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Topic: Hydraulic pump for robotics driven by stepper motor 1000PSI (Read 4348 times) previous topic - next topic

swampdonkey

I've successfully tested the second version of a high pressure hydraulic pump. I'd like to make it open source.
But having some trouble getting the design simple enough that it can be made with a drill press.
There aren't any projects that I've seen coupling Arduino with high pressure hydraulics...
I'm wondering if anybody is even interested in building their own stepped motor driven hydraulic pump?


craigcurtin


I've successfully tested the second version of a high pressure hydraulic pump. I'd like to make it open source.
But having some trouble getting the design simple enough that it can be made with a drill press.
There aren't any projects that I've seen coupling Arduino with high pressure hydraulics...
I'm wondering if anybody is even interested in building their own stepped motor driven hydraulic pump?




I am very interested in this one

regards

Craig

PeterH

I can't see how your pump works but I'm interested to know why you decided to use a stepper motor to power it. Wouldn't a DC motor be cheaper and more efficient, or are you making use of the precise positioning capability of the stepper motor somehow?

zoomkat

Quote
But having some trouble getting the design simple enough that it can be made with a drill press.


The close tolerances required for high pressure pumps may be difficult to achieve with a drill press.
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swampdonkey

Valid point, however. This is not a production pump, it is for discovery/experimentation. Thus far, we've been pleasantly surprised by the longevity of the components machined by drill press and manual mill.

swampdonkey


I can't see how your pump works but I'm interested to know why you decided to use a stepper motor to power it. Wouldn't a DC motor be cheaper and more efficient, or are you making use of the precise positioning capability of the stepper motor somehow?



Precisely. We are also working on eliminating external directional control valving and simply using the forward/reverse positioning capability of the stepper for accurate hydraulic positioning control. However, this is down the road... so, DC motor drive is also an option.

Efficiency, in our case is not a design consideration. We are interested in high implement force, ease of DIY build, cost, and reliability.

zoomkat

Precise positioning capability of the end component (without feedback) will probably depend on the pump design. Getting linear pressure control from just the pump could be an issue.
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swampdonkey


Precise positioning capability of the end component (without feedback) will probably depend on the pump design. Getting linear pressure control from just the pump could be an issue.


Indeed positioning without feedback or simple physical stop is impossible. But this is far, far beyond the scope of this initial pump design.

wenger

I realize this is an old thread but its interesting so I thought i'd add a few thoughts in case someone else is interested in the subject and or to find out if Swampdonkey has done any more with the the idea or open sourced the plans as mentioned.  SD, I'd be interested in taking a look.  If you're willing to open source it you should anyway even if its not something that could yet be done just with a drill press as there are enough people with CNC (myself included) to make it valuable.  Something to consider though - even at a 1000psi, a hunk of exploding metal becomes shrapnel.  The pump block really should be a hardened metal I would think as opposed to something that could easily fail like aluminum.

I think this is great idea - most hydraulics are designed for a massive scale and there is a need for somewhat less powerful things and at a scale more appropriate for robotics.  The premise of modern hydraulics is based on a constantly running motor or engine and much of the infrastructure is designed to deal with power transfer and "clutch" systems via complex flow routing systems, diverters, valves, pressure release, etc, etc, much of this can be eliminated by using a direct drive system such as this.

Something I've thought about is that if you're going to use a system such as this directly coupled to a cylinder for example, you'll need to do something to equalize the fluid volume on either side of the plunger - e.g. in a typical DA (Double Acting) cylinder there is a larger volume on the back side of the plunger because of the amount of volume that is consumed by the rod itself in the front side cavity.  If you use a double ended cylinder it takes care of that problem but may not be ideal so if you are wanting to use a normal DA cylinder you'll need to come up with a way to "store" extra fluid between the pump and the back (small) side of the cylinder - I haven't tried it yet but I don't see why you couldn't literally just use extra hydraulic line for this purpose - line is expensive but so are connections so I think making an inline pressurized reservoir (not to be confused with a typical hydraulic reservoir which is not pressurized) would likely be more expensive than just using a longer hose for the back hose.  I think the math will be simple - just calculate the volume of the rod in the back cavity when the cylinder is completely retracted and then make the hose longer than the other one by enough to account for that volume.  Another of the big problems in larger scale hydraulics is heat dissipation it might not be a problem in your case but be aware of it as heat will make other parts of your system weaker and more prone to catastrophic failure.

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