Upgrading from Steppers to Hybrid Steppers (servos) questions

Hey Everyone!

I’m a n00b to the laser game and to LightBurn. This isn’t really a LB related question so I’m not sure if this post will be allowed.

Let me say first my laser is a 900x600mm 100 watt Chinese machine. It’s yellow/grey in color (does this even matter?) Has a Ruida controller and manual Z axis.

My question is does anyone have experience upgrading from the stock stepper motors to hybrid steppers & drivers. I’m looking to get some more speed out of my machine because of the higher power i need to engrave at a faster speed. I’m maxing out at 600 mm/s. It may seem fast but over a large its really not.

I’m not really sure what NEMA size my stock motors are but the measure 42mm squared with a 5mm shaft.

Also can I use one of the stock steppers and driver to automate the Z axis for auto focus?? I realize I need to add the sensor/limit switch to the laser head. Thanks for any advice or comments!

Jason

I don’t have any advice about upgrading to servos, but I’m wondering how fast you need to go?
The first thing I would try (relatively inexpensive) is to upgrade the power supply for the steppers to something higher voltage.

Steppers lose torque at high step rates because their inductance rises with speed and limits the amount of current they draw for a given voltage. Higher voltage is usually better as long as you stay inside the limits of your motor drivers.

My 80W chinese laser (ruida) uses 24 volts as the stepper supply, but the drivers are rated for 48 volts. If I was looking for more speed I’d try a supply rated at 36 or 42 volts and see if that got me where I needed to go.

When I built my CNC plasma cutter I started out with a 24 volt supply and later upgraded to a 40 volt supply and the difference in acceleration and top speed was amazing.

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Hybrid steppers (as I understand them) are not servos. They are simply stepper motors with encoders attached. They seem like a bit of a scam to me, but I am open to being convinced otherwise.

In my opinion, this is of little use on a typical Chinese machine that uses a DC laser tube. A DC tube can only fire so fast - not nearly as fast as a RF tube like in mainstream lasers (Trotec for example). I can run my machine at up to 800 mm/sec but there will be artifacts outside the intended engraving area. These show up as small dots or dashes. If fast engraving is of primary importance, then you need a different type of machine.

Aside from that, the addition of an encoder to a stepper motor does not increase its speed. You can probably speed up your existing motors by changing some settings - but I don’t recommend it because the engraving quality will suffer.

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Thank for the info on the power supply Hank! I will definitely keep that in mind. Actually I’ll probably give that a try first. I understand that higher speeds my quality of engraving will go down, but maxing out at 600mm/s is just too slow running at 15% on my 100 watt machine. Cutting and engraving leather goods mostly and even at those settings its a bit on the hot side, too much burn on the edges and engraving is a little too dark, plus over time is just too long. If I can get up another 100-200mm/s I think that would be better all around. I’m not doing photo quality stuff so high res engraving isn’t very important to me.

I also cut acrylic, plywood and MDF with the same machine so the 100 watt power helps with that.

Thanks again for your input, going to look at power supplies first.
Jason

Thanks for the feedback Rich! I appreciate your input.

Jason

If your stepper driver is the type with DIP switches then you can try to get extra speed by increasing the current. This is what I did to achieve a reliable 800 mm/sec on my machine. I am assuming that you have already tried to increase the max speed in software and found that the steppers start missing steps.

Increase the current too much and it will get too hot. It is a downside of steppers that the coils are always energized, even when not moving. If you can hold your finger on the motor for a few seconds then it is running cool enough.

If you do decide to increase the current you should monitor the temperature during a big job to be certain that overheating is not an issue.

Another thing is to be sure that things are moving smoothly and that you do not have the belts too tight. The tighter a belt is, the more torque required to move it - and the more likely the motor will skip steps. Too loose is also bad, but not as bad as too tight.

Lastly, increasing scan speed can actually slow down the overall engraving speed. It depends on the width of the item being engraved. As the speed increases, the time and distance that the laser spends accelerating and decelerating at each end increases. If you are engraving many things at a time you may find it to be faster to engrave at a slower speed with the machine engraving each item separately.

Thank you Rich for the info, I appreciate it. I’m going to try to increase the voltage and go from there. If I can get a reliable 800 mm/s I’d be happy with that. I did try increasing the max speed in the software but I was barely able to break 600 mm/s even when I set it to 800 mm/s.

I double checked the belt tension. They seem to be at a happy medium, not too tight or too loose.
Jason

How about just change to a 60 or 80 watt tube and power supply?

I guess that’s an option but would like to retain the power for cutting.

Be aware that cheaper CO2 tube power supplies cannot fire or switch on & off quickly enough for the detail you’d need at those higher speeds.I’ve tested our CO2s and found greatest detail at around 350-380 mm/s. Going up to 400-500 -600 mm/s caused a noticable loss of actual detail.

Thanks for the info. Funny you bring this up, I just watched a video yesterday morning about upgrading the power supply. Apparently the brand ZYE that comes stock in most units has a very high failure rate. Just happens to be the power supply I have in my unit. They will be upgraded in the near future.

If I change the power supply to 48v would that only run the steppers? I guess the rest of the system is 24v?

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That’s correct! I made almost a costly mistake by changing my power supply to 36 volts not realizing the rest of the system is 24 volts :man_facepalming::man_facepalming:. I cough it quickly when the display wouldn’t come on and crispy smell from inside!! Anyway back to the beginning.

I would also wonder if you might be nearing or potentially surpassing the threshold of gcodes/sec the controller can process, relative to the DPI setting and speed.(usually evident in stuttering I believe) I’m surely not an expert but wouldn’t increasing the speed would mean that the controller would be processing more commands to toggle the laser on/off for a said run?(IE some controllers can only handle 1000 gcodes/sec or something similar, 32bit controllers are probably higher than that number) Then there’s the maximum speed the laser tube can actually turn on and off as pointed out by @Stewey earlier in this post.

I believe that any one of these would function as a top limit to the obtainable speeds, which may not be within your desired speed range. Again I am no expert but these are the things I have divulged from too many hours trolling these and other forums :slight_smile:

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