Motor and Wheel Details

#1

Hi Guys,

Can you provide some more detail on the specifications of the NEMA 23 motors you are using?

Also, what is the diameter of the Delrin V wheels?

Thanks!

-Jeff

#2

@jwoody18 They’re 2.8A NEMA 23 motors (LDO-57STH56-2804AC) with TB6600 drivers. I don’t have the datasheet on hand but you should be able to find it.

The delrin v-wheels are very similar to other ones you can find online, like the Openbuilds ones: https://openbuildspartstore.com/delrin-v-wheel-kit/ except the inner bearings accept M5 bolts instead of 1/4"

#3

Thanks, Chris!

I see they make a 76mm body option (versus the 57mm in the design) in the same range that has ~50% more torque. Would that be a drop in upgrade to the LDO-57STH76-2804A? I believe I read the power supply can support up to 4A per motor? Looks like power would be ok?

-Jeff

#4

As Andy is the lead on this aspect of the design, I will quote him directly when I asked him about this:

You can upgrade. I would probably upgrade the power supply voltage and current first though.

In my opinion, I think your suggestion is something that we could look further into in the future. We designed the electronics system so that the driver boards could have a max output of more than double the average stepper motor current draw. For the time being, all of our beta-tested machines which were run for 8 months in varying conditions were running something close to our current electronics setup and they didn’t suffer any issues with a lack of torque.

#5

Pardon my lack of electrical experience on this question, but the data sheet for the motor family here seems to suggest that both the designed unit and the 76mm option have a draw of 2.8A, unless I’m not understanding something? If that’s the case, could a more powerful power supply reasonably be needed? How many amps is the included supply rated at delivering for the motors?

Data sheet here: http://ldomotors.com/uploads/product_attachment/path/8/LDO-57STH_Info_Sheet.pdf

I notice the rated voltage of the Longmill stock part is 2.5V and the 57mm motor option is listed at 3.2V, but it seems like they would both be driven off a 3.3V rail from the PSU. Is that correct? [EDIT: I see from the TB6600 page referenced in the post below that the input voltage to the TB6600 is 9V-24V, and the Longmill PSU spec is 24V IIRC, so while still unclear what voltage the TB6600 sends to the motors, if it is stepped down it happens in the TB6600 not on a 3.3V rail from the PSU].

-Jeff

#6

Chris,

Just throwing some more background info in here for my own (and others trying to learn) future reference:

From: https://www.dfrobot.com/product-1547.html

" How to control a stepper motor?
The fast way to control a stepper motor is just using a stepper motor driver (controller). And TB6600 arduino is just what you need.

TB6600 arduino is an easy-to-use professional stepper motor driver, which could control a two-phase stepping motor. It is compatible with Arduino and other microcontrollers that can output a 5V digital pulse signal. TB6600 arduino stepper motor driver has a wide range power input, 9~42VDC power supply. And it is able to output 4A peak current, which is enough for the most of stepper motors.

The stepper driver supports speed and direction control. You can set its micro step and output current with 6 DIP switch. There are 7 kinds of micro steps (1, 2 / A, 2 / B, 4, 8, 16, 32) and 8 kinds of current control (0.5A, 1A, 1.5A, 2A, 2.5A, 2.8A, 3.0A, 3.5A) in all. And all signal terminals adopt high-speed optocoupler isolation, enhancing its anti-high-frequency interference ability.

As a professional device, it is able to drive 57, 42-type two-phase, four-phase, hybrid stepper motor."

So it sounds like the TB6600 is the device that regulates the amperage that can be drawn by the stepper motor? And it supports both the 2.5A and 2.8 amp draws of the two different LDO motor options. I guess my question is, given the 4A peak capacity per TB6600, and the 2.8A requirement of the larger motor (vs 2.5A stock), why would it be necessary to upgrade the PSU before looking at upgrading the motors?

-Jeff

#7

@chrismakesstuff would you be able to ask Andy about my additional questions above? Thanks,

-Jeff

#8

He is on Holidays right now so incognito. Will be a little while yet.

#9

@jwoody18 you’ve got some good questions, I’ll ask Andy to get back to you as soon as he can :+1:

#10

@chrismakesstuff Hi Chris. I saw that the boards came in so I’m sure that’s keeping you hopping but I just wanted to check in after 2 weeks and see if you could get 5 minutes with Andy to get some feedback on my questions. Thanks!

#11

Ok so from what I’m gathering there are a few questions that I can distill into something that can answer.

Q:Can I use a larger motor on the LongMill (from the 76mm to 57mm)

A: Form factor wise, you can. There shouldn’t be any difference in terms of mounting. You just need to make sure you are getting the right size shafts (6.35mm) on the motor.

Q: Can the stock electronics that come with the LongMill provide higher currents to the motors?

A: The TB6600 drivers and the board are designed to be able to provide around 4A at the voltage set off the power supply. There is no step-down of the voltage happening, you can run stepper motors at a higher voltage than (which is normal is almost always done) specified in the spec sheet.

The drivers are all set to around 2.2 to 2.5A. The power supply is rated for 10A. Your power supply will need to provide more current if you choose to increase the current.

IF YOU WANT TO UPGRADE THE MOTORS AND OTHER STUFF THEN THESE ARE MY SUGGESTIONS

  • The first place I would upgrade is the power supply so that it has a higher voltage. At high speeds, a motor running at a higher voltage will have higher top-end torque. That means you can run the machine faster. In the LongMill, your speed is limited when the motors cannot provide enough torque to overcome the inherent resistance in the machine. By increasing the voltage, the motors have a shallower torque curve drop off that means that the machine can run faster at higher speeds.

