Cut Issue

[mtworks]

This problem is driving me nuts, and I hope someone can help. While cutting letters for a sign, as the tool cuts its final pass around the letters it cuts a thumbnails thickness too deep leaving a deep spot around the letters (see attached photo if I did It right) that takes an extra 1/2 hour to sand out. - Any Ideas?
3717 cut parameters below:

1/8" upcut spiral (tried a downcut with same results)
250" per min speed
depth of cut .125" total in two passes
15,000 RPM spindle

[paco]

Hi Leo!

Have you figured if it's mechanical or software? That would be the first step... come back if you need help on how to figure this out...

[ron brown]

Leo,

It appears to me you have a bad line on your file (or two, three...) if you are speaking of the arc under the letters as shown in you pictures.

Ron

[dmdraper]

Hi Leo,

Please describe how you set up your tool paths, e.g., did you create pockets to rough out the letters and then outline the letters for the "final pass"? Also, what CAM software are you using to create the .sbp file? This info might give us some clues as to what's going on and help us make suggestions.

Dave

[mtworks]

The sign I'm trying to cut is a simple oval with 2" lettering on a curve. it is simply laid out in partwizard- 1) drawing oval and then offsetting second oval by .35". 2)adding text, in this example "Palatino Lynotype" on curve, 3)letting partwizard calculate toolpaths using area clear with a 1/8" upcut or downcut(tried both). I have no other lines or parts of a drawing around the letters, its just a simple 20 min cut for sign- no frills. All of the letters have a deeper cut line around the entire letter the width of the bit as it makes its final cleanup pass around the letters. table flat, seems to be mechanically perfect with no problems elsewhere- I'm stumped

[paco]

Hi Leo!

Have you looked at the file (SBP) to see if if it ALWAYS at the same height (depth)?!... it should... from the begining of the 2D area clearance strategie to the end when its "clean" the letters surounding.

I've observed this too on some occasion; maybe your material is get some "stress" relief... from the "main" 2D area clearance... that's a reason that got me to consider vacuum hold down (when using "surface machining strategie")...

Did you get any different results from the up cut and the down cut?! Consider how the "main" 2D area clearance is done (conventionnal or climb) from when it's doing the "clean up" around the letters...

By the way, how deeper is it around the letter?

[Brady Watson]

Leo,
Paco has a very valid point regarding 'stress relief' of the material as it is being cut. Wood especially will move and cup on you as you cut it. What you might want to do is re-zero your tool on the top of the block, move it off of the material, drop it -.02" or so and ZZ. Then re-run the area clear to clean it up. At this point the material should not move much if any.

-Brady

[mtworks]

Thanks for all your replys, I will try your different sugestions monday. my blank is screwed down at four corners 15" appart so movement probably is not a problem- But the material I am cutting is Extira, so stress may be the factor. I will see if pacos sugestion on direction might help

[Brady Watson]

Leo...is the bit stil sharp? Extira has a tendency to be pretty tough on bits...and as a result, might cause the Z to lose position because it either is dull or it may have something stuck on the end of the bit (if it is not center-cutting)...just a few other things I thought of...and experienced.

-Brady

[Mayo]

I don't have Part Wizard but here's another suggestion. If you haven't already tried this, combine or convert your lettering into curves or graphics rather than leaving it as text, then combine that with your background shape, then let Part Wizard calculate toolpaths.

Sometimes certain font info can cause strange machining results - I've seen this in other software. So converting the text into graphics or curves essentially eliminates the font info.

[dhunt]

--- NEW CUTTING PROBLEM ---

Using a Vector-generated .sbp cut file of 1,279 lines length, the cut-file is closing at an abrupt end(somewhere around line 500?) leaving the ShopBot screen 'blank' as in ready-for-instructions.
(Win.98, ShopBot software 229,which has been working just fine,otherwise).

This is now the third time it's done this...come to a sudden end.
Just before its second malfunction(yesterday) it paused, and I hit the R key and it resumed okay.

Going thru the 1,279 lines of code doesn't seem to show anything out of the ordinary, but I'm no code expert.

Any ideas as to what our problem might be?

