[canman77]

Hey everyone,

I've done a lot of research on CNC machines here and have learned quite a bit, so many thanks for all the public information available. Very cool.

Last year, I bought a Chinese CNC machine for a little business venture I was working on. The listing I purchased from is no longer available (how convenient) but this is basically the same one I bought:

3 Axis CNC Router ENGRAVER Milling Machine Engraving Drilling 3040T Desktop | eBay

I have the same bogus blue box. It took a while to get the machine dialed in, and when it works properly, it does a great job. However, since the beginning, I've had stalling issues with the motors. I contacted the seller, they said it was normal, blah blah blah. They sent out a replacement motor and a replacement spindle, because the spindle wouldn't maintain a consistent speed. (I had to rewire the speed potentiometer with wire that wasn't 3 strands)

The original issue was with the z-axis motor. After messing with the motor tuning settings in Mach3, the z- and y-axes operate fast enough with no stalling. I think I had the y-axis running at around 1800mm/min. The z-axis was closer to 500-600mm/min, something like that. I kept having problems with the x-axis motor, so I swapped it out with the new motor the Chinese sent. It wasn't much better, so I started getting it dialed in as best I could. I thought I had it dialed in with the right speed and acceleration, very similar to the y-axis. But then suddenly it started stalling. So I lowered the acceleration and speed, which fixed the issue up until couple of days ago. I started getting a few stalls here and there, and then today when I was working on a project, I had major stall issues. I lowered the speed down to 400mm/min and acceleration to something like 10, and it STILL STALLS! I've seen videos of stepper motor machines hauling butt with no issues so I know it's possible and probably normal for the motors to go much faster than mine are, with no issues.

From my research, I've gleaned that it could be the power supply from the blue box. Or the motors are just garbage. Likely both. I removed the snap-in connectors from the motors to the parallel cable and soldered those connections because I thought the snap-in connection could be shaky. Didn't fix the issue.

I'm extremely frustrated with this machine, because for however long we've had it (October 2015) we've never been able to trust the machine. I run jobs on the machine and have to sit there and watch and make sure it doesn't stall. I'm not opposed to watching just to make sure nothing crazy happens, but I'm always holding my breath just waiting for the motors to stall, which happens way to often.

Is the fix here a better power supply/controller box? Are the motors junk? I would give you guys details about the motors, but the eBay listing that I originally purchased from had nothing like what the listing I linked to has. And even that listing doesn't give much detail about the steppers.

Any help you guys can offer is very much appreciated!!

[ger21]

A lot of people scrap all the electronics and replace them with quality components.

[canman77]

Dang...didn't see the Chinese CNC forum until after I posted here. My bad.

Regarding replacing the electronics...what would be the higher priority? The controller or the motor? I'd think the controller, since the motors still might have potential, yeah?

[gfacer2]

Well start with figuring out what you have. Figure out the specs of the drivers, motors and power supply. Figure out the weakest link or 2 and replace it first.

Sent from my LG-D852 using Tapatalk

[canman77]

So...I'm a total rookie and I'm not really sure how to find the specs on all these things. Could you direct me to a link that might explain how to do that? I can post pictures of what I have as well, but I may need some direction as to what to take pictures of.

I assume the drivers would be the IC's on the circuit board inside the blue box? If it would be better, I could post this to the Chinese CNC forum.

(I've built several electronic devices and know my way around circuit boards and components, but I'm not sure how to go about getting specs on the motors, drivers, and power supply.)

[gfacer2]

Well drivers are likely tb6560, the motors you'll have to google or ask or look at eBay or?

Power supply should be written on it or somewhat testable with multi meter

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[canman77]

OK, I'll test the power supply voltage...I don't think I'll be able to test for current unless someone knows a good way to test the current in these power supplies. I'll see what I can find about the motors, and I'll check and see if I can identify the drivers in the controller. I'll report back as soon as I have more information.

[canman77]

I took apart the controller, here is a gut shot so you can see what I'm working with:
http://www.cnczone.com/forums/attach...d=319374&stc=1

I believe I found the drivers. I only removed one driver board, as I figure they're all the same. The chip is an A3977SEDT. I'm looking around to see what others have experienced with these drivers but haven't found much yet. Here's a picture of the chip:

http://www.cnczone.com/forums/attach...d=319376&stc=1

The power supply feeding the motors outputs 20.4vDC without the motors/parallel port hooked up. With those connections made, it outputs around 19.4vDC. (The other power supply in there is for the spindle, which appears to output roughly 50vDC.)

Now for the motors...here's a picture of the label that was only on the replacement motor:

http://www.cnczone.com/forums/attach...d=319378&stc=1

I apologize for the picture being upside down. Photo bucket won't let me rotate them at the moment. In any case, I have no clue what these numbers mean. Except the 3A, I assume that's 3 amps?

[gfacer2]

Driver:Allegro MicroSystems - A3977: Microstepping DMOS Driver with Translator - note for 2.5amp and you have 3amp max motors so the drivers are underpowered which effects your max torque.

Steppers: who knows those don't have any hits on google but I assume you knew that. Maybe close to the 4408 here?1.8' Hybrid Stepper Motor 57HD, View hybird stepper motor, stepper motor from Ningbo Weixing Electric Appliances&Tools Co.,Ltd. on EC21.com
The torque is not super high on those but I don't really know what they should be ideally. The 2.5amp driver would cause its torque to be less.

PSU: who knows but it likely says the amps and volts on the side of the metal shell somewhere.

I really don't know how these stack up but there you go, My hunch says in order of issues are 1)Drivers are too low 2) motors do not have enough torque especially when driven underpowered.

