That's fantastic! If I was assembling this, I could see spending alot of time cutting the tabs away and the bits they leave behind in the openings. Wonder if this would work well, with wavy foam? And maybe with a 1/16 bit, they would release easier?

-Kwok

 

Wow! Were you using tables, too? Or just a bare P (Phlatprinter, not Pentium )? I could see without tables how those small bits might pop out if they didn't get melted to the foam. Would they get crushed under the rollers and be a nuisance or just fall right off? No skewing in relation to the two sheets? I would consider using this method for all cuts, complex or not, depending on how long the "blank" on the bottom would last. Three cuts? Maybe I'll pass. Ten with the right cutting depth? Sounds good for everything!

I think this deserves a "Congratulations!"

- Jeff

 

OK. I just tried out the tabless cutting on my MKI with a 1/16" bit. It works pretty well. Some of the small cutouts fell out, but they didn't jam up the machine so it cut out perfectly. I normally cut foam on my MKI with the skin side up. I put the skin on the scrap piece skin side down so that the foam was skin to skin. It really works quite well. I put in another file that is cutting right now. It is more complicated and should be a better example. I'll post results later this evening.

Tim

 

I keep a spray can of Aileens tacky glue handy. When I am cutting lite ply or balsa, I spray a very light coating (just a mist) onto a scrap piece of FFF and then let it set for 10 or 15 seconds and then place the ply or balsa on the scrap piece. I usually add a bit of masking tape to hold it place.

The scrap does two things for me, one it helps the rollers feed the material and two, it keeps all of the small parts attached to the foam where I have not added tabs, like slot cutouts and small circles.

I never thought to use the same technique for FFF parts or to totally eliminate all the tabs, but I can see this would be a big time saver. That is the part I hate most, having to separate all the parts from the sheet and then sand the little tab areas.

This is great tip!

 

UPDATE

The second sheet didn't go so well. About 1/4 of the way into the cut, the bit loaded up and the friction melted a wad of foam on the bit. The bit didn't break and I was able to break the lump off the bit (so it is reusable), but it was definitely not a success. Wondering if the bit might be a little dull. I haven't cut a lot of foam with it, but it has seen a fair amount of use. I'm also wondering if maybe the cut speed might be too fast in the X direction. I have the X set to 45ipm.

Tim

 

You might have the RPM too high, or the feed rate too LOW. You want the bit to be cutting and flinging chips (and their excess heat), not making dust. I run my MK1.5 at the slow rpm setting (8000 ?) on my Dremel and 100 IPM for X and Y.

 

I have not had any problem with this setup before trying the tabless cutting although I increased the X speed recently. I've cut 3 or 4 sheets with the 1/16" bit and X on 45ipm. I think these bits are up cutting bits which would push the chips into the sacrificial sheet without necessarily having a good place to go. Not sure why the first one worked and the second didn't.

Tim

 

How about just taping a piece of butcher paper to the top and bottom of the foam? Or maybe a piece of foam to the bottom and butcher paper on top? It May only work with some projects.

Can the foam be advanced forward after each part is cut to drop off the table end? Or maybe having the G-code stop the cutting process after each part is cut so it can be removed and then restarted the code where it left off?

 

If the intent was to save time, just adding the tabs would be a LOT quicker than stopping the program after every part, removing the piece, then restarting the code.
btw, M01 is the code to add a Pause to the program. iirc, just clicking on "Print" restarts the operations from that point, but "Cycle Start" is what you want to do to get it going again.

 

Yep, I understand saving time. I am familiar with CNC but a newbe to the PP. I would still think that if your making a one-off plane, stopping and pulling the cut piece out may be faster than manually adding tabs into the program.
Does the program have an auto-tab function so you don't manually have to add them in?
If it doesn't, maybe it could be added into the new software...something as simple as defining for every "X" amount of inches cut a tab is made?

 

Auto-tabbing has been requested. Not sure it would save much time. There would be a fair amount of deleting unwanted tabs and adding necessary ones. I think removing each piece would take longer than putting in tabs although if you figure in the amount of time spent cutting tabs to remove the piece from the sheet it might be close. I'm not sure it would work well though because one of the parts of the ferris wheel didn't have tabs on it and because it had no tabs, it fell out just before finishing the cut so there was some cleanup to do on that part as well.

I'm going to try a cut with the 1/8" bit on my MKI and see if it works any better. I am also going to try a new (sharper) 1/16" bit as well. It really doesn't make sense to me that one sheet that took 35 minutes to cut would work well and the next sheet fails 10 minutes into the process.

Tim

 

I just saw the video..didn't realize there was one there. Frikin work nazi's block video content. :evil: I guess they actually expect me to work. Now I see the problem. Forget my previous suggested solutions.
I guess the easy way out would be to not cut anything with that much detail

Can I get a script of the eiffel tower? My dad is French and would love to glue that together for a Christmas Present.

 

Sweet! Thanx!

 

OK. Tabless cutting on the MKI results round 2.
I was working on an instrument panel for a Falcon 10 (corporate jet) for work today and having trouble with the layout on paper so I decided to cut it with the MKI to help get it correct. The panel is 54" wide so that means 2 sheets. I cut the first sheet (the smaller of the two) tabless with both the sacrificial sheet and the cut sheet skin facing up. The only thing that kept it from being a complete failure was the lack of small cutouts. None of the pieces adhered to the sacrificial sheet. With the second sheet I ran it skin to skin. My MKI is completely stock and the waviness of the foam is a problem. If the forward pressure roller had the sand or lead shot mod or the spring mod, it would probably work better. This cut out failed due to the foam not being flat. The double pressure roller on the Phlatprinter III would pretty much eliminate this issue (I think).

I do have a thought on this though. A hybrid of tabbed and tabless might work well. I'm thinking that you might be able to eliminate about 75% of the required tabs with a sacrificial piece of foam on top. I'm still not sure it's worth the wasted foam. I have not tried reusing a sacrificial piece yet, but there are rough places in them where the bit penetrates the foam.

I have not yet tried a 1/8" bit with tabless cutting. That will be the next test. I also go my hands on a 1/32" bit with a .3" flute length. I'm going to try that too, but I think the flute length may be too short. I'm going to try that with tabs first.

Tim