No onion skin?

[chunkstyle]

O.K., I realize I'm clogging up the forums with my problems so I hope I don't get on anyone's nerves. In trying to cope with the spindle control problem I had run off a part file that I've been tinkering with all day. It's just two small parts, a cabinet side and a cabinet top. Top gets blind dadoed into the side. I just changed some construction settings and re-saved the file. Had the fit tolerance of the dado changed from 1/80" (gave good results off the Thermwood) to 1/128". Previous efforts were giving me a lot of slop. About 1/32" of slop in the fit. 3/8" bit was used and it mic'ed out .3746.

Trying to figure out where the extra slop was coming from I re-ran the parts and noticed that the onion skin pass was skipped. Checked my settings in the link and their all there. Don't know why it skipped it.

One last problem that has been jacking me up all day. I put a mz1.5 and a J2 90,0 in the footer. When the parts are cut it goes down to 97+,47+ and proceeds to plunge! Into the spoilboard if I let it. Has done this all day. I've rechecked the footer and all appears correct with the notation.

Any insights would be much appreciated.

Thanks,
Tim

[ken_rychlik]

For the footer problem, you could write a custom file for that.

Take C5 for instance and create a small file that does what you want.

Then just put C5 in the footer where you want it and it will run that file.

Kenneth

[Gary Campbell]

Tim...
Lets make sure you have your settings for the onionskin correct.

Go to SETTINGS > SKIN PASS

Set your Skin Thickness to a number > .035 to start

Set your Maximum Part Size to 3500"^2 to start
This means every part UNDER 3500 sq in will receive a skin pass

(under size to leave skin on)
Set your Max part Size to 30"^2
This means parts under 30 sq in will not have the onion skin cut during profile last pass

Set your Max part Width to 2.5"^2
This means any part under 2.5 in wide will also not have the last skin cut


using these settings you should be able to cut virtually any part with out movement, even with minimal to moderate vacuum

If you post the exact entries made in the footer box, I can look and see if there is a problem

[dlcw]

For the dado slop problem, make sure you've mic'd the material to exact thickness. This has burned me a couple of times. I've got my depth clearance set to .0156" and side clearance to .007". These settings have served me well.

Yesterday I was cutting a couple of small cabinets to show potential customers. For some reason the dados were sloppy. The previous 23 cabinet kitchen I did every dado was perfect. It turned out the the 3/4" prefinished maple I used on the sample cabinets was .71". On the kitchen I just finished the plywood was .714" enough to make perfectly fitting dados go sloppy.

[chunkstyle]

Kenneth, great idea! I will do just that.
Gary, how the heck do you know that? I musta missed it in the manual I couldn't figure out what those values mean. Why do I think you know san skrit I will compare what I have to what you've suggested and make the changes. Again Thanks.
Don, This is a topic that I have ben battling with for the amount of time I've been using e-cabs and outsourcing the panel processing. As I have ben made to understand it by the Thermwood folks, the dado width is made and impacted by the diameter of the tool cutting the dado and the distance of the end of the tool off the table when cutting the tenon thickness. This makes sense to me since the only point of reference the machine needs to have is how far off the table the bit needs to come up to determine tenon thickness. The thickness of the material would have no impact on this part of the joint (fit tolerance). the only way material variation would have an effect is that your tenon may bottom out in the mortise and the shoulder of the tenon would not abut the mortised members face. Our experience (me and the Thermwood shops') have sen a mixed result with our strategies developed around this notion.
I am not going to argue about what works and go with your suggestions. If it works for you I sure as heck hope that it will work for me. Thanks for helping me get over this hump.

Very much appreciated guys.

Thanks,
Tim

[Gary Campbell]

Tim...
I disagree with yor interpretation of the tenon thickness, for the following reason: The design material thickness is output as a variable called "&ZSHIFT" and the bit zero is shifted up from the spoilboard surface by that amount.

Using the example of designing with .750 material and a .375 depth dado, the bit is cutting at a programmed depth of -.375 and leaving .375 tenon thickness.

Therefore if your material is entered as thinner than actual, say by .040, then your tenon will be .040 undersize. Same happens for pocket dados, but the extra depth doesnt affect the fit. However, the location of the pocket dado will be located .040 too close to the top or bottom of the side panels.

I can assure you that accuracy pays big dividends. Audit your parts and find if or how they differ from the nest diagrams and fine tune your settings.

[chunkstyle]

Hmmm......

I'm trying to really get at the nut of this so bear with me.

Let's say that the material, in your example, was .040" thinner. The tennon will get cut using the .75" material thickness as a reference and come down to the table the desired % of the material thickness, correct? No matter how it does the math it has to finally make that determination that it must be "X" distance from the table surface. So no matter what the material thickness is doing, the bit is staying off of the table surface by our specified % of our incorrect .75" material thickness. So far so good?

All tenon's will be cut, if the tenon thickness was set at 50%, with the bit traveling at .375" above the table. Now we have .375" thick tenons on our parts, however the shoulder widths of the tenons are what will be off if the material thickness is rising and falling from the table surface, correct?

Moving on to the mortise, doesn't the program say "O.K., we know that the tenon thickness is 3/8" so we need a 3/8" mortise and we also need to add the little extra that he wants with the fit tolerance". Correct? (this extra addition of fit tolerance calculation might be getting added in the tenon cutting operation but it wouldn't change the fact that the bit would still come down a predetermined height off of the table surface). Now the bit comes down into the panel and routes out a mortise where the width has been determined and the depth will be calculate as so far off the table + depth clearance. Again, the material thickness will not have an effect, in my hypothesis anyhow, to what the material thickness is doing for the fit of the joint. If the material is less than .75" and the mortise is getting cut, the width of the mortise will be unaffected by this discrepancy but the depth of the mortise will get deeper and shallower since all the material deviation is on the side opposite the table side of the sheet.
So in my thinking, the tenon thickness should be constant regardless of the material thickness deviation (assuming our table is dead flat). It's the tenon shoulders that will vary as a result of the material thickness being inconsistent.
The mortise widths will be unaffected by material thickness variation. The depths will be affected by material thickness variation.

I'm not saying that this is right and would welcome any correction to how I'm thinking about this. I'm posting my logic for just that reason as it has been an ongoing issue and someone could get my mind right about this.

Again, thanks for all the help and advice. It's very much appreciated.
Tim

[chunkstyle]

Gary,

The Sheet Footer had this:

MZ 1.5
J2 90

The stopped position wasn't close to this and there was the added excitement of a plunge. Weird.

[ken_rychlik]

It may have something to do with ecabs running off of g code and your other commands running in sb mode.

Also having the commas and decimal points in there correct location is critical.

J2 90 won't work. You are telling it to jog both the x and y and not giving number for each with the commas.

J2,90,0 will

Kenneth

[chunkstyle]

Thanks Kenneth,

I'll try that.
Still no onion skin after using Gary's skin settings. Have Thermwood looking at the export file now.
I would be keen to know how the new construction settings that Don suggested will work. If only the onion skin pass would work!

Thanks for the help,
Tim