3 which are work well also.

I am, however, having a lot of trouble figuring out the motor tuning for Velocity and Acceleration. My machine is setup in MM, and my 'Steps Per' is around 33.5.

If I set a high velocity (like 8000 to 15000), the machine hums along fine and sounds ok when I jog with the keyboard, but when trying to do a air cut in Mach3 of some gcode, the machine like stutters or groans...?? I've tried to search the forums (here and others), and have watched a number of video (included Stainless Steel Ox) on configuring things, but not much is said about Velocity and Acceleration.

My controller is a Gecko G540, the motors are nema 23's and all are 1.8 degree.

Thanks in advance for any suggestions!

 

Happy new year @chadderuski !

By the sounds of it you are being a bit aggressive with your settings for a Ox style machine. Big commercial flat bed CNC rapid around between 10000-30000m/min but even then once they get cutting they spend 95% of the time at cutting/feed speeds. Having insane rapids on a CNC generally won't help speed things up much as the tooling and max chipload is the "bottle neck" that the rest of the system needs to be able to work well at.

I found I could jog my Ox around with (double belts and light spindle) at 20-30m per min but since dropped back to 8-10m/min. This is more than fast enough for most smaller cutting tools feed speeds and seems to not lose steps. I would spend more time and effort getting the acceleration setting dialed in as having good acceleration is key for the best cutting results.

Do you have a dial indicator? Zero out an axis on the dial, zero out your DRO and then give it a good workout. Lost of up to full speed to full stop moves is best and a mix of short jumpy moves and long moves. I use to use a little bit of Gcode so that I had a repeatable test that also had more declarations in one direction than the other. Once this is done jog back to the indicator at a slow speed so that you are close enough that you won't smash into it (I made this mistake when it lost MASSIVE amount of steps mid test and I used MDI to send it back to x0). If it reads 0 then you could push your settings further, if its out then back off. Once it stables still reduce it 20-30%

This is a base line so that you know while jogging and rapiding your machine should not lose stepps.... Big cutter loads are an easy way to lose stepps. Be conservative with your cutting and see if you get better results.

To get the right steps per use the calibrate axis function (on the settings page) to do a on cnc test. do some small tests to get it roughly right then a last test or two at 80-95% of the total size of the axis to get really accurate results. Also did you tune your stepper pots on the G540?

So to sum up... Drop your motor rapids back to 8m/min, accel to 0.05G and work up from there.

I tend to mumble so let me know if any of the above didn't make sense

 

Rapids? Meters or Millimeters? 0.05G?

Okay, you did loose me a bit. I am new to the cnc scene and still picking up on the lingo. On the motor tuning page in Mach3 I have "Steps Per", Velocity, Acceleration and a couple more setting that I don't recall.

8m/min well, that would mean 8000mm, you mean this for Velocity, right? What about the Acceleration? Is this why the machine sounds "odd" when doing small movements. Choppy? Should the Acceleration be very slow for doing small movements or higher?

When I set the Acceleration to a lower values, the motors are much more noise then when the values are high.

Sorry, but feeling kind of lost on what is should sound like and behave. I can't imagine a that my
vanilla Ox would have numbers much different than others here. Hence why I was hoping someone could give me some good starting numbers to work with.

Thanks.

 

Gettinging started is always the hardest bit but soon it will feel really easy so big ups for sticking with it!

Most machine/controllers give two speeds, Feed (G1) and rapid (G0) below is a little info but I highly recommend reading up on the basis of Gcode as it will come in handy for troubleshooting or restarting mid code.

G0 X100Y100X10
Rapid speed - as fast as your machine will go (set as motor velocity in the settings)

G1 F1000 X100Y100X10
Feed speed - Move at 1000mm per min ( The F value is set by the user/CAM to what is required for cutting/plunging and stays in effect until a new F value is entered)

The G setting I mentioned is the calc next to place you enter the accel value. I use this more than the value I enter as a benchmark... not sure why to be honest, just always have....

Have you tuned the little knobs on the top of the G54o? Having this set funny could also lead to motors struggling at slow speeds.



