Don't Just Fill Your Oils ...

... Track Them ?

Why? I'm glad you asked !!

Did you know that filling your way lube tank can tell you a story about your machine's performance. It can, if you use the information to your advantage. How?

The best way is to make an oil fill reminder form and post it on the machine. Each time oil, any type of oil, is added to the machine, have the operator jot down the following:

• Type of oil added
• Date and Time the oil was added
• Amount of oil added
• On a turning center, when the chuck was greased

This data can be used for the following :

Type Of Oil : this tells you which oil tank might be giving you trouble. If you're filling the hydraulic tank (a closed system) - WHY and WHERE is the oil leaking from. Low hydraulic oil could result in a loss of pressure and perhaps an un-chucking of a part being machined with catastrophic results. If you're replacing way-lube (which you should), what kind of schedule are you on. This list should show a difference in the frequency of the filling which will easily and early show a way-lube system problem and head-off major repairs.

Date and Time the oil was added : this info gives you a clear view of the filling schedule. Again, not filling the way-lube tank, for example, will be easily seen and catastrophe can be averted.

Amount of oil added : as above, this info gives you a clear schedule of the filling schedule. Filling the way lube tank once every two days instead of once every three days will show up and might signal a line break or other problem that can easily be spotted and repaired in time.

As with everything in life, the info gathered is only as good as the person viewing it. Teach you operators to be hands-on people and to pay attention to this list, perhaps every morning with the machine start-up. Simple ideas like this TIP can help extend your machine's life and cut down dramatically on your machine's down time and repair bills.

Live Long ... and Make Chips !!

Spindle Load vs. Spindle RPM

Which is the true test of how hard your machine is working ?

If you had to watch the spindle speed meter or the spindle load meter on your CNC machine ... lathe or mill ... to determine if your machine was working too hard, which one would you choose?

The truth of the matter is that although the spindle load meter does tell you the power draw on the spindle motor, the RPM gage is a more accurate representation of how hard the spindle is working. Most machines come with a specific rating for load % per a specific time such as (in laymans terms) : "You can run this machine at 100% for 30 minutes."

That is of course a true statement and you can watch the load meter while cutting and reach that spec. However, if you watch the RPM gage while cutting and see it fluctuate wildly - basically because the motor is trying to keep the spindle at the specified (programmed) RPM - you'll never reach that 30 minute time frame. Because the cutting is so heavy in this type of case, the motor must keep "powering up" to keep the programmed RPM specified. This takes much more power draw on the motor than simply running constant at 100% load for the 30 minutes.

The Solution : When your machine is cutting, watch the RPM gage first to insure that the cutting conditions are resulting in a smooth RPM for the spindle and not wild fluctations as the motor fights to keep the speed constant. Secondly, adjust the cutting conditions so that the load meter is as high as you think you want (there is nothing wrong with 70-75%) and then recheck the RPM gauge to make sure that the RPM's are smooth at those settings. Smooth RPM cutting will result in better life for the spindle motor and smoother surface finish on the workpiece as well.

Happy Chip Making !!

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Circle Milling Like a Professional

Milling a counterbore or doing other circle cutting using an end mill or similar tool can be a powerful and creative machining process. Most times replacing the need for a reamer, boring bar or other sizing tool. This type of cutting, when combined with cutter compensation gives the operator much more flexibility in adjusting the size of the finished hole.

However, the main drawback is usually created using simple programs and is usually found at the entry and exit points where a small tool mark can be created due to the tool pressure caused at the entry of the cut. With a little creative programming technique and some simple calculations, a much more efficient and "professional" program can be created.

In this post, we're going to take you step by step through a program creation to mill a circle using the "loop in - loop out" method which takes the cutter from the center into the side of the hole using an arc move - then cuts completely around the hole - then loops back to the center using another arc move. This type of cutting gives a real nice finish in the hole, helps maintain size a little better and leaves no tool mark at entry or exit points.

In our example, finish milling an inside round pocket using G02 or G03, a cutter mark will remain from tool pressure at the entrance and exit point of the arc. In order to create a smooth entrance and exit, some “tricky” machining technique must be employed because most machines do not have a “canned cycle” for the type of cutting explained here. Although this employs nothing more than simple G02 or G03 commands, the manner in which the codes are used and the type of process that results, makes efficient use of the simple codes and makes a more attractive and accurate workpiece.

The objective with the example below is to create a smooth transition into and out of the cut. In the example below, we are attempting to machine a 2 in. radius circle with a 1 in. radius cutter.

STEP #1 : We calculate the arc needed to move the cutter from the center of the pocket to the finish wall edge. In the example below, we use the following formula :

2.00 (pocket radius) - 1.00 (cutter radius) = 1.00

This is the distance needed to move from the pocket center to the wall edge, allowing for the cutter radius.

