Stencil

[tomahack]

I'm new to CNC and I have to make 1000 stencils in Lexan 0,05" thick. Bottom traces are 1mm wide with a "V" cut of 60 degrees. There is a lot of engraving too. I was leaning toward a BT32 Alpha to do the job. My question is: " Is it a walk on the park or completely impossible? I have the DXF file on hand. I will use the BT32 afterward to cut wood and alu.

Photo of the stencil: http://farm3.static.flickr.com/2308/2319236002_9bf48a4b58_o.jpg

Thanks a lot!

[gpari]

Easy as pie. I'm sure alot of us would be glad to run the job for you. (wink wink)

Gabe Pari
www.socalteardrops.com (http://www.socalteardrops.com)

[tomahack]

Thanks Gabe. The answer I was looking for. I will order my BT32 next week. :-)

Oh by the way, where can I find more info on fuse disconnect switches? Absolutely neccessary for Alpha?

[paco]

It would still be advisable to run some tests since V bit do not machine very well in plastics... if you base the investment of the tool on this job... it may cut through easy but you don't want to end up with clean up to do, don't you?!

It look to me that you need a pretty clean cut.

Don't forget about vacuum hold down as well.

[tomahack]

What are you suggesting regarding bits? Angle of cut is not critical. Something like a tapered mill? Yes, the cut must be clean.

http://www.bitsbits.net/index.php?main_page=product_info&cPath=20&products _id=52

[joe]

I'd vear on the side of caution as Paco suggests.

[mmccue29]

looks like a laser job to me

[tomahack]

I want to use the CNC afterward for wood and alu so laser is not an option.

[scottcox]

Jean,

Certainly not impossible, but don't underestimate the complexity of it.

Things to consider are hold-down method, time to cut, bit/feed/speed selection and your learning curve for the shopbot.

Bid high. Way high. And give your customer a couple of months lead time.

[tomahack]

Thanks for the advise Scott. Any suggestions for the best bit to cut in Lexan? I will probably use a vacuum pump with a jig to hold-down. Is 15 minutes per stencil realistic? Any advise is welcome. Failure is not an option.

[knight_toolworks]

you may want to hook up air cooling too. one of the single flute O bits from onsrud for the straight cuts. a v bit from centurion for your v cutting.

[Brady Watson]

As others have pointed out, I definitely agree that there is more complexity to this part than meets the eye. Give yourself plenty of time to do test cuts and R&D to get the cut quality and production time that this type of product demands. Any little jagged cut or mark, which can be caused by something as simple as a small chip of acrylic stuck to a guide rail or in the gear rack teeth, will result in a part that needs to be thrown in the trash. You cannot make a stencil with the smallest imperfection. Don't be fooled...this is a challenging job!

As others have mentioned, this is probably a job for a laser. Having tackled many challenging cutting jobs in an array of exotic materials, I would entertain the idea of subcontracting the cutting to someone with a laser, make my markup & pay for my Buddy that way. There are many little gems of information that experienced SB owners are trying to tell you in this thread...so don't take them as being negative...just realistic.

-B

[kfitz]

Definitely a laser job. No way I would do this with a 'Bot. Quality will be unacceptable.

[chodges]

I have a large bed high-wattage laser, and I would be glad to quote you on this job. It wouldn't hurt to "run the numbers" to see whether this would work better for you.

[tomahack]

Wow! Opinion ranges from "piece of cake" to unacceptable. Time is not a factor for this job. My main concern is if the BT32 as the capacity to do it. I know I will have to do R&D and multiple tests. Subcontracting is not an option. I did the price to pay the Bot with that job. Anyone else? Remember that thickness is only around 1mm.

[paco]

Jean,

I think it's feasible but if I put myself in your shoes, I wouldn't by the tool for and before having seen the cut result first. In my own shoes, if I had to quote this, I would want to make some cut test first then give a very safe quote. I really dislike second clean up work so that might be why I feel the way I do about this.

This is the kind of thing that look easy at first sight but with some experience cutting various material, I got this voice inside that say "watch out Paco..."

I did cut some stick and peel Lexan sheeting some time ago and I remember well the amount of time I spent tweaking the cutting specs...

You know what we say; "Mange pas ta chemise..." BTW; "Comment ça va à Montréal?!... avez-vous encore de la place a circuler en voiture aujourd'hui?!"
6481

[tomahack]

Hello Paco. It is a mess right now in Montreal. Never seen that in my life. 3/4 of my bay window is covered with snow. C'est l'enfer!

Very difficult to do cut tests without the tool. This is my dilemna. Buy or not buy. I really don't mind putting hours experimenting as long as the job is feasable. I really appreciate your concerns and I'm taking your advises very seriously.

[Brady Watson]

Jean,
Go visit Paco or another well seasoned SB Alpha owner in your area & pay them to test cut your parts. You'll see the results and know where you stand right away.

