Lowcost capable CNC - Make vs Buy? [Archive]

View Full Version : Lowcost capable CNC - Make vs Buy?

Andrewg

10-04-2020, 11:09 AM

Ok, you can guess the answer, because I wouldn't be writing here if I hadn’t concluded ‘make’ remained a compelling option (and wanted your help!). But I hope laying out some facts and reasoning will help others who come here with this question. And those who know better can correct/encourage me.

Since the arrival of cheap motion control systems gave birth to Home CNC, huge ingenuity has gone in to replicate the key expensive mechanical functions- linear motion and positioning. The standard solutions of profile rails and ballscrews were too expensive hence draw slides, bike chains, skate wheels, timing belts and V-slot. These have added to the part count and complexity of design but have (for some) found a sweet spot of performance and price that has attracted a lot more makers .

So in the maker ‘design around the problem’ corner we have people like Open Builds and Carbide 3D who offer a kit of parts based on skate bearing on V slot extrusion with timing belts or leadscrews. Today a Workbee (https://ooznest.co.uk/product/workbee-cnc-full-kit/#size-colour)or Shapeoko (https://carbide3d.com/shapeoko/)is available as a kit for around £1,400

To me this is a base line - For £1,400 I can be up and running in a fairly short time with plenty of support and a community to help me through the learning process. Granted the machine will have significant weaknesses, but at least I am cutting and learning.

However the continued superiority of the profile rail is evident in the multiple upgrades of these machines, resulting in the slightly bizarre solution of V-slot extrusion used as a base to bolt linear rails. Carbide 3D now offers a linear rails and lead screw or ballscrew upgrade for the critical Z axis. QED.

Meanwhile the increase demand for cnc systems has reduced the costs for key components like Hiwin profile rails and spawned cheaper copies. Add sites like Aliexpress and Banggood that allow access to the Chinese supply chain and the DIY builder can now use the correct parts, just of lower quality.

For some time it bothered me that few manufacturers seemed to be exploiting this route. After all the Chinese 3040 and 6090 machine that flood ebay are still mainly using unsupported round rails(Good enough for the market they target I guess?) The better Chinese makers like Omni CNC (https://www.omiocnc.com/products/x8-2200l-usb.html) do offer linear rails and ball screws in the 3040, 6090 sizes but don’t have a UK distributor. Another Chinese maker, Quick CNC supplies larger machines (6090 and bigger) which are available locally. Their smallest 6090 is marketed as the Laguna IQ in the States, and is available in the UK as the Itech K6090T (https://www.scosarg.com/itech-k6090t-q-series-desktop-cnc-router) for £5,400. The suspicion is that ti would be mechanically good but electrically more suspect.

More recently I2R (https://i2rcnc.com/)launched a new range of budget machines with their smallest 600x600 cnc available in the UK for less than £4k inc through Axiom in the US and StoneyCNC (https://www.stoneycnc.com/i2r-4-cnc-router-610mm-x-610mm-bed/a4116?c=3552) in the UK and sports linear rails and ballscrews. Felder, a quality woodworking machines brand have recently entered the budget end of the market with the badged Hammer 47.82 (https://www.felder-group.com/en-cn/products/cnc-machining-centres-c1953/cnc-portal-machine-hnc-47.82-p142995) (around £6-7k I believe), though interestingly with leadscrew not ballscrews.So the market is getting more competitive and crowded.

So to buy a ‘semi serious’ home machine, I am looking at £4k minimum and probably £5-6k. This remains a big jump from the £1,400 Workbee. It seems therefore there remains a sweet spot for DIY solutions if by smart sourcing and support from people on forums like this, I can design and build a machine in a reasonably short time for around £2k that exactly meets my needs (and works!).

I should of course acknowledge that for some the journey is the point, and I do feel the pull to test myself by building my own, but I am trying to make a more rational calculation. Many of the builds described here are epic and must have left the builder forever changed (and better for it one hopes) but a cold calculation of time spent and opportunity missed (assuming you want the machine to make things) would put the true cost of the machine far in excess of the £10k for a decent industrial no compromise machine!

I started writing this to convince me to stop reading this forum and dreaming of building...but it seams to have backfired. So I will now try and distill what I have learnt here and elsewhere into a plan of action.

