shell omala
Armin Mцller: Efficient Tooling - Workshop operations
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Workshop operations
A section of the online information system Efficient Tooling
By Armin Mцller with support of German Tool Consultancy & Services
Table of contents
Lubricants
Grinding processes: Introduction.
Rough grinding. Fine grinding.
Electrical hand grinding
TIG (WIG) weld
Cutting of semi-finished plastic materials:
Unfilled and filled plastics.
Machining of engineering plastics
Mill cutters
Cutting parameters: Definitions. Speed and feed.
Calculation formulas. Numerical values (mill).
Machine settings (mill)
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Nov 17
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Lubricants
Lubricants have very different functions in the machines and processes:
Lubrication and/or cooling, low or high temperatures.
Therefore, we have to use different lubricants for different purposes.
Viscositiy: The viscosity of an oil is expressed by a number. For general
purposes: Thick oil is 68, thin oil is 32.
Automotive oils have an SAE viscosity index. Two numbers indicate multigrade
oils (for cold countries only, do n't use them in PH). In general, we use SAE 30).
Lubricant guide
Follow the instructions given by the manufacturers of your equipment. If these
are not available, you can use the following guidelines. They refer to Shell oils as they are
available in the Philippines with a good technical service and for reasonable prices. If you
prefer other brands, ask your supplier for the equivalent types.
Shell Tonna T68 is an universal machine tool
oil for stick/slip, bearings and gear boxes.
Shell Tellus 68 is an oil for hydraulic systems.
Shell Tellus T32 is a special low viscosity
oil for compressed air lubricators and for use as household lubrication oil.
Shell Omala 220 is a special gearbox oil for machine tools.
Shell Rimula X40 is an automotive oil for diesel engines.
Retinax A is an automotive grease which is suited for machine
tools. (xxxxx Remark: Fettpresse und Schmiernippel xxxxx)
Standard kerosine is sometimes the lubricant for grinder spindles.
Shell Dromus B is a special oil for cutting emulsions. Never use it for lubrication!
Tapmatic cutting fluid is a special and expensive agent for thread cutting
Recommendation: Use Tapmatic fluid only for tapping in steel, in aluminium you
can use the Dromus emulsion and in plastics you don't need any lubricant).
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Grinding
Many of the following recommendations are
different from what most workshops in the Philippines do. Nevertheless they are the
rules as accepted all over the world. If you don't believe this
consult the standard handbooks (example ....).
Maybe, the difference came up as Philippine workshops started with profile grinding of very fine
structures for semicondutor tooling on grinders with manual table movement. Then they applied
the same technology for standard grinding on hydraulic grinders.
Definitions
Surface grinding is the grinding of flat surfaces.
Profile grinding is grinding of grooves, steps, chamfers, round pins etc.
Rough grinding is all surface grinding with tolerance up to ±0.02 mm and
surface roughness up to 1.6 µm. For roughness 0.8 µm, you can make a final fine
touch with the rough grinding wheel.
Grind wheels are standard components with an ISO coding system.
You find the ISO code on every grind wheel you buy. Use it when ordering.
General rule for the binding letter: Use for soft materials a hard binding and
vice versa: F to H for hardened steels, I to J for unhardened steels, K to N for soft metals (Al, Cu).
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Rough grinding
Rough grinding is all surface grinding with tolerance up to ±0.02 mm and
surface roughness up to 1.6 µm. The rules are:
Rough grinding is done on grinders with hydraulic table movement
Use grain size 46 (or 32) for rough grinding.
... even if
everybody tells you to use grade 120 of finer.
Use grind wheels with width of 12-30 mm. This depends on the size of your grinder."
Use coolant.
Cross feed 60-75 % of wheel width. This is 8-9 mm for a 12mm-wheel, but 18-24 mm for a 30mm-wheel.
... even if
everybody tells you your workpiece
would fly away when you use more than 2 mm crossfeed.
Depth of cut 20-80 µm. If you have or expect
problems with overload (workpiece overheat, workpiece moves, spindle motor overload),
reduce the depth of cut, but not the crossfeed.
... even if
everybody tells you to do quite the opposite.
The explanation is quite simple and understandable: Big crossfeed means you are using a wide
portion of your grindwheel. Mechanical instabilities can be balanced
much better and heat is distibuted over a larger surface.
