Engraving question

[Andy Gorman]

I know very little of engraving, but maybe this is something your tool supplier should be able to help you with. A friend of mine engraves and routs a lot and has found that some makes of bit are better than others, and perform differently.

I’m not much help here really; I don’t know why I answered. 😕

[Phill Fenton]

I’m like big G and now nothing what so ever about engraving. So I also have absolutely no idea also why I bothered to reply to this… except to say I would go with Big Gs advice 😳

[Robert Lambie]

for cutting perspex
perspex = plunge@700 travel@2000-2500
for cutting alloy
alloy 2mm = plunge@400 travel@1000

engraving. well i normaly do some tests in a corner mate. its been so long since i have worked our machine i honestly cant remember exactly.
i just stick my head in to check alls going well when works being run.

if you call AXYZ they will sell you a 6 bit double sided pack of engraving bits in various sizes. ask for them to be labeled. for some reason they think we can read 1mm high text in silver on a silver shiny bit? 🙄

[Eric North]

Every machine is different depending on how strong it is. Secondly wether it is computerised or manual.
We only use tungsten tipped cutters because they last longer. You will need a sharpening machine with a diamond wheel I am afraid. There are people who will sharpen them for you. You need two sets of cutters for this.
If you have a high speed steel cutter you will be able to engrave gravoply types , acrylic and maybe brass. But not phenolics or stainless. Cutter must be sharp (not pointed but the width of cut you require). cutter width is generally letter height divided by 8 unless you are using multipath. For normal lettering you will use a tapered cutter.
Generally tungsten will engrave anything. metals and phenolics are tough on cutters.
normally engraving is quite shallow. I suggest you set your machine to its slowest and start from there, moving faster until you reach the best speed for each material. Brass and aluminium are slower than softer plastics. Your machine may be to fast for stainless. use oil here. shallow cut first and then increase depth.

[Eric North]

just noticed posting times. does everyone work after midnight ?. Thought it was just me !

[Robert Lambie]

yeh mate.. i dont really start till midnight. we have lots on here till the early hours. :lol1: :lol1:

[Rodney Gold]

Hiya
There is no set formula , cos it depends on the HP or torque of the spindle , the motion contoller , the depth of cut , the diameter of the cutter , the materials , cooling system , machine rigidity etc.
We judge the settings by ear , you can EASILY hear whether the cutter is struggling , chattering or going too fast and conversely , can see if its too slow cos of the hot swarf chips.
The swarf is also a good indicator of cutting conditions. Clean cool fine swarf is generally an indicator of excellent cutting.

Basically a cut consists of 2 parts , a shear and than a chip.
You can see this graphically on the edge of a guillotined piece of metal , there is a bright smeary section and then a rough section , the smeary section is the shear , the rough the chip.
The thing is , one wants the shortest smear and the biggest chip. IE when the cutting edge bites into the metal , you dont want it to smear as this generates a LOT of heat , you want an almost instant chip.
Doing any serious engraving without a cutter grinder is lunacy , you can have the best engraving machine and if your bits arent 100% correct , you are b—d.
Various materials need various cutting angles , clearances etc.
We buy old broken Printed circuit board drill bits , which are normally solid carbide and 1/2 them and make our own cutters out of em , thus the cutters cost us pennies.
Carbide however is a very brittle material and often High speed steel (like for stainless steel engraving) is a lot better as the cutting edge doesnt chip. Titanium nitride coated tools are first prize tho. (slot drills , end mills etc)
Coolant and lubricants are essential in engraving
I cant give you speeds and feeds but can give you some tips for cutting various materials
Materials that generate a lot of swarf or are soft (normal brass , plastics , perspex , copper ) work best with a singl flute 1/2′ d cutter , 1/2ing the cutter is VITAL , if the cutter diameter is 6mm then it has to be EXACTLY 1/2′ d to 3mm – a lot of ppl that grind cutters “over 1/2” IE they 1/2 to 3.1mm or so (leave a little more meat on the 1/2) and dont take the back of the cutter away. You have to take a lot of the back of the cutter away , the idea here is to have the cutting edge hit and then allow space for the swarf (the bits that are cut) to escape. Not taking the back away makes it rub against the just cut part , generating enormous heat and thus remelting the swarf or actually work hardening the material.
The tip of the cutter is absolutely vital , it plunges and removes material and if not ground at exact angles will ruin any effort of the cutting edge , leading to burring and rough cuts.
You should NEVER have to go over engraving to clean it up.
The smaller the tip , the faster the spindle has to turn for the same feed rate . Plunge speeds are vital too , too fast into the material and you break the cutter , too slow and you “burn” the material.
The angle of the V you put on the cutter is also vital as it will determine ultimate line width and depth of cut. A cutter with a small angle (very steep) will not changes line width with depth as much but will be pretty fragile and thus you have to take multiple light cuts with it into harder materials. If for example you want to engrave stainless , a wider tip and a wider V angle will achieve better results without breaking a cutter.
We work EXCLUSIVELY in engravers brass when it comes to brass stuff , it cuts clean , dry and is a pleasure to work with , normal brass is 1/2 the price but burrs , needs parrafin or other lubricants etc. Same with stainless , you get a very nice free machining grade that works at 2x the speed with 1/10th of the headaches of commercial cheap grades. The extra expense is well worth it in terms of time and finishing operations.
For acrylics and plastics , slightly soapy water works wonderfully as a lubricant and coolant. For brass and aluminium (also use the HARDEST aluminium you can – soft stuff tends to clog cutters) Metylated spirits works wonderfully but has a low flash point and is thus a fire hazzard , Parrafin works ok on this too but is messy and often disolves double sided tape adhesive , a problem if you use this on a scrifical bed to hold material down. Far better are various metal cutting fluids the engineering industry use which are water soluable. We often use these without water and just smear it on the material , washes off when the material is removed. For SS and other really difficult materials , a recirculating mist or spray coolant system is the bee’s knees and often engraving without this is just not possible.
How far the cutter protrudes is also fairly important , long thin shafts reduce the stability of a cutter and allow it to “bend” , thus destroying the cutting geometry and will definately promote cutter breakage. The least protrusion from the bottom of a spindle is desireable. Top loading spindles suck as they generally have less support at the bottom of a cutter , a bottom loading spindle allows short bits (cheaper) to be used and provides a lot more stability.
For effective engraving , the power of the spindle motor is very important. the minimum power on even our smaller machines is about 1kw , we use variable speed and constant torque motors. The more rigid the machine , the cutter and the more power you have , the better the cut the deeper the cut and the faster the speed.
As a starting point , use engraving plastics , try 1/2 the max speed your table is capable of and vary the spindle speed , you will soon hear if the engraving “smoothes” out. If you cant get a smooth sound , then try a slower feed rate.
The biggest mistake a lot of ppl make is to use ultra slow feed rates into hard stuff , combined with VERY fast rotational speed. This burns material and can often work harden it(the heat generated makes the material hard and thus generates more heat and a viscious cycle results , the bit breaks and you cant EVER engrave or correct that section , worst with SS)
Experimentation on your machine is really the only way to optimise feed and speed , but prior to that , the correct cutter geometry is VITAL.
Generally , you can cut approx 1/3rd to 1/2 of the cutter tip with in terms of depth. If you have ground your cutter to a 1mm tip width , then the max depth cut you can take would be 1/3rd of a mm (rather a 1/3rd than 1/2)
Other limitiations are the motion control and feedback sensors of an engraver , for example our large format router engraves fine stuff FAR slower than our dedicated isels and small roland. the reason is the inertia and weight of the spindle motor , the machine has servo motors that sense position , and for small stuff it has to change direction real quick. The head is heavy and inertia tends to make it “overshoot” and the servo motor corrects the overshoot , however this makes for VERY jerky and rough engraving.
Hope this helps a bit.

