CNCzone.com-The Largest Machinist Community on the net! - Mechanical Calculations/Engineering Design http://www.cnczone.com/forums/ Discuss general mechanical design and mechanical calculations. en Sun, 22 Nov 2009 11:57:10 GMT vBulletin 60 http://www.cnczone.com/forums/images/misc/rss.jpg CNCzone.com-The Largest Machinist Community on the net! - Mechanical Calculations/Engineering Design http://www.cnczone.com/forums/ Need Advice on material! http://www.cnczone.com/forums/showthread.php?t=93906&goto=newpost Sun, 22 Nov 2009 00:34:00 GMT Hi everyone. I am going to be making a set of... Hi everyone. I am going to be making a set of connecting rods for my snowmobile engine. I need a shorter center to center distance so off the shelf isn't possible. My question is: If I machine these from 4140 should I have them thru hardened and tempered, or should I make them from a material that can be case hardened? The bores need a hard surface because they act as races for the needle bearings. Any info./ advice would be appreciated. ]]> Mechanical Calculations/Engineering Design captainDL http://www.cnczone.com/forums/showthread.php?t=93906 Gantry: planning to design moving open gantry http://www.cnczone.com/forums/showthread.php?t=93447&goto=newpost Sat, 14 Nov 2009 21:52:05 GMT Hi everyone. I would like to build a cnc... Hi everyone.

I would like to build a cnc router with the following characteristics:
-cutting area of x=4', y=3'
-acme lead screws
-moving open gantry (no undercarriage)
-steppers

I would like to see comments on how to drive the gantry over the X axis, if using two steppers or one stepper to drive the two X lead screws.

Rolando ]]> Mechanical Calculations/Engineering Design rdcd http://www.cnczone.com/forums/showthread.php?t=93447 3PH VFD Net HP http://www.cnczone.com/forums/showthread.php?t=93391&goto=newpost Fri, 13 Nov 2009 20:55:25 GMT I will be replacing a dead 1/2 HP 3PH motor on my... I will be replacing a dead 1/2 HP 3PH motor on my mill with a VFD driven motor. What I'm wondering is how much should I oversize the new motor so I can net 1/2HP after 1PH VFD?

I'm guessing a 1HP would be plenty but am wondering if anyone knows for sure.

TIA ]]> Mechanical Calculations/Engineering Design ogesII http://www.cnczone.com/forums/showthread.php?t=93391 Feeds calculation http://www.cnczone.com/forums/showthread.php?t=93337&goto=newpost Thu, 12 Nov 2009 19:53:33 GMT Hello i am new to the forum so please excuse me... Hello i am new to the forum so please excuse me if this thread is in the wrong place.
I work for a C.N.C. company in Manchester and I am trying to develop a simple excel spread sheet to calculate component cycle times. This is for the purpose of accurately quoting potential jobs. I have developed most aspects of the spread sheet and tested them with actual jobs with a successful outcome. I am struggling with the toughest part (turning). We use Fanuc controllers to control Colchester tornado T6M’s turning centres. We use constant surface speed (G96) I am finding it difficult to create a formula to find out the cycle time of a turning cycle (G71).

My first attempt worked well this is what I had:-


Simple turned peg.

Used a turning cycle (G71) and (G70) finishing cycle.

G71U1R1;
G71P10Q20U1W0.1F0.2;
N10G00X30;
G01Z-50F0.2;
X60;
Z-100;
X62;
N20G00Z2;
G70P10Q20;

So my depth of cut is 1mm
Feed rate 0.2
Spindle speed S250

As the feed is feed / rev (G95)
I need to find how many revs per second
60/250 = 0.24spr
0.24 x length of cut (50mm+2mm)
0.24 x 52 = 12.48 secs
Then worked out how many cuts (15)

12.48 x 15 = 187.25sec
187.25/60=3.12mins

This was correct to I applied the same technique to a second job COMPLETELY WRONG.

