Tabbing question... I think...

[mike79070]

Ok so i recently purchased a PRS Standard 96-48-6. What i am trying to do at the moment i consider a basic task of cutting masking out of sheets of cpvc. The masking is used for our wet-spray paint appication. A basic 6" Square piece of material with a 5.05" circle cut out of the center and .25" thick. Also having 3 tabs per vector at 0.03" thick and 0.3" in length with no 3d.... I currently use the zero plate on the top of the material to be cut....

The problem i am experiecing is that i cannot seem to get the tabbing correct. In one place on the table it may cut the exact depth i told it to and the tabs come out perfect but move three vectors down and it completly cuts through the tabs and into the table slightly. Now move three more vectors down and it doesn't even cut through the dang material! It seems to me that corner 4 normally does just as told but along corner 1 on x axis doesn't cut all the way through. In between 1 and 4 on y axis grooves the table.

I have made sure bit was tightened, surfaced the 2nd layer of plywood a total of 0.06" and installed a 1" sheet of mdf for the spoilboard that was surfaced0.03".

Are my tabs just to thin?
Is the suface not good enough? Do i need to surface both sides of mdf?
Maybe the operator needs to be shot in the freaking head? (not really cause thats me!!)

Any advice is greatly appreciated!!

From your nieghborhood amature.... lol

[Gary Campbell]

Mike...
Are you using vacuum hold down?
Is your spoilboard glued down?
When your parts are removed are the "bit tracks" in the spoilboard the same depth?

[Brady Watson]

Are you using vacuum hold down?
Is your spoilboard glued down?
When your parts are removed are the "bit tracks" in the spoilboard the same depth?

All very good questions...

-B

[dlcw]

Mike - are you taking 1 or 2 passes to do your cutout?

I've found that if my 1st cut is say .65" in a .75" thick piece of material and I do tabs the tabs remain from the 1st cut. On my second pass if I start at .65" and do tabs, sometimes the tabs remain and other times I've had the tabs removed on the 2nd pass.

Not sure why this is the case, but it happens.

[chiloquinruss]

How are you holding the material down? Also have you tried running with the dust collector turned off. I have had problems similar to yours and my solution was to turn off my dust collector. Seems the collector was pulling the material up into the cutter. Russ

[jerry_stanek]

when did you surface the MDF if it was more than a couple of days it could be that it is swelling.

[mike79070]

@ Gary

We do not have a vacuum hold down system on our Bot. We currently use low profile clamps to hold down the material being cut.

My spoiboard is secured with drywall screws. They are placed about 1 foot apart throughout the entire spoiboard and countersunk about 5/8". This is the same method i used to secure the 2nd layer of plywood.

I do not remember if the Bit tracks were the same depth but i will verify today and repost what i see...

@ Don,Russ and Jerry

I am using 2 passes for my 0.25" material, 0.125" per pass. The dust collection is a shop vac mounted to the top of the machine. The spoilboard was surfaced the day before use.

I am going to try to resurface spoiboard and z zero off the table surface to see what happens..


Thanx to all!!

[Gary Campbell]

Mike...
I think the bit track depth will answer your question. Check various locations.

If all are consistant, then you most likely have a hold down issue.

IF not, then you may have a bowed/warped spoilboard. This may be caused by humidity changes or your hold down.

If inconsistant, I would recommend glueing down the spoilboard, place weight to ensure bond, and surface the next day. Screws may seem easy, but often return not so good results when cutting depth critical parts.

[mike79070]

First i want to say thanx to everyone that chimed in!!


So here is where i'm at and what i did since last posting..

1) Changed bit out. ( not sure if this had anything to do with it )

2) Re surfaced spoilboard and started cutting material immediately. (Previously i had surfaced the spoilboard and waited until the next day to cut. I didn't think that it would have swelled up in that amount of time, but wanted to eliminate it from the scenario.)

3) Z zero from the spoilboard instead of the top of the pvc i was cutting. ( Did this to eliminate variations in thickness of the pvc. Not sure if there were any. )

4) Added additional clamps to hold material securely. ( After seeing the concerns about the hold down system. )


I would like to note that i like the table z zero better because i was able to stick a 0.06" sheet of magnet to the top side of the pvc and cut both at the same time without having to change any setting.

Also i will add that at this point i have only cut along the first 16" of the y axis between corners 4 and 1. Once i havecut toward the center of the table i should be able to tell if the hold down had more to do with the problem or if the other variables were the culprit...


Again thanx to all! Your advice got me where i'm at!!

[Gary Campbell]

Mike...
Good job! Glad you are working. I have found very few cases where zero to the top of material is better than the spoilboard. Many cases the same, but spoilboard usually proves to be better in the long run.

"I didn't think that it would have swelled up in that amount of time, but wanted to eliminate it from the scenario."

I have seen .040 to .050 changes in an hour. This was exagerated by the use of vacuum, which pulls a lot of air thru the spoilboard