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Is a CNC the right solution for me?

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Alex Sutcliff08/03/2021 11:16:16
3 forum posts

I'm looking to buy a cheap hobby CNC machine to cut circles in wood to make lids for glass container candles. I like the idea of having the flexibility of changing and improving the design with engraving later down the line but for now I just need to cut a decent circle and maybe rout out a lip.

I need to be able to bang them out fairly quickly with space for two at a time and be able to send the design from my pc in the Lounge to the CNC in the garage either remotely or via USB stick.

I don't mind having to do a quick sand down of the edges but I want to be able to do 50 in a day without a long cutting time or preparation past the initial setup.

The lids would be either MDF or pine 20 ml thick with diameter of 100 ml. I was looking at something like the 3018 or anything around the £200 to £300 mark. I wonder if this would be strong enough and fast enough for my requirements? How long might it take to cut this circle and what power input rating motor would cope with my wood thickness?

Any advice on this would be much appreciated

Alex

Martin Connelly08/03/2021 14:01:55
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1691 forum posts
181 photos

The speed of turning out parts will depend on a number of factors. The standard spindle as supplied is (I believe) 3000 rpm. This will limit how fast the part can be traversed without overloading the motor because at high speeds the tool may be trying to take a larger bite than it can cope with. For example if you wanted each edge of a 2 flute cutter to cut 0.01mm per edge on each pass you would need a feed rate of about 60mm/minute. For a 100mm diameter circle with a circumference of 314mm (100 x pi) it would take 314/60 = 5.25 minutes plus tool change time and lead in/lead out. If you used a single flute cutter double the time. If you need to do a number of passes due to depth or width being more than the spindle and cutter can cope with then multiply the time by the number of passes. Bigger diameter means more time, smaller diameter means less time. You may need to speed up or slow down the feed rate to suit different materials. The numbers above are just rough approximations but should give some idea of the time a part may take. Adding a lip will need a further time as will tool changes (unless you can do all the grooves first then all the lips later to save on tool changes). I have recently done a groove in some pine for a glass tube to fit in. I set it up at 30mm/minute but can't remember if I upped the feed rate once I had the cutting process going. I don't do a lot with wood so I probably went at it a bit cautiously at first, I use Mach3 so may have gone up to 90mm/min (300% is max allowed).

p1150666.jpg

The groove is Ø5mm tube is Ø104mm with a wall thickness of 3mm and may be cemented in or left as it is at the moment with leather wedging it. The outside diameter was also CNC cut from a roughly square workpiece. The centre is marked because I stopped the process after cutting the centre out to add a central clamp and remove the outer edge clamps. This may be sanded off at some point. Can you tell I am doing it for someone who hasn't completed the design yet?

Martin C

Oops some spelling errors crept in.

Edited By Martin Connelly on 08/03/2021 14:03:49

noel shelley08/03/2021 14:18:14
486 forum posts
14 photos

Hole saws would do this, quickly and also do the groove, in 2 operations. Much cheaper and faster. Or rotary table and small mill. Noel

Journeyman08/03/2021 14:28:34
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943 forum posts
173 photos

Sounds like you need a small CNC router. This 3040T from Amazon for example. I am not recommending this particular machine as there are many variations on the same theme as normal the good the bad and the downright ridiculous. They are however designed for woodwork rather than cutting metal the spindle speed is usually up to 20,000rpm.

Have a look at MYCNCUK for more/better info.

John

Journeyman08/03/2021 15:19:28
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943 forum posts
173 photos

Looking again at the original post, I think one of these small machines would be unlikely to cope with the 50 per day criteria. I would guess that in industry lids like those described would be churned out on an automatic lathe of some description.

John

David Colwill08/03/2021 15:32:40
739 forum posts
38 photos

I think if you are spending £200 / £300 you are going to end up with a project. I am not saying that it can't be done for that money but I think you are unlikely to get good results without a fair amount of tweaking and playing around. Like John said above there are some pretty crappy offerings in amongst the mediocre. an old Denford starmill or novamill with a modified head would do it, if you can find one.

David.

Steve Withnell08/03/2021 15:34:28
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832 forum posts
219 photos

I doubt anything 'hobby' will do 50 a day 100mm diameter and 20mm depth to be honest. Hole cutter and some sort of lathe fixture to tidy up the edges would be my starting point.

I cut some large gear wheels for a friend in 6mm MDF in sets of three sizes, the largest being 100mm. 15 wheels was 5 set ups and really tedious. I would have struggled with 20mm thick MDF, the machining time would have gone up 3x or so. I used a Sieg KX1, which was fine for the small quantity of thin wheels, if a bit tedious. I have the 3018T engraver from Amazon and it's certainly not got the guts to do that sort of work (it struggles to remove copper cladding from PCB with a 3mm cutter) even though the table size is a bit more amenable. I paid about £180 for the 3018.

