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Makesmith CNC information request

https://www.kickstarter.com/projects/makesmithcnc/makesmith-cnc-the-most-affordable-desktop-cnc-rout/faqs

Is there any way to purchase or build this product (especially the closed loop 9g servos?)

I understand it is not exactly the right place to ask but this seems to be the only place connected to builders and this is a machine I am keen to have.

Apologies and thanks in advance!

the code is available back in the git history (there is a link to the commit
floating around somewhere here, search for makesmith), there is a bug in the
last released version of code that requires fixing to compile on arduino core
more modern than 5 or so years old.

however, since it’s not maintained, and technology has moved on, it would be
easier to get a cheap 3d printer and attach a spindle in place of the hot end,
and much better supported.

There were accuracy/reliabiity issues with the magnetic sensors that were used,
with both the sensors and the servo control being PWM interfaces, it orked, but
not as well as it should have. I actually have a makesmith sitting in my garage
(one of the shaft couplings broke as I was building it and I got it moving but
never finished it). I’m in Southern California if there’s any reasonable way for
me to get it to you.

David Lang

Thanks David for replying.

I shall try to find that link. BTW, is there any way to integrate the closed loop servos with a commin-standard uno-ramps set up?

I have seen makerbase closed loop steppers which are simply plug and play. However, I suppose the pwm input may have something to do with it. (I am neither an engineer or coder, please pardon my ignorance)

Yes, a 3d printer model will be more sensible. However, it is the 9g servo mechanism which has caught my imagination. If somehow, I could replicate that, it would be a great help, and perhaps would allow me to make tinkering kits for local schools.

I live in Kolkata, India. If you could find a reasonable shipping option, I am in. However, let me tell you shipping rates are very erratic and at times even be double the cost of the product itself. You may want to ship electronics only just to keep costs from spiralling away. Let me know where the thing stands.

Sincerely yours,
SP

I am not aware of any common software that supports closed loop operation with
servos and magnetic sensors that the makesmith used. Most of the common CNC
software doesn’t support closed loop servos in anything other than a rather dumb
mode that just has them emulate open loop steppers (the only advantage being
that the servo will notice if they miss steps and catch up)

Yes, shipping from the US is not going to be worth it. Better for you to order
the stuff from China directly to reduce the costs (plus paying tarrifs to get it
into the US and back out again just adds to it)

The makesmith used an arduino with add-on board to drive the servos and read the
sensors. If you were to do it from scratch, a pi pico can easily drive lots of
PWM outputs (servos) and for the sensors, rather than using PWM from the
sensors (which requires an ADC to read them or very precise timing of each
pulse), I would look for magnetic phase sensors that give you a digital
interface. IIRC, the sensors that Bar used for the makesmith have that option on
the chip, but he didn’t use them (again, a Pi Pico is far better than an arduino
Mega for this)

David Lang

I see, so the quest for real closed loop continues.

Would you like to ship the electronics only? Even if it may come around 70$, I would consider it. I guess, I have found the laser files on the forum, which I can get cut locally.

And thanks, if you could find the encoders, that would be great. Or if a rotary encoder can be repurposed.

But let me caution you, I have no idea on programming. Will need some handholding to get it working again.

Unfortunately I don’t have any of the hardware for Makesmith left to ship :slightly_frowning_face:

It’s a pretty good project, but you might have to modify the design a little bit if some of the parts are hard to find. Especially the modified servos, I think we had those made.

continuous rotation servos should not be hard to get. There are a number of
magnetic angle sensors available now (I read an article yesterday that Tesla is
using them on their retractable door handles, so cheaper with better interfaces
now)

given how old the codebase is, I would suggest working from scratch.

quadralateral encoders are FAR more common than anything else, and much easier
to interface with. They give you a signal pulse on movement (you need a fast
enough system to be sure to not miss the pulse). Many motors are available that
have these encouders built-in (like the ones the maslow uses)

magnetic angle encoders like the makesmith used, have either PWM outputs, or you
have to query them and read the response, and Bar noted that the angle readings
are not actually that precise without calibration (which is not that hard to do
if you can rotate the shaft a known amount, say with a stepper, but if you are
doing that, is the magnetic angle encoder really giving you a lot of value?).
You also need special magnets with the magnetic field not going up through the
disk, but going across the disk.

