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Old Jun 08, 2014, 07:33 PM
AvB
Wind, hill, ... I'm keen ...
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Australia, QLD, Woody Point
Joined Nov 2006
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Well, some success ...

Gerry had a look at some files and couldn't see any problems, but he did suggest to try turning off the toolpath display before running the cycle. Apparently with large 3D files, Mach3's toolpath display uses a lot of screen resources, especiall with the widescreen 2010 Screensets. (which I'm using). He said it's OK to leave the toolpath on while you load files, just turn it off before you run the file.

I did this just now, and it's finishing off the cut no problems at all.

One thing is it's interesting how much the Z zero changes as the machine warms up. It still had the offsets saved from yesterday and when I ran it, the cut was a bit higher than where it left off. So I kept adding a poofteenth of a mm to the zero height until it started to cut at the right level. It helps to draw marks with a felt marker so you can see where it's cutting.

It's a bit noisy actually. I could only get the radiused endmills in 3 flute, not 2 (2flutes are better for plasticky materials). I don't think it's giving as good a finish as I got with the 4mm flat endmill doing the Angry Bird stabilizer, so I might switch back to that for the next side.
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Old Jun 08, 2014, 10:17 PM
AvB
Wind, hill, ... I'm keen ...
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I swapped to a 6mm flat endmill to cut the second half. As you'd imagine, it's a bit scary changing bits in the middle of a big smooth wing shape, but with a bit of clever trickery it has cut at the exact same level, perfectly!

But the other amazing thing is that like Mike says, the larger sharp square ended endmill gives such an excellent cut. Not just better, it's incredibly better. The first half done with the 4mm dia, 1mm cnr radiused endmill is good, but ridgy and needs a fair bit of finishing. But the second half cut done with a 6mm endmill and .5mm stepover honestly looks so polished it doesn't look like it needs any sanding at all! And a really lovely sharp lip! So much so that I think I'll run the same cutter back over the first half! I'd rather have the machine run an extra 2 hours than do an extra 2 hours of sanding!

I'm being tricky with this second side too, and have set the cut to stop before the tip, so that the parallel X cuts don't continue up where the wing shape starts to curve back. I've drawn a boundary over the tip area (no finesse required for this -really quick line draw in Rhino, and select as boundary) and created a separate cut, running parallel to Y. Then I've made another cut which pencils around the edges, to catch any corners missed.

There are always mysterious glitches.

Firstly when I ran the finish cut this morning it moved to the start spot and just shut down. Oh-oh. Rezero Z, check all, and couldn't find any probs so restarted and it ran without a hitch. Weird.

Then it ran super slow, and I found the G-code for the cut had a really slow feedrate (F500) repeated all through the file. I tried to regenerate it with Rhino/ Madcam and same problem. I deleted the cutter from the library, (although its speed settings looked fine) and replaced it and remade the toolpath, and this time it was OK.

Too much inexplicable mystery for me!
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Old Jun 08, 2014, 10:20 PM
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Wow great news Andrew , well done.
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Old Jun 08, 2014, 10:51 PM
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For me:

Anything computerish = ????????????????
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Old Jun 09, 2014, 04:52 AM
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+1!
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Old Jun 09, 2014, 05:25 AM
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This is good news Andrew - progress indeed. There is always a reason for the inexplicable glitches and, in my experience, nearly always down to human intervention The most common fault not associated with said humans is that of EMF or electrical noise. I suffered from this, sorry, my machine suffered from this, when I first got my water cooled spindle. It manifested itself by very small missed steps on one of the axes - so small that it was not evident till the end of the run when re-zeroing the machine. It took me ages to track it down. It does not sound like you are having this problem but oddities will happen now and again.

Instead of re-running the toolpath program, to change the feedrate, I just load the program into notepad or wordpad and do a find and replace. You have to make sure that you give the whole, Gcode word or you may replace things you didn't want to. In your case you could have searched for F500 and replaced with F1500 or whatever. If it was a single cutter program, this is much quicker.

