Scratch Build – In Progress Project: Blue Horizon - "MOTY" Nominee

I've been looking at the Mach website and there is one or two things i don't understand.

Are you using Mach to generate the tool paths for the part? as I was led to believe that Mach was an all in one type product.

SO do you have to generate the tool path via another program then transfer it to Mach which then makes the machine follow it?

 

If you ever have any interest in switching to a professional grade CAD program like Solidworks or Pro-E, you can buy the CAD/CAM package and the software can generate your toolpaths for you also.

But I agree that you might see cleaner results if you 1) alternate the direction of your path (horizontal vs. vertical vs. diagonal) and 2) slow your feed rate, and 3) decrease your step size from path to path. One of my co-works does most of the CNC programming for our company (uses Pro-E), a lot of which is for the pattern makers so having a smooth finish drastically deduces the amount of time they spend on an individual master-mold. I asked him what in particular he did to keep it so smooth and he said he gets them very close to the final finish just by keeping his step over very small. It makes the just sequence take longer but it saves a lot of time later.

 

Ah nice, can you set a cut depth too? Whats the name of that type of toolpath?

As far as I know Mach3 is just to control the machine from the G-code (toolpath) you give it. I've never seen anything to create the toolpath. I use Cut3D to create the toolpath, as its very fast and easy to use.

How small is small for the step over? I've been using 1mm for the finishing path, and in the opposite direction of the roughing. Yeah I've got a CAD/CAM software called Bobcad which is more professional than sketchup, but I find Sketchup more fun and easier to use, and with all the plugins available the possibilities are endless.

 

I'd have to ask him when he comes in but I imagine its only a few thousandths. 1mm is still almost 40 thousandths of an inch and if I had to guess I would guess the step over he uses is probably .006 or something close to it. Try running a test piece and cutting your step over down to a .5mm (still .02in) and I imagine you will see a significant difference. If your not concerned about run times then I would suggest even going down to .25mm.

Like I said, it makes your sequences take a lot longer but if you can just running it during the day and then go about your day it shouldn't matter all that much. I know that some of the more complex parts we run on our machine have 36-48 hour run times for 1 part.

Also, I don't know what the material is called, but we use a specific grainless material (some type of epoxy resin cast I think) for nearly all of our machining and the finishes come out really clean. My co-worker actually just called in sick so if he is in tomorrow I'll ask him what he uses for step-overs and the name of the material if you want. I think you'll see a difference with just the step-over but if you used a more consistent material than wood you will also probably see better results and have a lot less work to do to keep the finish smooth

 

Thanks, yeah that would be great for if I need to do anymore CNC.

 

Sure you can set a cut depth. You can do pretty much anything in MasterCAM. It's simply a constant-overlap toolpath. I think in the program it's just a contour surface finish.

MasterCAM just came out with a SolidWorks add-on. I haven't used it yet. All I did in the toolpath you saw was import the .SLDPRT into MasterCAM. SolidWorks > SketchUp any day. I can't even use SketchUp because I've been using SolidWorks for so long. It's like driving a Tesla then going back to a Toyota.

As for step size...it depends on how long you want it to take. Since this is wood and not something like stainless steel, you can really crank up the feed rate to high heavens if you make the step size small enough. Depending on the size of the ball end mill you have, the step size to get a required scallop height would be different (Read This). For a 0.25" ball end mill, something like a 0.07" step over will give you a 0.005" scallop height, which will be just slightly noticeable to the naked eye.

If you want to get crazy, go down to a 0.001" scallop height. You can't even feel that.


Edit: From the HAAS CNC website..."A cusp height of 0.00003" to 0.00005" (0.00076 to 0.00127 mm) will produce a very fine finish." Cusp height, in their case, is scallop height.

 

.002 is generally a good scallop height for finish milling for the record. I believe we use .001 because it shows up when you form cast iron

 

It also depends on the type of material and the amount of post-processing you want to do. Something like wood where it's very easy to sand, you don't need a super smooth surface. If you're doing aluminum and don't want to spend hours sanding, then you want as fine as possible. The numbers are typically a "gut-feel" call based on the applicaton and amount of experience you have.

Anyway...I want updates!

