What cnc machine should I choose to buy? - Page 1
Forum section: electronics / general

author: Alexandros81
author_rank: Regular Contributor
timestamp: December 24, 2017, 04:18:59 pm
content: Hi from Greece.I want to get a cnc router.I want to use it to:carve in wood (make reliefs in wood)make pcb(s)At the moment I am not interested in using any other material such as alluminium.I am thinking of getting a 30x20 cnc 3-axisBy looking at ebay I wonder what does it mean when it is said "not intended for industrial use"?Should I go for something like this:https://www.ebay.co.uk/itm/USB-CNC-Router-3020T-3-Axis-incisore-Fresatrici-Engraver-Macchina-Engraving-NEW/332488176556?hash=item4d69d6f3ac:g:jR4AAOSwonBaKSA9or something like this:http://www.ebay.co.uk/itm/EU-Stock-3-Axis-DIY-Desktop-Mini-CNC-Router-Kit-3018-Engraving-Milling-Machine/142634822153?hash=item2135b2aa09:g:PD4AAOSw30tZr9wKI will be producing 4 encraved pcs of wood a day and maybe 3 pcbs a week. Budget up to 650eurosthanks

author: Bicurico
author_rank: Super Contributor
timestamp: December 24, 2017, 06:07:36 pm
content: All machines that fit your budget have serious issues:1) Low precision. Probably too low for any PCB work.2) Low repeatability.3) Reduced Z axis limits. Bear in mind that longer tools will further reduce the Z axis travel.Finally, a decent CAM software needs to be considered, as well as a matching post processor.Regards,Vitor

author: cncjerry
author_rank: Unknown
timestamp: December 24, 2017, 07:10:09 pm
content: I think you are looking at two different machines with separate requirements. To begin with, for PCBs you only need about .05" of Z travel unless you are drilling as well, then you might need 1/2". For wood routing in 3D you need several inches of Z travel. Also, wood doesn't require the precision of PCBs. I would look at those PCB specific units and then try to find a wood router.There are small PCB milling units that seem to crank out one or two PCBs before the backlash gets bad. I have a lot of money in CNC machines and have never had very good success making PCBs. Drilling - yes, milling - no. You really need a 25K RPM spindle and lots of practice. Even with the right spindle the tracks get wonky as the torque from the entry into soft copper could cause the entry to look like a comma. Even my best boards had small pieces of swarf that needed to be cleaned away. Some people have success. I've plotted decent boards on my CNC mills with permanent markers (fine sharpies) that I then etched. Most of us that tried routing PCBs using isolation generally gave up and went to ExpressPCB and others after a while. You can't beat those OCB services these days . A friend sent me boards for Scotty's Spectrum analyzer that are gold plated, purple coated and just beautiful. I don't know where he had them made but I wouldn't even think of routing them when you can have them done for that cheap. I paid like $250 for the boards and if you go to Scotty's you'll see how many there are.Jerry

author: nctnico
author_rank: Super Contributor
timestamp: December 24, 2017, 07:12:35 pm
content: IMHO a CNC machine is the wrong tool for making a PCB especially nowadays with many cheap PCB manufacturing services around like Seeedstudio. If you need a PCB quick then etching will yield better results for a lower price.

author: Alexandros81
author_rank: Regular Contributor
timestamp: January 06, 2018, 07:06:11 pm
content: If I go for a cnc machine for wood routing for the purposes mentioned abovewhich cnc is good?Can you suggest one so that I can have a look at the specs?Alexandros

author: AntiProtonBoy
author_rank: Frequent Contributor
timestamp: January 07, 2018, 07:00:15 am
content: I've been also eyeing the exact CNC models OP linked. I want to use it for artistic wood carving. Would be cool to know if someone had experience with those machines.

author: Kjelt
author_rank: Super Contributor
timestamp: January 07, 2018, 09:46:36 am
content: Sorry to say but engraving is almost zero force, so to engrave wood you look at 2mm v cutters going one mm into the wood.That is a totally different order then for instance putting a 6mm cutter 3mm into wood.IMO if you want serious woodworking with a cnc you need a heavy machine with heavy costs.I have a Heiz HIGH-Z S720Thttps://www.cnc-step.de/cnc-fraese-high-z-s-720t-kugelgewindetrieb-720x420mm/It costs over 3k€ and I have bolted it to the bench, and although it is not bad and works well on wood and plastick, for heavy jobs it is still a toy. The people at cnc forums laugh at it and have machines waying a thousand kgs. The spindle I use is low price still costs 250€ about the price of the entire cnc machine you were looking at.I just want to prevent a big desillusion on your part. So for soft wood a few mm at a time it might work.For woodcarving the biggest challenge is speed (or it burns) and accuracy and repeatability. If the stepper misses a few steps due to high force the workpiece is scrap. And yes this has happened to my 3k€ machine as well since it has no servos.