With a small crossfeed, you use only the edge of your grind wheel, you
get local overheat and the edge of the grind wheel wears out very fast
(using 2 mm crossfeed on a 30 mm grind wheel is like using a 3 mm grind
wheel!).
When you get load problems, you reduce the pressure by reducing the depth
of cut which generates the pressure (and not the cross
feed).
For roughness 0.8 µm, you can make a final fine
touch with the rough grinding wheel.
You can dress and clean the grind wheel by a rotating dresser. This is much
cheaper than using the diamond dressers which are for profile grinding
For cutting, use special cut-off wheels (fibreglass-reinforced).
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Fine and profile grinding
Fine grinding is profile grinding (grinding of grooves, steps, chamfers,
round pins etc.) and surface grinding with specification reqirements
higher than rough grinding. The rules are:
Grain size is 60-120 (the grain size depends on the needed
edge radius, and normally not on the required
surface roughness).
Width of grind wheel 3 - 12 mm.
No coolant.
Cross feed 10-25 % of wheel width. Depth of cut 10-25 µm.
Cleaning of grind wheel with rotating dresser, dressing (of
edges/chamfers) with diamond dresser.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Electrical hand grinding
For rough work (tubes, construction work), use
large grinder with 180 mm wheel diameter, for fine work (pins etc.) and for polishing a small
grinder with 100 mm diameter.
For cutting, use cut-off wheels (2.5 or 3 mm wide, for special purposes 1.2 mm wheel
for the 100 mm grinder). Cut-off wheels are available in two grades metal or stone. Don't use
the wrong wheel.
For grinding, always use grinding wheels (about 6 mm thick), never cut-off wheels.
For polishing, use polishing adapter with abrasive paper grade 120-200.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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TIG (WIG) weld
TIG welding is an electric (DC or AC) welding process using
the workpiece as one electric contact (as usual in electric welding),
a pointed tungsten (Wolfram) electrode as the other electric contact (W = Wolfram is the
chemical symbol of tungsten, therefore both names TIG and WIG are used),
an uncoated filler rod to supply the material for the welding,
a protective atmosphere of an inert gas (Ar = Argon or He = Helium).
Standard steel welding is done: DC, electrode negative, Argon. To optimize ignition and
life time of the electrode, the following materials are used:
Pure tungsten (type W green): Bad ignition and short life time.
Tungsten sintered with thorium dioxide (ThO2, type WT20
red): Good ignition and reasonable life time. Emits some radioactivity.
Tungsten sintered with cerium dioxyde (CeO2, type WC20
gray): Good ignition and good life time. No radiation.
TIG (WIG) weld: Practical advices:
Inert gas must be oxygen free. Take care of hoses, reducer etc.: Must be leakfree.
Switch gas off only after electrode is cold (temperature below 250°C).
Safeguard good inert gas circulation by avoiding air turbulences
and draft (no electric fan!).
Electrode angle is 2 x 25° to 30° (approx. Ø = height of cone).
Electrode tip absolutely free of burrs.
Keep electrode as much as possible in electrode holder.
Hold electrode 15° inclined against perpendicular to workpiece.
Welding direction from right to left.
If you have a computer conntrolled weld machine, make use of
electronic pre-settings and foot-switch.
Pulsed DC welding improves results for fine work.
Don't touch workpiece with electrode (bad ignition and life time).
Store and keep electrodes clean (contamination).
Blue tungsten electrodes are proof of oxygen. Regrind! Better change and
regrind electrode before making rejects.
Take care of good housekeeping. Modern TIG welding is CNC precision machining.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Cutting of semi-finished plastic materials
In general, semi-finished plastic materials are purchased pre-cut from the material supplier.
This is the most efficient way to get the materials. Stocks are minimized, material control is easy
and the cutting operation is left to the experts. Nevertheless, in the daily workshop operation
the need for cutting arises now and then. Therefore, below we give some hints how to do the cutting
of unfilled and filled plastics with simple
tooling.
When ordering pre-cut plastic materials, you have to include your machining allowance (depending
on your process control 1 to 5 mm). The supplier might add an additional allowance for his cutting
tolerances, but his commitment is to deliver the size you ordered and not more.
Perpendicularity is a major issue. The supplier is aligning his cutting process under exactly 90°
but process tolerances are unavoidable. Perfect perpendicularity cannot be expected. Therefore, the
supplier's commitment means: It must be possible to cut a perfect rectangular with the ordered dimensions
from the semi-finished product. The user has to find the optimum clamping to achieve this.
