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Please Help!!
« on: August 09, 2014, 06:50:56 PM »
Hey guys I really need help. I have been at this for 6 days now with no luck. I have a brand new 4 X 4 cnc router. I am getting chatter on my cuts and I can't seem to solve the problem. I am not sure if it is settings in mach 3 or if it is something with the machine. I am cutting 1/2 inch HDPE. I am using the manufacturers recommended bit, and I have used the g wizard feed and speed calculator to determine bit deflection with still no luck. I am losing so much money and need to get this machine up and running. The manufacturer hasn't been much help. They have had me do a bunch of stuff over the phone which hasn't fixed th problem and they are saying the machine might have to be sent back which isn't an option. I am attaching my XML. Any help would be appreciated.

Offline ger21

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Re: Please Help!!
« Reply #1 on: August 09, 2014, 08:49:20 PM »
Any pics of the cut? Are you just looking for better cut quality?
What kind of machine?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Please Help!!
« Reply #2 on: August 09, 2014, 09:05:04 PM »
The machine is from a company called Industrial CNC. it is the Apprentice 404 model. Yes better cut quality. The edges currently aren't up to the standards my customers expect. Also I am using an Onsrud  63-781 which is a single flute spiral upcut O flute. 3/8 cut dia, 3/8 shank, 3/4 flute length, 3 OAL currently running about 18k at 35 ipm. I have done about 60 test cuts at all differendt feed rates and spindle speeds and this is yielding the best result so far.

Offline ger21

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Re: Please Help!!
« Reply #3 on: August 09, 2014, 11:21:28 PM »
Looks like you've got some flex in your machine somewhere.

I'd try about 70ipm, at 15000 rpm. Climb cut, leaving about .02 for a finish pass, also climb cut.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline Tweakie.CNC

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Re: Please Help!!
« Reply #4 on: August 10, 2014, 05:09:10 AM »
Hi John,

Strange one this...
HDPE normally cuts like butter with excellent surface finish even without using a specialist cutter.
My guess is that you have a mechanical issue with your machine where something is loose (perhaps loosened in transit).
I would be inclined to first check that the spindle motor is firmly attached and everything there is sound then check the grub screws locking the drive components for the X and Y axes and finally check (by trying to move by hand) there is no backlash (slack) in any of the axes.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Please Help!!
« Reply #5 on: August 10, 2014, 09:18:11 AM »
This feature of your machine may be in need of better adjustment if possible (X/Y Anti backlash Rack and Pinion).  Run a good backlash test to see if there is any looseness.  The machine is listed with X,Y,Z, Traveling Position Accuracy of +/- .002", which seems rather "loose" to me.
John Champlain

Offline c30232

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Re: Please Help!!
« Reply #6 on: August 10, 2014, 04:14:35 PM »
John,

I am not a router guru, however, I do have substantial experience in the high speed machining of wood, wood composites, and some plastics.  The issues/problems are same as with a router.  I also own a few routers one of which, that by its photo, is the same or very similar to yours.  We did purchase the machine used, thus I cannot compare it to a new one or your exact machine.  That being said, we have discovered/confirmed that a rail set on one axis is not exactly parallel and that seems to induce chatter.  Rigidity is key and our machine, 4 x 8, is lacking in that department.  I have not experienced anything I would attribute to backlash.

Does your part have chatter on all sides?  If yes, then I would explore movement in the part.  I am currently machining .125 aluminium with reasonable results.  We also, use a strobe to troubleshoot our other types of tooling.  It is more difficult on a router because of the short linear movements, however, you can see tool deflection, spindle movement, chip load, and so on.

Again, check your hold down.    

Re: Please Help!!
« Reply #7 on: August 11, 2014, 08:20:59 AM »
Thanks guys. I am leaning toward machine flex. All the steel on this machine has no corner braces. For example where the spindle is mounted is a vertical 3/4 inch steel plate and then a horizontal 3/4 inch steel plate bolted together creating an "L" shape. Now i am no professional as far as cnc machines go but I have been in the building and construction industry all my life. Basically it doesn't matter how thick the steel is the only support you are getting is from the bolts. The gantry is the same. There are just vertical 1 inch steel plates bolted to the gantry beam. With me putting a very small amount of pressure on it I can cause it to flex. I would think a precision machine should be a little sturdier than that. I am going to try adding some corer braces and I will update. Unfortunately I am just going to have to bolt them in right now due to my small mig not being able to weld steel that thick but I am sure if that is the cause I should see some improvement and if so I will have some strong and thick gusset plates welded in. Any thoughts on this would be great. Thanks again!

Offline ger21

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Re: Please Help!!
« Reply #8 on: August 11, 2014, 10:09:02 AM »
Looks like that machine also uses round supported rails? Those are not the most rigid, either, as they typically have a bit of play in them.
I'd start at the spindle, and start reinforcing every place you can find movement. If you grab the collet of the spindle, and push and pull with a decent amount of force, you shouldn't see any movement at all, if you want good quality cuts.

Unfortunately, most of these lower cost machines are just not that good, and the claims of the manufacturers or often rather "optimistic". A decent ready to run 4x4 machine will typically start in the $10K-$12K range.
You get what you pay for.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Please Help!!
« Reply #9 on: August 11, 2014, 10:13:04 AM »
I paid 10,500 + shipping, + computer + software, etc, etc for this one. I figured I was getting a decent machine but apparently not. The manufacturer is saying it might be my computer not giving a consistent pulse stream. I find it hard to believe that its not mechanical though considering one axis is way worse than the other.