Engraving a Book Cover in Wood: CNC or Laser?

      A very unusual project proposal (thousands of book covers engraved in plywood) leads into a discussion of laser engraving versus CNC engraving. August 16, 2012

Question
I have a small one man shop and have recently been asked about the feasibility of manufacturing a run of engraved or embossed book covers for a cookbook he is getting ready to publish. His idea is for a simple 1/4" plywood front and back cover with a simple illustration and title on the front. Normally, I wouldn't really take this too seriously, until he mentioned that he would finance the required machinery and that the first printing would be in the 5,000 to 10,000 range. That definitely got my interest. I've been looking at smallish CNC routers as well as laser engravers and would be interested in what the experts out here think.

My initial impression is that the laser engraver seems pretty simple to operate, requiring only decent printing software as opposed to complex programming, doesn't create the mess that a CNC machine would, and takes up relatively little space. Also the price seems reasonable and I can definitely see a myriad of other uses for my woodworking business. I've worked with some small CNC routers, have a basic knowledge of CAD and am familiar with some of the drawbacks; they're messy, loud, require frequent maintenance, bit sharpening, etc. What do you think?

Forum Responses
(CNC Forum)
From contributor E:
If you are really going to consider this I would like you to know what you are getting into. To jump into this you will probably earn enough money to pay for the machine but you will earn every minute of every day. If you buy a less expensive machine you will be buying a lower power machine. Which means you will take longer to engrave the covers. If you buy a higher power machine you will spend twice as much to be able to do it faster. The laser works by burning into the surface, or burning away the material. It controls it's depth by the power and speed by which it is set.

I would be reluctant to do this because one customer wants to engrave 5,000 of anything. A standard book cover is 8x10. That's 80 square inches. If you’re lucky you will cover 8" wide x 1" tall in say two minutes. Each book cover could take 14-16 minutes to complete. That is about 70,000 minutes or just under 1,200 hours of engraving. That's 145 days of just loading the machine. Now there are companies that make superfast machines just for this process but you would be looking at 100k plus.

I know companies that have a say 100 machines running the same thing at the same time. They also have machines that are running multiple copy heads - more bang for the buck. I would look into taking this on but not doing the work, let someone else worry about the 145 eight hour days. Take your cut and make some money.

I've been there, if you are still really considering it, take a sample of the book cover art work and there material he wants to engrave it into and go to your local trophy shop and have them engrave the cover. He should tell you the run time because most of them get paid by the minute. Maybe I am wrong about the run time maybe I'm not. See what he charges for the service. Then multiply out the numbers. It's a very inexpensive lesson to have some else this first. The laser is easy to use, yes but it is not a plug and play device.



From contributor K:
Buy two small units that way you are loading one while the other is engraving.


From contributor M:
Ten thousand pieces is a lot, but you could easily engrave this with an inexpensive CNC. I just threw down a test. Times New Roman text, 1/2 inch tall 1/4 inch MDF, all the words on your cover and add a minute or so for the pot. It’s a quick and dirty programming time, three minutes. It ran on my machine in 14 minutes, that is a good quality engraving in 1/4 MDF, not a pencil trace. My machine is large and heavy, not designed for this sort of work. A lighter bridge gantry machine would run much quicker. I would guess with a little thought and the right machine 10 to 12 minutes or better would be easily achievable, possibly even better. A light pencil trace would run faster still but would not look as good.

On a CNC router this could be done in nested format making loading and unloading one sheet result in 40 finished parts per 4 x 8 sheet if you respect grain, 46 finished parts to a 49 by 96 if grain is not respected. Work other projects while it is cutting. At ten minutes per part a 40 part sheet would run in 6.6 hours. 12 minutes equals eight hours. The thing is, this means many months of work for one machine in one shop. This may not be feasible for you, or maybe it is.

