No onion skin?

[Gary Campbell]

Tim...
Did you ever find what caused the no skin problem?

[chunkstyle]

Hi Gary,

No, Thermwood had a look at the code generated from the link and we went over it together. There is proper depth in the tool paths to create the onion skin. Why it is not performing the last tool path for the onion skin removal is anyone's guess.

I'll have someone looking at it tomorrow and maybe..., just maybe...., we'll get this straightened out. I'll report back with the results.

Tim

[Gary Campbell]

Tim...
Let me know how it works out. No second pass is something I have not seen or heard of yet.

RE your post of 07-30-2010, 08:54 AM :

You need to be aware that once zeroed to bed, the material "design" thickness is output as a variable (&ZSHIFT), which in effect, rezeroes the tool (only when cutting) to the "design thickness" above the bed. This also adds ability to cut multiple thickness' in a job.

If you add this to your scenario above,(design thk = .75, actual = .71 tenon = 50%, 3/8 deep) I propose the following:
Tenons will be proper thickness, as you say.
Tenon dado will be .040 (less clearance) too shallow resulting in gaps between parts.
Tops and decks will be misaligned from ends by .040 (short)

Lets do the other way. (design thk = .71, actual = .75 tenon = 50%, 3/8 deep)
In this scenario you would get the following:
Tenons will be proper thickness.
Tenon dado will be .040 (less clearance) too deep.
Tops and decks will be misaligned from ends by .040 (overhang)

Now lets throw in one more scenario: Zero is to top of material and the zero location, either due to warp, thickness variation or low vacuum caused by used spoilboard, results in error of .040 too high:

Tenons will be .040 too fat.
Tenon dado will be .040 too shallow.
Tops and decks will not fit into the ends and tenons will need to be trimmed for both length and thickness.

How about .040 too low at the zero point:

Tenons will be .040 too thin and will rattle.
Tenon dado will be .040 too deep.
Tops and decks will be moveable by .040 (overhang) to flush and hard to assemble.

I realize that .040 is an extreme example, but half that is common and .020 too tight or loose is just as undesireable to deal with as .040.

Here is what I recommend for those using files requiring zero to top of material:

Get a very accurate material thickness by averaging from other than edge locations. (after some test cuts)

That first you zero to bed, MZ to design thickness above bed, Zero Z.
do NOT do a manual toolchange and rezero during file.... unless you:

Add an off spoilboard zero block and add code to MZ, &zshift and rezero for bit changes during the SB Link file.

Cut in batches of same material thickness. Repeat zero as above for new material.

Call your Congressman (or ShopBot cuz it makes more sense) and see if these files can be changed to zero to bed.

[chunkstyle]

Hey Gary,

I agree to everything that you are saying about the material thickness as it relates to part alignment.
I've had issues with fit tolerances of tenons to dado's. This was an are where there was some confusion about material thickness having an affect on fit tolerance of the tenon going into the mortise.

I'm just gunna copy and past what I sent Thermwood about the onion skin.

Here tis:

The onion skin not working was a bit of a red herring and here's why:

First attempt to cut an e-cab twd file using the link. Parts were 1-cabinet
side, 1-cabinet top. Blind dadoe joinery. Other parts were omitted from
cabinet. Saved as batch job.

Ran parts and the machine cut them out in three sequential passes. The last
outline pass was the onion skin pass. First two passes were conventional,
last pass was climb cut.

Next was the off fall outline cut. Only I didn't realize that the code had
an outline cut tool pathed. This was mistaken by me as being an incorrect jog
to the location that I specified in the footer (x 90, y 0).

The spindle was moving to an odd location (something like x 94 and y 47).
Thinking back on it I realize that it was making a screwy toolpath for the
off fall cleanup. It would then travel down to the end of the table bed and
actually go into the -X!

from there it would travel down the Y until it was located about an inch
into the area where my parts were located and proceed back up the X and into
the parts.

Made another turn and traveled down the Y axis untill it hit a proximity
switch, having strayed into a negative position on the Y axis.

We ran that file a coupla times and got the same result. Very weird. Checked
the code and the machine was doing what was written from link.

Ryan, from Shopbot, was up messing with it yesterday. Found that if we
changed the bed size from 49x97 to 48x96 the problem went away. We are
leaving it this way and there doesn't seem to be an issue (so far?) with
nesting material that's been set up as 49x97.

Why the first run file went in the sequence it did and the subsequent files
(changed construction settings/ fit tolerances on the original and resaved)
I have no idea. Same with the screwy off fall tool pathing and how it
related to bed size.

Weird......

[Gary Campbell]

Tim....
All of the items you described seem predictable to me. That is to say, that I "know a friend" who had most of those same problems with certian combinations of erroneous settings. Is that why I have the table set to 48x96?

The obvious.... can you set your max penetration to .8+, your outline cut to climb, and check thru cuts last and run opposite direction in the perimeter cuts section. Then set your move speed for the bit and rpm to get adequate chipload?

Or can I assume, that since Ryan is there, its working now?