JAZZCNC

10-04-2020, 02:59 PM

It's simple really.!! . . . If you need a machine for business and have the work for it then buy one or have one made by someone like me as you are up and cutting quicker, so earning quicker. I've built machines for people costing £5k and the machine as paid for its self within the first few months or even weeks in some cases.

However, if your DIY and it's just for pleasure and have the time, patience along with the tools then just get on with it start building forget how long it takes, it doesn't matter. What matters is how you do it.
If you try to cut corners and do it on the cheap then at best you'll have an under-performing machine and at worst you'll have a pile of expensive scrap. Cheap solutions like using Mdf, linear draw slides, chains and even belts if not done correctly are a waste of time if you want a serious machine.
The only way to have a machine that's worth the effort is to do it correctly from the start and buy components that are fit for purpose. This doesn't need to be expensive either, many secondhand industrial components can be found that even if 10+ yrs old will still be far far superior to any of the cheap alternatives used.

However, you don't even need to do this if you are prepared to buy from china and look around. With £2k if you shop around and buy wisely you can build a very decent machine that will match and in some cases greatly outperform many of the machines you mentioned. You just have to wait and get your hands dirty, which is half the fun if your into DIY.

Forget any Cheap hack routes they don't work well or last longterm.

It really is that simple. If for DIY Build it good with decent bits. If a business just Dig deep buy it and earn it back quicker.

Andrewg

10-04-2020, 04:12 PM

JAZZCNC

10-04-2020, 05:20 PM

Indeed Jazzcnc,
So given I don't have a business case, but want to explore what the capability would bring to my workshop....the choice comes down for me at least to buy a Workbee or build my own for a budget of £1.5 to 2k. This forum shows that this second route is viable and is the route I am keen to take.

Forget the WorkBee or any of those you will be disappointed I promise you that.!
The Budget needs to be 2K to do it right if building DIY.

I should say I want a machine to cut hardwood in my furniture making workshop. 600x600 work area because I don't have the space and have plenty of processes for which this is big enough. Also helps with accuracy keeping small I believe. Want to cut joinery so 0.1mm repeatability. It will be a workshop machine that won't run all the time but when used needs to be reliable and quick (5m/min cutting?). A build I can complete in two weeks full time ideally..(planning, dreaming excluded)

600 x 600 is the perfect size to start your first DIY build. 5Mtr/min cutting no problem, if done correctly you'll double that with a bit to spare.
0.1mm repeatability, again no problem and easily able to achieve better if done correctly.
Building within 2wks could be a stretch for your first build and would require everything to go perfectly and put in some long hours. And obviosuly you have to have everything needed to hand.
For reality's sake, I'd allow your self a full month for fully built and working machines and work shorter hours.
Don't underestimate how long some of this stuff takes, just the wiring alone could take a full week if you are not used to doing it.

Frame
Stiffness directly effects performance so important. Unlike manufacturers, DIYer does not worry about shipping, so a steel frame, welded ideally. Epoxy leveling process allows imprecision to be addressed. However I would like to go Ali extrusion and shimming if possible alternative to avoid epoxy and steel working plus flexibility to extend/change frame in future.

Again Ali extrusion is perfect for first machine as it's easily worked with and accurate. However, you must use the correct type, size and not go with the light duty stuff often found on machines like the Workbee's etc.
It's also very very important how it's all fastened together and plates etc. Done correctly it's very strong and perfect for wood routers.

Mechanics
Linear rails, ballscrews and correct support bearings sourced from good chinese supplier as set. Leadscrews seem possible compromise that many designs accept, attractive as their lower profile nuts allow leadscrews to more easily fit between bearing rails and keep design simole. Guess wear and lower efficiency not a killer for home machine that operates fewer hours or am I wrong?

Don't compromise go with ball screws every time. A quality lead screw and nut that can get close to ball screw efficiency/accuracy will be just as expensive as Chinese ballscrew and won't be massively better in quality.

Dual drive Y axis seems to be preferred for simplicity now electronics can cope with squaring Gantry especially if drivers have stall detection.This especially of value to me as I want to be able to machines end of pieces held vertically through table.

Not strictly required on a machine this size if just cutting woods. However, it is better if you want to cut aggressively or want to cut very hard materials or aluminum, brass, etc.
Not all Drives have stall detection, in fact, very few do, even then they only work in a limited way. A much better solution is to use Closed-loop Steppers which have come down in price massively. Far better than the standard stepper system.

