Shop Doc Blog

Shop Doc – Custom Macro programming

By Dan Murphy on May 17, 2013

Today’s Machining World Archives August 2010 Volume 06 Issue 06

Dear Shop Doc,

One of our operators came from another shop and told us that we can use Custom Macro for tool life management, but he doesn’t know how. I checked the manuals but don’t see anything obvious. Can you help?

Through the Grapevine

Dear Grapevine,
Custom Macro programming, also known as parametric programming, is capable of performing many different tasks, even ones not specifically outlined in the programming manual.

Macro programming allows the use of variables, logic, arithmetic, conditional branches, and custom alarms. For tool life management, we’ll need to use most of those functions. Ideally you should make a flow chart to outline the sequence of events that need to take place. In this case, you want to check the life remaining on all tools and either run a part or have the machine generate an alarm to notify the operator that a tool needs to be changed. Since all this needs to take place before machining, you can put that part of the Macro at the beginning of the program.

You should use variables to hold the life count and the life number for each tool. I like to relate the variable register number to the tool number. Let’s assume there are four tools and they are T0100, T0300, T1100 and T1400. We will use variable numbers 501, 503, 511 and 514 to hold the life count and variables 101, 103, 111 and 114 to hold the tool life value. Values stored in variables 100-149 are lost when the power is switched off. Variables 500-531 retain the value at power down.

O1234; (Machining program number)
#101=1000; (Tool life value for T0100)
#103=500; (Tool life value for T0300)
#111=775; (Tool life for T1100)
#114=2300; (Tool life value for T1400)

Setting the tool life from the program ensures that the proper values are used and saved. Next, you need to check the life of each tool. For this you can use a conditional BRANCH statement.

IF[#501 GT #101] GOTO 1000; (If the count in #501 is greater than the life set in #101 skip to line N1000)
IF[#503 GT #103] GOTO 3000;
IF[#511 GT #111] GOTO 11000;
IF[#514 GT #114] GOTO 14000;
(Normal machining program goes here)

At the end of the program you need to add to the tool life count and list the alarms. With the alarms you will also reset the tool life count so that you don’t have to rely on the operator to remember.

(End of normal machining program is here)
#501=#501+1; (Add one to the tool life count of tool T0100)
#503=#503+1;
#511=#511+1;
#514=#514+1;
GOTO 9999; (Skips over alarms and goes to M30 code)

N1000 #501=0; (Reset life count for T0100)
#3000=1 (TOOL LIFE OVER CHANGE TOOL T0100) (Alarm to stop machine with message)
N3000 #503=0;
#3000=1 (TOOL LIFE OVER CHANGE TOOL T0300)
(Repeat for #511 and #514);
N9999 M30; (End of program)

The GOTO statement will cause the program to skip over the alarms while the previous IF GOTO statements will cause them to be read. There are lots of different ways to program this. Submit your program in the comments on the Shop Doc Blog at www.todaysmachiningworld.com.

Dan Murphy
REM Sales LLC

Posted in Columns, Magazine, Shop Doc, Shop Doc Blog | 1 Response

Shop Doc – Micro Beginnings

By Peter Bagwell on May 14, 2013

Dear Shop Doc,

I have recently been asked if my shop does “micro” machining. I’ve done some work on small parts recently, but I’m not exactly sure what is meant by “micro.” Any thoughts?

Small Beginnings

Dear Small Beginnings,

One of the problems with the term “micro” is that it is often used to defne a very small portion of a wide array of categories. Maybe you’ve been to a microbrewery or have a computer that uses a microprocessor. In each case, the prefx or adjective “micro” defnes a small-scale or very small feature of the original term. To date, the term is loosely used in machining to refer either to the exact measurement of the parts, such as in microns, or to a small range of work, in the neighborhood of 1 mm or less.

In May 2010, I posed a similar question to exhibitors and attendees at MM Live—the Micro and Precision Manufacturing Event for North America, in Cincinnati, Ohio. As an exhibitor myself, I thought micro meant sizes under .050”, as this was the smallest tool in our catalog and very near to the 1 mm dimension. I often referred to parts from this diameter up to .500” diameter as Swiss, so everything smaller I considered micro. A large number of attendees defined micro as being smaller than a certain dimension.

