Mold Engineering

Calculating Screw Thread Properties

2011-04-28T19:34:00.002-04:00

Metric screw sizes are calculated as follows:

Minor diameter = Major diameter - (1.226869 x pitch)

Pitch diameter = Major diameter - (.649519 x pitch)

The tensile stress area = ((root dia + pitch dia) / 2)^2 * Pi/4

Inch screw sizes are calculated as follows:

Minor diameter = Major diameter - (1.299038 x pitch)

Pitch diameter = Major diameter - (.649519 x pitch)

The tensile stress area = ((minor dia + pitch dia) / 2)^2 * Pi/4

Calculate Optimum Diameter For Cutter Or Part

2011-04-28T19:28:00.000-04:00

When machining, it is occasionally desirable to calculate the appropriate diameter of either the cutter (i.e. milling) or the workpiece (i.e. turning) when the Surface Feet per Minute are known, and the RPM's are established.
The equation used in this calculation is: Diameter = (SFM / RPM) / (Pi * 12)

where, SFM = Surface Feet per Minute,
RPM = Revolutions per Minute, and
Pi = 3.141592654

When using DZynSource Mold Engineering Software to do the calculation, go to "Machining Calculations" / "Surface Feet Per Minute" and then choose "Diameter" from the option boxes.

Enter the RPM's and he surface feed per minute in the appropriate text boxes. Press Calculate. The answer appears in the Answer frame.

Use the Clear button to clear all fields, however this is not necessary in order to do another calculation. You may simply type over the previous entries.

You may send the page to your default printer by pressing Print.
Press Menu to return to the main menu selection area.

DZynSource Mold Engineering Software Feature List

2011-04-27T21:38:00.004-04:00

DZynSource Mold Engineering Software Feature List

Unit Conversions Section - Over 300 separate conversions

Converter for Hours into Days or Weeks

D.C. Electrical Calculations: 9 Different Ohm's Law Calculations

Fluids Calculations:

Bubbler sizing Continuity Eq.
Equivalent Hydraulic Diameter - General Case
Equivalent Hydraulic Diameter - Annular Channel
Hydraulic Cylinder Calculations
Pneumatic Cylinder Calculations
Pressure Losses (Darcy's Equation)
Pressure Loss or Flow Rate Through an Orifice
Pressure Losses in Valves and Fittings
Reynolds Number Calculations

Galvanic Table

Gate Sizing: Hot Tip, Edge Gate, & Sub-Gate

Helix and Cam Angles

Hot Runner Checklist - set up as a word processor so you can add your own items.

Machining Calculations:

           effective Cutter Diameter
            Feed Rate / Feed Per Tooth
            Inches per minute <> Inches Per Revolution
            Surface Feet Per Minute
            Surface Roughness
            3-Sided Cutter Angle Calculator

Material Properties:

36 different molds making steels, aluminums, and high conductivity alloys.

Can open up to 4 properties lists for easy comparison.

Mold and Plate Weight Calculator: steel or aluminum, based on solid block size

Molding Calculations:

Chiller Sizing, includes the number of BTU's of heat to be removed per hour, the gallons per minute of water required to remove the heat content of the plastic.

Clamp force table, by material type

Cooling Time Estimator - Ballman Shusman method

Colorant Let Down Weight Calculator

Minimum Mold Open Time- time for the highest part to drop below the mold

Pounds or Kilograms of Material per hour

Plastic Shrink Rate Table and Steel and Plastics Size Calculator

Tie Bar Stretch

Production Calculations:

Pounds or Kilograms of Material per hour (Second location, for convenience)

Molding Capacity: single or multi-molds. Parts per minute, hour, day, week,4 weeks, and year.

Converter for Hours into Days or Weeks (Second location, for convenience)

Number of cavities required, based on production needs.

Number of plastic parts that can be molded in a given time.

Time to mold a certain quantity of parts.

Runner Size Calculator

Strength of Materials Calculations:

Beam Deflections, 9 different loading and support scenarios

Circular discs, fixed or supported circumference, uniform load or spot load

Round Cavity Expansion, due to internal pressure. Through bore or blind pocket.

Elastic Strain:

Uniform Cross-section, single material

Uniform Cross-section, two materials assembly

Tapered Cross-section, single material

Hoop Stress

Leader Pin Bend Calculator, with 1, 2, or 3 moving plates; with plate weight estimator

Long Column with central loading, critical load calculator

L/K Test to determine if the long column calculator is the appropriate method.

Moment of Inertia Calculator, also calculates area, Radius of Gyration, Section Modulus, and distance to extreme fiber of 10 common geometric shapes.

Mold Plate Expansion due to internal pressure. Designed especially for side action molds. Includes blind or through pocket comparison.

Surface Finish Tables: SPI/SPE comparison, RA vs. RMS inch and metric, grinding grit & VDI

Thermal Calculations:

Thermal Expansion Coefficient calculator for 30 different mold making metals. Calculate expansion, initial size, or final size.