But again going back to usage and Budget, using a single screw setup is much cheaper and if you don't plan on cutting aggressively or harder materials then it could be wasted.
The other thing is that if you design the machine and plan the control box correctly it's not a very difficult upgrade at a later date to just stick another ball screw on and fit another drive in the cabinet.
I've built many machines for people like your self who were on tight Budgets and didn't exactly know what their needs were going to be so this approach was taken (all my small machines are electrically designed to do this). Very few actually found they needed to upgrade and those that did then it was a simple few hours to upgrade which they did them selfs.

Principle design challenge are the plates required to mount the components and join it all together. Aluminium can be machined with wood tools. Aluminium tooling plate is already flat, so either they can be cut and drilled myself or waterjet cut by contractor. Adjustability is principle to adopt rather than precision.

If you cannot make them your self by any of the methods you mention then I suggest you get someone to machine the parts rather than cut them on a waterjet or laser. unless they are thin parts. Both water and laser leave a taper on the edges of thick parts which can cause you more grief than it would to cut them your self with a hand router.

Gantry
Make it L shaped and use stiff large box section or extrusions. Extrusions make fitting everything much easier. Rails on front or top&front. One thing that eludes me is how best to join two extrusions to make L, what fitting works that way?

The best method for the "L" gantry is to bolt into gantry end plates with the ends. On a narrow gantry like what you want you'll get away with just one Bolt in the center which goes from the underside into a T-nut on the upper profile.(or can drill and tap the profile directly) However, it's important that you have a piece of material which is a nice tight fit that goes into the slots between upper and lower profile. This stops movement from sliding and the single-bolt clamps the profiles together. More bolts could be added but on short length like this it's not required.

Electrics
Nema23 steppers are big enough for small/medium machine (exact force and inductance to be determined), matched with proper drivers (digital, stalll detection?) and serious power supply (toroidal). Homing limit switches, inductive for accuracy and reliability. Get shielding and earthing of wiring right. Think through positioning and routing of everything.

Electrics are the KEY to a great machine. Take your time, don't cut corners and if the budget allows use closed-loop steppers, in fact, save up a little, wait a little longer if needs be, it's worth the wait.

Electronics
Mach3 and printer ports are old hat. Ethernet and UNCNC or Acorn seem to get thumbs up, though there are also dedicated controllers and open source solutions based on grbl are getting better.

Again KEY don't cut corners. Forget Grbl or open-source, yes it's getting better but it's still miles away.
If you want quick and good at a reasonable price then go with UCCNC and one of there controllers like the AXBB, there is nothing better for a wood router for the money.
Or if your like a challenge then take a look at Linux CNC and Mesa but get ready for a big learning curve.!

Build challenges
Machine accuracy is determined by build accuracy, so need a dial indicator and know how to use it!

A good design should make build process one of bolting together and aligning ideally, plus lots of wiring.

What have I overlooked?

Design is VERY VERY important and if done with a forward-thinking attitude then you can have a great machine for not a lot of money.

Lastly, let me just say don't get caught up in the "Steel is better than Profile" or " Must use Steel if want a strong machine" because it's often said by those who haven't built a machine using it.
I build machines using both or Mixture of both as is often the case and I can tell you now profile is more than good enough for any router which is to be used in a DIY environment or even a Small/Med business environment where speed and high material movement rates are not required. Accuracy and repeatability can still be achieved with a profile just like it can with Steel, that's down to how it's built the design and components used.

Good luck if you take this route and if I can help just ask.

Kitwn

11-04-2020, 06:55 AM

Andrew,
Sounds like you've done your research (Reading MYCNCUK with a pack of HobNobs and a large pot of tea?), I'm looking forward to reading the build log. Jazz will love you for not having actually bought any bits before asking for advice :thumsup:
My only suggestion would be to make the bed a bit longer if you have the room for it. My own machine can cut a little over 600 x 900. It doesn't affect the gantry in any way and I've never had a project that needs all that area at once yet, but a bit of extra length has proved necessary on occasions. My woodwork projects seem to regularly require parts that are narrow but a bit longer than a 600mm square machine could cut in one. Mostly accessories for my wife's weaving hobby.

