sherline mill vs router for aluminium ...

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12-22-2011, 06:17 PM
CNCpatriot

sherline mill vs router for aluminium ...

Hi,

I have a basic doubt.
Sherline mills 2000 series r available for less than $1000.
What r the tasks which a cnc router can do , but a sherline mill cannot do?
How come so many people are trying to build there own CNC routers?

Is it to cut larger size parts or faster production rate or ?

In particular I would like to do profile cutting in aluminium and plastics like nylon, PU.

With router , bcos of high rpm, I get melting problem with plastics .
Also the higher rpm in routers causes my endmills to break, even if there is a small runout in the tool.

Both the above problems are not there in a sherline, as the rpms are less than 3000.

So are shelrine mills more suitable for profile cutting in aluminium and plastics compared to a router?
What r the tasks which a cnc router can do , but a sherline mill cannot do?

regards
12-22-2011, 06:44 PM
louieatienza

Quote:

Originally Posted by CNCpatriot

Hi,

I have a basic doubt.
Sherline mills 2000 series r available for less than $1000.
What r the tasks which a cnc router can do , but a sherline mill cannot do?
How come so many people are trying to build there own CNC routers?

Is it to cut larger size parts or faster production rate or ?

In particular I would like to do profile cutting in aluminium and plastics like nylon, PU.

With router , bcos of high rpm, I get melting problem with plastics .
Also the higher rpm in routers causes my endmills to break, even if there is a small runout in the tool.

Both the above problems are not there in a sherline, as the rpms are less than 3000.

So are shelrine mills more suitable for profile cutting in aluminium and plastics compared to a router?
What r the tasks which a cnc router can do , but a sherline mill cannot do?

regards

With a CNC router, you could do larger work, though depending on your set up, may not be as solid or accurate as a Sherline. I think a Sherline would perform better with harder materials such as steel, and I've even seen some titanium machining done on them.

The downside with Sherline is also it's upside. It's size makes it ridgid for small work, but then it's small. As for routers, you could buy a spindle and VFD, or get a SuperPID for your router. Also, with higher RPMs you could theoretically increase your feedrate, within the limits of your machine's ridgidity and spindle power. But they are two different beats, meant to do two different things. There is a 10K rpm spindle option for the sherline, and you could also retrofit a router attachment when you need more speed.
12-24-2011, 05:08 PM
Phife

I use my CNC Router all the time to machine hard plastics like acrylic and nylon, the trick is to use the correct bit.

I have extremely good results from the Onsrud series O flute upcut bits for hard plastics.

I run at 75IPM and 18000RPM and I have no melting, and very crisp clean edges.

Ive also done some aluminum engraving and machining with the router with no problem, again.. using the proper bit.

So a CNC router can be used instead of a Sherline, the advantages are larger work area, and faster machining times, but it would probably cost you more to build a good sized and ridged enough machine.
12-26-2011, 12:53 PM
wizard

Isn't this bit of a silly question?

By that I mean the Sherline is a very specific small mill. A good product certainly, but a physically small machine. CNC routers on the other hand come in all sorts of shapes and sizes. So you really can't ask a general question like this because we would be comparing a very specific machine against a complete unknown.

As to building my own router I'd probably go that route before buying a Sherline but that is only because I know that I. Have needs beyond the Sherlines capability.

As to spindle speeds and cutting issues do realize that you dont have to run a high speed spindle. Routers can be built with all sorts of spindles. However if you are breaking tools and have high runout maybe you need to look at both your current spindle and the actual tooling you are using. Melting plastic though kinda indicates the wrong cutter, also a gummed up cutter can lead to breaks.

As to which machine is more suitable I can't answer that as I don't know what you are doing. Like I said at the beginning the Sherline is an excellent little machine, it may be perfectly suitable for your needs. However I'd go with even a relatively small router before I'd go with a Sherline. For my needs it would have the capabilities that the Sherline doesn't have.

