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Abdul Baseer Hai
09-17-2006, 1:42 AM
Hi all
I have been asked by a client to engrave a number of wedge shaped granite pieces. The granite is 24inch x 12 inches and one side of the wedge is 5 inches, sloping dowm. He wants four lines of text and a four inch logo egraved. the engraving has to be deep enough to be color filled.
I need help on pricing as I have no idea what to quote and how to go about color filling for outdoor use.
Thanks
abdul

Rodne Gold
09-17-2006, 4:06 AM
Firstly , you need to do a trial piece and time it , charge for the time , I would suggest at least $2-3 per minute of engraving time and a set amount for filling
In terms of colour filling , well you need to mask the piece before engraving it and engrave thru the mask and colour fill with the mask in place , cos granite and marble are porous and paint on the unengraved surfaces will tend to stain it. The mask will make colour filling a snap. (use paper application tape used in the vinyl sign industry or use polyester based vinyl as a mask - polyester vinyl is laser friendly most mirror finish vinyl is polyester - if the sign vinyl doesnt stretch its most likely not PVC)
The paints used on automobiles will work well for outdoor use.
Heres an easy way to level the slope , use another sloping piece under the top sloping piece , but upside down , the slopes will level each other out.

Mike Hood
09-17-2006, 11:53 AM
A couple of chunks of "playdough" work well for levelling odd shapes as well.

Dave Jones
09-17-2006, 12:02 PM
I could be wrong, but from his description I was thinking he meant the piece is non-rectangular, with one edge (left or right) being 12" tall in the Y axis and the other edge being 5" tall. I was thinking he meant more of an angular cut outline rather than a sloping thickness. But I'm just guessing. If that's true, then he doesn't need a second piece under it.

Abdul Baseer Hai
09-17-2006, 7:02 PM
Thanks all

will post picture once it is done.

Rodney:

how much weight can the explorer table handle???

Abdul

Mike Hood
09-18-2006, 12:17 AM
Not sure what the weight limits would be in Z axis but for heavier items you could possibly support the table from underneath once the focus was set. I wouldn't think puting a real heavy load on the servos would be a good idea.

Thomas Hempleman
09-18-2006, 1:46 AM
Just a caution: as Rodney said, granite and marble are porous. Some pieces act like a sponge. I discovered this the hard way. I used modeling clay to support an odd shaped smooth granite rock that a customer wanted engraved. In the few minutes time it took to engrave, the granite absorbed something contained in the clay. I was left with a discoloration where the clay had contacted the granite. This stain was impossible to remove and I ended up getting another piece of granite and starting over. Since then, I have always used wood jigs and supports, even though it's not as handy as play-dough and modeling clay.

Rodney: Quick question - why do you suggest charging so much for laser time on granite and marble? I have always heard that laser time is one to two dollars per minute so that's what I've always charged. Am I ripping myself off?

Rodne Gold
09-18-2006, 3:12 AM
I recon the table can take about 100 lbs at max , but with GCC's pass thru sysem , you can use supports outside the machine to take larger slabs. IE support outside the machine and dont use the table. fiddly for focus , but we have done some really large items this way.
I terms of the laser time and charge , well this is not just acrylic sheet , its expensive material and is not a simple thing to set up , thus the increase in price.
I always charge in accordance to the item being marked , the more risky and expensive the item , the more I charge. a laser is a very expensive machine and to use it to do cheap markings on cheap items is somewhat a waste.
There really is no formula for pricing , ideally you would charge what the market can bear. Sometimes my customers say "Is that all?" when I think its expensive and sometimes they winge about price when Im close to the bone in terms of charges. Also depends on lost opportunities , doing 10 000 items at 50c a minute might tie up your machine for a month , thus more profitable jobs are turned down. We actually often charge a lot less than $1 a minute , but I have 6 lasers here and thus can accomodate varied jobs , but would rather have all my machines working at a reduced rate than one or 2 doing only choice jobs.
We also optimise cycle times by various strategies and thus achieve huge savings , for example I had to do 8 000 Rowmark flexi tags and we got cycle times down from over a minute a tag to 14 seconds , we charged $.80c a tag including supply of material 3" x 1" , material costs came to 15c - so we scored significantly on laser time (over $2 a min).
Time based costing is also very problematic , for example our Explorers can engrave 2x the speed of our old mercuries (we have spirits now) and it would have been silly to reduce the price of engraving an item to 1/2 cos of that.
We have a really odd situation where I live , folk have bought yags at 4x the price of a co2 and have reduced the price of engraving items to a 1/4 of what would be a fair co2 price. If these machines were working on a continual cycle 24/7 , this would be a good strategy , however workloads for these folk have not increase in proportion to the speed at which the Yags work , so essentially they are getting 1/4 of the t/o (or perhaps a little better) with a machine that costs 4x. Seems that the old adge that turnover is vanity and profit is sanity doesnt quite apply.