In general, sheets of thicknesses between 1 mm to about 50 mm are cut. Round material is available
in diameters starting from 6 mm up to 125 mm and more. When very thick blocks are needed, large
diameter rods might be used and squared (example: from a Ø 125 rod, a square of 75 x 100 can
be made). A high percentage of the material is wasted, but sometimes it is the only possibility to get the
dimensions needed.
Cutting semi-finished plastic materials is relatively simple. Potential problems are overheating
of the workpiece and cutting tool wear when reinforced or filled plastics are cut.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 May 17
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Cutting of unfilled semi-finished plastic materials
Unfilled plastics (like unfilled PVC, POM and PTFE) are normally cut by using sawblades on band-saws,
sawing wheels on circular saws or manual saws. By design, band-saws have maximum sawing width (for a medium
sized saw it is 400 mm). Standard hardened steelblades do an excellent job on band-saws, using the more
expensive HSS blades or blades with HSS teeth has no advantage. Problems arise from local overheating
of the workpiece, therefore, the following rules should be observed:
The toothing of the blade should not be too fine. Ideal cutting condition is when 3 to 5 teeth are in
the workpiece. Example: 10 mm thick material → 2 mm distance between the teeth → 12
teeth/inch.
In general, compomises to finer blades are necessary as sometimes thinner material has to be cut.
Some suppliers offer sawblades with combi-toothing (example: Blade 1014 has wide teeth with 10 teeth/inch
and narrow teeth with 14 teeth/inch.
As the forces are small when cutting plastics, thin saw blades are recommended (they are cheaper
and cut less material away).
A good saw blade is hardeneded in the teeth only. Make scratch test with a hardened steel needle:
Blade must be scratched, teeth must not be scratched.
Our recommendation for bandsaw blades of general use for unfilled plastics:
13 mm wide, 0.65 mm thick, toothing 10 teeth/inch.
Our preferred manufacturer: Rцntgen, Germany. You may ask German Tool for
availability.
When using bandsaw blades, the welding and tempering of the blade needs attention. A brittle
welding is prone to breaking. A too thick welding prevents stable guiding of the blade. We recommend
two tests after welding:
- Roll the welded portion over a round material of Ø 100 mm (or even better 80 mm), it must
not break.
- Measure the thickness of the welded portion, it must be less than 110 % of the blade thickness
(example: 0.65 mm blade, welding are not thicker then 0.72 mm): Don't measure over the cross-cut teeth!
When many band-saw jobs have to be done, the fabrication and use of a thickness gauge is recommended.
When cutting plastics, lubricants are not needed.
Local overheating of the workpiece will cause clogging of the chips and sticking of the chips on the
saw blade. The best prevention is high cutting feed rate. Saw blade speed should
be above 200 m/min and feed must be as high as possible (depending on workpiece thickness up to 600
mm/min). To say it simple: Fast cutting prevents overheating.
It goes without saying that dull blades make bad cuts and cause overheating.
Remove always all (clogged) chips. Interrupt sawing for cleaning if necessary.
Look to your chips. When they are sticky or even molten together your sawing is wrong.
What to do if you don't have a band-saw or similar sawing machine? A manual power circular saw does a
reasonable job. The restriction is the thickness of the material (in general 40 to 50 mm). We recommend
to use a carbide tipped saw blade (type CT). Observe the following:
Again: Fast cutting is good cutting.
Again: Remove always all (clogged) chips.
Our recommendation for the circular saw:
Blade diameter Ø 160 mm. Speed 5800 r/min. Power 1.0 kW. Max. cutting thickness 55 mm.
Example AEG K55.
Our recommendation for the blade: Diameter Ø 160 mm. Thickness 2.2 mm. 40 carbide
tipped teeth CT.
Preferred type: Bosch 2 608 640 743 is locally available for very reasonable price. It is delivered
with adapters for hole diameters Ø 19, 20 and 25.4 mm.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 May 17
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Cutting of filled and reinforced semi-finished plastic materials
Cutting filled or reinforced semi-finish plastic materials is some more complicated. Many phenolic
(PF), polyester and epoxy (EP) plastics and composites are filled with more or less abrasive fillers.
Examples are the G10 and G11 EP-grades and the composite CAS761. In general, the manufacturer does not
disclose composition and quantity of the fillers. Therefore, cutting processes has to be adapted for the
particular materials.