Chiller Sizing, includes the number of BTU's of heat to be removed per hour, the gallons per minute of water required to remove the heat content of the plastic. (Second location, for convenience)

Thread Properties:

Three wire size, also includes largest, smallest and best wire size. Inch and metric.

Pipe Threads: Tap drills size for N.P.T. and B.S.P.T. threads, with & w/out pipe reamer.

Properties of Threads: includes major, minor, and tap drill diameters. Also includes tensile stress area and a torque calculator.

Trigonometry

Circular segment calculator

Decimal degrees to Degrees, Minute, Seconds Converter. Works for both directions.

Right Angle Trigonometry.

Roll Dimension Calculator, Obtuse and acute angles.

Sine plate gage block calculator.

Tooling ball dimension calculator.

Unscrewing Mold Calculations

Vent Calculator

Vent depth table, by material type.

Vent width calculator.

www.dzynsource.com

New Release of DZynSource Mold Engineering Software

2011-04-01T12:32:00.000-04:00

April 1, 2011

A new version of DZynSource Mold Engineering Software is live on our web site. Now with more features than ever. You can now calculate how much a mold cavity will expand, with either a through-hole, or a blind cavity pocket.

Circular disc bending and deflection can now be calculated. This is great for check the strength of a round core with a top center gate. There are a total 4 options in this section: perimeter fixed or supported with uniform load, or smaller concentric load on either support type.

There's a new capacity and utilization feature that covers single or multiple mold packages, and automatically calculates how many parts per day, week, 4 weeks, and per year all based on your input.

There are many more additions to the software, and I'll be posting on them in the near future.

www.dzynsource.com or www.moldengineeringsoftware.com

Sønderborg Værktøjsfabrik A/S Purchases DZynSource Software

2011-02-20T19:39:00.001-05:00

Jan Hansen, Tool Design Manager at Sønderborg Værktøjsfabrik A/S in Sønderborg, Denmark, is another new DZynSource customer. Welcome Jan.

Another DZynSource Mold Engineering Software Commendation!

2010-12-29T20:30:00.000-05:00

We have another new commendation:

“Every mold making company should own a copy. Great idea, great implementation.”

Jim Philippe / Tooling Engineer CORNING LIFE SCIENCES

Thank you, Jim.

New DZynSource Commendation!

2010-12-23T12:39:00.000-05:00

We just received a new, and very nice, commendation about our software:

“ I am impressed with your software; talk about practical and useful! Anyone in the business can sure appreciate what you have done.”

Brett Niggel, Designer, Studio One Eleven

Thank you for the kind words, Brett!

A Partial List of DZynSource Features

2010-12-06T20:53:00.000-05:00

Unit Conversion Section

D.C. Electrical Calculations

Fluids: Bubbler sizing , Equivalent Hydraulic Diameter - General Case, Equivalent Hydraulic Diameter - Annular Channel, Hydraulic Cylinder Calculations, Pneumatic Cylinder Calculations, Pressure Losses (Darcy's Equation), Pressure Loss or Flow Rate Through an Orifice, Pressure Losses in Valves and Fittings,
Reynolds Number Calculations

Galvanic Table

Gate Sizing, Hot Tip , Edge Gate, Sub-Gate

Helix and Cam Angle Calculations

Hot Runner Checklist

Properties of Metals Tensile strength, yield strength, elongation, impact strength, reduction of area, all at various hardnesses.

Molding Calculations: Chiller Sizing, Clamp Force Requirements, Cooling Time Estimator - Ballman and Shushman Method, Minimum Mold open Time - Time for highest part to clear bottom of mold, Mold Fill Time Calculator, Pounds or Kilograms of Plastic per Hour - Also in production calculations, Tie Bar Stretch .

Production Calculations: Quantity of Cavities Required, Quantity of Parts that be can molded, Time to Mold a Quantity of Parts, Pounds or Kilograms of Plastic per Hour - Also in molding calculations.

Runner Size Calculations

Machining Calculations: Effective Cutting Diameter, Feed Rate / Feed Per Tooth, IPM <> IPR, Surface Feet Per Minute, Surface Roughness, Three-Sided Cutter Calculator.

Strength of Materials: Beam Deflections - 9 different loading and support scenarios, Elastic Strain - How Much a Part Stretches or Compresses under Load, Hoop Stress - Stress and Strain in Circular Rings, Long Column Sudden Failure Calculations & the L/K Long Column Test, Moment of Inertia, Section Modulus, Area, Radius of Gyration, and Distance from Neutral Axis To Extreme Fiber in 10 Standard Geometric Shapes, Mold Plate Pocket distortion, Through Pocket and Blind Pocket.

Surface Finish Comparison Tables

Thermal Calculations: Expansion, Initial Size, Final Size, Coefficients of thermal expansion for 30 common mold making materials.

