Fit Clearance and small shoulder

[frank134]

Ok so I am up and running with e cab. Cut out a few boxes from some oak and they turn out ok. So then I switch to some cherry and it was off from the oak by .002. The Dado and Tenon are really tight. Is there a formula at what to set the fit clearance or do I have to just keep track of the difference thicknesses of the plywood? Also there a small shoulder at the end of each Tenon how do I get rid of it.
Thank for any help.

[Gary Campbell]

Frank...
Looking for a little more info here....

You say off from Oak by .002. Can you explain further?

Were the 2 files cut with the same dado %, depth & fit clearance?
Was the bit changed or the tacle surfaced btween the 2 files?
Do you zero to the top of the material or the spoilboard?

The plywood thickness has no effect on the dado/tenon fit. The settings, the accuracy of your Z zero have much more effect on the dado accuracy.
You may want to re-mic the parts to see if they are the same thickness as the design value.

What is material thickness?
What is tenon %
What is actual thickness of tenon as measured with a digital mic?
(the tenon thickness should be the mtl thickness * dado%. My guess your actual is thicker.)

When the outline cut and tenon dado do not line up at the tenon shoulder it is almost always a mechanical issue. Usually the X. Double check pinion to rack clearance and your pinion grub screws.

[frank134]

ok. First I sorry I am running blind dado.
the .002 is the difference in thicknesses between the too plywoods.
yes the two file were cut with the same dado% and fit clearance
the bit was not change and I rezero to the top of the material

I have to take a pic of the last thing as I don't know how to say it.

[Gary Campbell]

Frank...
I am pretty sure that I know, and have seen your problem. Check the pinions and grub screws. If the X are loose, check the Y also. I will be at the shop in the morning. Call if I can help

[frank134]

11599

I hope this work. gary this is the problem I have been having. How do I get rid of this?

thank
frank

[Gary Campbell]

Frank...
Only 2 causes for this, as far as I know.
1) Mechanical (most likely) check pinions and grubs as above. Make sure parts didnt move. (is tenon similar on other end of part?)

Mic the tenon and see how it compares with your design value
Did you mic the tenon thickness?

2) when using different bits for outline & dado, 1 has size listed improperly

I am sure that 1) wins in your case

[frank134]

the part did not move and all the tenon are the exact same. Everthing on the machine is as tight as I cam get it. there no movement of any kind. and all the cut are very precise. all tenon are the exact same all seven. so when I but them together i have a little should at each end. Rasing the center. I am using the same bit for both job. there has to be a setting some where to set the tenon depth into the material.

[Gary Campbell]

Frank...
Have you mic'd the parts that I requested?
I need the material thickness (design)
Tenon % (design)
Measured tenon thickness
Measured tenon length

[frank134]

as soon as I can get back in the shop tommrow I will get what you ask for.
thank

[frank134]

Ok Gary I think I got what you want to help me.
e-cab setting
Dado depth .375
Depth clearance .025
Fit clearance .03
Thickness % 53
Link setting
.05 dovetail radius crunch
100 male dove feed rate
.05 material1161811617
11615

11616

11617

[Gary Campbell]

OK Frank...
Here goes......

1) Tenons at .3995 means your z zero is too high by about .025 or...
your spoilboard has shrunk in that area by the same amount.
Can you see any variation in the depth of the bit tracks from the outer edges towards the center of the zones?
Run your vacs for a while then surface table
zero the bit to a known solid area of the table
when done MZ,0 to confirm adjust if needed
MZ,.702 (material thickness)
ZZ to set zero to design thickness
Note: as you run with vacs on, spoilboard can shrink in the areas that have more flow.

2) I still feel that your shoulder problem is mechanical as stated above, but cut direction could contribute to the problem. Can you have this job nested and email me an export?

With the job nested, press the export button (lower right of the main screen) save this file to a known location, attach it to an email and send to me at the address in my signature (below left)

I will look over and adjust your settings, if needed and send them back for you to load and cut.

[frank134]

Gary I know I have a little problem with the vacuum holding thing down. That why I wanted to build the new system you just made. Plus the plywood I use is not the best and I made a mistake in my math. so I got the tenon to fit good now.

The problem I am trying to solve is the indent in the shoulder. If the problem was mechanical, wouldn’t it show up in all the cuts. Beside at the end of the tenon it leaves a piece the same thickness as the indent in the shoulder ( I cut this off with a utility knife before I took the picture). Plus then I put the tenon in the dado (as in left side of cabinet to deck (deck with dado) the deck sticks out past the side about the same as the offset in the shoulder of the tenon.

I will sent the file tomorrow

Thank Gary

[Gary Campbell]

Frank...
Since you are using a single bit there are only 2 causes for this problem. Machine or Bit deflection, or possibly a combination of the 2. The export file will let me see your bit diameter, speed, direction and stepdown. This may allow me to eliminate cutter deflection.

It will also enable me to determine how hard you are pushing the machine. You need to know that it is rare that you would be flexing the machine on cuts that shallow. Same goes for the bit. That brings us back to the motion parts being out of adjustment.

I use a magnetic base dial indicator stuck to one of the legs. I set the dial against a vertical point on each of the side plates. Push each side of the gantry hard in both direstions and see how far it moves. My guess is around .030 +/-

Standing by for the file

[ken_rychlik]

Or sloppy bearings in the router??? It seems like there has to slop in there somewhere.

