CNC lathing

[bandsawgal]

Hi Andy, I have been learning a lot from Ralph (Handi) as I continue to operate the CNC. This is great and Ralph has been more helpful to me than you can imagine!! Thanks for letting this thread run on so I can get over the initial bumps of handling this type of machinery safely. THIS SITE IS GREAT!
Bandsawgal

[bandsawgal]

Hi Ralph, Well I think if you check the thread out, you'll see that I have practically written a book here on CNC operation questions..lol
I worked on the CNC on Friday and cut full length boards for the first time. The vacuum pressure was pretty low so I thought I should ask what is the appropriate level (for safety reasons). I know whereinabouts it should be, but the question would be, "How low can you go before you know definitely that it is not safe">?
My boss seems to feel that if the board is larger it should be okay with less vacuum pressure as long as the spindle speed is lower? Is this accurate? After all the board did not move but the gauge was quite low. (Actually I should write down the readings for it to give you a better idea eh?)
I'm going to have to start calling you Professor CNC soon!)
Hope your weekend is nice. I'm having server problems here so its hard to connect lately until they fix their dilemma (so don't think I've disappeared as I would hate to miss any of your messages !!!
Bandsawgal

[handi]

Bandsawgal,

Your boss is mostly right. The holding power is directly a function of square inches. The larger the part, the more vacuum area is "weighing" it down. So even if you are only drawing 2 pounds per square inch, a 24 x 48 panel would have 1152 square inches of holding area for a total holding power of 2304 pounds!

You said he wants to keep the spindle speed down. Just to keep terms clear, "spindle speed" is generally used to describe the RPM that the spindle is turning. "Feed speed" is how fast the head is moving during a cut. When you are not confident in the holding power, keep the RPM (spindle speed)higher, and reduce the feed speed.

As far as the vacuum gauge readings go, I'm not sure what to tell you. What does your gauge read? Inches of Mercury? Centimeters of Water? There are several gauges. Your best bet is to keep close track of what does and does not hold well, and soon you will know by looking if it will hold.

Lastly, are you using spiral tooling (bits) yet? A good downshear spiral will reduce the side pressure of the cut, (the tendency to push the board)and press the board down onto the table, improving the holding action.

Hope this helps,

Ralph

[bandsawgal]

Hi Ralph, Thanks for clearing up the difference between spindle speed and feed speed. I will have to get a handle on all the terminology!!
I worked on the CNC a lot this week and I had a great time. I even followed your instructions when I (gulp) accidentally tripped the safety during a cutting process.
My boss is happy that I have progressed so well on the machine considering that I have had little instruction from anyone there. I, of course, immediately explained that it was due to "Ralph's expertise"..lol (They think its something like Murphy's law in reverse...)
Anyway, I am going on vacation tomorrow, FINALLY for two weeks (well deserved) so I will not be on line.. I sincerely hope though, that you are around when I come back as you have been a total life-saver and I'd hate to miss hearing from you.
So before I go, I'd like to offer you the award for
"Best thread coping with woodworking female in CNC distress"
Thanks Ralph... hope to talk to you again in a few weeks.
ps. good luck with the article in Woodworker's Journal, I'm sure it will be great!
Bandsawgal

[handi]

Bandsawgal,

Enjoy your vacation, when you get back all rested, we'll see if we can't get you a raise

I spent today fixturing and programming a 5 part wood cabinet door cut out on the 3 axis CNC... takes about 5 minutes from rough blanks (sized for thickness only) to finished door ready to assemble. Lots of fun!

Ralph

[bandsawgal]

Hi Ralph! I'm back (the pesky Bandsawgal is back)Now I think I'll take you up on that offer to get a raise.. lol..(you are a sweetheart)...
I have been running the CNC for the past 3 days this week.
All seems to be going well with the exception of some operator messages (alarms!) that keep popping up as the program runs.
I suppose that is something to do with an error in the parameters of the program itself? Oddly enough the program will continue to run okay even with the alarm??
I wanted desperately to get my paws on the operators manual during my vacation time to learn the programming language of this machine, but I couldn't.
Heres a question though,...
When the wood moves (due to inappropriate vacuum suction) and I shut the program down asap.. why does the bit continue to spin?
Now I doubt if I am using the right wording for everything(I imagine you are gasping right now at my pathetic attempt to sound like I know what I am talking about but I hope you get the idea here. I seem to have problems shutting the spindle?/bit? down during these events and it usually takes several tries before the machine responds.
What is the exact procedure Ralph should I need to stop the program quickly from running and return it to home to set for my next cuts on fresh plywood?
Also, my boss just passed me a CD on another CNC router that uses rollers not vacuums to hold down the plywood. He seems to want my opinion on it and since I've never seen one operate, I'd love to know which one you prefer overall? vacuum versus rollers? and why? Also, have you ever been to the Woodworking show in Toronto, usually in October? I heard it was big.
BTW...Vacation time was NOT long enough ... lol..
I know, I'm back 5 minutes and already I have talked you to death lol...
Have a nice day in the shop.
Bandsawgal

[handi]

Bandsawgal,

Welcome back.

First, what are you doing to stop the program? Is there a pause button? Hitting the E-stop would shut everything down, but then you'll need to reboot and re-home the machine. Let me know what you are trying to stop the program run.