Thread Properties: Properties of Metric and Inch Threads, Course and Fine, Major Diameter, Tensile stress area in inches and millimeters, Minor diameter area, tap drill size, and torque calculator

Three Wire Measurement, Largest Wire - Threads per Inch or Pitch Know, Smallest Wire - Threads per Inch or Pitch Known, Best Wire - Threads per Inch or Pitch Known, Measurement over Wire - Threads per Inch or Pitch Known,

Pipe Threads: Tap drill sizes for N.P.T. and B.S.P.T threads, with and without pipe reamer,
Trigonometry: Chord, DD <> DMS, Right Angle Trigonometry, Roll Dimensions, Acute and Obtuse angles, Sine Plate Dimensions, degrees, minutes, seconds, or decimal degrees, any sine plate length, Tooling Ball Dimensions.

Unscrewing Mold Calculations - in threads per inch or by pitch, Stroke per revolution, Number of turns required, Minimum stroke, Cam Rise, Total Rise for stroke.

Vent Calculations: Table of typical vent depths, by material and a Vent Width Calculator.

Extensive Help files with a great deal of data and reference information.

Plastics Today Article about DZynSource

2010-12-06T20:30:00.000-05:00

The article that I mentioned in a previous post has been released today, December 6, 2010. Their web site appears to be down for maintenance at the moment, but I am sure it will be up soon.

http://www.facebook.com/l.php?u=http%3A%2F%2Fwww.plasticstoday.com%2Fimm%2Farticles%2Ftessy-plastics-dzynsource-mold-engineering-software&h=5efda

ProWrite Communications Doing Article about DZynSource Mold Engineering Software

2010-11-20T19:20:00.000-05:00

I got some really nice news today. Clare Goldsberry, Owner at ProWrite Communications, Sr. Editor at Modern Plastics Worldwide, and Senior Editor at Canon Communications, is going to write an article about DZynSource Mold Engineering Software. I am honored and quite excited!

Clare saw a press release that I issued this week about Tessy Plastics buying my software. She remembered my name from when we were both writing for Injection Molding Magazine. She was a senior editor, at the time, and I was writing book reviews for the IMM Book Club. Thank you Clare.

I'll post a link to the article, when it goes live.

Side Action Flash, Part 1, Mold Engineering Software

2010-10-29T15:22:00.000-04:00

Have you ever seen a mold with the side action flashing across the split face? Have you checked the design and the steel over and over only to find that the dimensions appear to be correct? The flash problem may be due to an under-designed mold plate. This is particularly true with “A”-side action molds for large parts, and even more so when the side action is contained in a mold plate with a “through-pocket”, like the one shown below.

In this case, each part has 1.25 square inches of surface area for the cavity pressure to generate force on. This force must be overcome by the strength of the plate. Let’s assume that the cavity pressure is 10,000 p.s.i., which is not an unreasonable assumption. This is a 4-cavity mold, so the force trying to separate the slide faces is 50,000 pounds.

You have two types of plate distortion to calculate here: one is the stretching of the 2 legs that form the upper and lower boundaries (the ends) of the pocket. You can get a better visualization of that in the DZynSource Mold Engineering Software screenshot shown below. The other distortion is the “bow” of the sides of the pocket, again see the DZynSource screenshot.

You can see from the calculation here that the center of the plate, left as designed, would blow apart approximately .0012 inches, which would probably flash when molding a polypropylene part. In this case, as you can see in the drawing, the plate weakness was overcome by installing an interlock between the slide pocket plate and the stripper plate. This interlock gave the plate enough additional strength to mold flash-free parts. Of course, if the designer had the DZynSource Mold Engineering Software, this problem could have been avoided by doing “what if” scenarios with plate sizes and thicknesses to come to a more robust design that would not flash without extra mold components.

How Much Will That Round Tapered Part Stretch or Crush?

2010-10-18T15:05:00.000-04:00

When an object of round tapered cross section is subjected to tension or compression within the elastic limit of the material, the deformation can be approximated with the equation:

¶ = FL/(p E R1 R2)

Where

¶ = = the deformation

F = the load or force

L = the length of the object in the direction that the force is acting

p = Pi (3.14159265358979)

E = the Modulus of Elasticity of the material

R1 = the radius at the small end of the cone

R2 = the radius at the large end of the cone

This equation works for tapered cylinders that don't get too small at the small end. The answers become meaningless (they approach infinity) as the radius approaches zero.

You have to use several menus to get to this form. From the Main menu, choose “Strength of Materials”; from there choose “Elastic Strain”. Once the Elastic Strain sub-menu is open, you have three choices; choose “Tapered Cross-Section, Single Material”.

When entering the required information, it is imperative that the units used are consistent. For instance, if pounds per square inch are used for the modulus of elasticity, quantities must be entered in units of pounds and inches.

First choose whether you want to use p.s.i. or N/mm²; next choose how many places beyond the decimal point you like the answer carried.

Enter the Force, the length, the large radius, the small radius, and the Modulus of Elasticity in the text boxes next to the questions asked. When entering modulus of elasticity values like 30,000,000 pounds per square inch, as would usually be used for steel, you may enter as 30e6 as a shortcut.

Press Calculate. The strain and stress values are shown on a separate Answers form. Answers are valid if the stress is from a static load and is within the elastic limit of the material in question.

Use the Clear button to clear all of the text boxes; however this is not necessary in order to do another calculation. You may simply type over the previous entries.