Glad to hear the end mill works for you.
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Old Jun 09, 2014, 05:48 AM
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Sounds good Andrew, your starting to learn the black art of BS'ing the machine, I agree with Mike you'd want to track down whats causing the issues so you don't come home to a spoiled mould.

Keep up the good work.
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Old Jun 09, 2014, 05:31 PM
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Quote:
Originally Posted by AvB View Post
But the other amazing thing is that like Mike says, the larger sharp square ended endmill gives such an excellent cut. Not just better, it's incredibly better. The first half done with the 4mm dia, 1mm cnr radiused endmill is good, but ridgy and needs a fair bit of finishing. But the second half cut done with a 6mm endmill and .5mm stepover honestly looks so polished it doesn't look like it needs any sanding at all! And a really lovely sharp lip! So much so that I think I'll run the same cutter back over the first half! I'd rather have the machine run an extra 2 hours than do an extra 2 hours of sanding!
Does a flat endmill really give better results than a ball nose when milling molds? That's very interesting.
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Last edited by martig; Jun 10, 2014 at 12:52 PM.
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Old Jun 09, 2014, 05:50 PM
Where is the inspiration
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Moira
Joined Feb 2006
825 Posts
Good News Andrew.
I guess finding this answers another question I asked eailer today (What after the Angry Bird)
Any pictures?
Are you sealing your MDF used to back your corian?
you could have some movement in the hotbox, or after time as the MDF changes its moisture content.

I will be very interested to how this progresses.

Re CNC, its like driving a car. When you learnt you had to think about every gear change stearing....... and now you can do it while talking on the phone, whilst holding a coffee between your legs. It will all become second nature once you have the process.
Maybe a phrase that helps remind you of all the checks to do before hitting go?

l also had a good laugh about the farting / scratching your balls statement. I thought it was only me.
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Old Jun 09, 2014, 06:58 PM
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Joined Oct 2004
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I have had my veloxcnc for 2 years, once i figured out the mach program, 2 d cutting is a piece of cake, 3d modeling is the only thing holding me back right now, Once you learn to cut all your
friends control horns out and multicopters for all of them you will start wanting to find a program that someone in your collaborative team also models in, this will help you the most.

Then they can utilize your machine with their programs, work projects out for you and you can also learn. If you buy a reasonable program that none of your friends have, the learning curve is much steeper.

That is my hang up, my friends all have solidworks and mastercam.

I experienced the same hang up as you with getting things done, and spent a lot of money on molds, by the time i got them the interest was not there anymore in the project.

When you have the tools to do the job, it wil cause you to learn the process.

good luck, Doug.
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Old Jun 14, 2014, 08:08 AM
AvB
Wind, hill, ... I'm keen ...
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Just an update ... too busy to look at it during the week, but I got back into it this morning. All going well, then I created a small toolpath within a boundary, something I'd done a few times before , and didn't check it before running it - and it had been created on the bottom of the material not the top! Disaster, it ripped instantly right deep into the material. I couldn't believe how much power the CNC has. The 6mm flat endmill cut to a depth of about 25mm, and across about 80mm, before I could stop it. It pretty much jammed in the slot, but the slot was very very neat! Made me realize I don't need to worry whether cutting a couple of mm deep is a strain on the machine! It could pretty much cut its entire bed in half in a blink if it was told to. The cutter didn't get damaged either, which was good.

Anyway, it's all part of learning so I mixed up some fast setting gelcoat and filled the slot, and later milled it down again. But somehow I was having trouble with the levels. It seemed to be on zero at one end, but at the end that had been gouged, it seemed to be just a bit out. I created various paths and adjusted Z levels to try to fix it, but couldn't get it perfect, and I decided that the gouge must have disturbed the workpiece a bit, even though it's screwed down well.

So I decided to go back to square one. As I said, it's all good learning. I reset the zero 0.3mm lower, created a reference Z zero surface, and am re-running all the cuts. Which is not so hard really, now that I've done it once I know how to do it. I've re-done one half of the wing shape and it looks really great.