  • Ask yourself why you need to make the upgrades. Every component of the LongMill is designed to work together in harmony, and components have different limits and working boundaries. Are the motors worth investing money in first before upgrading other parts of the machine?

  • A side note. The LongMill’s electronics are passively cooled. However, there is a plug available to add a 12V fan. If you choose to increase the power going through your electronics I would suggest using it.

Hope that helps!

1 Like
#12

Perfect, thank you for confirming.

Ahh, this is good to know. With no step down in voltage the issue is clear.

So the spec sheet talks about a rated voltage of 2.5 for the 56 and 3.2 for the 76 - both at 2.8A but I’m still a bit confused. 2.8A x 4 = 11.2A of draw plus any other draws from the controllers and ancillary circuits. Which is more than the 10A of the 24V supply. Of course 10A at 24V is much more current than 10A @ 3.2V, but if you choose to run the stepper motor at a higher voltage is there a corresponding drop in amperage demand?

I guess what I’m wondering is how to square the 10A supply with the 11.2A of fully loaded demand.

Do you have a sense of what the full amperage load is at 24V for a system under normal operating load? In the past ISTR electrical engineers I’ve worked with talking about designing for no more than 80% current load to allow for inrush and fluctuations as well as minor changes or variances that are unforeseen initially.

As a secondary question, what is the max amp load for the machine (excluding the router load) on the 110/120V input side. I have limited circuits in my shop and need to plan for where I’m going to put the table from an electrical perspective.

If the voltage is at 24V and the current is set to 2.2 - 2.5A, and the motors are both spec’d at 2.8A (albeit at slightly different low voltages), is there any need to adjust the current setting when using the larger motor? Aren’t they both getting a lot more 24V current than 2.8A @ 3.2V?

Would you be able to share a link to the datasheet or part number of the specific TB6600 implementation you are using? If I’m understanding my research correctly the TB6600 is the underlying chip from Toshiba and various people have implemented drivers around it with varying specifications.

To say it differently, the question wasn’t so much “Can the stock electronics that come with the LongMill provide higher currents to the motors?” it was “Can the stock electronics support a drop in upgrade to the 76-2804A given the above details on the extremely close power requirements that are both below the 2.5A @ 24V stock setup?”

This is an excellent data point. So moving to a 48V supply would yield an improved torque curve if that was the goal.

Hmm I see the TB6600 is 9V-42V (actually, I take that back, without knowing which TB6600 based driver is used I can’t say for sure). I wanted to do some PSU research but need more details first.

This is totally fair and understood. It’s what we’re paying you for. :slight_smile:

For my application, I’m very interested in feed rate through baltic birch and 1/2" to 1" thicknesses with 3/8" or more depth of cut. That is to say, I’m interested in optimizing cutting time and quality for that particular material. As there hasn’t yet been much information provided on feeds and speeds at the higher end, it’s a bit hard to tell what the machine will be able to do in it’s stock config.

In the mean time, the MillRight Mega V campaign launched and they published some impressive videos and specifications up front about feed rates (up to 500 ipm in some cases) as well as detailed torque and other ratings. Looking at their design, it is similar to the LongMill in many positive respects but they definitely went with a beefier PSU and beefier motors. Plates and railes look to be of similar thickness, wheels are larger and they have a rack and pinion system. Either or both of those, in concert with the PSU and motors may be necessary to achieve their numbers, but I’m curious if a material boost can be seen between Longmill feeds (not really publicly known or understood yet, to be fair) and the upper range of the Mega V range.

The most material different I’ve been able to discern, pouring over the published specs are the PSU and motor specifications been beefier, this the line of inquiry. Especially since the same series motors from LDO have drop in replacements (as long as shaft diameter etc are confirmed identical as noted by Andy above).

I’m happy with my decision to support Sienci, I like what you’re doing, I like that you’re Canadian, I like that you seem like very honest and transparent guys and I like supporting entrepreneurs. I just want to wrap my head around how I might be able to easily goose the supported feed rates for my application by cribbing some of the beefier specs from the Mega V
and applying them to the Longmill.

-Jeff

PS:

Noted and always good advice. Especially given the potentially multi-hour run times and the tendency for most shops to get warm anyway. Even more so if the machine gets located in a housing to suppress sound and thus has reduced airflow. I used 2x80mm fans (so 2RU tall fans in server rack speak) in a product in the past and their large size allows them to spin slowly and move a lot of air and they lasted well past 5+ years in 24/7 use cooling a 2RU industrial product. Highly recommend them. Small fans are noisey and don’t move nearly enough air.

I found the part number and can highly recommend this one: https://www.digikey.ca/products/en?keywords=EFC0812DB-F00

#13

Another quick spec question. The LDO datasheet I found listed 56-2804A but not 56-2804AC. If you are able to scare up the datasheet or point me to what the C stands for I would appreciate it.

Thanks!

-Jeff

#14

Here’s a copy of the spec sheet

#15

Thanks @andy

Would you be able to look at my electrical questions above and comment as well?

Thanks,

-Jeff

#17

Hi Jeff,

The drivers will limit current draw based on what it is set to, and usually the motors will not draw full current simultaneously or at all unless they are subject to stall/overload (drawing too much current will be the least of your worries haha).

For the 24V, 10A power supply, the max draw from it should be around 240 watts (give or take). But you probably will not get to that most of the time.

In terms of the general info on steppers, I would recommend going online to learn more. Here’s a good place to start: https://reprap.org/wiki/Stepper_motor

For details on the TB6600 drivers, you can refer to this: https://toshiba.semicon-storage.com/us/product/linear/motordriver/detail.TB6600HG.html

Hope that helps,

Andy