[belgrado]

Hello cnc musical instrument builders .

I myself am a guitar builder from Brussels Belgium .
I built myself a compact cnc router about 6 months ago .
I have been routing lots of different hardwoods for the past time .
Because of the different nature of these woods in hardness resin content and so, it has always been a bit of a tryout of what routerbit and which feeds and speeds to use .
Sometimes a straight bit will clog up after a period of routing and then it makes my router motor ( aprox 1 1/2 hb, kress fme1050) suffer quite a bit .
For cutting out solidbodies and so it is a bit difficult for me to find a good routerbit .The actual time of machining isn't a big issue to me I just need a decent finished router cut .
Maybe it's possible in this thread to share your expieriences with different routerbits and feeds and speeds .


Greetings and thanks ,

Paul

[ger21]

It seems like everyone always says that they don't care if it takes a long time to cut. The problem is, is that if you want the best tool life, you need to cut as fast as possible. You'll need to determine the max speed through trial and error, but you should try and cut as fast as you can, and still get an acceptable finish. Cut quality should be the main factor in determining your top speed. Most home built machines are limited due to spindle power, but the workaround for that is to take shallower passes, at higher speeds. It's also important for tool life, that you clean out the chips between passes, so the tool isn't re-cutting the chips you already cut on the previous cut. Cutting through a cut already packed with chips causes a lot of heat, which is the main factor in tools getting dull. You're best bet is probably upcut spiral solid carbide. Also, you may want to leave a little extra material, and use a very sharp new bit for a finishing pass. But you need to be careful, as it can be easy to get tearout when doing a finishing pass in solid wood.

As for spindle speeds, find a tool from Onsrud's catalog that's comparable to what you're using, and use their chip load charts to get you in the ballpark.
https://www.onsrud.com/xdoc/FeedSpeeds

[belgrado]

Gerry

Thanks for the reply and usefull info .
It would be nice though to share some routing expierience on different woods ( feeds and speeds ) with other luthiers or woodworkers.
I have used some miniature (2mm) spiral routerbits ( thooted for printedcircuit boards ) for routing ebony and so in 1.5mm passes . It worked great and no tearout .
Sometimes it's easier to rout woods that have what I call a dry crisp texture .
Alder for ex is for me pretty difficult to rout cleanly .
Wood is a combination of softer and harder areas so it's really guessing what to do .
When you rout with a hand router you feel how fast to go .


Paul

[ger21]

All my experience is with a 10HP spindle, cutting mostly oak and maple. I use mostly 1/2" diameter tools, and almost always use chipbreaker spirals.
http://www.vortextool.com/standard/p...fm?groupID=266

With a sharp, new tool, I'll cut up to 250 ipm at about 15K rpm, and about 1/2" depth of cut. Depth of cut will vary by the size of the part, mainly because small parts don't hold as well with a vacuum hold down, so I take shallower cuts and make more passes.

[belgrado]

Gerry ,

I looked at the link . The router bits look quite similar to the miniature printed circuitboard bits I used for thin ebony cutting .They sort of cut and rasp the wood in one operation.
Compared to your 10 hp spindle I play in the minor league with my 1 1/2 spindle .
I know alot of people in the US use porter+cable motors on their smaller machines .
What are the cutting limits and relyability in cnc of those ? I have 2 models #690 lying around here and I had been thinking of using them as the spindle instead of the "Kress ".
I'd be happy to hear somebody's experience .

Paul

[Sinistersam]

In my own personal opinion, porter cable tools are about the best tools money can buy. I use the 690 on my machine. at 1.75 HP, it seems its always starved for power, even on the minimal of cuts. I'm not happy with the performance at all. As others have stated, if your going to go buy a router, get a porter cable 7518 minimum. This is the largest router porter cable offers I believe. 3.25 HP, soft start, constant speed, 5 speeds, 10,000 rpm being the lowest. I would also have to agree with them on this. Even then, the 3.25 HP might not be enough. Maybe someone else can chime in on this and give some feedback on the 7518's.

[belgrado]

Thanks for the reply Sinistersam,

I own 2 P+C 690 for manual woodwork .
They are great and very solid indeed .What feedrate are you using on a cnc with the 690 's ? and how long can you let these motors run in one operation without overheating them ?
This type of cilindrical router is ideal to mount on a cnc machine .
In europe this design was banned for sale for about 15 year ( because probably some politician woodworker found they weren't safe enough .)
We got stuck with plunge routers only for the past decades.
Bosch apparently got a licence to sell their cilindrical again .( with the plunge base )
I run the P+C with a 220v to 110 v transformer on 50HZ so it runs a bit slower .
I'm planning on building a more solid machine in the future so I'll better go for a big router motor as you suggest .

thanks ,

Paul

[Sinistersam]

I took a small video of the router using 4 feeds. Cuts are through oak using a 1/2 inch box bit, 1/2 depth. speeds are 40, 50, 60, and 70ipm. I agree with ger21 about using the spiral cutters. They would most definitely improve speeds, feeds, and quality. Also at 50 ipm, the regular router bits don't have enough clearance behind the blades to keep from contacting the material. You could grind a relief on them, but they still would'nt compare to a spiral cutter, but at over $100.00/piece from that link, I think I could make do with some standard endmills. I don't have an answer about the overheating. All of the cutting I have done is short term. That is a good question though. Another thing to keep in mind would be the bearing life if you were to cut at a high rate. Not really a big deal to replace them, just something to ponder. I really don't think it would matter what router you purchased, hand routers were just not designed to take that kind of stress without replacing some parts now and again. VIDEO (5.5MB)

[ger21]

You could grind a relief on them, but they still would'nt compare to a spiral cutter, but at over $100.00/piece from that link, I think I could make do with some standard endmills.

If you buy three, the price drops to around $70

[belgrado]

thanks for de video Sinistersam,

From what I hear the cutting noise of the router seems quite normal .
I got some 10mm upcut spiral bit right now and I'm going to cut some hardwood soon .With the straight bits it works ok but depending on the wood the cutter becomes slightly loaded with resin or dust ,this makes the cutter less sharp and the motor suffers too much after a while +burn marks on the wood.
I think the chip clearing with the spiral cutter wil be much better for my purposes .
I 'll have to experiment with cutting speed and feedrate though.


Greetings ,,
Paul