If I was going to build a makesmith-like device today, here’s what I would be
looking at

start with a Pi Pico, it has lots of I/O to read encoders and PWM outputs to
drive hobby servos (open loop)

continuous rotation servos are readily available (and it’s not hard to modify
standard servos to be continuous rotation, just remove the stops and set the pot
in the servo to mid-range instead of coupling it to the output shaft)

encoders are readily available, or they can be made with a couple optical
sensors. If you have access to older mice that have a ball instead of a optical
sensor, you have a couple sets of encoders in them that you can use (and the
disks to activate them). you may need to do some level shifting to couple 5v
sensors to the 3.3v pico, or you may be able to make it ‘just work’ :slight_smile:

The pico can be programmed via the arduino IDE, and is significantly faster
than the stock arduino chip, so adapting the grbl gcode interpreter and motion
planner should not be that hard to do. The hard part would be changing the
output from driving steppers to having PID loops to match the measured position
and velocity to what the planner is looking for. Not a utterly trivial task, but
not rocket science either (and then not hard to adapt to more sophisticated
motors)

David Lang

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Thanks for replying Bar, I guess i might have to mod things a bit.

Dlang, I understand your point. However, you may be be giving too much credit to my (otherwise nonexistent) electronics and programming skills.

I guess some of the parts I will have to source from china, with whom in the etherning, we are experiencing a blockade/import restriction in retail goods. I had wanted to get a resin printer but couldn’t get a single seller who would mail it. While the indian distributors are willing to fleece me thrice their price anyday.

The mouse idea sounds interesting, let me look for them a bit.

Nevertheless, I was also looking for alternatives during which, I came across this PM35 type bipolar stepper.

“Stepper Motor - Bipoloar 48 steps - 24V - 600ma : Buy Online Electronic Components Shop, Price in India : electroncomponents.comStepper Motor - Bipoloar 48 steps - 24V - 600ma : Buy Online Electronic Components Shop, Price in India : electroncomponents.com

I can source it for around a dollar, while a 9g servo may cost just below double its price. This would also allow me to utilise the common uno-ramps setup, which I have lying around.

I know that servos have some advantages, but does the 9g servos beat the performance of PM35 in price and performance? Just asking.

(If it’s alright, I would really appreciate if someone could help me with the adaptation of this stepper in place of the 9gs)

48 steps, driving a common 1/4-20 threaded rod (like the makesmith used), gives
you a resolution of ~1/960" and would let you use common grbl (or other)
software, so that would probably be a much better approach.

If you were to find that it doesn’t give you enough power, gearing it down with
belts 2:1 or 3:1 would still give you pretty good resolution

David Lang

If you are willing to do open loop control with stepper motors, I think that is going to be the easiest route.

You can find some pretty cheap and decent little machines on Alibaba these days which are very similar to Makesmith

they are not any special servos, and are not closed loop servos. They are
standard hobby servos like these

David Lang

dlang and bar, thanks for the confirmation on the steppers.

The problem comes with the chinese imports. Even the amazon link that you posted for servos dont ship to my place due to the border issue.

Meanwhile, here is a very simplistic design that I found. Mini CNC Mill | Blog | Garrett Goss
Though makesmith’s jigsaw puzzle design is still attractive to me.

I will post my developments here, if it is permissible.

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Very much so, we would love to see how things come together

Thanks Bar.

Just a quick update. In my search, I have come across this simplistic mill.

Its design seems allow swapping the nema 17s with the PM35s as only the relevant bracket needs to be changed. The T slots can also be substituted for other equivalent but available extrusions.

I would perhaps use a thicker smooth steel tubes and threaded rods so that the impact of their possible bending on the performance is minimised.

Printed bush/bearing will allow again to choose from a variety of available sizes.

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