-B

[tomahack]

Great suggestion. I will contact you Pascal.

[harryball]

Doable, for quality you would have to go slow, perhaps too slow to make it feasible in production. I agree that having a test cut by another botter would be your best bet in helping you make a decision. Brady and Paco make good points. In the end, if you can get the quality YOU want at a speed YOU can live with, the bot will do the job. If not, I think a laser is the logical next step.

Now... I can't help you with the several feet of snow. I'm in Georgia, our temps ranged from 78 degrees to 28 degrees this week with a short snow shower to cap things off.

Good luck, keep us posted.

/RB

[joe]

When I'm told a job will be a "Slam Dunk" or "Easyasy as Pie", I get the He-wo-Jeebees.

[tomahack]

I will send a sheet of Lexan to Paco.As I said, speed is not really an issue. I don't mind doing only 2 stencils an hour. Thank you all, you are a big factor in favor of buying a Bot. I will keep you posted.

[gene]

Have laser will cut for cash

[gpari]

How would you do that with a laser?? Lasers can't chamfer the edges of the cut... Also, most of the laser jobs I've seen can't pierce cleanly without lead-in-outs.

I'm sorry, I just don't see what is so hard about this job. Lot's of things have the potential for going wrong with every project we do. We experiment to find the right bits, feeds, speeds, etc. all day long. How is this job any different?

I guess I may have inferred that it would be ok to order a machine based on a single job, not knowing what the end result would be and if that job would end up being profitable. Seems like the job was bid before even knowing how it would be done. For that, I'm sorry. I was just saying that this looks like a good job for a bot, and definitely not impossible!

My $0.02, for what its worth.

[chodges]

Gabe, you are right - a laser can't chamfer the edges of a cut. But I guess I don't understand why a stencil would ever need anything but straight cut edges.

We have both a laser and a bot, and there are times when one is better for a particular job than the other. In my opinion, this job would be better to do on the laser for a couple of reasons:

The "kerf" (cut width) of our laser beam is .007" This allows for the cutting of very sharp corners. I can't buy a bit for my ShopBot anywhere near that small, so my corners are going to be more rounded if I rout them.

There are no "hold down" issues with a laser. This particular project would produce a lot of free pieces, and this could be considerably more difficult to manage if cutting with a router.

Lasers don't use lead-in or outs, so pierced areas are extremely crisp.

And lasers produce a flame-polished edge on the side of cuts in plastics vs. tooled edges that a router would produce, which would make for a cleaner stencil if done with a laser.

I agree that this stencil probably could be cut on a ShopBot, but I think the end result would be better if done on a laser.

[normand]

Salut Jean
Fait tu les stencils pour Genemax? car il y a les droit d'auteur à respecter.

[Brady Watson]

The main challenge with this project is scale, and the level of quality needed within a given timeframe. The Bot is an excellent tool for cutting most kinds of stencils...and that in itself can be a very profitable business if the product falls within the range of what can realistically be done on ---> ANY <--- CNC router, regardless of brand.

How was the sample you showed made originally? If I had to guess I would say that it was either injection molded or heat stamped. It was not cut using a rotary cutting tool of any kind. The edges on the bevel look polished. You are not going to get polished edges with a CNC router...and it appears that you are not going to get a bevelled edge with a laser. I'd put my money on the original being cast or injection molded.

The other thing that is not readily apparent is that this part also needs to be silkscreened with a label for each stencil, and the logo. Silkscreening a t-shirt is one thing. Setting up a precise jig to do very tiny letters is something entirely different, especially when you need to produce 1000 of them.

I don't believe that anything is impossible...but I do believe that there is a 'right tool for the job' and that a CNC router isn't it in this case. If the part was proportionally larger by 25% or more, then that would make this project less of a challenge, but by no means a proverbial walk in the park.

-B

[tomahack]

Normand: Les droits d'auteur ont étés payés.

Brady: The stencil on the photo was made with a CNC. Stencil size is 7,5"x9". What would easier specs for you to deal with a CNC?

Charlie: Beveled edges are easier for carbon tip pen . Corners on the cuts are not sharp. Radius is 0,35mm. Don't need sharp radius.

Gabe: I love your trailers!

For those who'd like to see the dxf file, let me know.

As I said, time is not really a contraint. I got one year to complete the order(1000). Initial order is 200.

[tomahack]

Brady: The stencil on the photo as I said was entirely CNC made in 0,030" Lexan with 0,5mm traces.The mold for such a project is way too expensive I was told ( $60,000 ).

Beveled edges is a must. If not, the tip ( 0,5mm) of the carbon pen will break. So, sorry, laser is out of the equation.

[Brady Watson]

That's great news! That info would have been helpful earlier in this discussion. Now that you have the specs, all you need now is a sample.

-B