author: Bicurico
author_rank: Super Contributor
timestamp: January 07, 2018, 10:03:23 am
content: Hi,As I said before, these Chinese CNC mills are toys. Great to learn, do some experiments and if you like to use them to keep busy improving them as a hobby, that's fine.Just to put this in a different light: some cutting tools cost MORE than the whole Chinese CNC mill!It doesn't matter if you just want to cut plastic, wood or other "soft" materials: you will still need positional tolerance and repeatability.Take a look at these Roland CNC machines:https://www.rolanddga.com/products/3dThey are certainly more expensive, but still cheap, compared to a "real" CNC machine. I see them often in educational facilities and small companies that make components to produce fashion items (belts, shoe components, etc.), where "soft" materials can be used and precision is not so important.The next step in quality is to invest in a Haas CNC machine:https://www.haascnc.com/index.htmlThey basically represent the low cost CNC mills. Mass-produced in series (as opposed to individual fabrication on most competitors), they are cheap and, well, not so good, when compared to DMG, FPT, IMSA, Mikron, just to name a few.Pricewise and speaking out of my head, the numbers are vaguely:Chinese eBay CNC: 150-500 EuroRoland: 5000 EuroCheap router from small but reputable manufacturer: 10.000-40.000 Euro, depending on size and spindle and accessories like automatic tool changeSecond hand mills: 20.000-500.000 Euro, depending on age of the machine, controller, state of the machine, size, number of axis, accessories, etc.Haas CNC: 40.000 Euro (VF-1)Regular high-quality CNC: 100.000-1.000.000 Euro (or more)Hope this puts your quest into perspective!Finally, bear in mind that you need a CAM software for 2D, 2.5D and 3D programming. While simple 2D and cycles can normally be programmed on the controller, any 3D CAD file will need to be programmed in a CAM software.While there are some almost free options (take a look at Autodesk range of products like Fusion with HSM, ArtCAM and PowerMILL), you will need to have a matching post-processor. This can be from easy to configure yourself to extremely complex requiring the service of a professional CAM supplier. Note that many of the Chinese sellers include a CD with cracked software - normally ArtCAM. Used to belong to Delcam, was bought by Autodesk 3 years ago. This could mean legal issues.Regards,Vitor

author: Kjelt
author_rank: Super Contributor
timestamp: January 07, 2018, 01:48:37 pm
content: Quote from: Bicurico on January 07, 2018, 10:03:23 amFrom your own link the prices start at 10000 euro ex VAT.

author: Bicurico
author_rank: Super Contributor
timestamp: January 07, 2018, 01:58:02 pm
content: As I said, I did speak out of my head and did not make a full price survey specifically for this thread.But while CURRENT Roland CNC machines may indeed cost 10.000 Euro, I have seen cheaper ones staring around 5.000 Euro (as I recall it).I *think* you can sometimes get much better prices on sales, stock clearances or if you manage to buy it as an educational machine (because you or a family member is a student).I MAY be wrong on this, as the last time we had a Roland CNC in our office was probably more than 15 years ago and prices/condition may have changed.And please don't take my responses in a negative way - I am trying to just argue what you need to consider, if you don't want to get disappointed:- axis travel in X, Y, Z- bear in mind that you need to eventually subtract the tool length from Z axis travel and that there are min/max heights of part you can machine- precision in X, Y, Z- repeatablility (aka: you go to X10Y10Z10 5 times - will the machine hit the same spot, even if it has a positional error due to precision, or will it go to different places?)- spindle: speed, how to select speed (fixed speed, manual potentiometer, automatic through NC code "S")- what controller: what are the capabilities, does it support drilling cycles, etc.- how fast is the machine?- ...Also, note that professional machines need clean compressed air and three phases, so the normal home plug will not do.Finally, bear in mind the noise, vibrations and, above all, the particles that will be blown in the air. These machines are not suited for office - they require a shop floor!Regards,Vitor

author: Galenbo
author_rank: Super Contributor
timestamp: January 20, 2018, 03:12:08 pm
content: Quote from: Alexandros81 on December 24, 2017, 04:18:59 pmNo CE markNo safety barriersNo dust/waste collectionNo decent calibration possibilityNo automatic feedNoise above comfort levelNo automatic zero-ing of axesNo coupling with production softwareNobody to service the machineNo support/long time supportNo replacement parts availableNo greasing of the spindlesNo reports generation