Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: JohnM34 on August 09, 2014, 06:50:56 PM
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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.
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Any pics of the cut? Are you just looking for better cut quality?
What kind of machine?
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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.
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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.
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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.
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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
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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.
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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!
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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.
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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.
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Gerry’s comments are sage; however, I encourage that you not toss in he towel just yet.
When I shopped for a project specific router I looked at a machine that appeared to identical to the one you have. That is, the same appearance, color, size, and configuration. It was used by the then owner to machine plastics. The parts that I saw coming from the machine were just fine.
I did not buy the machine and a several months later I continued my search. During the search I stumbled upon the same machine at its new owner’s shop and he too was machining plastic with excellent results.
Certainly the seller of the machine has a vested interest in not accepting fault on behalf of the machine. But, the seller also has a vested interest in your machine performing as it was designed.
As I said before, just as Gerry noted, rigidity is key, but don’t get caught up in how much you can move a static machine by leaning on it. And keep in mind that the part/material shown in your supplied photo can be machined with excellent results using fixtures and a handheld router. Is your machine less than a fixture and handheld router?
I am very new to Mach but not to PC based controllers. I am not yet persuaded that the computer is your issue, but I can positively tell you that a computer can make difference with other control software. Although Mach seems to have addressed those issues, I would listen somewhat to your manufacturer’s rep.
I assume your machine has a centerline drive? I have a small router that has a centerline drive. When we set it up 15 years ago I believed that it would never work properly/accurately. I set up the old dial indicators and leaned on the gantry. Yep the old dials starter to spin. Well, 15 years later the machine will hold about ½ thousandth. The tool defection is greater than that.
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That's the problem right now. I used to do all this same stuff by hand with jigs and got stellar results. Just takes to long and I can't keep up which is why I bought a machine. If it was an intermittent problem I can possibly understand the computer issue as far as an inconsistency in pulse. It appears that there is extreme vibration though. It seems to be in the machine though not the work piece. I have clamped screwed and glued pieces down and gotten the same results. I have tried different bits, spindle speeds, and feed rates with no change. The y axis isn't bad but the x is horrible which is why I am leaning toward machine. I would think if it was software or computer related it would be on all axis not just consistently on one of them. Rigidity is the only thing I can think of at this point.
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Oh my! I sent you an email, hopefully you can respond.
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If you just jog the X axis back and forth, without cutting are you getting the extreme vibration? If so, then you need to get rid of that. It sounds like a mechanical issue, perhaps due to rack and pinion alignment.
Yes, while rigidity is very important, it's also possible to get good results with poor rigidity.
On my wood machine, with skate bearings, I can push and pull the spindle about 1/8" of an inch, and yet I can get much better cuts than you are getting.
I seriously doubt that it's a software issue, but anythings possible. For it to be software, you'd see really horrendous movement, very rough and jerky.
Also, go back and try my suggestions earlier, about climb cutting, and making a finishing pass.
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As I keep bracing it is improving. Before jogging around was creating a very loud vibration and just turning on the spindle would cause everything to vibrate. Now I can barely hear it jogging around or the spindle running. Even at 24k rpm its extremely quiet. Hopefully eliminating this vibration will have a positive effect on the cutting as well
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What type of router motor does your machine have? You say that the "vibration" starts when the router spindle is turned on????. If yes, then you have a balance issue. Tightening or bracing everything does not solve the problem, it only makes it less noticeable.
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Some water cooled 3 HP china motor. I don"t think it's the motor. I have done fine line engraving that has come out perfect. I would think it wouldn't if there was an issue with a balance issue in the motor. I only have a problem when the machine is under a load from actually cutting material which keeps taking me back to a flex issue in the structure
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I am surprised that a decent part can't be produced following Gerry's advice. I have a similar spindle and it performs as well as our high buck spindles. But keep in mind that engraving does not product the same spindle load. If by chance you have a bad spindle the heavier load my induce the vibration.
As I noted earlier, we use a strobe to troubleshoot chatter issues. It really removes much of the speculation 90% of the time.
Did you visit a happy owner nearby before you selected your machine? Perhaps they would run a part for you to compare. Or did you get a demo from the seller?
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1. With the spindle / router not running, when you jog, do you get vibration? One axis at a time for now!
if yes,
1A. Is the vibration constant when jogging, ie; jog the full travel length, and when jogging does it change when at say the start, 1/4 of travel,1/2 of travel?
2A. Do the same as in 1A, but at three rates of velocity, say low, medium, high , and max velocity. Is the vibration constant or changing?
Reply the best you can to the above,
BTW, Can you post a pic of the machine since the Industrial CNC Site didn't show one.
RICH