BDH

11-04-2020, 08:14 AM

JAZZCNC

11-04-2020, 10:25 AM

Thanks Andrew & Jazz for the very useful questions and answers, they have helped me to understand DIY CNC a lot better although my 'need' is for a smaller machine but one that will tackle steel.
Brian

If you want to cut steel and the parts will fit then buy a Milling machine is my advice. Building a machine to cut steel is at a different level to one for wood/aluminum.

The principles of the building process are the same but machine design, materials, and components are very different.

BDH

11-04-2020, 10:44 AM

Many thanks for the quick reply Jazz, I already have 2 milling machines but neither would be suitable for CNC. Looks like I'll have to look for another!
Brian

Clive S

11-04-2020, 10:52 AM

Many thanks for the quick reply Jazz, I already have 2 milling machines but neither would be suitable for CNC. Looks like I'll have to look for another!
Brian

Why? what would the problem be.

JAZZCNC

11-04-2020, 11:05 AM

Many thanks for the quick reply Jazz, I already have 2 milling machines but neither would be suitable for CNC. Looks like I'll have to look for another!
Brian

Unless they are weak flimsy things then I'd be surprised if they couldn't be converted to CNC and have probably been done before. What machines are they.?

Andrewg

11-04-2020, 11:24 AM

Ah Kitwin, the siren call of ‘just make it a bit bigger’! But I take your point, extra Y length does not change the design or performance significantly.

And thanks for the appreciation Brian, I had hoped this would be of value to others. However others have already steered you away from gantry routers for steel

So where has Jazz left me:

Budget and spec is realistic (Hurrah) but time under significantly! I can live with the greater time commitment, though I expect I will be tempted into stretching the budget when it comes to the motors.and electronics. Definitely worth press on then:

Frame
Wood and plastic cutting router, so aluminum extrusion frame keeps things simpler for me.(avoids welding and steel work) Plates I will definitely be looking to cut/drill my own so will want to keep design simple.

It's also very very important how it's all fastened together and plates etc. Done correctly it's very strong and perfect for wood routers.
.
Sure I will need to come back to what joining methods for extrusions are best once I have a first stab at the design.

Mechanics
Ballscrews all round, but only 3
Single Y ballscrew will save a bit of budget, however I do need to cut ends of boards set vertically. With an under-table ballscrew and cross brace, I will needs to have the spindle sitting forward of the bearings enough to do this. I only need 65mm of cut distance beyond table. Is that a sensible design option?

Gantry

However, it's important that you have a piece of material which is a nice tight fit that goes into the slots between upper and lower profile.

I get the material in the slots to lock the two extrusions together, but see that 10mm aluminium bar is not a standard size so what to use? Options seem to be either machine a ½” aluminum bar down to 10mm slot size on a router table or forget the slot filler and have multiple bolts. By creating a gantry length ‘washer’ with regular clearance holes along it, I could use it as a guide to drill the access holes in the lower extrusion, then install bolts in it to mate with slot nuts in the upper extrusion, so they are bolted every 50mm or so. Avoids having to machine material to tolerance?

Electrics
Tempted by closed loop steppers - looks like for 2nm nema23 steppers it is about £40 stepper plus £20 driver vs £80 for closed loop motor and driver, so maybe extra £20 per axis well spent. Where will I see the benefit besides getting error rather than inaccuracy due to missed steps?

Electronics
There are enough challenged already, UNCNC it is.

Design is VERY VERY important and if done with a forward-thinking attitude then you can have a great machine for not a lot of money.

But still all down to the design, so guess I need to fire up Fusion360 and start designing. Plan to start from the Z axis and work out axis by axis. The Z seems a simple matter of sandwiching 15mm linear rails and 1605 ballscrew between two plates and getting the heights and clearances right...we shall see.

BDH

11-04-2020, 01:04 PM

The mill that would be most suitable for converting is a Graham Engineering one with a round vertical column but I thought that I would need to replace the leadscrews & nuts etc. As a manual machine with DRO it is very useful.
The other machine is a Tom Senior Major Mk2 ELT in horizontal mode.
If anyone has any ideas about how one of these could be CNC'd then I'd be most interested.
Brian

Kitwn

11-04-2020, 01:10 PM

Andrew,
As my wife, an accountant, has often said, you have the triangle of Time, Quality and Cost. Decide on the level of any one and the other two are inversely proportional.