John Haine08/03/2021 15:34:35
3784 forum posts
220 photos

Do you mean 20mm thick? Your first post said ml.

If materials include MDF you will definitely need to use TCT cutters, HSS will wear out very quickly. A material that might be very nice is Valchromat, a coloured version of MDF using a different resin which is much less hostile to cutters and produces much "friendlier" dust. Google for your nearest supplier. Would need much less finishing too.

I agree with John, look at mycncuk for info on experience with the cheap routers and which are the best suppliers.

As for your lounge/workshop operating model, it depends on what connectivity you have and what the CNC controller runs on. If it was Mach 3 on a PC then you might access a server or your lounge PC to get the files, but TBH I am more comfortable if there is no Internet connection on my Mach 3 PC and prefer to use a USB stick to transfer programs. You would need to be in the workshop to mount the blank and keep an eye on the cutting (at least at first).

HOWARDT08/03/2021 15:39:22
707 forum posts
25 photos

A standard router mounted in a table would be quicker. At 20mm thick routing out on a cnc in one pass on a cheap CNC I would say is a no go. Quicker to rough saw on a band saw and rout the shape with a template.

not done it yet08/03/2021 15:40:54
5790 forum posts
20 photos

OR you could just make your own. Good enough to cut aluminium so easily manage wood.

Just an idea...... Link

https://youtu.be/qab0aceb7uw

Alex Sutcliff08/03/2021 19:07:16
3 forum posts

Thanks for all your feedback. I'm looking at the cnc option over the circular saw or simple router option because it would also serve as a hobby besides just making the lids. I'm just using the lid manufacturing to justify the purchase if I'm honest!

As for the spec, in hindsight I think the lids would be 14-18mm thickness as a maximum and the more realistic output expectation is around 150 per month but in batches of maybe 15- 30 in a day. I would also consider swapping out for pine if this would be easier to cut through than MDF.

I don't know if this all put together would make any difference if I increased the budget to £500 to get a better machine perhaps but that's the most I would want to put into this hobby I think.

Frances IoM08/03/2021 19:52:37
1072 forum posts
27 photos
as others have said MDF is a pig - hard on cutters, you need very good dust extraction as you definitely don't want to breathe the dust thrown off by routers - make sure the router has good extraction as the fine MDF dust will take days to fully drop out of the air.
Mark Easingwood08/03/2021 22:28:29
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28 forum posts
6 photos

Hello,

I have no experience of these mini routers, but I am doubtful that they would have enough power to do what you are suggesting, up to 50 times a day. In industry today, I expect they would be produced on automatic lathes, or CNC routers. In the past they would probably be produced using an overhead router, such as a Wadkin LS. Using appropriate jigs. (Used mine today, only to cut plastic tho!)

Handheld woodworking routers run at around 20,000 rpm, and are rated at around 1000-2000 watts. I use a 2000 watt router, with ½ inch cutter, ½ inch depth of cut to rout softwood staircase strings. In hardwood ¼ inch depth of cut is more comfortable. The downside of routers are noise and dust. The dust goes everywhere, as Frances said, and the high pitched noise, annoys everyone.

As HowardT said, a handheld router inverted in a table, and suitable jigs would do what you want, Bandsawing first will save a lot of strain and dust, and will mean you only need one pass around the outside. Both MDF and softwood will leave you a sanding challenge.

Using real wood, will mean routing against the grain, in two of the four quarters, leaving a rough finish, the less close grained your timber, the worse it will be. Sanding the edges of MDF is tricky, as the fibre ends tend to flick back and forth as you sand, it's a bit like sanding the bristles on a scrubbing brush!!

Turning the blanks on a lathe, would allow for sanding the edges at the same time.

You also have to work out how to hold your blank, whatever machine you use, as you are machining through 360 degrees, clamps are a nuisance. You can use a couple of wood screws, if the holes don't matter, otherwise you are into vacuum chucks, and more expense.

Wadkin LS

Wadkin LS Operating Guide

The operating guide, probably from the 1950's or 60's, has lots of information on jigs etc, including Tap and Die box making, my favourites are the jigs for spectacles.

Mark.

AJAX08/03/2021 23:33:08
182 forum posts
42 photos
Posted by Alex Sutcliff on 08/03/2021 11:16:16:

I'm looking to buy a cheap hobby CNC machine to cut circles in wood to make lids for glass container candles. I like the idea of having the flexibility of changing and improving the design with engraving later down the line but for now I just need to cut a decent circle and maybe rout out a lip.

I need to be able to bang them out fairly quickly with space for two at a time and be able to send the design from my pc in the Lounge to the CNC in the garage either remotely or via USB stick.

I don't mind having to do a quick sand down of the edges but I want to be able to do 50 in a day without a long cutting time or preparation past the initial setup.

The lids would be either MDF or pine 20 ml thick with diameter of 100 ml. I was looking at something like the 3018 or anything around the £200 to £300 mark. I wonder if this would be strong enough and fast enough for my requirements? How long might it take to cut this circle and what power input rating motor would cope with my wood thickness?

