On the edge of material being too thick....

[Chuck Keysor]

Hello again. Here is a curious problem.....

I have a PRT alpha, 5' by 12' bed, with a 5HP Columbo spindle.

Cutting a new piece of my railing stock, had 2" thick stock mounted on a .7" thick board, all secured and ready to go. After zeroing the x and y axis on the corner of my stock, I zeroed the long (5 inches?) 1/2 endmill onto the top of my stock. As usual, after the C2 operation, the z axis read out said the bit was at Z= 1". I loaded the cut file, and as soon as I ran it, I had to jump on the STOP button, as my bit was not making a .25" deep cut, but a .75" cut. Before I hit stop, the bit had plowed a 3 foot long groove that was well below the finished height of the part. (I guess I'll have to patch that with Bondo....:().

So I couldn't figure out what had happened. I started all over, and created a new cut file, and verified my roughing pass depth was .25". I went back in the shop, and re-zeroed x & y, then re-zeroed Z with the C2 routine. When that was done, the read out said the bit was 1" above the top of the material, but I looked, and it wasn't! It was only 1/2" above the material. As I scratched my head, the #4 control panel LED began to flash red....

After looking, it seems as though I am the hair edge of having my stock be of such a thickness (2 inch thick stock mounted on a .7" thick sled). With my long endmill mounted up as high in the collet as it will go, there is about 2.7" of endmill sticking down below the collet. On playing with the router on the z carriage with the power off, it looks as though I am right at the physical maximum height of what I can cut, or actually just a bit past it.

a) I wonder why my Bot told me I had a z clearance of 1" inch, when I only had 1/2", and why it proceeded on, to mess up my part, instead of blinking a light and locking me out????

b) Since I don't have a slightly shorter 1/2" end mill, I can't put in a shorter one that will still work to get through my 2" thick material.

c) Can I simply change the z-retract height to be something like 1/2 inch instead of 1 inch? Will that get me out of the woods, or will I simply run into something else that will get me?

d) If choice c is the right one, how do I change the Z-retract? I know I should try to figure that out, but I find some consolation in having a problem that someone else can learn from, and that someone else can help with.....

Thanks, Chuck

[ron_moorehead]

I have had to do the same thing in the past when I had a project that was really thick and to long of router bit. you can find the file my_variables.sbc under the custom folder in the SbParts folder on your computer. Look for the following entry in the file. Change the value for "&my_ZzeroSafeZ=" to something like 0.25 that should give you the clearance to move safely over your part.


' these values are used in the ZZero routine
&my_hasZzero=1
&my_ZzeroThickness=0.125
&my_ZzeroInput=1
&my_ZzeroSafeZ=0.5

[Chuck Keysor]

Thanks Ron! I'm going to go down to the basement now, and turn on my Bot.

Your suggestion is just in the nick of time. A friend of mine, who is a traditional woodworker is telling me to just make these parts by hand, and has offered to come and help me do it....... Thanks, Chuck

[Chuck Keysor]

Hello Ron.... Good news and bad news......

a) Good news, I changed the value you said, and after doing the C2 zeroing procedure, my bit was sitting at .25" above my stock! Thanks!

b) Bad news,,,,, I loaded the part file and said start, and I got an error message I have never seen before:
Parameter Error
Parameter Value Below Range for VS-
Setting to Lower Limit (.05)!

I completely shut down SB3 and my SB Control box. I restarted them, did a new C2/z zero, loaded the part file, and I got the exact same error message.

And, I then did it all over again, just to make sure, and got the same results.

What do I do now??? Any suggestions welcome, thanks, Chuck

[adrianm]

Is this a part file generated from PartWorks/Aspire?

Sounds like you've selected the wrong feed rate unit for the tool in the database such as inches per min rather than inches per second.

[Chuck Keysor]

Hello Adrian! I generated this part in Aspire 4. It is the first file I have made in Aspire 4 actually, so there is all too high a probability I have messed this up in the set-up. I did the same thing when I first set up Aspire 3!

Thanks, I'll check that right now..... (I was working on my other reply to you, but I had to go back to Rhino to check my original model height, and I got a notice from Rhino to install a new update,,,, and now I am messing with that!)

Are you by any chance with Vectric, (as I see you are from the UK)?

Thanks, Chuck

[adrianm]

I'm not employed by Vectric but I'm one of the beta testers so I tend to jump in on the Vectric type questions when I see them.

[Chuck Keysor]

Hello Adrian. Hmmm, I just checked, and my file is in fact set up to cut at 5inches per second at 12,000 RPM, plunge of .5 I am cutting pine with a half inch endmill.

I looked at the roughing toolpath window, and then looked at the tool database settings to see my speeds and feeds.

Where else could I have messed up the affected VS parameter? Thanks, Chuck

[ron_moorehead]

Copy the first 20 lines of the shopbot cut file your having problems with and post it to the forum here so we can look it over.

[Chuck Keysor]

Ron, I just came up from the basement, and need to give an update....

I noted in the Aspire toolpath material set-up window, there was a retract height shown, and I think it was set for .5 inches, but it wasn't equal to the .25 value I had set in my z retract height in SB3. Maybe these aren't even related, but I changed the Aspire value to .25" and I reloaded my cut file. This time, it started to run, though because my confidence at this point is low, I may have bumbled into something else without even knowing it that let the file run this time.

Anyway, after maybe 25 minutes of cutting, the roughing pass looked like it was almost done. But while the gantry was moving, and over the middle of the part, but the bit was clear of material so not cutting, the spindle turned off. I went and looked at my monitor, and there was a message saying my stop button had been activated. Well, it hadn't been. I looked at it, pulled it, it was not depressed, and I had put it down after the first 10 minutes when it seemed everything was going safely.

So I figured it was a fluke, and my coordinates were still good. I reloaded my part file and told it to go again, figuring I'd watch a lot of air cutting. Well, in the second pass, it was clear that something was out of alignment, as I was suddenly cutting into wood, and not air! Right now, my confidence is near zero, and I have taken maybe two days to make nothing but a bunch of wood chips........ Though since I try to be positive, at least I haven't broken any bits.

Chuck