What is very feasible though: sub quantities of 500 to a thousand to shops already set up with this equipment, make the total turnaround a few weeks instead of months, and take your cut that way. There is a lot of excess capacity out there and it would be a win-win scenario to take advantage of it. You will avoid a lot of complexity a one man shop does not really need, lessen your risks since 20 machines will not ever be broken at one time, build relationships that you can leverage in the future, learn a lot about CNC on the way and maybe make a few bucks too. Reach far and wide geographically, since the shipping costs of these things would be relatively small via common carrier.



From contributor H:
First, definitely laser over CNC. The things said above are indeed tempered by the much smaller than thought amount of surface involved. Second, on another note, your customer might not be too happy about seeing the cover of a yet to be published book up on the web. I'd consider asking the webmaster to remove that photo.


From the original questioner:
Good point Contributor H. Although this is only a preliminary design, I wanted to show the simplicity of it. Also, Contributor Mark - he wants to use 1/4" oak plywood to get the old-timey look. MDF would not look good. What could I expect for tearout with a CNC router?


From contributor K:
If you use a laser you will need a tablesaw to size the plywood. With A 4X8 CNC you could engrave and then cut out covers.


From contributor C:
As someone who owns both a laser and a CNC I would go with the laser. The precision of a laser is unmatched. Also there is a lot less work to do afterword with the laser than there is with the CNC. Depending on the size of the laser you could do multiple covers at a time. You could even cut the covers out, giving them a finished edge. You also have the contrast on the letters from the laser burning them which would make the covers easier to read.


From contributor L:
This seems like a really expensive way to make a cover! I wouldn't use plywood but rather veneered MDF. Ever worked with 1/4" ply core - yuck! Watch out for bearers of large number's that approach very small shops!


From contributor M:
I agree with Contributor L in that veneered MDF would be nicer to work with, engraving requires constant thickness for good results and 1/4 ply is not likely to give you that. You may have voids unless you use a very good board. MDF would work fine and have very little trouble with chipping using a sharp v shaped bit. I ran my sample with a miterfolding bit; I might use something smaller and pointier if going for volume production. Very good edges can be achieved on a router including a two sided round over in one or two passes free from any need to sand more than a light wipe.

If you engrave, the router makes lettering like a headstone has utilizing a lot of small movements, many of which have a z component. Three axes have to me mixed and this means lifting the whole head against gravity constantly. The Z component of moves is often slower than the x/y component is, so to follow a path the slowest axis is the limiter. Lasers don't really have to do a lot of z moves since they really sort of "pocket". A router can also pocket, but with very small letters would have to use a very tiny bit and these tend to be very brittle and thus limiting in terms of resolution and speed. If you use a router you will want to engrave, I would say.

Contributor C has good points, and laser can give you very precise “pocketed” lettering, you can literally do a small typeface with perfect clarity and get and a whole set of effects from contrast in color. The edges can be made perfect, though I don’t think you can get around the charring completely. No eased edges. All in all I agree if I had both I would likely use the laser too.



From contributor K:
I think I would put my money on the large format router over a laser for speed. You can do 45 at a time without reloading the table, even with a manual tool change to cut the covers to size. I think it would be a lot quicker and more accurate than trying to cut the covers out on a tablesaw.


From contributor R:
If you use a CNC consider adding a plastic mask to the surface. Then you can paint the cuts for contrast and just remove the mask when dry. The laser will leave a charred surface, so no painting or color fill needed to highlight the lettering.


From contributor H:
I'm going to add that there are two ways to do this on the CNC, engraving and carving. Engraving is when you use a typically 60 degree or 90 degree V-bit that goes along the center line of each letter and creates a V-groove that defines the letter. It's actually a little more complex than that but it gives the general idea.

Carving is when a similar bit goes back and forth over the design moving across it at about a 64th to 100th of an inch with each pass. This would not be an efficient way to do this project. However it is the way the laser would run the covers.

As such, the CNC would probably be faster but the laser would give you color contrast because of the burn. The CNC on the other hand would give you a deeper more hand carved sort of appearance. I think the final decision here is best determined by what your customer wants these to look like.



From contributor K:
You could also do something like this.

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From contributor Y:

Here's another idea.

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