Estimating burn time - by area?

[Steve Busey]

Do any of you have a rule of thumb to share on how long an engraving job might take?

I was first approached to engrave a pair of Kanji symbol in the center of a large (23"dia) wooden platter for a martial arts school. I'd have to rotate the paltter in my Helix to do both symbols, but no problem. I gave them a price estimate based on what similar sized jobs have run.

Now they're coming back and asking about adding 3" high text all around the rim. Now I'm out of my familiarity zone. Again, I'd have to rotate the platter and break the text into at least two passes. But I've never done an engraving that swung nearly the full 24" of my workspace. Any thoughts on quoting something like that? Do you have a rule of thumb that maps to the square inches involved? Or width/height?

Thanks for any expertise you can share...

[Dan Hintz]

I would suggest running a small time trial. You can speed things up by splitting each half into two smaller sections to reduce time spent moving across empty space... one piece will encompass around 120 degrees of the rim, the next the remaining 60 degrees. Rotate 180 and do the second half in the same way. It will take more upfront work to split it up properly, but it could save you a lot of engraving time. At a high resolution (to get a deep enough burn), I would expect a straight up engraving of a 24" square to take well over an hour... you can reduce that significantly by splitting it up as mentioned previously.

[Joe Hillmann]

As a place to start I figure at 80 percent speed restoring takes about 20 minutes per square foot. That usually gets me in the ballpark so I can give an estimate.

[Steve Busey]

Thanks, guys - that makes sense.

One thing about breaking up the job into smaller pieces scares me - that's a so-far unexplained phenomenon where sometimes an edge of something I'm rastering gets clipped off. I haven't done enough testing to isolate what causes it - might be when an object is "selected" and near a page border, maybe when I'm doing "center-center" positioning. Just not sure at this point. I'd have to run a cardboard test before I put a 23" wood platter in there and press "Go"!

[Joe Pelonio]

With time you can do a decent job estimating based on experience, but after 7 years I still prefer doing a sample (for which I charge) and then quote for the quantity ordered based on that time. Unfortunately that's not practical for one-off jobs. Always figure it will take longer than you think. If you want you can always lower the price and have a happy customer, raising it is never well received.

[Shaddy Dedmore]

You could always run it once with the lid open, if your laser does it that way. Lifting the lid usually turns off power to laser, but will still run real-time so you can get a timed run.

[Mike Null]

How long does it takes to do a full sheet of labels or name tags? Use that plus your estimated positioning time.

[Richard Rumancik]

. . . One thing about breaking up the job into smaller pieces scares me - that's a so-far unexplained phenomenon where sometimes an edge of something I'm rastering gets clipped off. . . .

Are you converting to a bitmap and then rastering each bitmap? (That's what I'd probably do).

If so, maybe you could try to increase the "paper size" on your graphic so there are a few more pixels of white space before it gets to black. Not sure if this will help but just an idea to try. You would have to edit the bitmap in PhotoPaint.

Do you have PhotoGrav? If so, you could use PhotoGrav as a time estimator. I haven't tried it for a while but some years ago I used it to estimate a job and it seemed pretty good. You need to spend some time setting up the parameters though (turn-around time and laser speed etc.) The theory behind it is in the manual. You don't actually have to use PhotoGrav for your graphic, just pretend you are, and get the time estimate. Of course this also assumes a bitmap file.

[Jack Johnson 3]

Simple math

Work out the area of the job:

Say 200mm sq

so, it is 200mm high and 200 mm wide

what is the machine step over rate, lets say 0.2mm

how many times does 0.2mm go into a height of 200mm

200/0.2 = 1000

so, you are going to do 1000 lines that are 200 mm wide which means that the overall cut length is 200 x 1000 = 200,000 mm

what is your cut rate: say 100mm/sec

it will take 200,000 / 100 seconds which is 2000 seconds / 60 = 33 minutes.

Simple as PIE
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If you PM me then I will show you how to estimate practically any job
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[Vicki Rivrud]

Hi Jack,
Seems like an interesting way to do an estimate quickly.

I'd like to know more to save time instead of running a simulation or test sample especially in this economy.

So many times the customer is fishing or it's another shop looking to lowball me.

All the best,
Vicki

[Richard Rumancik]

Jack, if you were rastering a rectangular box then you would know the length of the raster line and the number of lines. However many graphics are not enclosed in a box, or the stroke length is variable. If you have lines of text you need to account for variable line length and white spaces between.

You would have to determine your maximum speed by testing, but what is ignored is the fact that the laser has to come to a complete stop on each end of the stroke. So the velocity is not constant - it is more of a trapezoid. The PhotoGrav software takes this all into account.

[Joe Hillmann]

For one off's do you really need to be that accurate in your timing?

[Steve Busey]

Jack, thanks for the math - but my Epilog doesn't speak millimeters, so I'll have to refigure how to digest all that...


For one off's do you really need to be that accurate in your timing?

Yea Joe, I'm just just trying to come up with a fairly accurate cost estimate - so neither of us have false expectations on the final cost.

[Dan Hintz]

Jack,

Those calculations also don't take into effect ramp up / down time... the smaller the engraved item, the larger the percentage of scan time is spent in ramp up / down, and it can become a significant portion overall. For large boxes, I'd take your calc and add a good 10%, for small boxes it may be as much as +50%. Of course, others have already brought up the problem with this calc on non-square engraving areas or if your machine can speed up or skip over white areas.

[Mike Lysov]

The easiest way to do it and it's only required to do once is to engrave a small square 1" x 1" filled with black. Then you know the maximum possible time to do 1 square inch. The next time any client ask you to do 10" x 10" or 6" x 6" you just can calculate it in a second. I know it will be more most of the time than it actually takes but you can change it a bit reducing the cost if you see some job does not have all the area filled.

I would not recommend to do a test run even with an open door for a big job unless you need to do a lot of them. For just one you are actually end up doing this job twice just to get a right price for it.

[Dan Hintz]

The easiest way to do it and it's only required to do once is to engrave a small square 1" x 1" filled with black. Then you know the maximum possible time to do 1 square inch. The next time any client ask you to do 10" x 10" or 6" x 6" you just can calculate it in a second. I know it will be more most of the time than it actually takes but you can change it a bit reducing the cost if you see some job does not have all the area filled.

Again, this is a bad idea... a 1" square will be significantly slower inch-for-inch than, say, a 10" square. BUT... do a 1" square to estimate really small jobs, and a 10"x1" rectangle to estimate larger jobs (divide the result by 10 to again get a per-inch speed estimate)

[Bill Cunningham]

I charge $1.20 per sq inch ..Area x $1.20 = charge.. Simple :p