Plastics with modestly abrasive fillers
We experienced that G10 and G11 have abrasive fillers, but with restricted abrasiveness. Therefore,
we recommend to observe the following guidelines:
G10 and G11 can be cut on band-saws with hardened saw blade teeth.
Saw blade wear is significant, blades become dull after a relatively short time. Also blades with
HSS teeth show the same effect and are not a reasonable alternative.
G10 and G11 can be cut on manual power circular saws with carbide tipped
blades. Wheel wear is not a big issue.
Plastics with highly abrasive fillers
We experieced that CAS761 has very abrasive fillers and that the dust from cutting is very irritating.
Bandsaw blades from steel are not suited for cutting CAS761. Even under best conditions they become dull
after 10 to 20 min operation.
The best experiece we have with cutting CAS761 is to use a manual power grinder with a diamond wheel.
Cutting feed rate is very reasonable. Dust removal is a problem. One possibility is to flash the
cutting area with 5 %
Dromus emulsion, but very likely you get a mess and cannot see any longer your
cutting lines. Mechanical dust exhaust is more complicated, but cleaner and more efficient.
Results from standard cutting wheels are disappointing, but they can be used if a diamond blade
is unavailable. Cutting on circular saws with carbide tipped wheel is possible, but slow and
unefficient.
Our recommendation:
Bosch angle grinder GWS 18-180. Input 1.8 kW. Wheel diameter Ø 180 mm. Speed 8500 r/min.
Tyrolit diamond blade X-PERT (BT42) Ø 180 mm.
Please, consult German Tool for availability and prices.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 May 17
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Machining of engineering plastics
General
Most workshops who start to machine engineering plastics are experienced in the machining of steels.
But there are some fundamental differences between plastics and steels which makes a different approach
advisable:
1.Plastics are less hard and
less tough than steels. Cutting forces and the heat generated during cutting are significantly
smaller.
2.Maximum operation temperatures of plastics are significantly lower than
of steels. Therefore, the heat problem is workpiece overheat and not cutter overheat.
3.Heat conductivity is very low (even in comparison to stainless steel). Heat
cannot go into the workpiece, it "sticks" at the cutting surface where it is generated.
Some rules hold both for steel and plastic machining:
4.Heat generation and tool wear are
per cut, more or less independent how wide or deep the cut is. Less cuts make the process more efficient
(as long as the process is stable).
5.Sharp cutting edges of the tool reduce heat generation and tool wear,
and they improve surface quality.
6.The heat generated by the cutting process goes partly into the chip,
partly into the workpiece and into the tool.Optimum cutter geometry and optimum cutting parameters
means that taking most of the heat when flying away (blue chips whwn cutting steel or slightly molten
chips when cutting plastics).
Recommendations for machining unfilled thermoplastics
=Cutting tools: Standard HSS cutters have optimum cutting geometry
for steel, but they also can be used for plastics. For heavy-duty operation, special cutters with high
positive rake angles (5 - 15°) and large room for chip removal are recommended.
Take care that cutting edges are always very sharp.
Carbide cutters have a longer tool life compared to HSS cutters.
Carbide inserts with negative rake angles are less suited for plastic machining.
=Milling cut parameters (given by Rцchling Technische Kunststoffe):
Speed 200 - 500 m/minFeed 0.1 - 0.5 mm/flute
With the median values of 300 mm/min and 0.3 mm/flute, a four flute
Ø 10 mm endmill cutter should be operated at 900 r/min and 1000 mm/min feed
rate.
The high feed rates support the heat removal. As the heat is "sticking" on the workpiece,
the heat is leaving the cutting area as fast as the feed rate is set.
If the optimum speed and feed should result in unstable machine
conditions, feed and speed should be reduced.
Example: 200 m/min and 0.2 mm/flute with the above cutter means 600 r/min and 500 mm/min.
=With the high feed rate, more and larger chips are cut. Good chip removal
is very important.
=In general, plastics don't need any lubricants during cutting, but cooling
the workpiece is essential. Besides water and water based emulsion, compressed air is a good coolant for
unfilled plastics which also supports the chip removal.
Special remark when machining PC: Cool only using air or clean water.
=When drilling: Preheating of the tool to 120°C is necessary for Ø
above 100 mm.
Recommendations for machining filled engineering plastics
Recommendations for filled or reinforced plastic materials are different as many fillers are
abrasive or dust-generating during machining.