Some said micro meant parts smaller than 8 mm or .250”, or 1 mm. Kyocera’s booth advertised a .250” dimension on their sign. However, when I asked them about it, they explained that although they make a wide variety of small tools, the ones they considered to be micro sized were really those .125” or smaller.

Photo from JMMedical

A few attendees believed the term “micro” referred to parts that were smaller than the human eye can see. The MM Live show had a wide of variety of these parts on display, and it seemed that every other booth had a microscope or magnifier of some type to help you see their wares. One of the most intriguing answers to define micro came from an exhibitor at Makuta Technics Inc. He said they use the term micro not to refer to a part’s size, but more exclusively to the feature’s size. You may have a part not considered to be a micro machined part, but if the features and tolerances are small enough, it may require what is commonly known as micro machining. This can lead to a lengthy discussion about tolerance, and if a part with +/-.001” variance can be classified the same as a part with +/-.000010”.

I believe micro machining refers to parts with an overall size or feature in the neighborhood of 1 mm. The features are not as large as common Swiss machined parts, nor as small as a nanometer (one billionth of a meter), but you will still need some form of glasses to make out the details. My suggestion is to not split hairs, but just state the size of the features you are comfortable making. The number of people who agree on the definition of the term “micro” is very small.

Peter Bagwell

Posted in Columns, Magazine, Shop Doc, Shop Doc Blog | 5 Responses

Shop Doc – Why are there big differences in price from one rebuilder to the next?

By Dave Johnson on May 10, 2013

Today’s Machining World Archive: May 2010 Vol. 6, Issue 04

Dear Shop Doc,

I recently decided to shop around for quotes to rebuild my 1-1/4” RB8 Acme-Gridley.
I sent the RFQ out to three different rebuilders and received three very different prices.
Why is there such a big difference in price from one rebuilding company to the next?

Confused in Cleveland

Dear Confused,

This is a very common situation in our industry today, but a little knowledge can go a long way towards helping you evaluate quotes for your rebuild projects.

Many companies mistakenly assume that the term “rebuild” means the same thing to every supplier. This is not the case, and there can be a great deal of difference between machine tool rebuilders as to what constitutes a machine rebuild. These differences have a substantial impact on what it will cost a rebuilder to do the job, what will actually be done to your machine and what condition your machine will be in when you get it back. For Rebuilder A, it may be standard practice to replace every bearing in the machine, and just about every part with a new part, while Rebuilder B might have the practice of evaluating all of the current parts in the machine and then reusing the ones that pass inspection. One rebuilder may always strip the machine completely down to the castings, inspect them carefully for damage or needed repairs, then repaint the machine inside and out, while another rebuilder may consider that to be more work than necessary.

The differences in opinion about what work must be done when “rebuilding” a machine is the main cause of the wide range of price quotes. Some of the better rebuilding companies offer a written procedure detailing what they do when they rebuild a machine. Many also offer what is commonly called a machine “re-condition,” basically a mini-rebuild, which is also subject to discrepancies from company to company regarding what work is included. A written procedure for machine re-conditioning may also be available.

A great way for a customer to deal with these discrepancies is to write their own detailed outline for what work they want to be performed, and use that as the platform for every rebuilder to bid on. Be sure to include as much detail as possible and outline what is acceptable to you with regard to reusing any current parts on the machine. Also, consider if you want the electrical system to be addressed, if there are attachments that will need to be rebuilt or added, and if there are any other upgrades such as adding a PLC, that need to be outlined. The more detail you have going into the quoting process the more accurate your quotes will be, and the fewer surprises you will have down the road.

David Johnson
Champion Screw Machine Engineering, Inc.

David Johnson is the Rebuild Manager for Champion Screw Machine Engineering, Inc. in Wixom, Mich. He can be reached at djohnson@championscrew.com

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Shop Doc: Mr. Bone Screw

By Peter Bagwell on April 19, 2013

Mr. Bone Screw

Dear Shop Doc,

I’m going to be rotary broaching a 9/64” hex in titanium. The hole is a blind hole about .160” deep. I’m worried about hydraulic pressure building up during the broaching operation. What are my options?