Any advice on this would be much appreciated

Alex

I use an old but fairly capable CNC router at work. I'm assuming it cost a few thousand when new and is presumably more capable than the one you mentioned. However, I would not want to use it for a batch run in the quantities you suggested. I prefer to use a CNC laser (cuts 6mm timber with ease) and sometimes use this to cut MDF templates that can then be used with a handheld router and bearing-guided router bits. A decent handheld router (with 1/2" shank) and sharp cutters can make very short work of cutting timber and man-made boards.

JasonB09/03/2021 08:19:23
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Moderator
20289 forum posts
2218 photos
1 articles

The biggest problem with the smaller machines is they don't have much grunt so feeds and depth of cut are quite low. I did see a video of a 3018 Pro doing a profile cut which is what you would need to cut the circle from a board and it was feeding at 200/min with a depth per pass of 0.25mm. ( did sound a bit low) Your 15mm thick x 100dia circle would need 60 passes of approx 300mm length so that is going to be 90mins per cut. Plus any additional time to form the lip and engrave.

By comparison my hobby mill would be quite relaxed going at 600mm/min and 2mm depth per pass so just under 4mins and that could be speeded up if needed. That could be improved more with a faster spindle as I'm topped out at 5000rpm

If you are having a lip than holding won't be such an issue as you can cut out the majority of the disc retaining it with say 3 small table. Then snap it out of the parent board and hold the other way up to machine the lip which will remove all traces of the tabs, simple MDF nesting jaws would hold the lid without marking and same jaws could be used for any engraving so minimal costs as the jaws only need making once and you are not spending out on miles of tape & glue or running a vacuum table all day.

CNC is also the way to go for any engraving unless as easy to change the pattern on the screen and bung in a USB stick.

As well as keeping the working enviroment dust free your main need will be to keep dust out of the cut, these small machines tend to run 1/8" cutters so you don't want them getting clogged up in a relatively deep slot so air blast to clear and the n collect the dust or run a vacuum constantly.

SillyOldDuffer09/03/2021 08:42:43
Moderator
7042 forum posts
1549 photos

My take, CNC is right for you, but the proposed workload and obnoxious material is brutal cruelty to a small hobby machine!

Trouble is hobby tools aren't rated to work hard continually so pushing them too hard or for too long risks overheating the motor or cooking the electronics. But a more powerful hobby machine would do it, and industrial grade CNC would eat the job.

Dave

Emgee09/03/2021 09:11:39
1988 forum posts
250 photos

Alex

Have you considered this type of attachment for a bandsaw

Lumberjack BSC254 Variable Circle Cutting Jig Accessory Attachment for Bandsaw

You still need good dust extraction but less of a problem with sawdust.

If the sawn finish was unsatisfactory it would be fairly simple task to sand to improve the surface finish.
The router you mention should be capable of the lip and engraving, the router can be working as you saw the next blank.

Emgee

Alex Sutcliff09/03/2021 09:15:10
3 forum posts

Okay thank you. I am open to falling back on a handheld router jig with a cheap hobby cnc or laser for decals but It sounds like I could also do it all by CNC if I just need more power.

@Jason b you mentioned your hobby machine would cope but dare I ask what machine you are using?

@Silly old duffer how much more of a powerful machine are we talking? Any suggestions?

John Haine09/03/2021 09:34:18
3784 forum posts
220 photos

As you are machining wood products a router would be a better bet than a conventional mill, the latter generally being limited in maximum spindlespeed which even though the spindle power is higher than a hobby router would limit the feed rate. I think Jason has a KX3 - these are nice but the usual suppliers in the UK seem to have dried up, however the new price is a few grand if available.

Regarding the material, I would repeat my recommendation of Valchromat over MDF. It's a much nicer material to machine, kinder to cutters and the dust is far less toxic than MDF, and needs little (or no) finishing to be decorative (and it's coloured). It is more expensive and hardish to get hold of. For specials you could consider Corian, lovely to machine, offcuts can be had from specialist kitchen suppliers often for free. Also available in various colours and finishes.

For quick routing at useful depth I guess you would need the equivalent of a reasonable handheld router as the spindle, at least 800W but better 1000.

JasonB09/03/2021 10:57:54
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Moderator
20289 forum posts
2218 photos
1 articles

Yes as John says I have a Sieg KX3 which is a far more substantial machine though with not a lot more X and Y movement and that has a 1000w brushless motor.

Finish on hardwood hardly even needs sanding

Engraving and boring melamine faced MDF

For the sort of volume you are talking about then a higher end hobby gantry router with decent slides, ball screws and a proper spindle motor would be the way to go rather than threaded rod and a basic electric motor with collet chuck stuck on the end which is what the cheaper 3018 type machines have. Something like the Smallest of these comprehensive kits and that would also give you the capability of non ferrous metals and plastics.

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