You may send the page to your default printer by pressing Print.

Press Menu to return to the main menu selection area.

How Many Surface Feet per Minute is That?

2010-10-18T14:54:00.002-04:00

It is sometimes desirable to calculate the quantity of surface feet per minute attained, when the diameter of the rotating cutter (i.e. milling) or the work piece (i.e. turning) is known, and the RPM's are established. The equation used in this calculation is:

SFM = (Pi * Diameter * RPM) / 12

where, SFM = Surface Feet per Minute, RPM = revolutions per minute

You can find the Surface Feet Per Minute calculator under the "Machining Calculations" sub-menu.

Enter the diameter and revolutions per minute in the appropriate text boxes. Press Calculate. The answer appears in the Answer frame.

Use the Clear button to clear all fields, however this is not necessary in order to do another calculation. You may simply type over the previous entries.

You may send the page to your default printer by pressing Print.

Press Menu to return to the main menu selection area.

Compression in a Multi-Material Component With Uniform Cross Section

2010-10-07T21:43:00.000-04:00

When an object is constructed with two different materials, and both have uniform cross-section, and both are subjected to the same tension or compression within the elastic limit of the material, the forces, stresses, and deformation can be predicted with the following equations:

F1 = F * (A1 * E1) / ((A1 * E1) + (A2 * E2))

F2 = F * (A2 * E2) / ((A1 * E1) + (A2 * E2))

¶ = (F1 * L) / (A1 * E1) = (F2 * L) / (A2 / E2)

Stress1 = F1 / A1

Stress2 = F2 / A2

Where

¶ = = the deformation

F = the total load or force acting on the objects

F1 = the load or force carried by object 1

F2 = the load or force carried by object 2

L = the length of the objects in the direction that the force is acting

E1 = the Modulus of Elasticity of the material for object 1

E2 = the Modulus of Elasticity of the material for object 2

A1 = The cross-sectional area of object 1, perpendicular to the force

A2 = The cross-sectional area of object 2, perpendicular to the force

It is assumed that the object is constructed in such a way that there is no slippage between objects 1 & 2.

When entering the required information into the DZynSource Mold Engineering Software, it is imperative that the units used are consistent. For instance, if pounds per square inch are used for the modulus of elasticity, quantities must be entered in units of pounds and inches. See the previous article to see you access this calculation from within DZinSource.

First choose whether you want to use p.s.i. or N/mm², then choose how many places beyond the decimal point you like the answer carried.

Enter the Force, the length, the outer objects area, the inner objects area, and the Modulus of Elasticity for each object in the text boxes next to the questions asked. When entering modulus of elasticity values, 30,000,000, as would usually be used for steel, may be entered as 30e6 as a shortcut. The area of 10 basic shapes can be calculated by choosing Strength of Materials, Moment of Inertia from the main menu, choosing the desired shape, and entering the required information.

Press Calculate. A separate answer page appears with the values for Force 1, Force 2, the deflection, and stress induced in each component are shown. Answers are valid if the stress from a static load is within the elastic limit of the material in question.

Use the Clear button to clear all entry fields, however this is not necessary in order to do another calculation. You may simply type over the previous entries.

Press OK on the answer page to close that page.

You may send the either page to your default printer by pressing Print.

Press Menu to return to the main menu selection area.

What The Heck Is Modulus of Elasticity?

2010-10-03T01:18:00.000-04:00

The Machinery's Handbook defines Modulus of Elasticity as follows: "Modulus of Elasticity, E, (also called Young's modulus) is the ratio of unit stress to unit strain within the proportional limit of a material in tension or compression". In general, the Modulus of Elasticity, for steel is 30,000,000 p.s.i. Some steels are as low as 28,000,000 and some as high as 34,000,000 p.s.i.

Stress equals the force or load applied divided by the area that the force is applied to, or Stress=F/A.

Strain is the deformation, elongation or compression, that the material undergoes as a result of the force being applied to it.

The shear Modulus of Elasticity, G, also known as the Modulus of Rigidity, is also the ratio of stress to strain within the proportional limit of a material, but in shear. It is usually expressed as a percentage of the Modulus of Elasticity, E, in tension. The Modulus of Elasticity in shear, G, is usually about 38% of the Modulus of Elasticity in tension, E.

Some values for Modulus of Elasticity for some common materials are as follows:

Aluminum, Alcoa QC-7 10,300,000 p.s.i., or 71,000 MPa

Brush-Wellman's Moldmax XL Beryllium Copper 17,000,000 p.s.i. or 117,000 MPa

Brush-Wellman's Protherm Beryllium Copper 20,000,000 p.s.i. or 138,000 MPa

Ampco MoldMATE 90 22,000,000 p.s.i. or 152,000 MPa

Steel 30,000,000 p.s.i. or 207,000 MPa

How To Calculate The Effective Diameter for a Toroid Type Cutter

2010-10-03T01:09:00.000-04:00

When cutting less than full depth with a toroid shaped cutter, the effective cutting diameter is smaller than the actual diameter of the cutter, and dependent on the depth of cut and the corner radius. This effective cutting diameter is used for feed and speed calculations. A toroid shaped cutter is a flat bottom cutter with corner a radius that is less than half of the cutter diameter.