Mr. Bone Screw

Dear Mr. Bone Screw,

You have a few options available. But first, let’s talk about the hole. Be absolutely sure to drill it deeper than the broaching depth. You will need to leave room for chips, fluid, etc. The deeper the hole, the more room is available for swarf to get out of the way.

The first option has to do with your pilot hole. A pilot hole drilled to size will create significantly more pressure than one drilled oversize. The oversize hole allows air and fluid to escape. This larger pre-drill diameter also reduces the size of the chip while broaching. The chips are also sure to be separated. A standard 9/64” hex has a dimension across the flats of .1425”. Drilling the pilot hole about 3 percent larger, requires a drill size of .147”.

The following tooling options are all intended to reduce pressure while broaching. Most of these options are commonly available in the marketplace.

Spun, Ground Diameter – Eliminating the sharp corner from the broach reduces chip size and depth and strengthens the broach at the corners. Rotary broach failure is often a result of chipping at the corners.
Broach Pressure Relief Holes – Small holes added to the center of the broach and used in conjunction with secondary holes drilled in a cross direction allow the fluid and air to escape.
Broach Holder Relief Holes – A relief hole in the broach holder allows air and fluid to escape completely. Air and fluid are pushed through a center relief hole in the broach, and out of the holder through its relief hole. This option is currently available from Polygon Solutions and reduces cost of broaches requiring two vent holes.

Here are a couple tips to make sure you get the most out of your tooling. Make sure the broach is aligned with the pilot hole. This may seem obvious, but many machines can be off center by more than a few thousandths. Most broach holders have end play built into them. The broach will follow the hole. But double check it anyway; this is a common troubleshooting problem. Also, if you’re going to be broaching titanium, upgrade to a premium broach material, such as M-42 or PM T-15. These broach materials are very hard and include elements like cobalt to enhance their strength.

As you can see, all of the information here has to do with reducing the forces required while broaching and strengthening the broach. Hopefully these tips will relieve some of the pressure created when trying out a new machining operation. If you’re still uneasy, run the broach in aluminum to get a feel for the set-up.

Peter Bagwell is a Rotary Broach Product Engineer at Polygon Solutions. He is a frequent contributor to Today’s Machining World’s Shop Doc column and is also an Essential Oil enthusiast. To contact him, go to www.polygonsolutions.com.

Posted in Shop Doc Blog | 4 Responses

Shop Doc – Tangled Up in Tennessee

By Dan Murphy on April 10, 2013

Today’s Machining World Archive: April 2010 Vol. 6, Issue 03

Dear Shop Doc,

We are running a long aluminum part on our CNC Swiss and have problems with the long stringy chips building up in the machine and getting wrapped around the part. We’ve tried every “aluminum” insert under the sun and have 2,000 psi coolant, but nothing works. Please help!

Tangled Up in Tennessee

Dear Tangled,

There is a new chip control technology for aluminum that I’ve found to be very effective. It’s a PCD (polycrystalline diamond) insert that has a 3D chipbreaker. Up until now, manufacturers have been unable to produce 3D chipbreakers in the ultra-hard polycrystalline diamond material. A new process has been developed that uses a laser to etch a variety of 3D chipbreaker shapes into the PCD. The inserts are made by Becker Diamont.

They have a video on YouTube that can be found at: www.youtube.com/watch?v=gLRJdMDvbpY. A brochure can be downloaded at: www.ranitool.com/ChipBreaker-ranilowres.pdf.

On a Swiss I’ve found that it’s the feed rate that is critical to getting the chip to break. In general, a larger depth of cut requires a slightly higher feed rate. On a fixed headstock lathe, you can also vary the depth of cut and the feed rate for optimum results.

Other possible solutions include milling a flat or narrow slot along the length of the cut before turning. I prefer to use a narrow slotting saw to cut an off-center slot along the turn length. A narrow slot has less chance of generating an out-of-round condition on the turned diameters. Milling the slot off of the centerline of the work prevents the slot from hitting the turning insert squarely. The slot being off center along with the rotation of the work causes the slot to hit the insert and travel by it on an angle. This eliminates any pounding caused by the interruption while providing enough interruption to break the chip.

Problems with grooving and cutoff tools can often be solved by using a peck cycle like G75, which is like a peck drilling cycle, but from the cross axis rather than along the Z-axis.