Further if I build tha machine my self it is pretty much a certainty it will have the capability I want. This is the one big advantage to a home built router, you can effectively can size it to your interests. You could even make the spindle assembly swappable or run two spindles at the same time. Your imagination and sound engineering being the only real limits.

Quote:

Originally Posted by CNCpatriot

Hi,

I have a basic doubt.
Sherline mills 2000 series r available for less than $1000.
What r the tasks which a cnc router can do , but a sherline mill cannot do?
How come so many people are trying to build there own CNC routers?

Is it to cut larger size parts or faster production rate or ?

In particular I would like to do profile cutting in aluminium and plastics like nylon, PU.

With router , bcos of high rpm, I get melting problem with plastics .
Also the higher rpm in routers causes my endmills to break, even if there is a small runout in the tool.

Both the above problems are not there in a sherline, as the rpms are less than 3000.

So are shelrine mills more suitable for profile cutting in aluminium and plastics compared to a router?
What r the tasks which a cnc router can do , but a sherline mill cannot do?

regards
12-26-2011, 03:04 PM
CNCpatriot

Thanks for the messages.

I tried building a DIY CNC router few months back and faced these problems of plastic melting and
tool breakage, excessive noise when machining aluminium. etc. This was my first attempt and my structure was not super rigid and Iam still working on improving my design .

So wondering if a low-rpm spindle is the right starting point for a DIY cnc machine?
Later when the machine's design and rigidity improves , I can perhaps try a high-rpm spindle like the routers.
Also the 20K+ rpm is quite scary for a new machininist like me.
Also at lower rpms I can use normal HSS tools for aluminium , without blunting the tool .

Some questions:

1) Is a low-rpm spindle the right starting point for a DIY cnc machine?

2) Where do i get a low rpm DC motor spindle like the sherlines?
( without having to use speed reduction pulley arrangement etc. would be even better).
While I find tonnes of routers for sale online like dewalt, bosch, makta etc., I dont find many
off-the shelf low-rpm motors( less than 3000 rpm) with tool holding collet arrangement etc.

3) Say I manage to improve the rigidity of my router machine. What are the benefits I will get by upgrading to a higher rpm router spindle? Faster cutting speeds: will that be the main advantage?

4) In sherline mill, Iam able to take a 1/8" deep plunge cut in aluminium at ~10 IPM with a HSS tool.
What feedrates can I typically expect to cut this in a commercial CNC router machine using carbide endmills?

some points:
-- my router size is ~ 2'x2'.
-- Iam trying to use it as a general purpose fabrication machine. Iam not building for a specific application like wood design etc. The more my machine can cut, the better for me.

Thanks for your inputs.
12-26-2011, 03:36 PM
ger21

You can always use a SuperPID with a router motor to get 5000rpm, up to the routers maximum.

As others have mentioned, using the right tools makes cutting plastics much easier, even at higher rpm's. Small tools will always be problematic, as the chips tend to pack into the cut more, and this is a big source of melting.

Quote:

4) In sherline mill, Iam able to take a 1/8" deep plunge cut in aluminium at ~10 IPM with a HSS tool.
What feedrates can I typically expect to cut this in a commercial CNC router machine using carbide endmills?

Commercial machine can mean many things. Smaller routers ma not be rigid enough to make that same cut, but should be able to make 4 passes at 100ipm or more, which would be 2.5x faster.
Larger commercial machines might be able to make that 1/8" cut at 200-300ipm, maybe even 500ipm. But these machines might cost $50,000-$100,000 or more.
12-26-2011, 07:50 PM
louieatienza

Quote:

Originally Posted by ger21

You can always use a SuperPID with a router motor to get 5000rpm, up to the routers maximum.

As others have mentioned, using the right tools makes cutting plastics much easier, even at higher rpm's. Small tools will always be problematic, as the chips tend to pack into the cut more, and this is a big source of melting.