=Carbide tools are required.
Carbide inserts with negative rake angles are less suited for plastic machining (the preferred
choice are ground inserts with positive rake angles).
=Speed should be 80 - 100 m/min while feed rate should be 0.1 - 0.5
mm/flute.
=Use water or water based emulsion for cooling and dust removal (not compressed
air!).
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Nov 17
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Mill cutters
Mill cutters: Introduction
A German supplier for tools has more than 1000 different kinds and sizes of mill cutters in its
catalogue (and nearly all of them are available from stock). The choice in the Philippines is some
smaller, but it is always worth to spend some attention to the good choice of cutters. There is
no one "best" mill cutter, the
price-performance ratio depends on the workpiece (material, required accuracy and surface) and
on the machine tool. The following should help to make the good choice of mill cutters for diameters
up to 12 mm for use in small and medium sized workshops. For these purposes, normally massive shaft
cutters are used. These cutters have a cylindrical shaft which is clamped in a toolholder. The
whole cutter is made from the same material.
Other types of cutters are arbour cutters and insert cutters. They are for larger diameters,
in general.
Shaft cutters: Cutter material
Cutters from hardened tool steel are used in wood working. For machine shops, HSS or carbide cutters are
the choice. Both from HSS and carbide, many different grades and with different prices are in the market:
Standard HSS cutters (without Co) can be used for not too heavy work (plastics and aluminium and maybe
mild steel).
Cobalt alloyed HSS cutters are today the industry standard, they are named HSSCo or HSSE. Cobalt
improves the cutting behaviour at high temperatures which is essential when cutting steels.
Some people prefer the cheaper standard HSS
cutters and reduce the feed rate to keep the cutter temperature down. In general, the overall costs
are higher when doing this.
Carbide cutters are more expensive (two to three times the price of an HSSCo cutter). And they
have some disadvantages: Carbides are much more brittle than HSS, carbide cutters break easier than
HSS cutters. Therefore, carbide cutters should be used only when really needed.
A German recommendation: "The milling machine must be completely free from play and vibrations. The
workpiece has to be clamped rigid and vibration-free. Choose highest possible feed rate."
Plastic materials with abrasive fillers (example: Composites for PCB-pallets) need always carbide
cutters. For work in steel and aluminium, carbide cutters have longer lifetime and efficiency.
Shaft cutters: Coated cutters?
Many high-end cutters are coated. Coated cutter have an extremely hard, very thin layer of
titanium aluminium nitride (TiAlN) or similar
compounds. The coating allows higher feed rates. Under optimum process conditions, coated cutters have
a longer tool life and make better surface roughness. In some cases, coating can facilitate easier chip
removal. The overall performance of coated cutters is much higher, but they are more expensive.
There is no discussion that coated cutters are excellent in mass production with controlled tool life.
For small and medium sized workshops, their advantages become less relevant. In general, processes
cannot be completely optimized, higher feed rates cannot be achieved. If the tool life is not 100 %
controlled, the coating will wear out. A coated cutter with a bad coating is worse than an uncoated
cutter. Coated cutters can be reground, but then the coating
is lost.
Shaft cutters: Centre-cuttingTwo types
of shaft cutters have to be distinguished: A centre-cutting cutter (right) has one cutting edge
which goes over the centre. As the whole cross-section of the cutter is covered by cutting edges, the
centre-cutting cutter can be used for vertical cutting, it can make holes and slots. If no cutting
edge is at the centre of the cutter (in the centre is a "hole"), the cutter is non-centre-cutting
(left). If such a cutter would be used for cutting a hole, it would break as the centre of the hole is
not cut at all.
Shaft cutters: Chip removal
One important function of the cutter is that it allows and facilitates the removal of the chips.
Practical experience shows that many cutters break as a chip removing channel is clogged by "baked" chips
(and not as the feed rate is too high). Chip removal is less critical for side and face mill
processes, but extremely important for slot milling and drilling of holes.
Engineeering plastics and aluminium are (or should be) milled with higher feed rates than steel. Higher
feed rate means bigger and more chips. Therefore, chip removal needs more attention in fast-cutting
workpiece materials.
For chip removal, cutters have chip removal channels. But they have two negative side effects: The
channels make the cutter mechanically weaker and don't contribute to heat removal through the tool.