So I must need another formula but I have no idea what
I bet you all know what is coming and that is has anyone tried to do something similar is so what calcs did you use?
Thank you for the time. ]]> Mechanical Calculations/Engineering Design Redic http://www.cnczone.com/forums/showthread.php?t=93337 Rack and pinion spring loading question http://www.cnczone.com/forums/showthread.php?t=93316&goto=newpost Thu, 12 Nov 2009 15:10:23 GMT What's the reason for spring loading the pinion gear assembly against the gear rack? If the rails and gear rack are aligned properly shouldn't you be able the mount the gear in a fixed (rigid) position? This is providing that there is a mechanism to adjust it for wear and initial position. What am I missing?

thanks ]]> Mechanical Calculations/Engineering Design microdot http://www.cnczone.com/forums/showthread.php?t=93316 Help please i am formula illiterate http://www.cnczone.com/forums/showthread.php?t=93197&goto=newpost Tue, 10 Nov 2009 18:32:06 GMT Could someone please help me understand what this... Could someone please help me understand what this stuff means and how to use these formula's to figure out the proper stepper motor size for my application?


hen a stepper motor is selected, eight different things must be considered:
Operating speed in steps/second
Torque in oz-in.
Load inertia in Ib-in.2
Required step angle
Time to accelerate in ms
Time to decelerate in ms
Type of drive to be used
Size and weight considerations

Some of this information will be provided from application specifications, such as the size and weight considerations, step angle, and the operating speed. Other information must be calculated. Several formulas are provided to help you with these calculations.

Calculating Torque
The formula for calculating the torque is


Calculating Load
The formula for equivalent inertia to overcome friction in the system and enough torque to start or stop all inertia loads is


Frictional and Rotational Acceleration Considerations
The formula for calculating the torque required to rotationally accelerate an inertia load is

Buy the Book


Purchase Industrial Electronics from Prentice Hall.

64 ratings | 3.70 out of 5 Print
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nice information
in the doucment the information given is very use full thanks 2 authour
- nirmal, n++. speak4nirmal@gmail.com - Feb 12, 2008




Legal
Excerpt from the book published by Prentice Hall Professional (http://www.phptr.com).
Copyright Prentice Hall Inc., A Pearson Education Company, Upper Saddle River, New Jersey 07458.
This material is protected under the copyright laws of the U.S. and other countries and any uses not in conformity with the copyright laws are prohibited, including but not limited to reproduction, DOWNLOADING, duplication, adaptation and transmission or broadcast by any media, devices or processes. ]]> Mechanical Calculations/Engineering Design native34 http://www.cnczone.com/forums/showthread.php?t=93197 Angle iron http://www.cnczone.com/forums/showthread.php?t=92979&goto=newpost Fri, 06 Nov 2009 22:51:02 GMT I am going to use 1/4" thick angle iron to support 2" thick stone on a building. Can anyone tell me if there is a chart or calculation to figure if bent 1/4" steel is as strong as regular 1/4" angle iron of the same dimensions? ]]> Mechanical Calculations/Engineering Design kadamsflk http://www.cnczone.com/forums/showthread.php?t=92979 Help understanding concept http://www.cnczone.com/forums/showthread.php?t=92878&goto=newpost Thu, 05 Nov 2009 18:10:13 GMT Could someone please explain the paragraph below... Could someone please explain the paragraph below in a for dummies explanation for me please as i have no understanding of this please see below?

The place to start is to determine the load torque in oz/in. Be sure to include the torque necessary
to accelerate the load. Next come up with the maximum speed the application has to operate at in
full steps per second. Multiply the two together and then divide the result by 4506 to calculate the
power in watts necessary to meet the application requirements. Pick a motor at a power supply
voltage that provides a 40 percent reserve power margin above your requirements ]]> Mechanical Calculations/Engineering Design native34 http://www.cnczone.com/forums/showthread.php?t=92878 Simple Calculations for a simple mind. http://www.cnczone.com/forums/showthread.php?t=92813&goto=newpost Wed, 04 Nov 2009 18:26:01 GMT So Gecko's site gives the following calculation for determining push:

In. oz. * TPI * π / 8 = lbs of push

According to this if I have a 380 oz-in stepper, driving a 10 tpi screw, I should achieve 1491.5 lbs of push (of course losses will result in a lower real world situation)

380 x 10 x π / 8 (or 0.3925) = 1491.5 lbs

Is this right? If so, I think I have been over buying steppers! ]]> Mechanical Calculations/Engineering Design cr8zy1van http://www.cnczone.com/forums/showthread.php?t=92813 <![CDATA[Newb ? - CAD Part interference & mating part dims]]> http://www.cnczone.com/forums/showthread.php?t=92810&goto=newpost Wed, 04 Nov 2009 17:40:28 GMT Hi, Im a beginner Alibre design 12 cad user,... Hi, Im a beginner Alibre design 12 cad user, making my first tool design in CAD for steel machining. I have a fundamental question regarding the conventional method to define the final mating surface of parts for CNC level machining.
If I have 2 aligned and mating surfaces such as a dovetail and slide or rod through bushing, or even gear mesh what is the conventional method to designate the allowable / or desired fitting space for precision assemblies?