Commercial machine can mean many things. Smaller routers ma not be rigid enough to make that same cut, but should be able to make 4 passes at 100ipm or more, which would be 2.5x faster.
Larger commercial machines might be able to make that 1/8" cut at 200-300ipm, maybe even 500ipm. But these machines might cost $50,000-$100,000 or more.

You can see videos of commercial VMCs cutting 6061 at over 800 IPM and 1x diameter for doc... But these machines have 10-40HP spindles and weigh over 10 tons. Flood coolant and through-tool coolant also removes chips efficiently in aluminum.

In general, provided your macine can handle it, you want to create chips that are large enough to draw heat away from the tool. This creates a dilemna in some DIY machines since this usually means a deeper DOC, but either the spindle is not powerful enough or the machine is not ridgid enough. Endmill manufacturers usually base their feed and speed calculations at 1x diameter for doc for pocketing, and 1/2x for profiling. Otherwise you're heating up the bit and prematurely wearing it out, because you're using the bottom of the bit more than the edge, which cuts more efficiently. But since this is not easy to achieve we sometimes have to compromise some tool life to get results...

Like Gerry says, a SuperPID will give you the low end speed for plastics. I typically run about 6000-7000 rpm at about 30-50 ipm for acrylic. With a single flute spiral-o-bit, I can run the router much higher, and this is in fact what I did before getting a SuperPID. Also for softer plastics (and sofer aluminums as well) I find a slow spiral-o (or even a straight o-flute) help form curly chips better. The key is the o-flute geometry which allows the chips to form and curl.

For aluminum I run at about 72 ipm, and .125" doc at 12k-14k rpm for a 1/4", 2-flute endmill. I prefer bits with a lower helix angle, since I find it easier for me to produce good chips. I use WD-40 mainly as a lubricant. Also for finish passes, I'll either raise the rpms or use a 3-flute bit.
12-27-2011, 09:37 AM
wizard

It sounds like you have significant machine design problems.

Quote:

Originally Posted by CNCpatriot

Thanks for the messages.

I tried building a DIY CNC router few months back and faced these problems of plastic melting and
tool breakage, excessive noise when machining aluminium. etc. This was my first attempt and my structure was not super rigid and Iam still working on improving my design .

Well noise can be a bad sign. But the net separates use from actually experiencing that noise. It might be better to get a feel for what the machine is doing, and what is vibrating. However if you do have machine problems it would be best to correct them first before trying to resolve other problems.

Quote:

So wondering if a low-rpm spindle is the right starting point for a DIY cnc machine?

It might be, it all depends upon your interests. If you really want to be able to switch to different materials and cutters it might be advisable to consider a two speed or variable speed drive.

Quote:

Later when the machine's design and rigidity improves , I can perhaps try a high-rpm spindle like the routers.

Some others have suggested other ways to control spindle speed but much can be accomplished with an AC motor, inverter and pulleys these days. This of course requires that you build a spindle or source a suitable one.

Quote:

Also the 20K+ rpm is quite scary for a new machininist like me.

Take the required safety precautions and your personal risk is minimized. This isn't anywhere near as bad as doing your first set up on a planner mill with 4 20HP heads. I think they where 20 HP each it was an awfully big machine.

Quote:

Also at lower rpms I can use normal HSS tools for aluminium , without blunting the tool .

If you will be doing various materials I don't really see how you can get buy with out a variable or multi speed spindle.

Quote:

Some questions:

1) Is a low-rpm spindle the right starting point for a DIY cnc machine?

The right starting point? There really is no right point, however there is no point in installing more spindle capability than the machine can handle. You could direct drive with a 3400RPM motor if you wanted.

Quote:

2) Where do i get a low rpm DC motor spindle like the sherlines?
( without having to use speed reduction pulley arrangement etc. would be even better).

I'm a big fan of AC induction motors driven by 3PH inverters. It is a good cheap way to a spindle drive. The alternative is the so called brushless DC motors but that is generally bigger investment.