STEP #2 : Next divide the total distance in half to obtain the radius needed to swing an arc from the center to the outer edge as calculated above.

1.00 / 2 = .500

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Cutter  Compensation  Note : 

Some controls will allow for the activation of CUTTER COMPENSATION on the example program block #1. In that case, you can calculate the same as above but do not compensate for the cutter radius, instead call the cutter compensation G Code and compensation offset number on the program block. In our example, the program block would be :

G02 G91 G42 X2.00 Y0 R.500 D12 

In this block, we are using G42 (cutter compensation right) and storing the radius of the cutter in offset #12. Using cutter comp as above will allow for the easy adjustment of the pocket size by adjusting the value in offset #12. Don't forget to cancel the cutter comp with G40 after the tools cutting is complete.

Creating a "CYCLE" : 

Using a simple combination of sub-programming, you can take the example above a step further and create a simple Z axis step-down cycle resulting in the roughing of the above example with little effort.

In the program example below, we are taking the circle cutting routine created above and storing it in a sub program. The main program will step the Z axis down - call the sub-program to machine the hole at that depth, then return to the main program which will in turn move the Z axis to another depth and start the process again. This "cycle" repeats until the total depth is achieved.

Main Program : 

{ start and position the tool to the hole center as normal }

G01 G90 Z-.100 F15.0 ; --- move to the depth of the first cut

M98 P1111 ---------------- call Sub Program O1111 which does the cutting as above

G01 G90 Z-.200 F15.0 ; --- move to the next depth of cut

M98 P1111 ---------------- call Sub Program O1111 again at the new depth

G01 G90 Z-.300 F15.0 ; --- move to the next depth of cut

M98 P1111 ---------------- call Sub Program O1111 again

G01 G90 Z-.400 F15.0 ; --- move to the next depth of cut

.... etc. till the desired depth is realized

Sub Program : 

O1111;

G02 G91 X1.00 Y0 R.500 F10.0 ; -- circle to the hole edge

G02 I-1.00 ; --------------------- cut the complete circle

G02 X-1.00 Y0 R.500 ; ------------ circle back to the center

M99 ; ---------------------------- return to the main program

This is just one example of the combination use of the sub-programming feature and "simple" programming codes to create a user cycle. You can always use your initiative and create some other ideas. Maybe think about these  : 

How can you put the Z axis move in the sub-program as well ?

Call the sub program and repeat a set number of times ?

... any others ?

Happy Chip Making !!

Check out our Real World World machine shop software at www.KentechInc.com

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Your Way Lube System - Friend or Foe ?

Your CNC machine is equipped with an automatic oiler system. Great ! You won't have to think about oiling the machine and an alarm will tell you when the tank is dry. What a great device ? Right ?

Well, that is the design. Unfortunately, along with the "automatic" description of the system comes the "out of sight, out of mind" aspect of the system. Because many people know it is an automatic system, many people put it out of their minds and simply wait for the alarm to come up showing that the tank is empty and needs to be filled. But what if that alarm never comes on because the tank isn't empty ? Why wouldn't the tank be empty ?

As your machine gets older, the way lube system will require service just like any other mechanism. The main problem, which often gets overlooked, is that the "tank empty" alarm never comes on because the tank never drains and nobody ever notices it. Now your machine runs for months on end with no lubrication on the ways and when you finally notice a problem, it's too late. Here is the "Rest of the Story ..."

PROBLEM :  The machine's ways are not receiving any way lube oil.

SYMPTOMS - IN ORDER OF SEVERITY :

• Positioning / Repeatability Problems
• Axis makes noise when moving
• Axis Drive motor overload alarm coming when the axis is moving

POSSIBLE CAUSES :

• Way Lube Pump burned out.
• Way Lube Pump distribution flow set too low.
• Way Lube Pump filter CLOGGED
• Way Lube line BROKEN
• Metering Units are CLOGGED

POSSIBLE CAUSES EXPLAINED :

(1) Way Lube Pump Burned Out : If the way lube pump is burned out, obviously there will not be any lube getting into the system. These pumps are usually set using a timer system. There is basically two types of timer systems used :

• The pump is on a cam and the way it works is that the pump is always running. One gear turns another which acts like a step-down system and the second gear raises a "primer" lever. When the lever reaches the top of the stroke, the "primer" lever is released and the oil is pushed into the lines. This whole cycle can take 5-20 minutes meaning that even though the pump is always running, the lines get lube only every 5-20 minutes.
• How to Check It : Take a flashlight and look in the tank or remove the oil tank. Once looking inside, you can see the main gear that should be constantly moving. It may be at a very slow pace, but you will see it moving.

