Engraving

[paul_capobianco]

I am a new shopbot owner. I got this idea that I can engrave with it. I am having a lot of trouble with the integrity of the letters. For instance the 8's or the o's are very deformed. I have bought engraving bits down to .015. I am trying to use a .030 bit. I also used a 3/32 end mill bit. The first time I did it the letters looked ok. But now it seems no matter what type face I use the letters come out lousy. I can literally see the bit jump and move as it cuts the letters. Like on the edge of the upper left portion of the 8 the bit will move ever so slightly and cut out a portion of the letter that it shouldn't. I know this isn't a lot of info but if you could help a little I would appreciate it. I have a porter cable router on the 4'x8' prt shopbot table. I am using the Rowmark 1/16 plastic engraving stock.
I have 187 of these 1" x 7" plaques to make and I don't want to be held hostage by the engraver that I usually use. He takes forever to do anything. I figured that I could get these done by now.
Thank you!

[barrowj]

Paul, Shortly after i purchased my shopbot several years ago, the pinion gear on one of the x axis had come lose and was pulled away from the rack. This caused the exact same problem that you are describing. The letters that required any use of both axis like an O would be deformed. I would call tech support for assistance with this as they fixed mine within seconds. After that problem, I check my gears regularly to be sure they are on the rack properly. Good Luck.

[jkforney]

Paul
Are you using Part Wizard to do the letters. If so check the tolerance setting. If the setting is to high it can do strange things to text and vectors. Mine is .001.

If this isn't the case and you have checked your mechanical set up as Joe states, maybe you could provide a little more info and we can help.


John Forney

[superior]

Hey Paul: How are you holding the engraving stock? If your letters are the usual engraving size, .125" or less, ANY slight movement will distort the letter. Also, a lot of cad programs don't have the vector/bezeling capabilities of sign writing software. This may be asking a bit too much of the equipment, also. I have found evern .250" letters can be a real pain to work with.
Just my two cents worth...
Doug

[Brady Watson]

Paul,
From what you wrote, sounds like your bit is climbing on the material. Aside from the obvious speed and feed settings, I would look at your toolpathing strategy.

You should be climb milling the inside cuts and conventional cutting the outside cuts. If not, the bit will climb and will also leave climb marks on your part.

You will have to change this for each toolpath in PartWizard.

-Brady

[K Simmerer (Unregistered Guest)]

Paul,
I'm on the "something is loose" track with Joe. I ran into this with a router at work (not a Shopbot) but the theory is the same. First you need to determine if it is a mechanical or a software problem. Turn on the control box and fire up the SB program to get the servo's to hold. Then grab ahold of the router and try to move it back and forth in x axis direction, then try the same thing in y. That rascal should be rock solid. If anything moves or clunks something is loose. In our case there was excessive clearance between the pinion gear and the rack. This wouldn't show up in large items but it sure did when we tried to engrave 1/4" letters. If there is play or clearance, wiggle and observe should pinpoint the problem. If all appears tight check your material hold down. If that also checks out then look at a software problem. Preview your cut with Windows version and zoom in at the problem area. I say, if it doesn't show in the preview, you are probably still missing a mechanical problem, loose pinion set screw, loose router mount, loose turnbuckle tensioner, material moving, something loosened up in the gantry or trolly framework back to visual inspection.

Good luck,
PS Shopbot tech support is topnotch, don't spend too much time without contacting them.

Keith

[barrowj]

Paul,

Keith has some good advise, however, do be careful moving the machine as the motors will act like a generator and blow a driver if moved without unpluging the motors first. Let us know how it all turns out.

[artisan]

Your machine could actually be just fine. Text is a funny animal and converting it to code for cutting can be tricky. You can see this by zooming in on your vectors after the conversion. It makes sense that "8's and 0's" would be deformed if your resolution is too low or your tolerance setting is too low as mentioned above. Curves are are merely a number of straight lines to the Bot. The more lines (resolution), the more true your arcs and circles will be. I'd be interested to know what software you are using to author your work....and what coversions you are making to get to the Bot....D

[K Simmerer (Unregistered Guest)]

With the motors on you should have to generate 80lbs of linear force to overcome the stepper motors. Shouldn't have to jiggle it that hard to bring out any play, but Joe is right about moving them unpowered. Just make sure you are powered up as I described. The machine is perfectly capable of doing what you are trying to do. I have V-carved letters as small as 1/4" in marble tile with perfect results.

[serge]

I am interested in carving letters on to marble but I thought that this could not be done, specially because of the water involved in the process. I read that k simmerer is doing this. How can this be done

[billp]

Serge,
I've had some luck carving letters into marble. It's not really that complicated.Marble is not as hard as many people suspect (it's the glaze on the surface which many people confuse with granite, which IS very difficult to cut).
I use a regular carbide V bit, but when I draw up my cutting file I set it up do the cut in three passes. I usually do;.05,.15,and .25". Between cuts I use a small paintbrush to "paint" water into the areas which have already been cut, and this softens up the area for the next pass. One word of caution, place some sort of plastic sheeting around the perimeter of your machine, and along the bottom of your Y axis because the slurry you will generate is going to go everywhere, and stick!
If I'm carving signs, I usually place a paint mask over the marble, cut through the mask, then paint my color into the letters with the mask still on. When the paint dries, I peel off the mask, and I'm done...Bill P.

[gerald_d]

Here (http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=30&post=8137#POST8137) are two examples of small text.

Bill, what spindle speed would you typically use for marble?

[billp]

Gerald, I usually run the PC router at 10,000 rpm. here is a shot of a memorial plaque I had done out of a piece off of the "sample rack" at the Depot. One square foot costs about 10 bucks..
5544

[gerald_d]

Thanks. Darn impressive!

[artisan]

Nice looking letters Bill. Is that a 60 degree bit or a 90....?

[billp]

Darrell
It's a 90 but actually I think the letters came out a little deeper than I would have liked. I might try a 60 degree bit at .25" next time, and go with .20" for the 90. As you can see some of the letters just about touch and it takes away from the crispness of the plaque. A surprising thing about this process is that it really does not dull the bit as much as most people expect. I have since used the same bit to carve other signs in wood with no discernible fuzziness. I think the water "bath" not only aids in the cutting process, but it also keeps the bit cool. It might be interesting to hear from someone who tried both water AND one of those cool air jets...

[K Simmerer (Unregistered Guest)]

A little water to cool the cabide bit is all it takes. You can use a mask, but I have had good luck with just shooting it, then razoring it off, just like razoring paint off of glass, quick and clean.

[K Simmerer (Unregistered Guest)]

The Depot will also make one or two cuts at no charge, I often have them cut them down for desk plaques.

Keith

[jamesgilliam]

Bill, the plaque looks great. I don't suppose you would share your feed rate? May keep me from ruining a good piece of marble. Thanks