Ultimately these other options add cycle time while the PCD insert will likely reduce cycle time and improve uptime.

You will pay more for PCD, but it almost always costs less than a polished carbide insert due to the vastly improved tool life.

Another added benefit is that once you start breaking the chips up, you won’t have to empty out the chip bin nearly as often. Those long wiry chips create big air pockets that take up a lot of space.

Dan Murphy
Tsugami REM Sales

Dan Murphy is a regional sales manager for REM Sales LLC., a U.S. Tsugami importer. He can be reached at dmurphy@remsales.com.

Posted in Columns, Magazine, Shop Doc, Shop Doc Blog | 4 Responses

Shop Doc – Indexable Carbide Inserts for Single Point Turning

By Jim Rowe on March 27, 2013

Today’s Machining World Archives September 2007 Volume 03 Issue 09

Dear Shop Doc,

We are frequently utilizing indexable carbide inserts for single point turning processes in our shop. It appears that most of these inserts are available in M (molded) or G (ground) tolerances. Can you tell me the benefits of one over the other? Also, how will I see the performance advantages from the more expensive G inserts?

Weighing In

Dear Weighing In,
Let’s first briefly touch base on how an insert is made. Several powders which make up the substrate of the carbide are molded into the shape desired. The next step is to “sinter” or basically bake it. This sintering process actually shrinks the insert to the size desired, with a tolerance for its thickness and inscribed circle dimensions.

At this “molded” point, all that is left is to prep the cutting edges, then inserts are ready to make chips. There isn’t any other cost involved other than packaging. Some of these molded inserts will be coated, which is one more step that adds to the cost. A subsequent grinding operation can take place on the edges, and or top and bottom of the inserts. This will ensure each insert will be held to a given tolerance.

A great reason to use ground inserts is that once you establish the centerline of a turning insert, the next insert should be sitting at the same height. Incorrect centerline height is one of the most common causes of poor tool life in turning applications.

Also, as you index the insert from cutting edge to cutting edge, you should be able to reset any wear offsets (on a CNC machine) or back off any adjustments to the starting position that the last tip of the insert started at, and begin with a good part or dimension that this tool is cutting. Each manufacturer states their tolerance on their insert. Typically it is the third letter in their insert nomenclature

In some cases, to maximize machining effectiveness when cutting materials such as aluminum or titanium, a slicing or shearing action is exactly what is preferred. This is obtained by further grinding a sharper cutting edge on the insert.

Jim Rowe
Mahar Tool Supply

Posted in Columns, Magazine, Shop Doc, Shop Doc Blog | 2 Responses

Shop Doc – Polygon Milling on a Small Part

By David Cogswell on March 21, 2013

Todays Machining World Archives May 2008 Volume 04 Issue 05

Dear Shop Doc,

We are trying to make a part of beryllium copper that has a .025″ square pin on one side. The length of the square pin is .140″ long, then transitions to a diameter of .035”, and then to a shoulder at .150” diameter. The problem I am having is that we have to turn the raw material down to .035″ before we polygon mill the .025″ square. We’ve done polygon milling on much larger parts but this is our first time on a small part. We are using a CNC Swiss lathe that has opposing X- and-Y-axis gang plates that are controlled separately.

Poly Gone

Dear Poly,

I know exactly what you are trying to attempt. What you’ll need to do is adjust your methodology to account for the fact that you need to turn the raw material from .250″ diameter to .035″ and polygon mill at the same time. What is happening in your current method is that after you turn the .035″ diameter, the material is no longer supported by the guide bushing. To fix your problem, you need to turn the .035″ diameter at the same time you are polygon milling.

Two actions need to be taken:
1. Tooling: In the Z-axis plane, the turning tool needs to be closer to the material than the polygon tool. The reason for this is to turn the diameter before the polygon tool starts creating the fats. I know in most Swiss machines this is already built into the tool holder geometry where the live tools are typically further away from the guide bushing compared to the turning tools. If this is not the case, then you’ll need to make some physical adjustments so that you can set the tools properly – either by shimming the polygon tool or grinding the shank on the turning tool. Then find the distance between the two tools in the Z-axis plane. As an example we’ll use .010″ as the distance between the two tools.