Could you post a video of your machine running as to be honest I do most of my "tuning by ear" these days as mucking about with a dial etc is far beyond the accuracy that I need to hold for most of my projects. The last time I set up my accelerations I just jumped into the menu and mucked about with the values till things sounded good without beign visably wobbly when I made lots of small jerky moves. You may not know but you can use the up and down arrow while in the menu to test each axis.

Last thing to check... have you got good cooling to that G540? I had a studdedy axis for a while that I tracked back to a dodgy fan that would stop from time to time.

 

Probably be the weekend before I can attempt a video. I have changed things up a bit. I reduced things down to velocity 4000 and acceleration 100.

I think it was the Acceleration that was causing my problems. I was set WAY higher before and I think that was causing the machine to try and jack-rabbit
around .

I need to review how to measure backlash again, but at 20mm I appear to be getting .001" on my x and y, and the z over 6mm is out of square by about that much.

However, if I pull or tug (gently, just with the finger), I can easily deflect around .005" which is probably the give in the rubber of the GT3 belts.

What I don't get now is how the kit seller I bought from said the GT3 belt/pulleys were "better" than GT2, but from attached image (also somewhere else on this thread),
the GT2 have better accuracy....????

Should I switch to GT2's ??




After slowing the machine down and seriously reducing the acceleration, I did re-tune each motor using the pots on the g540. They didn't seem to need much.
Another thing I've noticed: my x and y motors stay pretty cool (from my kit supplier), but the Nema23 I bought from the openbuilds store gets pretty warm. Not
too hot to touch, but much warmer than the others.

Any idea why one motor would be hotter than the others?

Playing with G Code and just drawing things for now. Will update later!

 

Is gt3 not the exact same as Gt2, but just called gt3 on the Obuilds store since it has a 3mm pitch? It makes 0 sense to me that a 2mm thick belt would be less accurate then a 1mm belt of the same material.

 

The GT3 belt is about twice as thick as GT2 (see graphic) and according to the videos the reason they recommend using is because it's stronger. I just got my OX up and running and I'm pretty new to this so I don't have a lot of experience how well it holds up and I can't attest to accuracy but so far everything I've cut has been dead on. I think it depends a lot on what your cutting and how accurate you need it to be. I eventually want to convert my X and Y to lead screw that in my opinion would be a lot more accurate than any belt.

 

is there some one here who have tried Bosch GMF 1600 on the OX CNC Machine.
I would like to use my router in my cnc, but it is a little on the heavy side at 5.8 kg.
do any some advice.
thank you in advance, and thanks for OX machine Fantaskisk well made, praise for the openbuild team
info Bosch GMF 1600
GMF 1600 CE Professional Multifunktionsfræser Overfræsere | Bosch Professional

 

I've made several mounting kits for routers up to 6.5 kg (14.5lb)
These people haven't asked me for a smaller kit yet, so they must be working.

 

How much sag? I'd love to mount my 3hp on but am using a 611 now.

 

it sounds good, I will make a CNC machine with a working area of approximately 1200 x 1200.
but im thinking can i use same bild to a 3D printer.
so 2 maskine in 1.

 

Yep, you're right. I did a lot more reading and although the GT2 belts are about 4 time more accurate they lack the torque ability of the GT3 belts.

Also, what ever I said about backlash (.001 phaw!) was way off. LOL!

Somewhere on this forum someone has posted a good video on how to measure backlash properly, abut I cannot find it. And most of what I find on youtube isn't really helping me.

Does anyone remember that post I'm talking about? I can't find it using the search either.

I've been "drawing" my cuts and so far I'm not getting round circles, or circles that complete. I end up with a gap. Moving vertically or horizontally, the machine
doesn't seem too bad, but diagonal movements are off.

Could it be my belts are the same tension? Anyway, ideas on how to "tighten" things up would be helpful.

Thanks!

 

I'm not sure if this is what your looking for but in "resources" there a tutorial section this is what I used to calibrate my machine.

HOWTO Calibrate your OX | OpenBuilds

There's a link to a conversation about calibrating. One other thing to check are the set screws on your pulleys. I had a couple of loose set screws that were causing me grief. I went ahead and drilled and tapped the set screws to 4mm so I could get a larger Allen wrench and torque them down a little tighter. I also added a little dab of Blue loctite.