The formula used to calculate the effective cutting diameter is as follows:

Effective cutter diameter = 2 * (((R ^ 2) - ((R - Depth) ^ 2)) ^ 0.5) + (D - 2 * R)

where;

Depth = the depth of cut

D = the cutter diameter

R = the corner radii

In the DZynSource Mold Engineering Software, you enter the cutter diameter, the corner radii, and the depth of cut in the appropriate text boxes, Press Calculate, and the answer appears above the Calculate button.

Use the Clear button to clear all fields, however this is not necessary in order to do another calculation. You may simply type over the previous entries.

You may send the page to your default printer by pressing Print.

Press Menu to return to the main menu of DZynSource Mold Engineering Software.

How To Calculate The Effective Diameter for a Ball Nose Cutter

2010-10-03T01:03:00.000-04:00

When cutting less than full depth with a ball nose cutter, the effective cutting diameter is smaller than the actual diameter of the cutter, and dependent on the depth of cut. This effective cutting diameter is used for feed and speed calculations.

The formula used to calculate the effective cutting diameter is as follows:

Effective Diameter = 2 * (((R ^ 2) - (R - Depth of cut) ^ 2) ^ 0.5)

where,

R = The Cutter Diameter divided by 2

In DzynSource Mold Engineering Software, simply Enter the cutter diameter and the depth of cut in the appropriate text boxes. Press Calculate. The answer appears above the Calculate button.

2010-09-30T21:48:00.000-04:00

Calculate Chiller Tonnage, And Other Interesting Molding Facts

You can calculate your required chiller tonnage, gallons per minute of water cooling, and amount of material to be processed per hour in one quick step with DZynSource Mold Engineering Software.

From the main menu, choose the "Thermal Considerations" command button. This is one of the few calculations that can be chosen from more than one sub-menu within DZynSource. It can also be found under the "Molding Calculations" sub-menu.

The blank form for doing this particular production calculation is fairly self explanatory. You first choose the unit of weight for the plastic molded part. In my experience, the part weight is usually measured in grams. The industry that I work in, caps and closures, packaging, medical disposables, and so forth, the parts are fairly small and usually measured in grams. The ounces and pounds are there for the molders, moldmakers and other personnel that work with the larger parts. So, choose the unit of measurement for the part weight, enter the number of cavities in the mold, and enter the cycle time in seconds. If the mold is full hot runner, then there will be no cold runner to allow for and you enter zero for the runner weight. If the mold has any amount of cold runner, enter it in the text box next to "Enter runner weight in grams". The unit of weight for the runner changes with the units chosen for the part weight so that they are always in the same units.

You'll need to enter the specific heat for the plastic being processed, and the units need to be in BTU"s per pound per degree Fahrenheit. If you click on the command button a list will appear with some generic materials to choose from. In this case I'm choosing an 8 gram part made from polypropylene homopolymer running in 32-cavity hot runner mold. Hence no runner weight. I've entered 450 degrees as the mold temperature and 170 degrees as the expected ejected part temperature. In general, a 5 degree rise in water temperature, between the in and out of any water line, is considered acceptable for general molding. 3 degrees is often used for technical molding. I entered 4 degrees here to sort of split the difference

Now that we've entered all of our information, it's time to press calculate. You can see that the answer box tells us that we'll be processing over 290 pounds of material per hour, and that that material will contain over 54,000 BTU's per hour of heat that must be removed. To do that, we need to force a total of 27 gallons per minute of water through the mold. The chiller capacity required to accomplish this transfer of heat is 4.52 tons.

You can press clear to clear all fields and start again, press "Print" to send a copy of the form to the default printer, or press "Menu" to return to the Main Screen. Calculations are quick and easy with DZynSource Mold Engineering Software. If you have any questions you can send them to sales at dzynsource.com. Visit us on the web at http://www.dzynsource.com or www.moldengineeringsoftware.com

DZynSource Mold Engineering Software

2010-09-27T22:04:00.003-04:00

Well, we have a new web address, but the old one works too. The new address is http://www.moldengineeringsoftware.com/

The original address, http://www.dzynsource.com/, also works just fine. It will, hopefully, make it easier for people doing a search to find us.

How Much Plastic Do You Need?

2010-05-31T20:40:00.002-04:00

Calculate Amount of Plastic To Be Processed Per Hour

Calculating the amount of material per hour that you will be processing is a fairly simple calculation, but with DZynSource for Molds it's even easier.

From the main menu, choose the "Production Calculations" command button.

Figure 1. DZynSource Main Screen

This is one of the few calculations that can be chosen from more than one sub-menu. It can also be found under the "Molding Calculations" sub-menu.

So, choose the unit of measurement for the part weight, enter the number of cavities in the mold, and enter the cycle time in seconds. If the mold is full hot runner, then there will be no cold runner to allow for and you enter zero for the runner weight.