2. Programming: To program this you’ll need to understand how to utilize tool offsets. For the turning tool, just program it in the normal fashion where you call the tool and the offset. For example: T0101 – Tool 01 and offset 01. For the polygon tool just call up the tool position without the tool offset. For example: T0200 – Tool 02 and no offset. For the G-Code, simply add the distance between the two tools to your programming of the turning tool to get to the linear dimension of the .025″ square.

In your particular component, (using the example of .010″) you’ll want to program your turning tool to .150″ in the Z-axis to account for distance between the turning tool and the polygon tool. This will give you the net result of producing a .025″ square that is .140″ long. If you need to contour the shape of the square, then the programming gets much more complex and you’ll do just the opposite of my example. You’ll have to use the polygon tool offset and omit the turning tool offset, then control the path of the polygon tool in the program. However, you’ll still need to keep the turning tool in front of the polygon tool and account for the difference.

Happy Machining!

David Cogswell
Director, Precision Machining Operations
Bal Seal Engineering,
Medical Products Group

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Shop Doc – Stringy Aluminum Chips

By Dan Murphy on February 26, 2013

Dear Shop Doc,

We are running a long aluminum part on our CNC Swiss and are having problems with long stringy chips building up in the machine that are getting wrapped around the part. We’ve tried every “aluminum” insert under the sun and have 2,000 psi coolant, but nothing works. Please help!

Tangled Up in Tennessee

Dear Tangled,

A brochure can be downloaded at: http://www.ranitool.com/ChipBreaker-rani-lowres.pdf.

On a Swiss I’ve found that the feed rate is critical to getting the chip to break. In general a heavier depth of cut requires a slightly higher feed rate. On a fixed headstock lathe, you can also vary the depth of cut as well as the feed rate to obtain optimum results.

Other possible solutions include milling a flat or a narrow slot along the length of the cut before turning. I prefer to use a narrow slotting saw to cut a slot off center along the turn length. The narrow slot leaves less chance of generating an out of round condition on the turned diameters. Milling the slot off of the centerline of the work prevents the slot from hitting the turning insert squarely. The slot being off center along with the rotation of the work causes the slot to hit the insert and travel by it on an angle. This eliminates any pounding caused by the interruption while providing enough interruption to break the chip.

Problems with grooving and cutoff tools can often be solved by using a peck cycle like G75, which is like a peck drilling cycle, but from the cross axis rather than along the Z-axis.

Ultimately these other options add cycle time while the PCD insert will likely reduce cycle time while improving uptime. You will pay more for PCD, but it almost always costs less than a polished carbide insert due to the vastly improved tool life.

-Dan Murphy
Tsugami REM Sales

Dan Murphy is a regional sales manager for Rem Sales LLC., a U.S. Tsugami importer. He can be reached at dmurphy@remsales.com.

Posted in Columns, Favorite Videos, Shop Doc, Shop Doc Blog, Videos | 2 Responses

Shop Doc – Vexed Hex

By Dan Murphy on February 7, 2013

Dear Shop Doc,

I have a part that has an internal hexagon that needs to be put into the part in relation to milled features. Is there some way that a wobble broach can be oriented to the C-axis on my CNC Swiss?

-Vexed Hex

Dear Vexed,

On a full featured CNC Swiss there is a unique solution to this issue. As you know, rotary broaching holders offer no way of orienting the polygon shaped broaches to the work. The method that follows will also allow you to broach faster and will never “spiral” on a deep broached feature.

If your CNC Swiss has a Fanuc control equipped with the polygon cutting option, you should be able to use an adjustable angle live drill unit to wobble broach the hexagon shape while holding angular relationship to other live tool features on the work. Here’s how; mount an off-the-shelf rotary broaching bit into the angular drill unit and set the angle to 1 degree. This puts the broach in the same attitude as it would be if it were sitting in an ordinary rotary broach holder. If you have a CNC lathe or Swiss with a programmable B-axis, simply command the live tool B-axis to a 1 degree angle.

Use the G51.2 polygon cutting command to orient and synchronize the live tool spindle to the work spindle. Ordinarily this command is used for cutting external polygons on the work using a polygon attachment and cutter, but it works just fine for wobble broaching.

