# How to tell how powerfull a motor is needed. (Pancake making machine)

Hey guys I am a pancake artist. Yes, I make art with pancakes. I thought it could be fun, as I been working with arduino, and coding in gernal, a lot. I am new to motors and no matter how you do this it needs to be using a motor; Or two.

Well the machine itself is easy enough you have a picture input
(depending on how much money I can pull its either a SD card or bluetooth but thats irrelvant for this question) and the machine will print it as a pancake. The blacker a shade is the more delay before going to next shade (was considering 4-8 shades of gray). However as I am new to motors and this machine its importen it get from A to B within seconds I was wondering: "Which measure do I need to look for to be sure it can get to A-B in x amount of seconds?"

After reading the chapter of motors in my eletric book it seemed to be the RPM I need to look at. I found the formular of:
cm/s = radius × RPM × 10.472 - Taken out of my electric book.

Which converts it into cm/s which is what I need.

Am I totally wrong here? Or am I hitting something right?
I dont know the exact measurements but I was thinking of having a 13 cm long line to travel at for both axies.

I can't picture your machine from your description. Maybe you can make a drawing of what you have in mind and post a photo of the drawing.

If you need precise control you may need stepper motors but I would like to understand the project better before being more definite.

...R

Hey dude. I don't know how to explain it more precisely. Its basicly a 3d printer, however its only limted to 2d. I think its quite clear that this machine prints a pancake based of a picture. The problem I am running into is that the motor needs to be not only precisely but also fast. My budget is quite limited and therefore I would love to use as minimal power as possible.

What the motor is going to drag is the tube thats holds pancake mix.
The reason why I am asking for how powerful it needs to be is cause it needs to get from one end to another within a second. I don't even know if this will be a problem for a motor I just want to be sure.

Lets take a case:
We have motor one who can travel lets say 6 cm/s...
if my x axis is 12 cm long it will take that motor 2 secs to get from one end to another.
And that line of the pancake will before gradually more brown cause it gets to cook more.

Did that make it clearer?

Else here is a kinda bigger explaination:

This is a picture it will be able to print out. It will start with the darkest shade (1) and fillout pancake mix till that shape is made. It will then wait a bit (1-2 secs) to go to next darkest shade. The waiting time makes the shape 1 to cook more than shape 2 and therefore become browner. But if there go too much time for this to go from one end to another the colors might blend togother cause of too long cooking time.

That sounds like you want to extrude the pancake mixture from a moving nozzle onto a stationary plate - presumably onto the heated cooking plate?

I presume you are planning to have two motors - one for the X-axis and one for the Y-axis.

Is the colour difference only due to different cooking times? Or do you need to change to a different coloured mixture.

In general it sounds exactly like a 3D printer without a Z-Axis (up/down) motor and stepper motors are almost certainly the best option. There is some background reading in stepper motor basics. It includes some suggestions for measuring the required torque.

However in order to figure out the required torque and speed you will need a good idea of the mechanical arrangements for holding and moving the nozzle. The obvious options are a leadscrew or a toothed belt. The toothed belt will probably be better for speed, but will require a motor with more torque.

Keeping cooking materials, steam, fat etc etc out of the mechanism will also be a very important part of the design requirement.

...R

Let me see if i got this right the speed of a stepper motor depends on the pulse and steps pr revolution. I found this online with my new vocalbulary:

Step 4

Calculate the RPM for a motor that has a 15-degree stepper angle and takes 24 steps to perform one revolution. If the motor is driven with 260 pulses, the answer is (260 pulses / 1 second)(1 rev / 24 pulses) (60 seconds / minute) = 650 RPM.

I have the formular for rpm to m/s up in first post but did the speed fell as torque increase?

Why not just buy a machine for \$179?

https://www.kickstarter.com/projects/1853707494/pancakebot-the-worlds-first-pancake-printer

spil778:
but did the speed fell as torque increase?

Yes. The torque of a stepper decreases with speed. Some of the manufacturers' datasheets include speed/torque graphs - Google is your friend.

But, as I said earlier, you need to figure out the mechanical design before you can estimate the torque required.

...R

The normal 3D printer mechanics used toothed belt, which will of course risk melting in the
heat from a hotplate so some thought needs to be put into drive mechanism layout to keep
sensitive parts away from the plate!

Clearly this is motion control, so we are talking stepper motors or servo-motors. Making
your own servo-motors is possible, it takes an encoder per motor, but its not as simple
as using steppers (which is why they are used a lot in 3D printers and CNC machines).

To get fast motion you need a low-impedance motor driven from a chopper driver from
a high voltage supply. Think 24V or 36V supply, something like 2A NEMA17 steppers
driven from DRV8825's.

Belt drive is always a lot faster than leadscrew, so that's a given - MXL rubber/kevlar
belting or similar (don't use T2.5 or T5 urethane/stell belt, its too stiff).

Look at the kickstarter design and other 3D printers for inspiration. For linear bearings
you can simply use plastic block with a hole running over stainless steel rod I think,
linear ball bearings are overkill given the accuracy needed. Avoid any part that's not
stainless or aluminium, the steam from a pancake will rust anything in ordinary steel
rapidly.