Plain old DC motors are actually a dime a dozen. Your local motor supply shop should have several sources to choose from. Most DC motors (brush type) are generally lower speed motors. Actually they are often too slow for modern machining.

Quote:

While I find tonnes of routers for sale online like dewalt, bosch, makta etc., I dont find many
off-the shelf low-rpm motors( less than 3000 rpm) with tool holding collet arrangement etc.

That is normal, you would have to buy the spindles and motors separately.

Quote:

3) Say I manage to improve the rigidity of my router machine. What are the benefits I will get by upgrading to a higher rpm router spindle? Faster cutting speeds: will that be the main advantage?

Possibly better finishes. Possibly more importantly you can run very small cutters.

Quote:

4) In sherline mill, Iam able to take a 1/8" deep plunge cut in aluminium at ~10 IPM with a HSS tool.
What feedrates can I typically expect to cut this in a commercial CNC router machine using carbide endmills?

This goes back to my original comment, there is only one Sherline but hundreds of CNC router manufactures out there. Those routers are designed to server a wide range of needs. You may have one capable of 35 IPM while another capable of 350 IPM. One may be targeted at the wood working industry, another the aluminum industry and a third a general purpose machine.

Quote:

some points:
-- my router size is ~ 2'x2'.
-- Iam trying to use it as a general purpose fabrication machine. Iam not building for a specific application like wood design etc. The more my machine can cut, the better for me.

Thanks for your inputs.

Then make isn't stiff as possible to accommodate a wide range of materials. I would be concerned about the square format but that has a lot to do with what I would expect from the machine.

It might even make sense to have swappable spindles, one high speed and another that runs under 3400RPM.
01-05-2012, 12:56 PM
CNCpatriot

spindle choice for DIY CNC ...

Hi all,

I am still waiting for a feedback regarding my basic question. Any inputs will be of gr8 help.

1) What is a good choice for spindle for a DIY CNC machine?
Iam facing some problems with 10K+ rpm router spindles like : safety, plastics melting, tool breakage at high RPMs, wearing out of HSS tools at high rpm etc.

But still Bosch/Dewalt/PorterCable routers seem to be a popular choice for the spindle in the DIY community. Why?

2) Iam looking for a low rpm alternative ( 100 - 3000 rpm) similar to the spindles used in sherline machines. What are the options available for this?

3) In the bosch router (1617 variable speed) user manual, it is recommended not to run the router at low rpms for long periods of time.
Now then if we use superPID and slow it down further : is that a safe thing to do in terms of the spindles performance?

4) Does a 2HP rated router deliver the same 2HP even at low rpms or is there a power vs speed curve?

regards
01-05-2012, 11:08 PM
ger21

Quote:

1) What is a good choice for spindle for a DIY CNC machine?
I am facing some problems with 10K+ rpm router spindles like : safety, plastics melting, tool breakage at high RPMs, wearing out of HSS tools at high rpm etc.

But still Bosch/Dewalt/PorterCable routers seem to be a popular choice for the spindle in the DIY community. Why?

a) Not sure what the safety issue is.

b) If you get melting, you're either moving too slow, or using the wrong tooling, or both.
c) HSS tools aren't a good choice for a router, except for very specific applications.

They are popular because they are inexpensive and work perfectly fine for most users.

Quote:

3) In the bosch router (1617 variable speed) user manual, it is recommended not to run the router at low rpms for long periods of time.
Now then if we use superPID and slow it down further : is that a safe thing to do in terms of the spindles performance?

You need to watch it to make sure it doesn't get hot. I've run my SP controlled PC 690 for an hour at 5000 rpm and it still remains cool.

Quote:

4) Does a 2HP rated router deliver the same 2HP even at low rpms or is there a power vs speed curve?

They only deliver 2HP for an instant, if you lock the spindle and turn it on. After the instant is up, it's fried.
During actual use, it will usually have more power at higher rpm's.

If you need a full 2HP at low rpm's, then a router is probably a poor choice for you.