[Mike Grant]

Thanks for the replies guys and Rodney Bie Danke! as usual you are a great help!

Just for the record I do have a Taylor Hobson grinder so grinding should not be a problem??? when I find out how to use it properly as it has no instructions and again common sense and flying by my pant seats are the order of the day.

Ah well! more experimenting coming up! 🙄

[Rodney Gold]

Heres a few URLS re cutters
http://www.antaresinc.net/FactSheets/Ro … raving.htm
http://www.pilotltd.net/engraving.htm
Dis altyd ‘n plesier om ‘n landsman te help:)
(translated – its always a pleasure to help a fellow countryman)

[Mike Grant]

quote Rodney Gold:

Dis altyd ‘n plesier om ‘n landsman te help:)
(translated – its always a pleasure to help a fellow countryman)

Ahem! Cough! Errm Umm! just to put the record strait I am not a fellow countryman, but my son is and my wife is a naturalised citizen, me, I was just visiting for 13 years :lol1: :lol1:

Just out of interest how are things out there under “Black Rule” We left in 93 so I should imagine things are a wee bit different now.

[Rodney Gold]

Oh – I thought you were originally Safrican.
Nothing changed much , actually its a lot better , there are less verkrampte rules now.
Business is good , the only difference is Black empowerment (preferential purchases from black owned or Co’s that empower previously disadvantaged)
Crime is still high here and one has to look at your personal security and live accordingly. For example , I would never let my kid go ride her bicycle in the streets unsupervised and security systems iro your house have to be robust unless you want to get burgled.
Imported goods are reasonable due to the strong rand , house prices are sky high , you wont get much decent at under R1 mill. Tons of tourists here over the festive season.
In essence , reality rules , whomever is in charge just goes along as it always was. The poor are still poor , the state is still as corrupt , there is just a slight shift of colour in the upper class/wealthy mix.
Whats such a pity is that we fought all these wars and spent so much money supressing ppl , had that money been used better , SA would be far better off.
We watch all these wars being fought against terrorists , we been there , done that – and realise that its an excercise in futility.

[Mike Grant]

Rod, I have spoken to many people here about SA and when the subject of Mandela comes up they all praise him for what he has done……….

I’ts a pity that when I ask them why was Mandela in prison that not one of them could tell me 😮 so how can they say he is a great man for the cause.

Once a terrorist ALWAYS a terrorist!

Now then chaps lets all lock up all the worlds terrorists for 20 years, then when they get let out of prison they will be well qualified to be PRESIDENTS of their countries. Now I think that is how it works isn’t it!!!! and the world will be a peacefull place to live in for the next 5000 years………………………………NOT!

Oh yes almost forgot lets throw in the odd Mercedes as well just to sweeten the pot!

Politics gone mad (hot) (hot) (hot)

Or is it just me! 🙄