Cutting sandblast mask

[GlenP]

Does anyone have any tips for cutting sandblasting mask in the bot? My plotter decided to give me grief and is about to go out the door any second. I am doing some vertical grain cedar signs and have tried to apply mask and cut with small cutter with no success. Using Hartco mask. With vertical grain tearout seems to be a issue. Any help would be great. PS- Anyone want to buy a plotter, works great....sometimes!

[chodges]

This may not be the answer you are looking for, but we have a used Gerber GS750 sprocket-fed plotter that is designed to cut sandmasking, and we are not using it anymore.

If you think this might be a good solution for your needs, we would offer you a good price.

[GlenP]

Thanks Charlie, I am in Ontario Canada (eh) so its a bit of a distance to ship. Really want to attach the mask to the wood and then cut with stencil with bot. I know Dr. Crumley has had some success with this on foam and hoping he will chime in...please. I had to walk out of the shop a few minutes ago and take a break from the plotter. I have never used it much and if I did it was for cutting mask to apply to rocks for sandblasting so never checked for accurate cuts. If it looked good and weeded out blast away. Now I am doing a few larger signs and it seems to be cutting short on the Y axis which is the length on the plotter. Frustrating the heck out of me. I am swamped with work and don't need any delays.

[zeykr]

Charlie,
I dropped you an email about the plotter.

Ken

[GlenP]

Your welcome Charlie
, anyone got any ideas about the topic.????

[cbradshaw]

Glen,If you are not cutting real small letters it will work fine. I used a drag knife called the vinyl mate to cut it. I had to use spray adhesive to hold the material flat. If you have a zeroing attachment zero the z position and tell the bot to cut .25 and it should work fine for Hartco material. It will work, but for small letters I prefer the vinyl plotter.

ps. If you use one of these tools don't forget that you DO NOT turn the router or spindle on.

[cbradshaw]

Glen,

I just checked and this company has stopped selling the vinyl mates.
http://www.littleeholdings.com/

[GlenP]

Hi Carroll, I read somewhere on here once someone was using a small bit to cut the outline of the mask..but I think it was on HDU. I am using vertical grain cedar. I was using my plotter for the job and it seems to be acting up. It is cutting the material too small on the on axis. Really screws up curves. Support from the company is next to nil. I am going to probably have to farm out the stencil to be cut if I don't use the bot. TIme is tight now that my plotter is acting up.

[myxpykalix]

GlenP you have a 4x8 plotter in the shopbot why not use it? Search for widgetworks unlimited for a dragknife.

[zeykr]

Are you using a downcut bit? I have better luck with getting sharp edges on mask with a downcut bit or by using a good vbit such as hersaf first, then following with endmill for pocketing.

[GlenP]

Hey Ken, I have tried a 1/8" endmill and going to try ball nose and vbit today. Have you pocketed vertical grain cedar before? Just wondering about tearout.

[zeykr]

Glen,
I've not done vertical grain. On face grain western cedar I've edged with the hersaf v pretty shallow to cleanly cut the mask then weeded and pocketed with the endmill. Can't find the speeds and feeds I used right now. On redwood I've had to speed up the rpm and move slower to reduce chipping.

[GlenP]

Well guys I may have lucked out for once. I took the toolholder out of my plotter and it fits the collett on the router. THe main part is slightly narrow but thier is a adjustment nut on the top which is fits perfectly into the collett. I removed my dust skirt and tried cutting some mask that was on a piece of cedar and it worked like a dream. Guess I won't need to a drag knife after all. Maybe I can get this sign done before the customer gets upset. I am still going to try and cut with a small bit and the router. As well try to perfect a simulated sandblast look with texture background.

[joe]

Glen,

We finished out two sandblasted signs last week using Hartco Mask. I have been cutting this on my CNC for years. Although I have a Gerber Tractor Feed plotter, cutting the mask directly on the panel is much more accurate and fast. I use a small roundover which has a needle point. It comes from Woodline and I believe the product # is 1318.


8607
This sign was done last month using Yellow Pine. It's now my favorite sandblasting wood.



Here's the steps.
Shellac the surface and lay down the mask.
-Z .09 or there about. Remember, you're only cutting through the mask. A slight score is all you need. I turn up the rpms to 14000 to protect the needle point.
Now all you have to do is remove the excess mask. You may need to use an exacto in some places but this goes fast.

To finish up, I use a 1/8" sprial and profile all the letter to the desidred depth. From there you can do and area clear.

I'f there is anyone who would like to pruchase a good Gerber HS15plus Tractor feed plotter, designed to cut sanblast mask, I'll sell it to you real cheap. I only paid $9,400 for it and will take $2000.

Joe Crumley
www.normansignco.com (http://www.normansignco.com)
8608

[GlenP]

Hey Joe, Beautiful sign as always. Thanks for chiming in. I knew you had a good technique. I also have a plotter that is no longer going to be used. I am going to try your technique on my next signs. I did however manage to use the blade holder from my plotter in the 1/2" collett and cut the mask already applied to the blank. Just like the drag knife sold by some others. It worked really well. Joe have you ever used the technique above on vertical grain cedar. Tearout is a real problem with the tight vertical grain.

[GlenP]

Joe you put shellac on that sign because it was painted, how about if is not painted, will the mask stay down or will it need a clearcoat or sealer applied to help stick to bare wood?

[joe]

Glen,

That's a tough one about the paint. For years and years sign artists have wrestled with pre-painting sign panels and then applying masks. To my knowledge no one has come up with a fool proof method. One of the reasons is the longer a mask stays on the panel, the tougher it is to get if off without pulling off paint. This particular mask is famous for not coming off easily. If it even gets warm while blasting or if left out in the sun, you'll probably have problems.

Everyone has their techniques. Mine is to apply mask directly to raw, or near raw wood. If there is adhesive residue left, I use a 8" disk sander with 120P.

Tear out: Cedar does get weak in the little serifs. For that reason I go around all the letters with a 1/8" down sprial. I step it down .12. and my usual completed depth is .40.

I don't know what your woodworking skills are but if you have the skill, vertical grain Yellow Pine is a very interesting option. It's cheap too. And there's virtually no tearout. This wood behaves like a hardwood. And it's realy, realy hard.

I get mine at Lowes. There's lots and lots of vertical boards. Choose the one with the core centered up.

Joe Crumley
www.normansignco.com (http://www.normansignco.com)