If the mold has any amount of cold runner, enter it in the text box next to "Enter runner weight in grams".
The unit of weight for the runner changes with the units chosen for the molded part, so that they are always in the same units.

Press calculate, and that's all there is to it. You can press clear to clear all fields and start again, press "Print" to send a copy of the form to the default printer, or press "Menu" to return to the Main Screen. The solved example below is for a 12-gram part being produced by a 64-cavity full hot runner mold that runs a 10 second cycle. As you can see, you'll be processing almost 610 pounds of material per hour. The equivalent weight in kilograms is also given.

Pneumatic Cylinders Made Simple

2010-05-26T20:03:00.002-04:00

Pneumatic cylinder calculations can be done in a matter of minutes, if not seconds, with DZynSource. From the main screen choose the "Fluids" command button. The Fluids sub-menu appears, and you'll want to select the "Pneumatic Cylinder Calculations" command.

The blank pneumatic cylinder form appears. As with almost all of the calculations within DZynSource, you must choose metric or imperial units to work with as your first step.

You are now offered the option of calculating what size pneumatic cylinder you need to accomplish your task. If you know the force that must be generated, you enter that into the text box provided next to the "Enter the force that the cylinder must generate" text. You are also asked enter the air pressure that will be provided to the cylinder. The sizing of the piston is based on this premise: you want to deliver a force that is double the minimum force required. A smaller cylinder will move slower, due to being under-powered. a larger cylinder will usually move slower too, due to the increased volume of air required.

The calculation provides a size, and you would choose the next larger size of standard cylinder. For example, if you needed to push with a force of 450 pounds, and you have a line pressure of 80 p.s.i., you would need a 3.758 inch diameter piston. You would choose the next larger standard size, or 4 inch diameter piston. See the picture below.

In this case we have calculated an appropriate piston size, which is 4.000 diameter. I next entered all of my know data for the project that I'm working on. The piston I chose has a 1.000 diameter rod, a 12 inch stroke, a compressed air supply at 80 pounds per square inch, and we need to cycle the cylinder 10 times per minute, or every 6 seconds. Press calculate and we see that the forward force will be just over 1000 pounds. The return force is always less that the forward force because we have to subtract the piston diameter from the piston diameter. The air cannot act on the area of the piston rod. We are also given the standard cubic feet per minute of air that will be required to run this cylinder at this cycle. This information is used to determine the extra compressor load, and to size the valves that will control the air flow. That's all there is to it.

Hydraulic Cylinder Calculations The Easy Way

2010-05-16T14:09:00.003-04:00

Hydraulic cylinder calculations need to be done quite often, as a matter of course, when designing molds. These calculations are done effortlessly, and in a matter of seconds, with DZynSource for Molds Software. The following steps show the beauty and simplicity of our software for doing this and other common mold engineering tasks:

1. This is the main screenshot from DZynSource for Molds, in this case click on the "Fluids" command button.

The Fluids sub-menu appears, and you choose the "Hydraulic Cylinder Calculations" command button.

The blank Hydraulic Cylinder worksheet appears, ready for you to enter your known data. The second article that I wrote on this blog used the following example:

You have a hydraulic cylinder with a 2.000 diameter piston, a 1.000 diameter rod, a 12-inch stroke, and want to extend the rod in .5 seconds, and the system pressure is 1000 pounds per square inch. Calculate the forward and return forces generated and the flow rate, in gallons per minute, of hydraulic oil required to accomplish the stroke outwatd in .5 seconds.

We'll enter this data into the Hydraulics worksheet:

First, choose the units that you want to work in, enter the data, Press Enter, and Voila, all of your answers appear.

Customers will very often call to find out how many gallons per minute their hydraulic pump will need to delivery to the mold, particularly with unscrewing molds. You can answer them in the blink of an eye, and not have to take the time to figure it out and call them back. What if scenarios are worked out fast as you can think of them. DZynSource for Molds really does save time, and enables you to create better designs.

As always, over designing is expensive, under-designing can be disastrous!

How to Calculate the SCFM Required To Actuate a Pneumatic Cylinder

2009-11-24T20:26:00.002-05:00

When designing with pneumatic cylinders, it is often desirable to calculate the standard cubic feet per minute (SCFM) of air required to operate the cylinder. This article will explain how to do that calculation.

Let's assume, for example, that you are using a double acting (reciprocating) air cylinder with a 2-inch bore and a 12-inch stroke. Let's further assume that it reciprocates at 10 cycles per minute using 90-P.S.I.G. of air. If you want to know what the required scfm flow-rate of the air to the cylinder is, use the following equation:

Q2 = P2 x Q1 / P1

Where;
Q2 equals the quantity of compressed air required to operate the cylinder based on the volume of the cylinder bore for a given stroke, forward and return.

P1 equals the atmospheric pressure, which is 14.7 pounds per square inch.

P2 equals the gauge pressure of the compressed air being used to activate the cylinder.

Q1 = the piston area * (2 * stroke) * the number of cycles per minute / 1728.

Q2 equals the volume of uncompressed air required.