Abdul Baseer Hai
09-18-2006, 10:02 AM
Rodney,

Outside support of the piece, using the pass through doors is an excellent idea. Never occured to me that i own one of the best machines around.
As the piece is smaller than the table, i intend to put a four foot metal shelf on the table, support it on the outside and place the granite piece on the shelf. I wil probably have to use manual focus.

Thanks again
Abdul

Mitchell Andrus
09-18-2006, 10:57 AM
Be sure to focus at all four corners.

Mitch

Rodne Gold
09-18-2006, 11:39 AM
Check your head and gantry clearance too , I think 5" items will clear no problem , but if you dont have clearance , you might have to use a shorter lens like the 1.5", the table goes down further then the door opening so measure up or put something of the equiv thickness in.
You will also have to manually defeat the magnetic sensors otherwise the laser wont fire at all , easy way to do that is use magnetic badge backs on em.
The clocking up idea is essential , ie make sure you are level , espcially critcal with a 1.5" lens.
To check its level , you can just run the head over the object with the probe a mm above it , will soon see if its clocked up.
Its a little bit of a mission lasering with the pass thru doors open as you lose your extraction and run the risk (albeit almost zero) of being hit by a stray beam. Wear the safety glasses that came with your laser or leave the area where you lasering , the closer you are to scatter , the more harmful the beam is.
I can tell you that in most likelyhood a dual job is required , IE use the laser to zap a mask and then sandblast. Granite will need a bucketfull of power to get depths where filling is an option and proabably have to run at 2-5% power or at least 2-3 passes faster , you are looking at potential run times of many hours. Lasering a polyester mask applied to the granite will take maybe 10 mins.
With photoengraving of marble and granite , the process is somewhat different as all you are asking the laser to do is leach the colour out of the stone.
It does not have to physically break the stone , whereas with color fills , you need to break the stone itself or vaporise it. Thus you have to hit the stone with a massive pulse to thermally shock it , cos the laser wont actually vaporise it. The thermal shock causes fracture. There are all sorts of problems with this and its not a particularily effective way of engraving. You will already be masking it , so you might as well get it blasted.
The only way you will get away with phototype stone engraving is if the granite is pure black and the paints sink into the porous engraved areas.
This is not going to be a simple job imho
For one its almost impossible to guarantee each wedge will be exactly the same , we import huge amounts of cut and shaped marble , travertine , granite etc from all over and in one crate , sizes and accuracy and squareness can vary a lot. This is going to require you recheck flatness for every single tile.
i dont think $50-70 a tile will be a lot if you are going to do a good job.

Abdul Baseer Hai
09-18-2006, 11:45 PM
rodney,

now it has started to make a lot more sense. It is not an easy job and i have to be very careful how I tackle it. I have lasered with the doors open (with the name badge magnet shunt). My 2" lens gives a 7.5 inch clearance so I can support the granite off the table, ( on a shelf)
I bought a absolute black granite tile from home depot and you are right. It takes ages to achieve any percievable depth.i have started to think that probably this wont be a viable project for me. This client owns a memorial shop and I dont want to drive him away. He was quite excited when i suggested that he could sell pet urns, with a granite facing and a picture of the pet lasered on it. do you have any other suggestions i could give him.

Thanks a lot for all your time.

Bachi

Guy Hilliard
09-19-2006, 6:49 PM
With granite (and marble) it is not necessary to engrave to a depth but to a contrast. A good contrast image can be achieved on both materials with very little depth.

Guy