 

I think that's a bad idea. while they have similar construction, they have different goals. Kinda like drying your cloths with a hair dryer. You may be able to make it work, but one is not ideal for the other task.


Also don't dry your hair in a in a cloths dryer. It wouldn't work out well.

 

Just curious ,
has anyone successfully printed 3d with their OX?

 

SO I've built a nice big one of these bad boys (approx 5 ft by 6 ft)and wired it, double checked to make sure it's made properly. Having all sorts of crazy issues with homing now. when I first run the controller software and open the port it's alarm locked (the limit switches are not engaged). if I bypass the alarm ($X), sometimes I can move the gantry around (using the keypad, tried this in both UGS and GRBL controller) but then, inexplicably, unpredictably, it will stop responding again (again, without the limit switches being tripped). I'm not sure what's happening here at all. My only thought so far is that maybe the step pulse value is off ($0). how many microseconds are the nema 23s and 17s rated for?

 

Try

Try removing the wires from the limit switches and E stop at the controller board. See if that improves the situation.
When I first wired my limit switches I was getting random noise all over the place. Had to run shielded cable, added .47 uF capacitors in parallel, and never did get my emergency stop button to work properly, as it sits 2 cm away from where I've mounted my power supply.

 

I'm running grbl control with a windows 7 machine I had issues at first and removed all of my limit switches as David suggested. Not sure thats what your problem is but it' a pretty quick thing to try. I have had a few of those errors you mentioned however it has typically been when I shut things down with my emergency stop.

 

Hey guys! We decided to build small OX for cadets of Odessa National Maritime Academy , Ukraine . The matter of the question is if someone can share the plans of the OX plates in .cdr format as we do not have license for Coral Draw products, but local producers requires them only.

thnks & brgrds

 

For those who have added the 0.47uF capacitor to their CNC Pro can you please post a photo or two of your configuration.

Thanks

 

Hello i bought parts from the parts store i bought a 8mm acme rod and an 8mm bearing and 8mm lock collar and they wont go together help please

 

@zombierunner You'll have to sand down a little bit the rod (put your rod in a drill)

 

The whole rod or just the ends

 

Sand only what is needed to get the bearing on the screw. Sand a little then check the fit, repeat until you get the bearing in place.

 

So I've had my OX running for almost a year now and I think I'm ready to make some improvements to it. I'm really considering eliminating the belts in favor of linear rail and screw drive or R & P. My ox is 700 mm x 1200 mm, which I'm probably going to reduce as well. I can count on one hand, the number of times I've actually used the full cutting area. Also, I want to beef up the gantry and the Z axis in hopes of getting better resolution and be able to take larger bites. I will also be upgrading to either Gecko and Mach3 or KL drivers and whatever control software is best for those. Anybody want to recommend a decent/proven method for any of the above?

Josh

 

I'm getting close to firing up my OX for the first time. I've been taking my time with the electronics, getting things where I want them. It's taken far longer to do that than I was expecting. Many additional parts were ordered, but I have a case for the electronics and plugs for all the steppers. Lots of parts were designed and printed on my 3d printer. I added limit switches to every axis. I got a touch plate for Z-min, I got an e-stop for the spindle.

I just have to finish off the cables/plugs for the 4 stepper motors. At least I hope that's all.

But the part that I'm most concerned about is left. Configuring the TinyG firmware to do it's thing.

I have a Raspberry Pi to host the serial connection, then I'll use ChiliPeppr to run everything. I wish it had an easy to deploy stand-alone version, like OctoPi is, but I added wireless to my shop now, so I'll manage.

 

Here's how I connected caps to my limit switch inputs. They're .47 uF 63v electro's but any voltage above 6v should work fine.
Make sure you have the -ve side (the shorter leg) connected to 0v.

 

Hi all! Im trying to figure out how to set the home switches on my ox. I have three switches but im going to use only the two of them for X-home and Y-home. I have done some experiments homing the Y axis, the problem is that after hitting the switch i cant jog around. The switch is wired at normally open end. Have you any ideas?

Kind regards