The area for a 2-inch bore = Pi/4 * D^2 = 3.14-in^2
12-inch stroke, Pressure, P2 = 90-Psig
Cycles = 10 cycles /min
Dividing by 1728 converts cubic inches to cubic feet.

Q1 = Piston area * (2 * stroke) * cycles/minute / 1728

Q1 = 3.14-in2 x (2 x 12) x 10 / 1728 = 753.98 / 1728 = .4363-ft3/ min (cubic feet per minute)

Q2 = P2 x Q1 / P1 = 104.7 x .4363 / 14.7 = 3.11 scfm (standard cubic feet per minute)

So, your compressor and valve must be able to supply 3.11 standard cubic feet per minute of air to operate your cylinder for this design.

When doing these calculations, disregard the piston rod cross-sectional area, and assume that the temperature remains constant. The value "P2" equals the gauge pressure plus the atmospheric pressure, which is 14.7 p.s.i.

The photo is courtesy of Parker Automation Products

How to Calculate The Pressure Drop Through An Orifice

2009-11-22T16:23:00.002-05:00

Sometimes we engineers and designers spend too much time and money designing around large water fittings because we think that mold performance will be significantly hampered by the use of small fittings. It’s not necessarily true, and I want to show you why, and what IS important.

Darcy’s equation is used to calculate pressure losses in fluid system pipes and drilled passages.

Darcy's equation is: (f * (L/D) * ((v^2) / 2g))

To calculate pressure loss, two additional factors are introduced as follows:

Pressure Losses = (f * (L/D) * ((v^2) / 2g)) * (.433 * Sg )

where,
f = a friction factor,
L = the length of the pipe or passage,
D = the diameter of the pipe, or passage, in inches,
v = the fluid velocity in feet per second
g = gravitational acceleration constant (32.2 ft per second / per second)

Sg = the specific gravity of the fluid, water is approximately 1, for other fluids consult your literature or fluid supplier.

The .433 * Sg factor converts what would be called "head loss", in units of feet, into pounds per square inch. Since L/D is a ratio, the units are unimportant as long as the same units are used for both length and diameter.

The factor “f” (friction factor) can be found on charts available from hose and fitting suppliers, and in most Fluid Dynamics texts. These charts usually require you to be able to define the surface roughness in the passage. The one that is probably the most familiar to engineers is Moody's diagram.

There are two equations that I use to calculate the friction factor, that have been found to be appropriate for molds. The first, used for calculations involving turbulent flow, is called Blasius’ Law, and is as follows:

f = .3164 / ((Reynolds Number)^.25)

The second, used for Laminar flow, is:

f = 64 / (Reynolds Number)

One more calculation is required. Darcy’s equation requires the fluid velocity, in feet per second, as input. Since we rarely know this, we must convert the quantity that we usually know, which is usually the flow rate in gallons per minute, into feet per second.

The conversion from gallons per minute to feet per second is as follows:

v = (GPM * 231 in^2 / 60 seconds per minute / Area in inches^2 / 12)

To calculate the area of our hole diameter (Area in inches input), we use the familiar A = ((D ^ 2) * Pi) / 4

GPM is gallons per minute; and there are 231 cubic inches in a gallon. We divide by 60 to convert from minutes to seconds; the A is area of the hole diameter, and the division by 12 converts inches to feet.

Finally, we have the tools required to be able to calculate the pressure drop through our fittings. We’ll do two sample calculations, one each for a .375 and .718” diameter holes, to compare the difference.

For the .375 diameter hole, and using 6 gallons per minute of 60-degree water, we’ll calculate the Reynolds Number:

Re = (3160*Q) / [(Diameter in inches)) * (viscosity in centistokes)]

Re = (3160*6) / (.375 * 1.12) = 37920 / .42 = 45,142

Pressure Losses = (f * (L/D) * ((v^2) / 2g)) * (.433 * Sg )

f = .3164 / ((Reynolds Number)^.25) = .0217

A= .375^2 * Pi/4 = .11045

v = (6 * 236 / 60 / .11045 / 12 ) = 17.43

Press. Loss = .0217 * (.375 / 1) * [(17.43^2) / (2 * 32.2)] * (.433 *1) = .139 p.s.i.

For the .718 diameter hole, and using 6 gallons per minute of 60-degree water, we’ll calculate the Reynolds Number:

Re = (3160*Q) / [(Diameter in inches)) * (viscosity in centistokes)]

Re = (3160*6) / (.718 * 1.12) = 37920 / .80 = 23,577

Pressure Losses = (f * (L/D) * ((v^2) / 2g)) * (.433 * Sg )

f = .3164 / ((Reynolds Number)^.25) = .0255

A= .718^2 * Pi/4 = .40489

v = (6 * 236 / 60 / .40489 / 12) = 4.75

Press. Loss = .0255 * (.718 / 1) * [(4.75^2) / (2 * 32.2)] * (.433 *1) = .0054 p.s.i.

Now, on a percentage basis, there is a huge difference, but on an absolute basis, you are not likely to notice any difference in mold performance by changing between these two fittings, in this situation.