Shaft cutters: Number of cutting edges
For smaller sizes, cutters with 2, 3 or 4 cutting edges (flutes) are in the market. How to make the good
choice?
More cutting edges give higher efficiency, the feed rate can be higher and the life time of the cutter is
longer.
More cutting edges allow less space for the chip removing channels which is very critical for very small
cutters.
More cutting edges make the cutting process smoother and the surface roughness is finer (at same feed
rate).
In the past, the two different types of cutters were used. The 2-flute centre-cutting slotdrill
is used for slots and holes. The 4-flute endmill was non-centre-cutting
(some endmills offered in the Philippines are still non-centre-cutting!) and was used for non-vertical
cutting for its better efficiency.
Today, the tool-manufacturing has improved and centre-cutting cutters are the standard. The 3-flute
centre-cutting endmill combines the advantages of the 2-flute slotdrill and of the non-centre-cutting
4-flute endmill. In particular, when using 3-flute centre-cutting endmills, small workshops have the
advantage to need only one type of cutter per size. In CNC-operation, they avoid additional tool
changes.
Shaft cutters: Length of the cutter
The choice is easy: Shorter cutters run more stable, are less vibration-sensitive and they are cheaper
(in particular, carbide cutters).
Use always the shortest possible cutter!
Shaft cutters: Regrinding?
In principle, all mill cutters can be reground. The face can
be reground, but also the outside cutting edges which is important for sidemilling.
Hint: Measure always
the cutter diameter after outside regrinding, the cutter diameter
is smaller after regrinding. In CNC operation, you have to correct the cutter offset. And in slot milling,
the slot will be narrower.
Your mill cutter were manufactured in a factory specialized to make these complicated products. After
regrinding, the cutter has to perform like a brand new cutter. Like making cutters, regrinding
is specialists' work to be done on special tool grinding machines. Before you
start regrinding, ask yourself, do I have such a specialist and the machine suited
for doing the job. If not, don't do regrinding, you might spend more for lost efficiency,
bad surface quality then buying a new cutter. Some companies offer professional regrinding
services.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2002 Jan 30
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Cutting parameters: Definitions
Cutting parameters: Definitions
Speed is the speed of the cutting edge against the workpiece (due to the
rotation of the workpiece on the lathe or of the cutter on the milling
machine and the drill press. It is measured in metre/minute (m/min).
Speed rate is the number of revolutions per minute (r/min) of the cutter
(or of the workpiece on the lathe).
Feed rate per tooth is the distance of the cutter movement between two
teeth. It is measured in mm/tooth.
Feed rate is the speed of the movement of the cutter against the workpiece.
It is measured in mm/min.
Use always
the correct symbols according to ISO 1000,
even when others talk about MPMM, RPM, MMPT and the likes.
Speed and feed rate per tooth are the technological parameters
of the cutting process. Tables (mainly from tool suppliers) are available.
Speed rate and feed rate have to be calculated. They are the machine settings.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Cutting parameters: Speed and feed
Speed makes the cutter turn, speed alone does not cut, but it is the condition for cutting.
Feed makes the cutting.
For each cutting process, there is an optimum setting of speed and feed. It depends on the workpiece
material, the area to be cut, the surface requirements, the cutter material and geometry, the machine and
cooling conditions. The optimum setting combines fulfilling the customer specification (dimension,
tolerance, surface appearance and roughness) with time-efficient processing and low tool-wear.
Recommended optimum settings can be got from handbooks, informations from material and cutter suppliers.
Sometimes, test cuttings can help to find the optimum settings.
What happens if the settings are wrong? We consider five cases:
Speed and feed too high
Cutter is overloaded and overheated. It might get dull and/or break. Workpiece may get overheated,
deformed or is flying away. Machine tool may be overloaded (large cutters only). Time-efficiency is
very high, but overall efficiency very low.
Unsafe and inefficient cutting.
Speed too high, but feed too low
The cutter is turning, but hardly cutting. Time-efficiency very low. Tool wear very high. Very fine
surface.
Safe, but inefficient cutting.
Speed and feed optimized
Customer specifiaction achieved. High time-efficiency. Low tool wear.
Safe and efficient cutting.
Speed and feed too low
Time-efficiency very low. Higher tool wear.
Unsafe and inefficient cutting.
Speed too low and feed too high
Very unstable condition. Cutter will break very soon.