• The pump is set to an electrical timer set in the controls PC (programmable controller) or an actual physical electrical timer in the cabinet. This type of timer only supplies power to start the pump for every cycle.
• How to Check It : On some pumps there is no primer lever but a light comes on on the tank when the pump is activated. Make sure this light comes on every 5-20 minutes or some other sign comes on to show the pump is activated every 5-20 minutes.

(2) Way Lube Pump distribution flow set too low : As stated above, the way lube pump usually is set using a timer system. The flow amount that gets distributed into the lines during every cycle is usually set and adjusted at the pump with a manual setting mechanism. This type of adjusting mechanism is usually a knob that can be turned higher or lower to set more or less flow. Also, just look at the primer lever. During the mentioned 5-20 minute cycle, you should see the primer lever raise slowly and then start to drop after reaching the top of the cycle. Check the stroke of the lever - short stroke, less flow.

• How to Check It : The normal pump usage is in an 8 hour shift, you should fill the tank every 2-3 days. Also, you should see way lube flowing onto the ways. Always remember, the more flow the better. Yes, it may contaminate the coolant but that is better than ruining the ways and thus the machine just to save a couple of bucks.

The photo above shows a way lube pump unit which includes a manual flow control device. Adjusting the white knob adjusts the amount of lube being distributed per one cycle of the lube pump. When this type of pump is working correctly, you can see the white knob rising slowly then retracting, pushing the lube into the lines. The amount of rise and fall, and therefore the amount of lube distributed, is determined by the flow adjustment.

(3) Way Lube Pump filter CLOGGED : The way lube tank usually has a filter between the tank itself and the oil line that starts the distribution. This filter is usually in the tank itself at the bottom of the primer lever or in-line right after the main distribution line leaves the tank. It will get clogged over time, especially if there is no filter at the oil fill hole or if someone takes off the filter when filling the tank.

• How to Check It : Disconnect the main lube line where it exits the tank to feed the system or after the in-line filter if so equipped. When the cycle reaches the pump stage as outlined above, oil should flow through this connection. The flow should be strong at this point. If not, remove the oil tank and search out the filter or remove the in-line filter. They can often be cleaned with a cleaner but the best remedy is to replace it.

(4) Way Lube line BROKEN : Oftentimes a lube line in the system gets crimped or broken during machining or during service. These way lube systems are usually "pressurized" so to speak and if the pressure is released at one point, say at the broken line, the oil will flow all to that point, depriving all the other lines of fluid.

• How to Check It : When the pump is in the pumping stage, the primer lever should fall slowly. This is due to the fact that it is pushing the oil into the system. If a line is broken, the primer lever will fall quickly as all oil is funneled to the broken line area only. On systems without a primer lever, the pump may have a pressure gauge on the pump. During the pumping cycle, the pressure should register for a couple of seconds as the oil is pumped into the lines. If the pressure is low or does not come up at all during the pumping cycle, a line in the system may be broken.

(5) Metering Units are CLOGGED : In order to create the "pressure" of the system needed for even distribution, each oil line leads to a "metering unit" where the flow is lowered and the oil is discharged. When the pump forces oil into the lines, they all fill and flow to the metering units where the flow is stopped. Each metering unit is set to discharge the desired amount or "drops" of oil and perform their individual duties. Since some areas require more lube, the metering units can be different for each line or area. Since these metering units have actual valve type components in their very small bodies, over time these units can be become clogged or the inner workings can become stuck.

• How to Check It : This is a much harder area to check. The best remedy and prevention is to change these units every year as part of a yearly maintenance program. Because these units allow only drops to flow through, they are harder to see when troubleshooting. These metering units are usually located in "clumps" around the machine. Several lines lead to these central areas and lube lines are branched out from here to the various areas of the machine. Replacement metering valves should be obtained from the machine tool builder or dealer to insure that you are getting the correct replacement part. When changing these units, pay close attention to the flow arrow that is commonly marked on the units themselves. This arrow shows the direction of installation and flow. Check the original unit before removal and replace accordingly.

The photo above shows an example of some metering units. These individual fittings are usually located in one or two main terminal blocks that feed certain areas of the machine such as the axis and ball screws. As the system fills with pressure and lube, these fittings discharge the lube at their pre-set flow rate into their lube lines. Over time, like cholesterol in the arteries, these units become clogged and no longer allow lube to exit and thus deny vital areas of the machine the way lube they require. As part of a yearly maintenance program, metering units in the machine should be replaced as a precautionary measure.

Due diligence and a little tracking will 

insure your Happy ( and ACCURATE ) Chip Making

 for years to come !!

Check out our Real World World machine shop software at www.KentechInc.com

Conversational CAD/CAM

Quoting & Estimating

G Code Conversion

CNC Training

.... and MORE !!!