Video of CNC machining a double sided part.

[Shinobiwan]

This was a cool challenge not least because there was over £300 worth of stock material at risk if I nobbed it up!

A couple of days worth of planning, many iterations of tool paths and simulations and a day spent building and testing the double sided jig. This made a really nice change of pace from the usually slap a sheet of 4x4ft on the bed and press go. I've only had practical hands on experience with the cnc for the past few weeks and only done a handful of jobs so at time I thought I'd bitten off more than I could chew with this but it came good in the end. The two sides lined up virtually perfect and I couldn't be happier with the results. I learnt a lot from this, not least that long cutters (105mm from the collet) are whole other ball game and first hand experience of the superiority of carbide vs hss when cutting highly abrasive materials as well as the folly of using too many flutes and incorrect chip load. Burned two cutters up because of that just on this one job.

I'll post some of the pics later but for now here's a video:

[D.C.]

That sir is some very nice work congratulations!

Is it your own design or a commission and do get to a video of the finished article?

[GEOFFREY]

Very impressive, that machine is certainly going to help you earn its keep. G.

[Iwant1]

As the others say, that's a nice example of your machine being used to make a living. I for one am glad you keep posting videos of the parts you're making. I will be doing the same once I've built my router.

It definitely was interesting to see how you get a smooth finish to something you want made, i.e. roughing out first then going over to get rid of those stepped cuts. I have a couple of questions, hope you don't mind,

how long did the whole job take, and did you watch the whole thing? lol

when you were roughing out the main shape why weren't you using the extraction, looks like there would be lots of recutting material?

How did your numatic extractor cope when you was using it? I'm thinking of buying a similar type of HPLV extractor and wondering how the the container size coped with the volume of chips. Also what's their duty cycle like? Could you leave it on for a few hours?

Thanks Adil

[Shinobiwan]

It definitely was interesting to see how you get a smooth finish to something you want made, i.e. roughing out first then going over to get rid of those stepped cuts. I have a couple of questions, hope you don't mind,

Yep same here. I always enjoy seeing how others tackled a job and it often gives me idea's. Utube has hundreds of cnc video's luckily.

how long did the whole job take, and did you watch the whole thing? lol

Too right I watched the whole thing! I'm still new at this so was shitting myself! Me and the machine don't quite have the level of trust where I'd walk off and go play some PS3 whilst it cut but we're working on it lol

Rear side took the longest and that's simply because that was the side I did first and bumped into all the problems there. By the time I'd flipped it over onto the front I'd got it figured out and things went like clockwork.


So for the rear side it was an entire day but only a couple of those hours were spent cutting. The rest was head scratching and making changes. The front side was 6 hours from start to finish including tool changes and pausing the machine occasionally to vacuum the chips.


If I did it again I think I could have it done within 8 hours quite easily, probably less because I was on the conservative side with speeds. I'll be doing some more two sided parts in the future such as wave guides but I want to make a permanent jig setup for those as its something I need to be able to do over and over rather than just a one off like these.

when you were roughing out the main shape why weren't you using the extraction, looks like there would be lots of recutting material?

To be honest I wanted to see what the cutter was doing since its the first time I've tried anything this complex. When its buried in a dust hood you don't see things going wrong! There was recutting going off but its only modelling board albeit the high density variety. Still its easy to cut although highly abrasive on cutters - think worse than MDF.

How did your numatic extractor cope when you was using it? I'm thinking of buying a similar type of HPLV extractor and wondering how the the container size coped with the volume of chips. Also what's their duty cycle like? Could you leave it on for a few hours?

Thanks Adil

The 35ltr drum fills up very quickly during a job like this. I think I emptied it 3 times and it does get tiresome however easy the numatic made it to do just that. If you can definitely go with a larger capacity. I'm going to be using an extra bin before the extractor that will add a couple of hundred litres.

It depends when talking about suitability and is up to the task. My model isn't quite up to the job when your cutting fast, the spindle makes more chips than the extractor can collect. If you slow the feedrate down for a short time it gives it time to catch up. I think really you want HVLP type for CNC's because the sheer volume of chips and dust, you need to be moving lots of air. Problem I had is I wanted a one size fits all sort of thing including power tool use so it had to be what I've got now. If I had more room I'd certainly have an HVLP just for the cnc since these are ideal.

I'm pretty sure the duty cycle is continuous on this one. I've had it running for hours. As a bonus it does kick out a fair bit of heat which is great this time of year!

[Shinobiwan]

Thanks guys.

[Shinobiwan]

And a couple of pics






And the two dead cutters. HSS isn't really suited to this material as its even more abrasive than MDF but a combination of 4 flutes and a hefty 105mm cutter stick out meant you couldn't whack up the feedrates to anything like what they should have been without massive tool deflection or possibly even snapping the thing. My fault of course, tool was totally unsuitable for the job but I got them cheap so couldn't pass. A 14mm dia 160mm long cutter with 100mm flutes would normally set you back £50+. I expect doing a finish pass in alu would have suited them much better! lol

Check the carbide 2 flute on the left though. Not a scratch on it and it ended up doing most of the work. Yup. In my initial set of toolpaths I naively thought using the long cutting to get through the whole material was a great idea - save time changing bits, keeps the code simple and smaller. Wrong! You really only wanted to be doing the bare minimum with those massive cutters, just the parts where only they can reach. Anything else, use something smaller! In the end I broke it up into three tool lengths, one at 40mm another at 75mm and the 105mm. That worked but for the profile around each part there simply wasn't enough room to clear the chips when that valley got deep and it started burning cutters within minutes due to massive rubbing and recutting of chips. In the end I had to flip the part over and come at it with the 40mm carbide cutter from both sides leaving only 20mm right in the middle for the long cutter to get at.

In hindsight there would be a couple of things I'd do differently. First off is pick up a carbide 2 flute long cutter and the other being to size the stock to just over the size of the part and that'd do away with the deep profile problem I had.

[Iwant1]

since its the first time I've tried anything this complex. !

Well you've done good, the machined outcome looks wicked.

Thanks for the extractor advice, Unfortunately I just bought a wv2, 2000w 90l extractor similar to yours. Made by Yorkleen LTD, but from my research they used to make for Axminister, and still do make for Record, and a few educational machinery suppliers. My thinking was similar to yours, it should be able provide extraction for a host of tools, and again similar to you, I plan to install a ducting system with blast gates everywhere.

Seems like I might have to get a HVLP system just for the CNC, just like I'm looking for a continuously rated compressor for this purpose.

Are these parts, going to be used as the actual speaker fronts that will need prep work and finishing, or are they for the moulds you were planning on making?

Thanks.

[Washout]

That is superb work and I love your speaker designs.

It has me inspired to make some enclosures for my new HTPC setup, although completing my CNC router is unfortunately at the end of a long dependency chain since I moved house at the back end of last year.

Cheers


Chris

[Shinobiwan]

Are these parts, going to be used as the actual speaker fronts that will need prep work and finishing, or are they for the moulds you were planning on making?

Thanks.

Hi again mate,

These are for moulds. Plan is to use polyurethane rubber with the masters used as the plugs, pour that in around them. Let it set and remove then afterwards its ready for casting. This way I can use high density resins with fillers to create my own solid surface/corian like material. Perfect for this application where you want to be getting rid of as much of the vibration as possible.