[frank134]

when why does this do it only on the tenon shoulder cut. no where else. And it the exact same on both side the and on every tenon. why don't i have the indent when it cut the whole side or deck out. why doen't it do it when it cut the dado out. If it was the machine it would show uo everywhere would it. If it was the bit the same thing. I think it cut the tenon to far into the material first. the tenon cut is a dado cut first , then the machine come back and finish the right, I think that first dado cut is to deep into the shoulder. but I will sent you the file for i am just learning.


I have a spindle. 4 hp.

[chunkstyle]

Hi Frank,

I've been having the same problem as you only less pronounced.
I've re-snugged my pinion gears several times and checked the play with the motors powered up. I can never get rid of any play and assume that there must be some gear lash for the gear boxes to keep from binding.
I'm using a .25" MC bit and running at 2.75"/sec., 2 hp. spindle on a PRS standard.
I wonder if it's bit deflection while cutting the tenon dado (shoulder cut). I'm cutting conventional which I assume would deflect the bit away from the tool path line and thus make the intended dado slightly undersized. Instead I get the dado slightly over sized and have a similar result to what you get. Bummer.
You've got Gary and Ken's attention so I am hopeful.

Tim

[ken_rychlik]

A pocket will be smaller with a climb cut. That may help if you try that.

I do run my pockets coventional though.

[robtown]

It seems pretty consistent. Does it happen on both types of plywood? It looks to me like it's cutting exactly what it's being told to cut. Make sure your bit definitions are correct (mic them all and make sure you have the correct values in there).

[frank134]

it even happen on the pink r-truff. That why I don't think it the machine or bit. you can push your finger thur this stuff.

[ken_rychlik]

I don't think you are getting what Rob suggested. If your bit is in the program as a .3 and it is a .375 in reality, that would cause what you have.

[frank134]

I measured my bit it is .248 and in the program i have it at .25. The offset is around .07. The machine cuts out dados anywhere there is a tenant or a dado. The it cuts out the peice of wood to turn a dado into a tenant. When it does this it cuts it too shallow by .07. I dont believe it is bit deflection because i am cutting through R-tuff (styrafoam essentially). I dont think it is a problem with the machine because my son does V-carves of letters and 3D images. If the machine was loose or something it would cause problems for him. On top of this the tenants are cut in both the x and y axis and they turn out the same .07 offset regardless. I feel like it is a setting that i am missing in the program. I talked to Thermwood about this and they told me that this was how the program works. I dont know anyone that would accept a cabinet with a .07 gap where the peices of wood join together.

[frank134]

Ok we found and era that I made in the shopbot link outline tool 3 was wrong. It was set to .3 something. So I set it to .248.
Also under operation tool set was not set. Change this to .248
This is what I am coming up with now.
The tenon is inset on one side and extending the same amount on the other side.
So I know this is in the setting. I will put up the picture and the new file.
11624

11625

11626

[Gary Campbell]

Frank...
I am a little confused. I assume the first file I received was the old one and the second has your changes. I have some questions.

How many bits are you using?
What is the measured diameter of those bits?
What tool number is assigned to each bit?

[frank134]

One bit
Size .248
My son noticed that after the bot cut the dado . It stop. When I tell it to continue it ask if tool number 3 is zero. I never notice that before. When we check for tool number three there wasn't one put in. so we added number 3 and set it to .248. Then when we got the same offset but not as deep and at the other the offset it was reverse. By the way when it start beginning it start with tool number 2 also set to .248.

[ken_rychlik]

If you are tool changing, having bit #3 could be an issue.

Change your bit number to 11. For single spindle machines, use bit numbers 11 thru 19.
Then make sure bit number 11 is set to do all the cuts you desire for it.
When you select rout/dado, you can choose to have the same tool cut that as well as the outline cuts.

Then make sure and delete any other bits that may be in there.

It should not ask for tool changes anymore mid file after that if you have the same bit number set for all cuts and drills.

There are LOTS of settings that cause wierd machine behavior if you don't understand and set them correctly.

It does sound like you are making progress and getting closer.

[Gary Campbell]

Kenneth...
The SB MTC files allow tool numbers from 1 to 19 for head 1, so Franks tool #3 is OK.

Frank...
I am sending you your file back. When you recieve it, press the import button and select the file I send. This will install tools and speeds that should work well, but are a little slower than your existing settings. Do a test and see if the tenons cut better.

[frank134]

thank gary. I will wait for your files. I will admit I am still have trouble with tool and setting. I thought I only had one tool install as number 11 and one drill bit as number 31. I don't know why the program ask for the second bit and call it number 3 when I didn't even have anything set up in 3.
but I will wait for your file.

[ken_rychlik]

Gary, Mine wouldn't fly with the low number tools, but that was a while back.

I remember kicking and screaming over it. lol

Did something get changed with that?

I'm still waiting for flip op pockets to cut conventional instead of backwards. I guess we are to small of fish to get attention.

[Gary Campbell]

Kenneth...
Stop pouting and just go change the file. Should be a line that says something like: "IF &tool < 11 THEN GOTO TOOL_ERROR " change the 11 to 1. Now you can use any tool number down to 1 :)

[ken_rychlik]

No problems Gary. I was just passing along the trouble that I had. Even if it was created by you.????:D

[frank134]

Gary….
I want to say thank you. I got the file back I sent you for E-cabinet. It how cut the blind tenon out
Perfect. I see you had some change in my shopbot link. I guess I own you another one. If it wasn’t for you guys on this site. I think shop would be getting a lot of return e-cabinet. Though e-cabinet did return my email asking for the files a little late.
Again Thank
Gary

[Gary Campbell]

Frank...
No problem. Glad I could help. There are a few little "tweaks" in that import file that hopefully will keep you cutting better parts.