A quick look at the equation shows us that the only non-linear relationship is the velocity, which gets squared. Therefore, proportional increases in velocity will have a greater effect on pressure drop that any other factor. This is why it is so important to actually engineer your mold design.

Let’s see what would happen if you used a fitting with a .125 diameter hole.

For the .125 diameter hole, and using 6 gallons per minute of 60-degree water, we’ll do the calculations:

Re = (3160*Q) / [(Diameter in inches)) * (viscosity in centistokes)]

Re = (3160*6) / (.125 * 1.12) = 18960 / .14 = 135,428

Pressure Losses = (f * (L/D) * ((v^2) / 2g)) * (.433 * Sg )

f = .3164 / ((Reynolds Number)^.25) = .0165

A= .125^2 * Pi/4 = .01227

v = (6 * 236 / 60 / .01227 / 12) = 156.86

Press. Loss = .0165 * (.125 / 1) * [(156.86^2) / (2 * 32.2)] * (.433 *1) = 21.829 p.s.i.

Keep in mind that 6 gallons per minute will provide a Reynolds Number of 8200 in six .344 diameter water lines, assuming 60-degree water with no glycol added, so it’s not likely that you would ever end up in a situation where you would try to push 6 gallons per minute through a .125 diameter hole.

The water fittings used on a mold are most often dictated by shop standards. If the molding department only has hoses with “353” series fittings, then that is what you will usually have to design around. If you are designing for a molder that has standardized on “251” series fittings, this may or may not be causing you problems. The point of the article is this: it is not always immediately obvious how much affect your choice of pipe tap and water-fitting sizes are having on mold performance. If calculations can be done in minutes, or seconds, does it make any sense to skip over this critical step? You can make better decisions if you have more information. As always, over design can be expensive, and under design can be disastrous.

This is a segment of an article that I originally wrote for Moldmaking Technology Magazine. The link to the original article is here:

http://www.moldmakingtechnology.com/articles/090604.html

One very real problem with small fittings is that they are often used with small inside diameter hoses. Do these calculations for 20 feet of hose with small inside diameter. You may find that your largest pressure drops are outside the mold. If you need to use small fittings, be sure to reduce down at the end of the hose, and use as large a hose diameter as possible.
It can be a little time consuming to run through all of these calculations manually, so it is best to either create a spreadsheet, or purchase a program, that will allow you to do “what if” scenarios quickly. Once this is programmed, the calculations can be done in a matter of seconds, or minutes.

How to Do Basic Hydraulic Cylinder Calculations

2009-11-15T12:03:00.004-05:00

Designing with hydraulic cylinders is very common in everything from injection molds to log splitters to Backhoes and more. Here are some of the most basic calculations used in these applications.

This article shows you how to do the three most basic, and common, calculations for designing with hydraulic cylinders. These three would be the forward force of the cylinder, the return force, and flow rate required for the forward portion of the cycle. The return flow rate and force are lower because the volume and area are reduced by the presence of the piston rod, and therefore is not included in these calculations. The working portion of the hydraulic cylinder cycle should be the piston forward movement, for the above-mentioned reasons.

The first choice to be made is the units you wish to work with, inch or metric.

To calculate the forces generated by the piston, you must enter the appropriate diameter or diameters and the pressure supplied to the cylinder, in the appropriate units. In order to calculate the required volumetric flow rate, you must also use the length of stroke and the time is seconds.
The familiar relationships for area are used to calculate these answers:
Piston forward area = (Piston diameter)^2 x Pi / 4

Piston return area = ((Piston diameter)^2 - (Rod diameter)^2) x Pi / 4

Force = Pressure x Area

GPM = (((Pi * (D^2)) / 4) * S) * (60 / 231) / T

where,
GPM = gallons per minute
D = Piston diameter in inches
S = Stroke in inches
T = time in seconds
the 60 factor converts seconds to minutes
If you have a hydraulic cylinder with a 2.000 diameter piston, a 1.000 diameter rod, a 12-inch stroke, and want to extend the rod in .5 seconds, and the system pressure is 1000 p.s.i., the calculations for force and gallons per minute are as follows.
Piston forward area = 2^2 x Pi/4 = 4 x Pi / 4 = Pi = 3.142 inches^2 (rounded)
Piston return area = ((2)^2 - (1)^2) x Pi / 4 = 2.356 inches^2

Forward Force = 1000 x 3.142 = 3142 pounds
Return Force = 1000 x 2.356 = 2356 pounds
Since the time to extend the piston rod is only affected by the diameter of the piston, we can ignore the piston's rod size.

GPM = (((Pi * (D^2)) / 4) * S) * (60 / 231) / T
GPM = ((3.142 x 4)/4) * S) x (60/231) / .5 = 19.58 gallons per minute.
Of course, if you are going to a have a continuously cycling hydraulic cylinder, you must do the flow rate calculations for both the piston side, and the rod side.
Do not exceed the manufacturers recommendation for pressure in your hydraulic cylinder. Make sure that there are pressure and temperature relief valves for safety, and if in doubt, get professional advice.
Picture courtesy Parker Hannafin.