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Rye
17-12-2015, 12:34 AM
Hi all, hope everyone is having a great December. Owned a Chinese 6040 with 1.5k spindle for a couple of month. Loving it - even though there is a little screech on the far-end of the y-axis :distress:

I've been making LED stands for acrylic engravings - mainly out of HDPE. Unfortunately, that stuff takes a lot of burning, sanding and polishing to get decent finish. So I'm looking for cheap materials to use that don't need as much work. I've made a few designs using a mix of aluminium, black acrylic and brass spacers. I'm also considering aluminium composite. Thing is I've not tried cutting any metals yet and I don't to rush straight in without getting any advice off you guys first.

What ER11 would you recommend for cutting aluminium - and aluminium composite. And what feeds, speeds, stepover, etc, would you recommend?

Thanks.

komatias
17-12-2015, 09:41 AM
Hi Rye,

good to hear you are having success with the 6040. Not sure what our screech is, maybe post a video of it and we may be able to identify it.

When you start cutting metals you will need some form of cooling, even if it is just an air blast. I would also suggest you use carbide tooling due to the speed that the spindle of the machine is able to run.

Surface finish of a milled part will depend on the rigidity of the machine, the nature and hardness of the material and your feed/speed settings. For plastics you will need to get specific endmills/cutting bits in order to get the surface finish you are looking for, google this. I think I came across some straight flute endmills a while ago for this particular application.

ER11 are the type of collet that your spindle can accept. You can purchase the ER11 collets on ebay for pretty cheap but you will be limited to a 7mm diameter shank tool. This is not an issue on the 6040 as most suitable small endmills have 3.2mm(1/8"), 4,5,6mm shanks anyway. Worth getting a collet set by the way, if your machine didnt come with it.

A good place to start for feeds and speeds is the feeds and speeds wizards (http://zero-divide.net/index.php?page=fswizard)

Another slightly overlooked parameter is what the gcode your CAM program outputs. Some programs will prefer to output straight lines for arcs which makes ugly curved edges.

Regards

Rye
17-12-2015, 01:00 PM
Hi Komatias,

Thanks for the reply. The screech occurs when the gantry is roughly between 15 - 20 cm from the front of the machine. Can be quite loud too. So I've been avoiding cutting on that area of the machine. The gantry also isn't quite square with the base of the machine. If I move the x-axis from one end to the other, the z will start fine before cutting into the spoiler board by about 0.25 to 0.50 mm(as a guess). I will make a video and upload it soon.

Despite the problems above, and a few mishaps, I have been managing to cut MDF, HDPE and acrylic, as well as engrave, reasonable well. Mostly been using 2 flute 3mm end-mills for cutting acrylic, and a cheap 60 degree v-bit for engraving (looks like it would take someone's head off if it flew off the machine.)

Unfortunately I don't have any single flutes for cutting aluminium (I've just put an order in). Do you think a 2 flute 3 mm end-mill, if I cut reasonably fast and shallow, will do the job? The aluminium will be thin: 1.5 to 2 mm. If I use composite sheets, it'll be even thinner.

komatias
17-12-2015, 01:46 PM
ah, squareness.....Yes the chinese machines are all over the shop by the time you remove them from the crate and worse when you want to use them. It comes with using the aluminium extrusion unfortunately.

If the Z is the issue, then you can skim the spoil board but realistically you will need to check each axis against the other.

We can go into details if you want.

For cutting aluminium, I recommended you get some cooling first. You may be more efficient with the single flute but that does not exclude 2 flute endmills, if you go shallow and fast as you note, but you may need to clear chips well when going deeper than an 1mm. You could get a shallower angle 2 flute endmill though which is specific to ali. I always wanted to give a mist cooling things a go.


With composite materials like the alu comp you are thinking of, you will need to experiment a bit. Typically on ply material it is recommended to use a downdraft or compression bit when doing the edges so as not to rip the top and bottom ply. Not sure if this will apply to your case but the option is there.

Rye
17-12-2015, 03:59 PM
Just been up to the "shed" and made a quick video. When moving X, the Z will cut into the spoiler from 0 to about 0.25 when it reaches the other end. So that's not as bad as I thought TBH. The screech on the Y though is great if you want to torture someone:


https://youtu.be/mRS_Ha_gHVI

Would like to get it sorted, although I am thinking of getting a new and stronger base/gantry made (in the summer) and using the motors, etc from the C6040. Be nice to know what some of you guys would charge for making it?

Chaz
17-12-2015, 04:43 PM
Just been up to the "shed" and made a quick video. When moving X, the Z will cut into the spoiler from 0 to about 0.25 when it reaches the other end. So that's not as bad as I thought TBH. The screech on the Y though is great if you want to torture someone:


https://youtu.be/mRS_Ha_gHVI

Would like to get it sorted, although I am thinking of getting a new and stronger base/gantry made (in the summer) and using the motors, etc from the C6040. Be nice to know what some of you guys would charge for making it?

Wow, horrible sound. Sounds like something urgently needs lube or realignment or both.

Can you disconnect the ballscrew from the frame and move the frame by hand? Might be worth a try ... if its free and quiet, id then investigate the ballscrew and its mounting.

Rye
17-12-2015, 05:11 PM
Yes, sounds sweet doesn't it..lol From the start I've mainly used the nice sounding side of the machine - so I'm not sure if it's a recent development or if it's had the problem from day one. I'll take the plunge tomorrow and see if I can find the problem. Just hope I've still got a machine when I've done...lol