HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
William K.
User Rank
Platinum
Re: Good inmformation: Hydraulic systems need to be designed, not just built.
William K.   6/6/2014 9:10:02 PM
NO RATINGS
pnachtwey  , you are quite right. Of course some folks do make lucky guesses. But, I don't choose to "design by luck", there are too many ways to be wrong.

And of course the first step is to size cylinders based on force and velocity needs. Next, translate that into flowrate, volume, and pressure requirements. Then, if there is more than one cylinder or other device, use the sequence of operations to determine the maximum instantanoius flow at each instant of operation. At that point it is possible to accurately size the HPU and decide if accumulators would be useful.

pnachtwey
User Rank
Iron
Re: Good inmformation: Hydraulic systems need to be designed, not just built.
pnachtwey   6/6/2014 12:57:35 PM
NO RATINGS
You don't guess, ever!!! We see this too often.  The first thing to do is size the cylinder this requires knowing how much mass must be moved how quickly.  Once the cylinder(s) are sized then the cycle times can be use to compute the necessary flow.

I agree about the using accumulators at the valve where the energy is needs.  Too many put the accumulators at the HPU and suffer pressure loses before the oil gets to the valve.

William K.
User Rank
Platinum
Re: Good inmformation: Hydraulic systems need to be designed, not just built.
William K.   6/3/2014 7:44:23 PM
NO RATINGS
PNACHTWAY, adding up the flows makes it possible to size the system flow capacity properly. Until the required flow is known, anything else is just a guess. Experienced folks sometimes guess better than accountants, but luck should not be involved in hydraulic systemn designing. If the peaks are short then an accumulator can help a lot. 

Servo valves are a special case and my advice is to add both the specified valve leakage and the flow for the maximum cylinder velocity. Often a servo system performance can be improved by adding small accumulators right at the servo valve.

pnachtwey
User Rank
Iron
Re: Good inmformation: Hydraulic systems need to be designed, not just built.
pnachtwey   6/3/2014 7:16:47 PM
NO RATINGS
I agree that the instantaneous flow should be know for each instance of the cycle. This makes it easier to size the HPU and accumulator. The HPU only needs to supply a little more flow than the average per flow per cycle.  For servo systems the accumulator should be sized and pressurized so the pressure doesn't drop more than 10% during the cycle so the system gain remains relatively constant.

William K.
User Rank
Platinum
Good inmformation: Hydraulic systems need to be designed, not just built.
William K.   5/26/2014 9:55:24 PM
NO RATINGS
This is a Good post that contains good information. But more information is also needed. Even if a system will only have a single hydraulic actuator with simple extend/return control, it is still mandatory to know both the required force and the needed velocity, in oredr to determine the fluid delivery flow required. In addition, even for that simple system, the duty cycle needs to be known in order to provide the required performance. For systems with multiple actuators you must know the sequence of operation to determine the maximum required flow. 

So if the system performance is important it is probably smarter to obtain the design assistance of a good hydraulic systems provider. The money spent will be far less than the amount spent to re-do a system that is not adequate, or does not last.

bobjengr
User Rank
Platinum
FLUID POWER SELECTION
bobjengr   5/10/2014 1:46:56 PM
NO RATINGS
 Excellent Post Peter.  My company designs work cells to automate manufacturing process.  In doing so, you would not believe ( or maybe you would ) the variety of existing "systems" I run across during one year's time.  Rube Goldberg would have been proud to witness some of the "designs" that are almost working. Most of these have been assembled just as you mentioned in your post--cobbled up with components existing in the back room.  Component make,  vendor model and part number have long-since been eradicated from the part making it impossible to tell what has really been used.   The real problem arises when  the "designer" either dies, quits or gets fired and someone is expected to troubleshoot.  That's when redesign and reconstruction most often occurs. 



Partner Zone
Latest Analysis
Last year you helped Design News and Allied Electronics crown its first-ever Gadget Freak of the Year, and we need your help again. Vote in round 2 of our second-annual contest.
The key to autonomous driving is not to forget about the driver, and to remember that passengers want a sense of control, as opposed to being utterly passive backseat drivers.
HP revealed more of its 3D printing plans in a recent webinar. Senior vice president of inkjet and graphics solution business Stephen Nigro spoke about how the technology works and expanded on HP's vision of open collaboration to commercialize its Multi Jet Fusion 3D printing technology for end-production, and open collaboration on new materials. He also said HP will create software to help users decide when to use Multi Jet Fusion versus conventional subtractive manufacturing.
Get a load of these strange product designs. What's in the water these design engineers are drinking?
The Dutch are known for their love of bicycling, and they’ve also long been early adopters of green-energy and smart-city technologies. So it seems fitting that a town in which painter Vincent van Gogh once lived has given him a very Dutch-like tribute -- a bike path lit by a special smart paint in the style of the artist's “Starry Night” painting.
More:Blogs|News
Design News Webinar Series
11/19/2014 11:00 a.m. California / 2:00 p.m. New York
11/6/2014 11:00 a.m. California / 2:00 p.m. New York
10/7/2014 8:00 a.m. California / 11:00 a.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Dec 1 - 5, An Introduction to Embedded Software Architecture and Design
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Last Archived Class
Sponsored by Littelfuse
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service