Going flying tomorrow! So I won't finish it, but I can see the light and then it will be a matter of doing the same things for the top side mould half.

Geez Corian dust is fine. I have a 1 micron cartridge filter on the vacuum unit, with a device that you rotated and internal flappers vibrate the cartridge flutes to knock the dust off so it falls down into the bag below. But the dust clogs the filter quite quickly, creating a lot of pressure in the plastic collection bag, and the dust also migrates through the filter so when you rotate the flapper thing, dust billows off the cartridge.
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Old Jun 14, 2014, 02:53 PM
Where is the inspiration
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Moira
Joined Feb 2006
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regarding the clogging up of the air filter, have a chat with Mike F. He is in to process of (Could even be finished) creating a cyclone.
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Old Jun 15, 2014, 04:35 PM
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William is right, I am about to start some very large moulds and the dust created would clog my filter bag within half an hour and reduce the efficiency of my extractor. For an eighteen hour operation, this would mean stopping the machine and cleaning the filter some 36 times!!! - not something I was relishing.

I looked at cyclones and found a manufacturer in the UK who made flat-pack cyclones but they are very expensive for what they are and besides that, they did not answer any of my emails. I did some more searching and found the Thien Separator and decided to give it a go. I logged my progress here

It works pretty well and traps 98% of the material but the very fine dust is still getting through but it now takes very much longer for the filter bag to get to the stage of needing cleaning. I still need to play about a bit more to maximise its performance but it is a massive improvement over the extractor by itself and well worth the little effort in making it.
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Old Jun 26, 2014, 05:44 AM
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Australia, QLD, Elimbah
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So ... anything you'd like to share with us Andrew???
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Old Jun 26, 2014, 05:59 AM
AvB
Wind, hill, ... I'm keen ...
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Just an update on nothing major! Not making any rapid progress, but learning I guess. Hard to believe after all this time I still don't even have one half of the Scratcho wing mould done!

As mentioned previously I got a really good cut on the first side (this is now a new cut at a lower level) and decided to re-face the flange at the matching level one night ... but somehow stuffed up the zero, (still don't know how) and it cut just a tad too low. So it was back to square one again ... reface at 0.3 mm lower and completely re-do the wing cuts. This morning I started the first side wing cut and the machine stopped inexplicably after about 10 mins. I called Justin, and he dropped over to have a look. It just stops totally, servos shut down and G-code stopped, with no warnings or messages. He suspected that the machine may be wanting code to the smooth stepper faster than the computer could send it (naive lay explanation here) and when it misses a position 5 times, it will shut down. So he wound back some settings in Mach3, and we tried again. All looked good but it shut down after about 2 hours. This time he reckoned perhaps there was some issue with the new screenset, as I seem to have had these shutdown problems since implementing it. OK, so I switched right back to the old screenset (had to remember how to make that work again - took me ages to remember to hit Tab for the Jog settings!) and I started again, shortcutting to recommence where it left off ... and all went well and then it shut down about 3 hours later, 2/3 thru the cut. Damn. This time, the spindle lifted and it didn't lose the Z zero, which is different to the previous times.

All a bit weird, but Justin's determined to get to the bottom of it. It's possible that it's just something that the PC is doing, like an energy save setting or update request so I'll need to look into that when it finishes this run.

One big issue I'm realizing is how much heat expansion affects the Z position! Probably not a big deal if you're carving wood, but when you're cutting wing moulds they need to look perfect. If the cut stops and then later when it's cooled down, I restart the cut at the same spot without touching the Z level, it always cuts a shade higher ... enough to feel a step with a fingernail. I'm guessing around 0.08mm, which looks bad. So if I stop and adjust the Z zero until it resumes the cut at the same level, I'll find about 5 minutes later that the cut is now deepening slightly! I can detect this mostly by the depth of the step at the trailing edge. So I'm learning that it's best to let it cut at the higher level and when it finishes, go back and cut that area again while the spindle etc is hot. Very finnicky stuff.
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