Has the49x97 table size "returns erroneous passes" been reported to Thermwood?

[chunkstyle]

Hey Gary,

Yes, I can set the max depth as you described. I've been running conventional on the outline and max depth at .375 with an onion skin thickness at .03". Are you saying set the outline passes in climb and onion to conventional? My thinking was conventional on outline and slightly oversized and climb on the onion and bring it to final dimension for outlines. I'm open to suggestions.
I set the minimum off fall to something like a gazillion inches square. That way it won't bother me with the off fall tool path again.
Seem's like you have to figure out what to throw out or turn off and set manually to get this to run.
Spent this afternoon cutting and trying to get my blind dado fit tolerances tightened up. I really hate ill fitting blind dados. I'm going to focus on just getting it to cut correct and try and ignore all the rest of what's weird or doesn't run right software wise or otherwise. I've got about a dozen sheets to get cut so I have to focus on whatever it will take to get that done. Table saw and biscuit joints, who knows.
Yes, I did write to Thermwood and told them about the issues with respect to table size and the odd tool pathing for the off fall. Maybe they know about it already.

Thanks for your interest and advice, It's appreciated.
Tim

[Gary Campbell]

Todd...
I've been running conventional on the outline and max depth at .375 with an onion skin thickness at .03". Are you saying set the outline passes in climb and onion to conventional? My thinking was conventional on outline and slightly oversized and climb on the onion and bring it to final dimension for outlines. I'm open to suggestions.

If you have your skin pass settings so that Skin pass is enabled (as above) then the perimeter cut direction is for the first pass. If run opposite direction is enabled the second pass will run the opposite direction of the first. Your max depth (per pass) setting will determine how many passes it takes for the "first pass". If set to conventional, your parts will be undersize with a watermark at the skin. (my guess) My advice is to run your first pass in the climb direction. This will be a deep pass and deflection will be away from the part. The conventional last (skin) pass cuts a very small amout (the deflection and skin) and cuts very accurately, as it is under lite loading.

I set the minimum off fall to something like a gazillion inches square. That way it won't bother me with the off fall tool path again.

Just check "No Off Fall Cuts" . No cuts will be made and nothing will be stored in Off fall database.

Ive Just finished up the onscreen recording of the Training Video. Sorry it wasnt ready for you last week!

Compare the cut widths and depths against those shown in the eCabs nest diagrams, post here and I will let you know what to reset. Usually, if dados are set to conventional and you are using normal feeds, then the fit problem is most likely depth related. Good Luck

[zeykr]

Tim,

I have also reported the misplaced off fall cuts. In my case it happened when cutting using a previous piece of off fall. My machine is a 6x12, but I have the area in sblink defined as a 4x8.

[chunkstyle]

Zeykr,

Well it's good to know that it's not an isolated problem. Hopefully the fix will be made from Thermwood.

Gary,
I'm getting nice results using the two pass climb and onion skin conventional. 15k on the .375" mortise compression and 2"/second. Minimal chatter and the perimeter dimensions are darn good! Making progress.
Do you set your pocket/ dado link setting as a conventional or climb cut?
Still working out the slop here. Conventional pass at a fit tolerance of .0015" gives me a looser than I like fit. Climb cut gives a too tight fit. Too tight a fit is what I would expect for a .0015" fit tolerance so I'm thinking of leaving it in Climb and adjusting my fit tolerance in my construction settings.
Gaining on it, I think.

[Gary Campbell]

Tim...
I think your rpm is too high for that move speed. try 12500 your bits will last much longer.


Do you set your pocket/ dado link setting as a conventional or climb cut?

I set mine conventional

Still working out the slop here. Conventional pass at a fit tolerance of .0015" gives me a looser than I like fit. Climb cut gives a too tight fit. Too tight a fit is what I would expect for a .0015" fit tolerance so I'm thinking of leaving it in Climb and adjusting my fit tolerance in my construction settings.

Do you really mean one and one half thousandths? My guess is that at those very conservative speeds you will not have any slop. If you do it is mechanical and your machines motion adjustments need to be tightened. I predict that as we audit these geometries that you have a Z cutting depth problem. This may be a result of erroneous thickness or initial zero. Heres how you find out:

After parts are cut, take a couple of your sides and measure the width and depth of the blind dadoes and the distance from the end of the panel. Take a few measurements and write them down.

Now open that cabinet in the eCabs editor and click on the nest button. DBL click on the sheet that the parts are on ans then again on the individual part. When the single part is displayed you can use the numbers of the cut geometry to see the exact cut sizes.

First: check the width of the dado against your measurements.
Second: Check the depth. These are the easy ones and if the width is right on, I am sure the depth will be off. Now check that the distance from the dado rectangle to the end of panel matches your measurement.

Now take your material design thickness and multiply by the dado %. That is how thick your tenon should be. You can also look on the nest diagram for a deck or top and it will tell you how deep the tenon dado cut is. Measure this from the top of material to the top of tenon. While you are at it, measure the protrusion of the tenon from the part. This should match the dado depth.

Report back, you can be good to go in the AM