Need advice for moving parts

Thread Starter

Anonym274

Joined Nov 6, 2019
3
How would I go about making a blade/knife move up and down automatically. It needs to be moderately slow and generate a decent amount of force.

I would also need this to be no bigger than a mete. Thank you.
 

djsfantasi

Joined Apr 11, 2010
5,705
A decent amount of force? For what? A machete? Or perhaps a Samurai sword? What is the decent amount of force needed for? Cutting cheese? Decapitation?

Much more information is needed . . .
 

jpanhalt

Joined Jan 18, 2008
8,137
A decent amount of force? For what? A machete? Or perhaps a Samurai sword? What is the decent amount of force needed for? Cutting cheese? Decapitation?

Much more information is needed . . .
Isn't it obvious? A decent amount of force is less than an indecent amount of force. But then, maybe it is more than that.

Six hours since the TS posted. Must be an urgent question.
 

djsfantasi

Joined Apr 11, 2010
5,705
Isn't it obvious? A decent amount of force is less than an indecent amount of force. But then, maybe it is more than that.

Six hours since the TS posted. Must be an urgent question.
Why are you making the assumption that a decent amount of force is less than an indecent amount of force? As you brilliantly observe, maybe it is more!

TS, sorry for the silliness, but when you ask a vague question and then go ghosting... this is what you get.
 

jpanhalt

Joined Jan 18, 2008
8,137
Remember Dr. Guillotin!!
How strange. I was just thinking of him earlier this evening. His invention was advanced for the time, and if modernized, would probably have more than a few advantages over drugs. It certainly makes an impression on observers. but is probably quite humane in the context of perceived pain.
 

atferrari

Joined Jan 6, 2004
3,489
How strange. I was just thinking of him earlier this evening. His invention was advanced for the time, and if modernized, would probably have more than a few advantages over drugs. It certainly makes an impression on observers. but is probably quite humane in the context of perceived pain.
From the original user manual (obviously in French language): Please verify that it is sharp before using.
 

Thread Starter

Anonym274

Joined Nov 6, 2019
3
Ok what I meant by “mete” is Meter and the purpose for this is to cut fruit, Hence why I need enough force to slice it. And no I am not beheading someone. Sorry for the lack of context and disappearing after posting this question.

At a guess, a "meter", but... still...
Hello,

What would be the purpose of the moving blade?
What is the need of the force on the blade?

Bertus
A decent amount of force? For what? A machete? Or perhaps a Samurai sword? What is the decent amount of force needed for? Cutting cheese? Decapitation?

Much more information is needed . . .
Why are you making the assumption that a decent amount of force is less than an indecent amount of force? As you brilliantly observe, maybe it is more!

TS, sorry for the silliness, but when you ask a vague question and then go ghosting... this is what you get.
 

DNA Robotics

Joined Jun 13, 2014
506
A gear reduced motor and a crankshaft is good for reciprocating motion.
A gear reduced motor and a cam pressing on a pivoting blade is good for chopping.
Consider a rotating circular blade like a meat slicer.
 

jpanhalt

Joined Jan 18, 2008
8,137
Consider a spinning blade or stacked blades with the fruit entering the cutting zone single file. Sort of like a food processor with limited number of hits per fruits. How big are the fruit? How many slices of each? How thick the slice?

Any sort of reciprocating device will also require a feed mechanism.
 

Thread Starter

Anonym274

Joined Nov 6, 2019
3
Consider a spinning blade or stacked blades with the fruit entering the cutting zone single file. Sort of like a food processor with limited number of hits per fruits. How big are the fruit? How many slices of each? How thick the slice?

Any sort of reciprocating device will also require a feed mechanism.
the fruits will be as big as an apple and the slices will be between. 1-3 cm each I could imagine.
 

atferrari

Joined Jan 6, 2004
3,489
For cutting, while the knife blade moves down it has to slide slightly.

Only those industrial tools cutting actual "cubes" of some vegetables do move only down, cutting by sheer pressure.
 

drc_567

Joined Dec 29, 2008
741
One initial design problem would likely be the construction or fabrication of a reciprocating blade to cut the fruit or vegetables. The alternative to a reciprocating motion is something that whirls or spins ...However, that seems to have unsafe connotations.
The one cm. or so slice thickness specification could be built with something called 'acme thread', a type of threaded metal rod designed for motion rather than fastening, in conjunction with a stepper motor.
 

jpanhalt

Joined Jan 18, 2008
8,137
Now that we know the maximum size, what is the texture? For example, peeled banana vs. orange vs. tomato. Your original description of "up and down" sounds more like a chopping /shearing operation, assuming blade is parallel to the surface. Now, if the blade is vertical, I would consider that cutting. Thus, you need to define whether the blade's movement is perpendicular to the cutting edge or parallel to it.

For something automated, I think a continuously moving blade/wire like a band saw, circular saw, or food processor would be preferred. Reciprocating motion is usually done with crankshafts or cams, but you could also do it with pneumatic cylinders.
 
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