Recommend a small commercial CNC machine

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22 Aug 2012 02:26 #23526 by tashiro
Please recommend a small CNC machine for me.

I'd like to buy my first CNC machine and I would like it to be small - desktop size if possible. I only want to make things like non-mechanical parts for scale models (i.e. toys) so it doesn't need to have ultra precision. I'd prefer one that had as many axes as possible because I'm more confident of my skill as a programmer than my skill as a machinist; I'd prefer not to do many setups.

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22 Aug 2012 02:36 #23527 by dangercraft
Hi,
Are you looking for a milling machine? Im not to familiar with desktop mills, however when you said toys, the first thing I thought was 3D printer, the range on these is jaw dropping, from the simple repraps to the resin+uv rapid prototyping setups, you might want to look into something like that.

Frank

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22 Aug 2012 04:19 #23529 by Todd Zuercher
I don't want to sound mean but what sort of machine do you want?

Just asking for a "CNC machine" is a little like asking for a recommendation for something with wheels.

Are you after a router, mill, lathe, laser, plasma cutter...

CNC could be just about any kind automated machine with a computer in it.

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22 Aug 2012 07:03 #23533 by tashiro
Todd Zuercher wrote:

I don't want to sound mean


Be as mean as you like!

Just asking for a "CNC machine" is a little like asking for a recommendation for something with wheels.

Are you after a router, mill, lathe, laser, plasma cutter...

CNC could be just about any kind automated machine with a computer in it.


I don't want a plasma cutter or a lathe, but my wishes are fairly vague and almost any other kind of automated machine of a desktop size would interest me. (After all this will only be my first CNC machine.) I visualize making things like pieces for the body of a model tank, such as the top of the turret. This is roughly a flat shape but, in the terminology of mold making, it would look better if it had mild undercuts.

If a mill can do only 3 axis motion, I visualize it as having to cut "straight down" on the work. So it wouldn't be good for mild undercuts. If there is a mill-like machine that can tilt its head and come in at various angles, that would be of interest. If there is an automated platform that can sit on the table of the mill and tilt the work piece, that would be of interest.

A small robot arm holding a router would be interesting, but I haven't seen such a machine advertised.that was Linux compatible.

A 3D printer would also be interesting, but my impression of 3D printing (for the home craftsman) is that it makes pronounced steps iin the sloped sides of the work. Is that correct?

I'd be happy with a machine that could cut hard waxes and plastic. It wouoldn't necessarily need to cut metals.


.

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22 Aug 2012 08:46 #23538 by andypugh
This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:

A 3D printer would also be interesting, but my impression of 3D printing (for the home craftsman) is that it makes pronounced steps iin the sloped sides of the work. Is that correct?

You do get some steps, but I think that they would often be concealed by paint.
Some good examples here:
blog.ultimaker.com/made/

I'd be happy with a machine that could cut hard waxes and plastic. It wouoldn't necessarily need to cut metals.

Have you seen this machine?

It seems to have been developed by en.pmc.org.tw/static.aspx?type=AboutUs who are a non-profit, so I guess one would need to find which manufacturer they developed it for.

If you have very deep pockets, then perhaps hobbyshopcnc.com/mini_mill_pro.htm

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22 Aug 2012 10:25 #23540 by BigJohnT
andypugh wrote:

This email address is being protected from spambots. You need JavaScript enabled to view it. wrote:

If you have very deep pockets, then perhaps hobbyshopcnc.com/mini_mill_pro.htm


Wow that is pricy but seems to be built well...

John

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22 Aug 2012 11:25 #23542 by andypugh
BigJohnT wrote:

Wow that is pricy but seems to be built well...

I fond the manufactures site:
www.minitech.com
You can spec-up their granite-based machine to well over $30,000. For some of the types of work they show micrographs of that might be quite good value.

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22 Aug 2012 14:20 #23549 by dangercraft
Those little mills are EXPENSIVE! :laugh:

I wouldn't mind having one though! :laugh:

As far as the 3D printers, the deposition type printers (ala reprap) due to the nature of the process cannot make a perfectly straight vertical wall...though if you had a reprap with a fourth and fifth axis bed, I don't see why that would still be the case. On the other hand, the UV "layering" machines have no such limitations since these work by cooking the top layer of resin in a pool with a pointed UV light source. There is a base that starts at the surface and moves down with each layer that is cooked. Cook enough layers and you have a 3D parts. Its pretty amazing what you can do with this type of printer. I don't know what the technical name for these are, but it used to be that you could get them REALLY cheap used... the expensive part was the resin.

Frank

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22 Aug 2012 14:39 #23551 by tashiro
I'd feel more confident in recommendations for machines than forum members actually own. Do most of the members in this section build their own machines? (If so, perhaps I should do that, although it sounds intimidating.)

When I surf the web for CNC machinery, I don't see many machines that advertise "Linux Compatibility", and I'm unsure of how the whole CNC software game works. My guess is that the biggest market is for machines that take some sort of data file as input and know how to execute it. I also guess that desktop computers are used to prepare this data file. So a Linux desktop system only has to produce the data file in the correct format. Is that correct?

As a programmer and somewhat competent mathematician, it would be more interesting to me if the desktop computer prepared very low level instructions for the machine (like move the head to (x,y,z), turn the head to angle theta etc.). I'm curious whether CNC machines use any sort of feedback. For example, I think it would be useful if a machine has probe that be used to "touch" the work and verify its current shape. ( I suspect that these wishes go against the wishes of the commerical market!)

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22 Aug 2012 14:54 #23553 by dangercraft
If I were to venture a guess... I'd say you should go through the linuxcnc documentation to understand what linuxcnc is and how it works. In essence linuxcnc is a controller, not a machine, and it easily does what you just mentioned.

I suspect most people that use linuxcnc, either retrofit used machines or make their own.

Frank

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