Example of the command when used for broaching: G51.2 P1 Q-1 R45.0;

The P value equals the ratio of the work spindle to the tool spindle. Q equals the ratio of the live tool spindle to the work spindle. The sign of the value determines the spindle rotation direction of the live tool. A negative value is usually the Vexed Hex counter-clockwise direction, which would match a clockwise direction on the opposing work spindle.

If the live angle tool attachment has a gear ratio to the commanded speed then you would use P and Q to compensate for that ratio. For example, if the live tool spins at 4,000 rpm when you program 2,000 then you would program values of P1 Q-2.

The R value sets the angular relationship of the live spindle to the work spindle. This allows you to adjust the orientation of the broach in relation to the C-axis of the main spindle. The value range is from 0 degrees to 359.999 degrees. I prefer to program a macro variable instead of a numeric value so that the orientation can be adjusted without editing the program. For example—G51.2 P1 Q-1 R#510: Variable 510 can now be used as an offset to adjust the orientation of the broach to the work.

Once you have commanded the polygon turning function G51.2, program the broaching operation the same exact way you would if you were using a conventional rotary broaching tool. In most cases you can broach at a much higher rpm using this method than you can with a rotary broach holder. You are only limited by the maximum speed of the main or tool spindle. Cancel polygon mode by commanding G50.2.

-Dan Murphy
Tsugami REM Sales

Posted in Shop Doc, Shop Doc Blog | 8 Responses

Shop Doc – Push Back Trouble Using Collets

By Dan Murphy on January 30, 2013

Today’s Machining World Archives January/February 2011 Volume 7 Issue 1

Dear Shop Doc,

On our CNC lathes we occasionally have trouble with push back when using collets on bar jobs. Our collets have smooth bores and I am wondering if a serrated collet would help or if it will just create more problems.

Chuck Force

Dear Chuck Force,

Serrated collets will probably help, but first let’s consider all of the variables.

Bar whip—Bar whip can cause the bar to act as a lever against the collet, prying it open. You should always use a spindle liner and/or a properly sized liner set in your bar feeder to minimize bar whip.
Collet bore—Most collet systems have some gripping range, but the bore of the collet can only be machined to one given nominal diameter, and that diameter fits the bar the best. Avoid using a collet that’s “close enough.”
Chucking pressure—The hydraulic pressure to the rotary actuator can be adjusted. Follow the manufacturer’s recommendation for the operating range and adjust accordingly. In general, you need higher pressure for larger diameter bar and less pressure for small diameters.
Maintenance—Make sure that the sliding components of your collet chuck are clean, lubricated and slide easily. Make sure your hydraulic oil is in good condition, the level is adequate, and the system is operating in the proper temperature range.

Serrated collets work by reducing the surface area of the collet bore, thereby increasing the pressure that the contact area of the collet exerts against the work. You can calculate the surface area of the collet bore using the formula: 2 π r2 + 2 π r h. Ignoring the area removed by the slots in the collet, a 1.0” diameter collet with a 1-1/4” land has 5.5 in² of gripping surface.

If the collet closes with 1,000 pounds of force, that force is distributed over the 5.5 in² surface area of the bore, resulting in a contact pressure of 181.8 psi. If you decrease the surface area of the collet bore by machining in serrations, you increase the contact pressure by a corresponding amount. This doesn’t multiply the holding force in any way; you are still applying the same 1,000 pounds of force to the task of holding the work. By applying the force to a smaller area with greater pressure, the collet can dig into (deform) the work. Whether or not the collet permanently marks the work (plastic deformation), or the work bounces back (elastic deformation) depends on the force applied.

Another option is to have the collet coated with a textured carbide alloy coating like Carbinite (go to www.carbinite.com for more info). The principle is the same as serrations, but instead of grooves cut into the collet bore, the bore is coated with a crystalline like carbide alloy. The coating has a texture similar to sandpaper, which provides tremendous grip.

Dan Murphy
REM Sales LLC

Dan Murphy is a regional sales manager for REM Sales LLC., a U.S. Tsugami importer. He can be reached at dmurphy@remsales.com.

Posted in Columns, Magazine, Shop Doc, Shop Doc Blog | 3 Responses