HI all, I'm looking at building my 2nd CNC (first one is a MPCNC), and want something a lot stronger, so was thinking something like the LEAD CNC. I'm having trouble understanding the specs for Nema 23's. For example, the following 2 steppers have similar holding torque, but one is higher current/lower voltage than the other. Nema 23 - 57 x 57mm : Nema 23 Bipolar 1.8deg 1.16Nm (164.3oz.in) ... Nema 23 - 57 x 57mm : Nema 23 Bipolar 1.8deg 1.26Nm (178.4oz.in) ... So does that mean I can run the first one at full torque with A4988/DRV8825 drivers? Is there any reason why the second one is better than the first? I feel like I must be missing something. I'd love to be able to run nema 23's from a simple arduino cnc shield if possible, since they are so cheap.
For performance you generally want to chose the lowest inductance configuration, which is typically also the lowest coil resistance or ohmic coil voltage. In other words, the higher amp ones are your best choice for performance.
Can you clarify what you mean by performance? Also with respect to the two motors I mentioned, will this be significant?
Both pages have a link to a torque curve. You'll note the one for the low amperage one starts a slight bit higher but then drops off very rapidly. As for how significant it will be in practice it's hard to say. @Peter Van Der Walt can give a much better explanation than I can.
Ok, that's helpful. So the lower voltage steppers have better torque at higher rpm. But running them with the A4988 drivers, for example, it seems the larger voltage one should still win? Since they will not be able to provide full current to the other one? Edit: Just looking at those torque curves. They cross over at around 160RM, which seems faster than I'd be planning to run them at (< 1000mm/s). So that looks like the performance wouldn't be an issue?
In my opinion, your best bet would be to not use those 3D printer drivers on a CNC router. Use an Arduino with some higher amperage drivers and then you can get much better performance. Many people - including myself - started with the CNC Shield clones and DRV8825 drivers. Then after having thermal issues on long cuts, even with heat sinks and fans blowing on the drivers, they (and I) upgraded to drivers much better suited to a CNC router. Smartest move I ever made with regards to my build and I have never had an issue with the electronic portion of my machine since I switched. I chose the DQ542MA drivers, but there are cheaper ones available. Or you can purchase something like the BlackBox from Openbuilds and have an all in one solution with much more powerful drivers. That being said, my issue may be that I was using 269 oz motors which, in my opinion are just barely adequate for my machine. I do not know what size you are planning on making. I have a 178 oz on my Z which works fine. My CNC router is 1500 mm long in the Y and I have a doubled up 80x20 beam for the X axis that is 850mm long. With the beam, a smaller 40x20 for the drag chain to ride on, the router, and all the other mechanical and electrical parts it is a lot of weight that gets pushed around. The DRV8825s on my 3D printer just have to move around a light weight heated bed and the extruder and hot end. I think my entire 3D printer weighs a lot less then the Y axis gantry on my CNC router.
Thanks for your input. I've come from the 3d printing world and have plenty of a4988's lying around, so was hoping to be able to use them. Also, my MPCNC uses them with Nema 17's and has had no issues so far (I only cut wood with it), but does feel like I'm getting to its limits. I was wanting to build something like a LEAD CNC and use it mainly for wood cutting/carving, but also would like to be able to cut aluminium. I like the idea of the BlackBox, but was hoping to be able to put something together myself that's a bit cheaper. So, if you (or anyone) has any advice on adequate stepper motors/drivers for a LEAD CNC (1000mm x 1000mm, although I might go a bit smaller on the X axis) that will be mainly used for wood, and some aluminium, I would greatly appreciate it! The DQ542MA's look great, but at $69 AUD each, they're a bit steep. What about something like the TB6600's? And for the motors, I was thinking about 1.2Nm (170oz.in) would suffice, but is that way too small?
I personally would not go with 170 oz. The 269 oz are in the same price range which is what I currently use. I cut wood, foam, plastics, and aluminum with it. I even accidentally cut a piece of thin stainless I found thinking it was aluminum. It didn't look pretty but it counts. Your X axis is going to be about 150mm longer than mine, so you will be moving more weight than I do. As I mentioned above, I am planning to take the 269 oz off and replace them with the 345 oz motors Openbuilds sells. The 269 oz work, but I want more torque. I have not used the TB6600s personally. Many people have. You just have to be careful where you get them because many are sold as TB6600s but when people have problems, or just open them up to look inside, they discover it does not have a TB6600 chip inside but an inferior one. If you do choose the TB6600s, I would definitely use higher torque motors than the 170 oz.
Yeah I've been doing some hardcore reading on stepper drivers and its put the fear in me about the cheaper stepper drivers. Unless someone knows a reputable source for some cheap ones, I'm probably going to buy these, which seem like a safe choice: Digital Stepper Driver 1.0-4.2A 20-50VDC For Nema 17, 23, 24 Stepper DM542T 714485493829 | eBay (interestingly, their ebay store has a much cheaper price than the one on their website) Here's something I cant get my head around. What is different about these 2 steppers that warrants such a price difference?? Nema 23 - 57 x 57mm : E Series Nema 23 Bipolar 1.8deg 1.9Nm ... Nema 23 - 57 x 57mm : Nema 23 Bipolar 1.8deg 1.9Nm (269oz.in) ...
My guess the difference is the shaft size of 6.35 vs 6 mm. The 6.35 mm may be a higher volume seller therefore cheaper.
I was looking at another one. Somehow I was looking at this one and took a wild guess. I think it was because I had looked through them earlier while checking out the previous two you linked and I was trying to figure out the difference between that one and the E series one you linked (prior to you linking them). Unfortunately, the data sheet for the cheaper one has a broken link so I can not compare the torque curves or other data not listed on the product page.
I emailed them yesterday and asked for the missing datasheets. They emailed me back today the sheets for the other motor. When I mentioned they were the wrong ones they said both have exactly the same torque curve. So then I asked why is there a price difference and their response was: Whatever that's supposed to mean???? I think I've now settled on which motors/drivers I want to get (pending someone telling my how bad an idea they are). I've asked a question about them on the OpenBuilds LEAD CNC thread (thought It probably belonged there). I know you mentioned the 269's would be much better, but for me they're almost double the price of the 170's, and I'm already way over budget (as always...). If the only difference is needing to go slower with the 170's I'm perfectly fine with that, If there's things they just cant do, then I'll reconsider.
