New Desktop setup ideas

[gsartor_1999]

My first CNC machine and my first post! This forum has been a treasure trove of learning!

Teaching in a middle school and had a donation that allowed me to purchase a Shopbot Desktop unit. Loving the learning process and impressed with the capabilities but I need some advice for set up-(photos would help).

I am specifically interested in ways to secure stock. I currently have a spoilboard attached to the T-slots and have surfaced that so that with the table surface utility. The only hold down method I have used so far is screws in the scrap area and have yet to add any sacrificial material beyond the surfaced spoilboard but I have also not cut all the way through any material yet. Does anyone have their Desktop set up in a way that seems to work well? Photos? Wooden Marvels guy seems to use his Desktop efficiently, are you here?

I would like the ability to engrave on anodized aluminum blanks, like dogtags, but not sure the best clamping method. A jig with a surface that will accept tape? I have not even tried engraving yet, mostly V-carve stuff.

I did the Bullshead sign from the Vectric tutorials and it turned out great! I did the open sign but flubbed it up twice. The first time I accidentally turned off the machine when I was watching it carve and then it was out of alignment and the second one was fine until the very end when the end mill drilled one mounting hole then did not raise to a safe z distance and put a trough right through the middle. I'm learning!

I am also looking for tips on what bits to get to augment the start up set and what to call that plastic that is two layers and typically used for indoor nameplates and such.

Thanks!

[steve_g]

Gina,
Welcome to the community!
Let me say that I'm not a desktop user and will let others with more expertise answer specific Desk top questions. I will say, however, that material hold down is often 50% of the battle. In my case... I seldom do the same project twice and tend to use Double stick tape by the case. I generally cut with an onion skin strategy, this allows ALL the tape to contribute to holding under the heavy cutting loads, making it easy for the tape on just a particular part able to handle the last .015". (Ask if you want more information)

One brand name of the multicolor plastic is "Color Core" any Sign supply house will stock it.

Tell me more how you are using the Bot on the Middle School level!

Steve

[zeykr]

Rowmark engraving plastic may be more what you're are looking for. It's often used for labeling control panels, desk name plates etc. Colorcore is thicker and usually used for outdoor uses such as golf course signs, playground equipment etc.

Holddown can be a challenge, but there are lots of methods. Do some searches here for cam locks, vacuum, great stuff pro, carpet tape, and when using screws try marking them using a drill toolpath first to be sure you don't hit them when cutting. If you haven't already, look at the web columns as some of them address hold down options: http://www.shopbottools.com/mPeople/webcolumns.htm


http://www.talkshopbot.com/forum/sho...ht=great+stuff

http://www.talkshopbot.com/forum/sho...ht=great+stuff

http://www.talkshopbot.com/forum/sho...ight=cam+clamp

http://www.talkshopbot.com/forum/sho...ight=cam+clamp

[Brady Watson]

Gina,
Welcome to the ShopBot Forum. Be sure to look around a bit, especially in the Show & Tell area, where people showcase what they have made.

Part hold-down is practically the entire job when cutting on a CNC. I think as you start to grown in your CNC experience, you will find several methods will be required to hold down various materials and parts.

The absolutely simplest hold-down method is heavy duty/high traffic carpet tape with fiberglass weave in it. Ace Hardware sells it all over the country. Ace Hardware Product Page It is 2-sided, has aggressive adhesive and the fiberglass weave makes it easier to get off than regular 2-sided tape.

My recommendation would be to lay some strips of carpet tape right on your t-track bed, and then adhere a 1/2" sheet of MDF to the tape. Press it down well. This will be what we with larger machines call a spoilboard. You can then put strips of carpet tape down on top to hold down whatever material you want, then just peel it off when done. Super easy!

Home Depot and Lowes sell 1/4 sheets of MDF that you can cut down to the table size of your Desktop. Don't worry about gouging or messing up the MDF when you cut your parts - it is meant to get 'spoiled', hence the name, spoilboard. When it gets a little ratty, or you find it isn't as flat as you like, you can machine the whole surface flat using the TableTop Surfacer in SB3 under the Tools menu.

Hope that helps!

-B

[bill.young]

Hi Gina,

We cut small tags with qr codes at Maker Faire out of engraving plastic. We generally cut a bunch of blank tags beforehand and then use this holding jig with a recess to keep them in place while cutting. It works really well, is quick to insert and remove the blanks, and keeps everything registered correctly for cutting.

The large recess at the bottom is just a finger hole to make it easier to remove the cut tags, and the two ramping grooves on the sides are to attach thin strips of wood or plexiglass to press down on the edges if you need extra hold...we rarely use them unless we're using an up-spiral bit that wants to lift the tags.

Bill

[WoodMarvels.com]

Hi Gina - I visit the forum every once in a while... Bill Young set-up my initial hold-down system along with Angus Hines so they are to thank for that! It worked great for larger models but now that I'm getting into more detailed things requiring multiple passes and finer pieces... I've resorted to increasing the screw count. At first, I used 2-3 and when I get cutting new stuff tomorrow... most of the new models will require around 10-15 screws. This is for a Desktop ShopBot using a standard double-flute bit!

The biggest issue I've found is MDF (base material - models made out of cheap 6mm plywood cut from 4ft x 4ft sheets) isn't very good when you screw things in and out... it gets looser and looser even if you move the screw holes around. Cheap plywood also tends to warp quick... hovering around the freezing point in the garage doesn't help much either when filming the cutting/assembling process either!

What I will probably end-up doing is building some sort of frame clamp that goes all the way around the 400mm x 500mm sheet of plywood and a jig around it, sort of like a reversed picture frame once I get a few more ideas fleshed-out. Using higher quality wood would help, but my goal is "proof of concept" and not "retail product" so I prefer to invest money in screws than firewood.

I'm always cutting through the same material thickness using the same board size with the same bit type. This makes my job very easier than most other set-ups.

Jon

[gsartor_1999]

Thanks for the photos-that looks like the perfect set up for my students to crank out things that can be customized quickly for other students. What kind of plastic are you using?

I love this forum!

[gsartor_1999]

Thanks for the info, Jon. I have been studying your videos and get what you are talking about. There is so much to learn and I am loving it! I figured you would be a good resource since you are actually using a Desktop. I got some birch plywood yesterday and plan on cutting some stuff out this week (while the students are on vacation and i have the time!).

Off to a sign store now to see if I can play the teacher card and beg and plead for some cheap scrap.