[canman77]

So when it comes to torque...if I get a better driver, I'd be able to maximize the torque on these motors. If I wanted to go even further, I'd need different motors with a better torque rating, yeah?

[gfacer2]

Pretty much.

You can see now what ger21 is talking about. The systems are kind of designed together so once you change out one component, you end up with the next one as the weak link. And its often no fun to wait weeks for a part, redo the wiring with new drivers and then find out the motors are the real issue. And if the power supply is 12v, that could be part of the issue too as higher voltages will drive the motors better (but your drivers max at 35v so 24v is the most common option in that range).

[canman77]

Yep...it all makes sense now. May as well upgrade the controller and the motors at the same time. Looks like I'll be doing some research on motors! Thanks for all the information. I may run some of this past the Chinese CNC forum and see if anyone has had a similar experience.

[bigdawg72]

I have that exact machine and am experiencing the same problem with stalling. The seller suggested loosening the nut on the lead screw. It helped. I am still not satisfied though and am looking at Gecko G540 driver/motor combos. Since I already have more $ in software than I do in the machine I figure what the heck I might as well spend as much on a driver/motor upgrade as I did the original machine. My thinking is that at least I will have good electronics and motors when I look to upgrade to a larger frame.

[canman77]

Interesting. I'll give that a try and see what happens. I'm in the same boat you are though, I'm still not satisfied and can't trust the machine. At least the frame is good!

[James Newton]

You've gotten solid advice here and I'm not AT ALL disagreeing with any of it... but... I want to add two ideas which are "cheap fixes" that might allow you to scrape by a while longer if you don't want to invest / learn new drivers / motors / supply right now:

1. Are the motors getting hot? If so, they are loosing strength. People will argue with me about this, but I've seen it too many time to be less than 100% certain: Hot motors get weak. And they get weaker over time. If you have room, attach CPU coolers to the motors with heatsink compound. Works wonders.

2. If the Z axis is always loosing steps down, then gravity is the issue. Offset the weight of the Z axis with a spring, weight over a pulley or even a bungee to the roof.

NOTE: THESE ARE NOT THE "RIGHT" WAY TO FIX IT! But as temporary "hacks" they can avoid your having to purchase my drivers and upgrading your system... ,o) wait... oops... No, you totally need to purchase a set of drivers from me and get that system running the right way...

[Jon.N.CNC]

Illegra or toshiba both chips will only output around 1a repeatable current before they fry themselves, get your self some mosfet drivers. material prices outweigh driver prices after a few jobs, trying to scrape by with smd chip drivers you will be throwing away more than the cost of the drivers in botched jobs.

[canman77]

James, thanks for the "hacks" and suggestions. The Z-axis doesn't appear to lose steps, but I might try the bungee cord attached to the roof anyways, because that just sounds fun. The X-axis is where my problem is at the moment. And the motors are cool to the touch when running, so I don't think they're getting weak. Of course, now I can't really run jobs because the X-axis gets stuck on even the slowest speeds, so the motors are always cool haha! I'll PM you about the drivers I need to buy from you!

Jon...I wasn't aware that these chips only output around 1A repeatable current. Does this mean they do at times provide the rated current on the data sheet, but that they're only consistently outputting 1A?

I'm also wondering...would the problem temporarily be solved if I got a motor rated at a lower current? I realize I wouldn't be able to run "heavy" jobs, but the heaviest job I've done is cutting surfboard fins out of G10. Which shouldn't be considered a heavy job at all in my opinion. I'd think a heavy job would be milling metal.

[Jon.N.CNC]

James, thanks for the "hacks" and suggestions. The Z-axis doesn't appear to lose steps, but I might try the bungee cord attached to the roof anyways, because that just sounds fun. The X-axis is where my problem is at the moment. And the motors are cool to the touch when running, so I don't think they're getting weak. Of course, now I can't really run jobs because the X-axis gets stuck on even the slowest speeds, so the motors are always cool haha! I'll PM you about the drivers I need to buy from you!

Jon...I wasn't aware that these chips only output around 1A repeatable current. Does this mean they do at times provide the rated current on the data sheet, but that they're only consistently outputting 1A?

I'm also wondering...would the problem temporarily be solved if I got a motor rated at a lower current? I realize I wouldn't be able to run "heavy" jobs, but the heaviest job I've done is cutting surfboard fins out of G10. Which shouldn't be considered a heavy job at all in my opinion. I'd think a heavy job would be milling metal.

Yes pretty much so. The rated current is peak and does not take into account the thermal losses. They will run nema 17's fine. Buying weaker motors is going backwards my friend.

[canman77]

I do realize it is going backwards...obviously it's better to spend the serious money for a much better system, I'm just trying to avoid it if at all possible.

That said...the motors seem to be OK when they're running properly. So the controller would likely be the first upgrade. Would the existing power supply in the blue box be OK with upgraded drivers, or is it better to have more than 20vDC available for use?

[Jon.N.CNC]

I do realize it is going backwards...obviously it's better to spend the serious money for a much better system, I'm just trying to avoid it if at all possible.

That said...the motors seem to be OK when they're running properly. So the controller would likely be the first upgrade. Would the existing power supply in the blue box be OK with upgraded drivers, or is it better to have more than 20vDC available for use?

3a motors with a 20v psu is not very good. take a look at either the cw5045 or slightly cheaper wantai mosfet drivers around £30 here in uk each. these will run your motors well. Both run at 20v just measure psu output voltage whilst running and watch for any drops in voltage.

controller wise can i recommend you simply want a non motion control opto isolated parallel port type bob around £40 and either a uc100 or uc300 motion controller. You then can use uccnc @ £30 its much cheaper than mach 3 and imo alot better.