Highly dangerous operation.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Cutting parameters: Calculation formulas
In tables, you find the parameters speed (m/min) and feed rate per tooth
(mm/tooth). Apply the following formulas to get the data for the machine
settings speed rate (r/min) and feed rate (mm/min):
[Speed (m/min)] * 1000
[Speed rate (r/min)] = ---------------------------
[Tool diameter (mm)] * 3.14
Correct the speed rate, when the calculated value is not available as
machine setting on your machine. Use the corrected value in the next formula:
[Feed rate (mm/min] = [Speed (r/min)]
* [Feed rate per tooth (mm/tooth)]
* [Number of teeth]
Correct again to available machine settings. Re-calculate speed and feed
rate per tooth from the corrected settings. Check that they are still reasonable.
If necessary, start calculation again.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Cutting parameters milling: Numerical values
HSS cutters, with lubricant Dromus B emulsion ( 5 - 20 %).
Liability disclaimer
mild tool/silv SKD11/SS Alum Plastic
steel steel steel hard
-------------------------------------------------------------------------
Speed m/min 30 20 12 70 200
-------------------------------------------------------------------------
Feed mm/tooth
- side/slot Ø 5 0.07 0.07 0.05 0.10 0.15
- face Ø 5 0.18 0.18 0.12 0.25 0.30
Standard depth of cut (in % of cutter Ø): 50 % for side, 20 % for slot and
face. For bigger cutter diameter: Don't overload spindle and workpiece clamping.
Reduce speed and feed when working without lubricant.
Reduce feed for final cut when low surface roughness needed.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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Cutting parameters: Machine settings milling
Machine settings for a light conventional milling machine.
HSS cutters, with lubricant Dromus B emulsion (5 - 20 %).
Liability disclaimer
Cutter mild tool/silv SKD11/SS Alum Plastic
Diam Flutes Speed Feed Speed Feed Speed Feed Speed Feed Speed Feed
-------------------------------------------------------------------------
Ø 2 4 1180 29 1180 29 1180 18 1180 37 1180 37
Ø 3 4 1180 37 1180 37 600 14 1180 58 1180 37
Ø 4 4 1180 46 1180 46 600 18 1180 73 1180 73
Ø 5 4 1180 58 600 29 600 23 1180 73 1180 73
Ø 6 4 1180 73 600 37 300 14 1180 93 1180 93
Ø 8 4 600 58 600 46 300 18 1180 116 1180 116
Ø 10 4 600 58 300 29 300 23 1180 150 1180 150
Ø 15 4 150 18 1180 235
Ø 20 4 150 23 600 150
Ø 30 6 75 23 300 150
Ø 60 8 37 18 150 150
Ø 80 10 37 23 150 190
Speed (rate) is in r/min. Feed (rate) is in mm/min.
Machine settings for a small CNC milling machine
HSS cutters, with lubricant Dromus B emulsion (5 - 20 %).
Liability disclaimer
Cutter mild tool/silv SKD11/SS Alum Plastic
Diam Flutes Speed Feed Speed Feed Speed Feed Speed Feed Speed Feed
-------------------------------------------------------------------------
Ø 2 4 3800 95 2500 60 1500 25 4000 130 4000 130
Ø 3 4 2500 85 1700 60 1000 20 4000 180 4000 180
Ø 4 4 1900 90 1250 60 750 25 4000 240 4000 240
Ø 5 4 1500 85 1000 55 600 20 3500 260 4000 290
Ø 6 4 1300 90 850 60 500 20 2900 260 4000 360
Ø 8 4 960 85 600 55 350 20 2200 260 4000 480
Ø 10 4 760 85 500 55 300 20 1700 250 4000 600
Ø 15 4 200 25 1150 240
Ø 20 4 150 20 850 250
Ø 30 6 100 35 550 370
Ø 60 8 50 30 250 270
Ø 80 10 35 25 200 260
Speed (rate) is in r/min. Feed (rate) is in mm/min.
Armin Mцller
and German Tool Consultancy & Services, Lipa, Batangas 2001 Feb 11
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750,"Maintenance"
"General rule: Use maintenance card in the GT maintenance system."
"Record all actions, measurements etc. in the logbook and/or on the"
"maintenance card."
""
"- |C|ar and generator maintenance."
750,"Maintenance"
Erledigt sind 700, 710, 711, 712, 714, 715, 720, 721, 731, 732, 734, 735, 736, 750
Offen sind 751 ff.
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