[dhunt]

Further to my post above, further examination of the design- and cut-files
seems to show that our stoppage problem is occurring between lines 595 and 611
which are copied,below,
(on the second of four passes)

J3,17.8219,5.4483,0.4000
J3,17.8219,5.4483,0.1000
M3,17.8219,5.4483,-0.3400
CG,,16.9080,5.0694,-0.2287,-0.7400,,-1
CG,,16.8997,5.0558,-0.1106,0.0583,,1
CG,,17.8219,5.4483,-4.0943,10.8992,,-1
J3,17.8219,5.4483,0.4000
J3,18.3815,5.7343,0.4000
J3,18.3815,5.7343,0.1000
M3,18.3815,5.7343,-0.3400
CG,,19.1552,6.1961,-5.5762,10.2207,,-1
CG,,19.1565,6.1970,0.0682,-0.1048,,1
CG,,19.2001,6.2250,1.0768,-1.6294,,1
M3,16.6718,6.2250,-0.3400
CG,,16.7658,6.0886,-0.5985,-0.5129,,1
CG,,18.3815,5.7343,0.4130,-1.9779,,1
J3,18.3815,5.7343,0.4000

These lines cover everything from the bit's first entry into the isolated pocket being cut
(in a decorative Victorian gingerbread ventilation panel),
until it exits that particular pocket,moving on to the next.
Hopefully some experienced eagle eye might spot The Obvious..?

[marshawk]

You know... I just had the same problem. I had four little plinth blocks lined up in a single toolpath and it stopped cutting after the second carving. The router stayed running but the cut program shut off.

The thing is that this was the first time that I used the inches/arc tool path instead of the inches.

Hmmm...

[dhunt]

Okay... running the file AGAIN proves that our involuntary shutdown of the cut-file is a random chaos thing, not related to any line or lines of code:
upon re-run,it sailed straight past our original 'problem area' and continued until it chose a new place to zap-out! :-)
Luckily this new zap-out was at the end of the third(of four) passes, and so we simply devised a workaround,
a finishing cut-file of one deep final pass to final depth
- and recovered the workpiece, if not our sanity..

Still, the problem of involuntary quitting remains:
might it be a (hardware)floppy-DISK problem?

We are using a floppy of only a week's usage,so far,
and if it happens again, we'll definitely be changing floppy disk!

Still.. any suggestions re. involuntary quitting would be appreciated.
Thanks.

[srwtlc]

David,

Are you saying that you're running this file off a floppy or are you just transfering it to the SB computer and then running it from the harddrive. I hope your just transfering it! If you run it from a floppy you could have some access problems that would cause it to hang on you when sb229 looks for and loads another block of code.

Scott

[dhunt]

Scott,
Thanks for the response: yes, we're running the cut-file from a floppy.
We're generating design,offset toolpath and numeric code on the design comnputer,
then exporting that NC to a floppy,
physically transferring the floppy to the comp. wot drives the ShopBot ... - a routine we've been doing for years.

I'm beginning to suspect this particular floppy!

Maybe I should... as you seem to be suggesting...copy the cut-file to the HD of the comp.wot runs the SB,
and then deploy the file reading it off the HD, not the floppy... worth a try.

[mossie_jim]

David,
May be as simple as dirt in your drive, or worse the read head is going bad. Seems if it was the disc itself the problem would occur at the same point in the execution each time.

Using the HD vs a floppy sounds like a good idea.

Jim

[srwtlc]

David,

If you do find that it is the floppy drive or the disk and you don't want to transfer files to the SB computer all the time, try using a USB key drive instead (assuming that your SB computer is USB capable).

Scott

[mikejohn]

I had problems with floppy discs themselves.
see here (http://www.talkshopbot.com/forum/cgi-bin/discus/show.cgi?tpc=26&post=27921#POST27921)
..............Mike

[dhunt]

Turns out it WAS the floppy.
As soon as we put the same cut-file on a brand new floppy disk,
it cut beautifully, un-interupted!
Must have been a bad sector on the (1 week-old) floppy...
and to 'prove' it, I tried copying 7 or 8 files from that suspect floppy to the HD,
and all but the 'problematic' file copied:
- that's when I knew something was up with the file ON THAT MEDIUM.
Many thanks,gentlemen, for your inputs.

[Mayo]

I also used to run files from floppy disk until I realized the router would stop and wait for more info as it was being accessed on the floppy disk. When I ran the cut files from the hard drive instead, the router never paused waiting for info and cut through entire files without stopping at all.