For instance if I have a 3/8 drill rod in a 3/8 hole, though a 1' steel plate bushing and desire a tight tolerance, snug fit yet free enough to rotate. Using manual milling methods I would bore & ream a 3/8 hole and usually it fits perfect. If happens to be just too snug I lap either part with 600 or finer to fit. How does one specify these tolerances in a CNC specification thay I will outsource to one or several shops?. I could adjust both surfaces by a couple of thousandth's or just one part surface... or privide a -/+ allowable tolerance and hole for the best during assembly?

My specifoc situation is the manufacture of a small CR machined steel tool that has several precision aligned components that are free to slide and rotate along various axis in its dozen part assembly. My assembly in Alibre identified this problem by pointing out offending part interferences when parts of the same exact dimesion are assembled with a mated constraint. I want to correct this in my part designs the right way or at least understand the industry standard from the start. Thanks for your help. ]]> Mechanical Calculations/Engineering Design pabmartin http://www.cnczone.com/forums/showthread.php?t=92810 Load calculation http://www.cnczone.com/forums/showthread.php?t=92788&goto=newpost Wed, 04 Nov 2009 11:52:39 GMT How do you calculate the sizes of square section... How do you calculate the sizes of square section EN8 mild steel bar to be used to pick up a load, if I know the weight of the load and the length of the bar. I need to lift a 1 ton injection moulding tool with a bar of 400mm length. The bar is bolted to the top of the tool at both ends and an eye bolt is secured to the middle of the bar. Both eye bolt and fixing bolts are 16mm. I know I have to build in a safety factor of about 4 to 1 so I really need this bar to lift 4 ton.
Any thoughts would be appreciated. ]]> Mechanical Calculations/Engineering Design Nigel Thomas http://www.cnczone.com/forums/showthread.php?t=92788 Can this Shaft Handle This Force? http://www.cnczone.com/forums/showthread.php?t=92704&goto=newpost Mon, 02 Nov 2009 22:03:29 GMT I've got a linear bearing situation where an extension spring will have about 500 pounds of force pulling on it. The linear bearing can adjust up or down to increase or lessen the force of the spring. I was wondering if anyone can tell me if a 3/8" Diameter 316 Stainless Steel Shaft can handle the amount of force or it will bend. See the pic below for an example.
Attached Thumbnails
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]]> Mechanical Calculations/Engineering Design Cartierusm http://www.cnczone.com/forums/showthread.php?t=92704 Crankshaft grinder lathe attachment ?? http://www.cnczone.com/forums/showthread.php?t=92440&goto=newpost Thu, 29 Oct 2009 13:28:34 GMT Ok I know they make a crankshaft grinder lathe... Ok I know they make a crankshaft grinder lathe but I can't seem to find a old one and new equipment is way out of my price range, I have heard years ago you could buy a crankshaft grinder attachment for the old atlas/craftsman lathes (can't find any of those either)

Here is my question : has any one every made a grinder attachment for say a 6"x36" metal lathe or is it even possible? if you have would you mind sharing some detailed pictures and any plans/draws yo may have so I could try to build my own ]]> Mechanical Calculations/Engineering Design Goldhunter_2 http://www.cnczone.com/forums/showthread.php?t=92440 Linear Bearing vs Linear Rail http://www.cnczone.com/forums/showthread.php?t=92134&goto=newpost Sun, 25 Oct 2009 04:33:45 GMT For a CNC plasma table is there any functional... For a CNC plasma table is there any functional difference between a linear bearing or a linear rail?

Linear rail being the supported round bar with pillow blocks vs linear bearings which have flat sides. ]]> Mechanical Calculations/Engineering Design microdot http://www.cnczone.com/forums/showthread.php?t=92134