 

+1

 

Thanks for the info Achron & sixfootsideburns

I've just found out that they will be doing there next batch of castings on tuesday, so I should have a video up then. In the mean time I might see whether I can start making the front panel door hinges.

 

Enough cobbler talk (though it is nice stuff to know, thanks ) Up-N-Date-N oh... Happy Holywater...er.. I mean Merry Christmas LOL (Here comes the flame-N)

 

Alright I spoke with my co-work and he doesn't specify a scallop height when he runs his tool path, he simply uses a step-over. The step-over we use is definitely smaller than most people would care to use but it achieves a near perfect finish that is equivalent to a finely sanded surface. The drawback to this is of course that you are creating a much longer tool paths when you do this. But in a case like this where you are having a casting done, I think its worth the time. Sanding may achieve the same finish but there is a larger chance that your surface will be uneven (as in not perfectly flat) if you sand rather than machine.

For a 1/4 inch ball-end mill he uses about a .004in step-over. Very small but it drastically reduces the amount of sanding that our pattern makers need to do to achieve a cast worthy finish.

Also, the material we use is by a company called Ren. The specific material is Ren 474. Probably a little to expensive for what a hobbyist material but you might be able to find a slightly different material of the same type for less. I believe he said a 2 inch full sized sheet (not sure how big full sized is) is about 200$ US. Soooo, expensive for sure. But just incase your interested in checking it out it is definitely a really sweet material. No grain direction, strong as hell, and finishes beautifully.

now.... As said...

CAN I HAS MOAR UPDATEZ PLEASE?

 

Merry christmas too , heres the update you wanted.

Wow yeah that is expensive, thanks for the info, it should come in handy next time



Heres the alu casting update:

First off heres a few pics of whats possible through casting:




I had no idea that sort of thing was even possible!



Heres how its made:



Each slice is made seperately then stuck together with a special resin. The sand itself is also mixed with resin to create a rock solid mould.



The mould on the left is placed inside the one on the right:



Heres another example of how the different moulds can fit together to create complex castings:



Here you can see the empty space where the aluminium will flow around the different moulds:



The top of the mould is then place on top:



The white tubes are where the aluminium will be poured down into the mould. They are made from a special ceramic which heats up fast and retains heat while the aluminium is being poured in. This is because as the aluminium cools down in the main body of the mould it shrinks, so the aluminium in the ceramic tubes must stay molten so it can flow into the main body of the mould as cooler parts shrink.

Heres is another of the moulds shown above but with the top half in place:



And heres the casting that mould makes:



The next example is how you can cast tubes:



The outer black sand is soft and is binded together with 5 - 10% water, while the inside sand is the rock solid resin based sand. The gap between black and light brown sand is where the aluminium flows.

Heres a pic with the top half of the mould in place:



Just before the video heres a few pics of the furnace:







They also have a rod similar to the ones fish tanks have which allows a gas to be pumped through and it seperates the gas into loads of tiny bubbles. They pump nitrogen through the rod while its in the molten aluminium which causes the impurities to float to the top.

The rod is pictured below (its the one with the pipe sticking out the end) :



Heres the link for the full screen video:

http://www.youtube.com/v/ERo-QR8nC7I?fs=1

^^^^^^^^^




Heres a pic after the aluminium had cooled:







I was hoping to get abit more of the mould making process, but they were having difficulties getting the sand to set as it was below freezing.

Just to show the kinds of size and complexity they can cast, heres a pic of a large brass sculpture they made:

 

It's getting interesting for me now a lot of the stuff was just over my head but now we are seeing aluminium casting can't wait to see your final piece mate, been a very complex route to get to this point, that brass sculpture is bada$$ .

 

That must be one of my fav posts of all time, mega-cool

 

+1

Moar pls?

 

Thanks guys , the next casting update will have to be in the new year now as they will be on christmas holiday before they get round to casting my moulds. In the meantime I'll try to think off something that I can make without know the exact measurements of the finished basic frame of the case.

 

Whoa, that workshop looks like something straight out of Mad Max or Water World. Very cool.

 

lol, it feels weird standing on a sand floor indoors too.

 

cant you take a showel and see if there is floor under it

Cant wait to see the final cast! Your really putting your efforts into this I love it!