HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Blogs
Guest Blogs

Don't Leave Fluid Power Component Selection to Chance

NO RATINGS
View Comments: Newest First|Oldest First|Threaded View
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
More Blogs from Guest Blogs
Manufacturers of plastic parts recognize the potential of conformal cooling to reduce molding cycle times. Problem is, conformal molds require additive manufacturing (AM), and technologies in that space are still evolving. Costs also can be high, and beyond that, many manufacturing organizations lack the knowledge and expertise needed to apply and incorporate additive technologies into their operations.
Machine vision and video streaming systems are used for a variety of purposes, and each has applications for which it is best suited. This denotes that there are differences between them, and these differences can be categorized as the type of lenses used, the resolution of imaging elements, and the underlying software used to interpret the data.
In the face of growing challenges for embedded technology engineers, designers should actually be designing for a new IoT -- the Internet of Tomorrow.
As today’s product design cycles are held to tighter schedules and budget constraints, it’s becoming even more critical to consider human factors up front to catch and fix problems during the initial development stages, when it’s faster and less costly to do so. Overlooking human factors at the beginning of the design cycle could lead to poor user experience, a decrease in effective product performance, and an increase in safety risk to the user.
Plastic part manufacturers are always looking for ways to reduce cycle time and get more productivity out of their injection molding machinery. One of the longstanding constraints in injection molding production has been cooling time. Removing parts from the mold before they have cooled induces warping or shrinking. But wait time works against productivity.
Design News Webinar Series
3/31/2015 11:00 a.m. California / 2:00 p.m. New York
2/25/2015 11:00 a.m. California / 2:00 p.m. New York
12/11/2014 8:00 a.m. California / 11:00 a.m. New York
5/7/2015 11:00 a.m. California / 2:00 p.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.
May 4 - 8, Designing Low Power Systems using Battery and Energy Harvesting Energy Sources
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6 |  7


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 Proto Labs
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2015 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service