Second, rollers are old technology. They do assist in keeping parts down, but tend to be cumbersome and can mar the surface of the part. Vacuum is really the best way, what you really need is a better pump. If you look around, you should be able to get a good used pump for around $5,000.00. It will make a world of difference. You want at least 5hp and 100 CFM or better. Check the used equipment listings at www.woodweb.com or go to woodworkingpro.com.

Hope this helps,

Ralph

[bandsawgal]

Hi Ralph! Sorry to take so long to get back to you but I have this horrible relentless cold/fever at the moment. One of the guys at work went fishing in near frigid temps over the vacation and brought it back as a gift to others in the mill, (with me being the lucky recipient)..lol..(cough)Please excuse any spellings errors as I am under the influence of cough medicine..
ANyhow, the CNC is a Fanuc, Stratos Series and if you are familiar with the older technology, (which I'm sure it is)(NO PAUSES JUST RESET ALL THE TIME?, then there are the 3 buttons down the lower right side... red (stop)green (to make the machine operate) and blue for reset.
We were instructed to shut the red button down if the plywood moved.. then moving to the left side is two buttons (red and green) for the bit. We are then instructed to push the red to stop the spin. I find it does not work. Am I making sense here?
I have to home the machine (using Z axis first of course) then when it is homed the red (stop) button finally works??? Shouldn't it work immediately??..
Now for the even bigger news.. My boss has the idea to go out and get the roller s to adapt them to the machine that we have!!!
(somehow).. !!!?
Since we work in 95% plywood, he seems to think it will be better than the terrible vacuum problem we've have previously..
WHAT SHOULD i DO RALPH!!! Since you are my saviour here truly with respects to CNC operations I am concerned now that he will go spend money needlessly on something that provides little less than what we have gotten from the vacuum!!!! this could be the raise aspect ... lol ,,, if i get it right.. Really though, I don't want to steer my boss wrong on this issue as he's a great boss but has difficulty understanding information in English as his mother tongue is French (though that has clearly never prevented him from learning about anything) . I want to help his business if I can in my own way but I surely don't want to misinform him and make him nervous of future investments.
What did you mean about the marring of the the part? Please explain. Also do you think he could adapt a Fanuc with a roller system and also utilize a vacuum system at the same time?
Has anyone done it before?
Okay, I'd better go to bed now before I exhaust you with my (medicine induced) ramblings...
One last thing though, I subscribed to the W.Journal today
Once I see that magazine, I'll probably have endless questions for you.. lol... (
Thanx Ralph
Have a good day tomorrow in the shop
Bandsawgal

[handi]

Bandsawgal,

I'll ask a friend of mine who is very familiar with the fanuc controller to see what he says about pausing.

As for the rollers, imagine a rolling pin rolling out dough...as you are rolling, you drop some cracker crumbs onto the top of the dough. The dough is no longer nice and smooth where the roller drove the crumbs into the dough. The same risk is run using rollers on plywood. Any chips that get spread over the plywood then rolled over by the rollers will tend to be pressed into the face layer of the plywood, leaving dents and/or scratches that then will need to be sanded out or something.

Really, the solution is to improve your vacuum situation. The ideal is to get a more powerful pump. Short of that, make sure that your vacuum board is LDF instead of MDF (light density fiberboard instead of meduim density fiberboard) Also, if you are currenty using 3/4" vacuum board, try switching to 1/2" or even 1/4" if you can get it. Thinner boards will allow for better vacuum. Also, seal the edges of your vacuum board to minimize air loss out the sides. Make sure that your gasket under the board is in good shape. If you regularly cover the back part of the table to increase vacuum on the front, (when you are not using the back)try running a strip of gasket across the bed under the vacuum board to separate the table into two "zones" Check the entire vacuum piping system, and be VERY sure that you have no leaks. Seal all of the couplings and joints with duct tape to insure that you are not loosing anything.

Lastly, Try cutting your parts in two passes. If you cut everything out but not all the way through (leave about .020" behind) then repeat the whole path cutting all the way through, you will virtually eliminate the movement of the board. By leaving the board "whole" on the lower face, from a vacuum standpoint it is the same as not cutting through. Then the second pass, since it is only cutting .020" of material, exerts very little side pressure on the parts, which will reduce part movement. If you are using standard straight cutting bits, I strongly suggest that you try out spiral tooling. The spiral bits slice more than chip, which also reduces the side pressure that is moving your part.

Hope this helps,

Ralph

[bandsawgal]

Yes thanx Ralph. As usual you have been super helpful.
I just figure that the bit should stop automatically before you home the machine but I guess there is a reason why not.
My boss is using LDF at the moment and we've managed quite well to seal off any areas that might lower the suction although I'm going to follow up with your advice.
My boss will be getting a second vacuum system this fall. He is looking into the rollers too (but only as a modification to this machine as far as I know.) Perhaps he won't need to after all when the new vacuum is added.
Anyhow this week I'll be on the bandsaw mostly as we've got a
lot of smaller hardwood pieces to cut. I cut all the weird and unique shapes..lol.
Well have yourself a good day in the shop.
Bandsawgal