Doddy

11-04-2020, 01:29 PM

Andrew,
As my wife, an accountant, has often said, you have the triangle of Time, Quality and Cost. Decide on the level of any one and the other two are inversely proportional.

Wow! Mine just nags.

JAZZCNC

11-04-2020, 01:37 PM

Mechanics
Ballscrews all round, but only 3
Single Y ballscrew will save a bit of budget, however I do need to cut ends of boards set vertically. With an under-table ballscrew and cross brace, I will needs to have the spindle sitting forward of the bearings enough to do this. I only need 65mm of cut distance beyond table. Is that a sensible design option?

Single or double ball screws it doesn't make any difference to if you can overhang or not. This is down to gantry design.
Many will sweep the gantry beam back from the centre of the bearing plates to recover lost tablespace. However, in your case this can't be done because you need the spindle to project past the end of the bed so your better with the gantry beam inline with the bearing plates.

There are other design methods, like having the long axis frame rails extend past the end of the bed. In this way you can have both methods and have any overhang amount you like(within reason). The cost is it takes up more physical room and slightly longer rails which cost more money.
I've used this design on several machines so that a 4th axis can be used on the end for turning and fluting etc. The same can be done with extending the gantry at one side and using the length of machine for longer work. (See pics)

Gantry

I get the material in the slots to lock the two extrusions together, but see that 10mm aluminium bar is not a standard size so what to use? Options seem to be either machine a ½” aluminum bar down to 10mm slot size on a router table or forget the slot filler and have multiple bolts. By creating a gantry length ‘washer’ with regular clearance holes along it, I could use it as a guide to drill the access holes in the lower extrusion, then install bolts in it to mate with slot nuts in the upper extrusion, so they are bolted every 50mm or so. Avoids having to machine material to tolerance?

Your way way over thinking this.!! . . . For machine this size it's not required. To be honest at this size you would get away with NO bolts. If not using the spacer method then 2 x M10 bolts spaced evenly along length and tapped into the upper profile will be more than enough.

Electrics
Tempted by closed loop steppers - looks like for 2nm nema23 steppers it is about £40 stepper plus £20 driver vs £80 for closed loop motor and driver, so maybe extra £20 per axis well spent. Where will I see the benefit besides getting error rather than inaccuracy due to missed steps?

Depending on which you get then the main differences will be smoothness and speed/torque.

The smaller closed-loop motors (<=3nm) all tend to be 3 phase and the motors use 0.9Deg step amount or 1.2 rather than 1.8deg found on typical hybrid steppers. This gives a smoother action but requires more pulses from the controller to get the same speed. But controllers like AXBB or UC300 etc have more than enough frequency so this isn't an issue.

Being 3phase they provide more torque and allow higher rpm's. Typical RPM where torque starts to drops away is 1000-1100rpm for hybrid stepper motor. With closed loop it's around 1500Rpm, but this does depend on other factors like quality and voltage etc. But in genral they are faster and stronger.

Larger (=> 4Nm) Closed-loop motors can be found either in 3phase or two phase versions.

But still all down to the design, so guess I need to fire up Fusion360 and start designing. Plan to start from the Z-axis and work out axis by axis. The Z seems a simple matter of sandwiching 15mm linear rails and 1605 ball screw between two plates and getting the heights and clearances right...we shall see.

Don't use 15mm for the Z-axis as it makes more difficult to build regards clearances and they are fiddly. 20mm cost very little extra and make for a much stronger and easier to build Z-axis.
Whatever you do don't cut corners on the Z-axis, it's THE one area you don't want to get wrong because it holds the tools so if it flexes or vibrates this will be seen in your work.!

Below are 2 machine designs, both can be single or twin screws and placed under the bed for protection. The larger one will extend past the end of the bed and the side, it also adjustable length 4th axis.

Edit: also a larger version with extended side rails for more front extension.

27791 27792 27793

Andrewg

11-04-2020, 03:51 PM

Your way way over thinking this.!! . . .

That is what I need - Keep me focused on the real issues

27792
Yes this is what I aspire to:Neat, clean, capable looking machine!
From your previous posts I am assuming I am looking at
- 45x90 extrusions on Y axis with two for the L gantry.
- 12mm Plate for ends and gantry sides
- 20mm linear rails all axis
- 1610 ballscrew, 1605 on Z driven via belt and pulleys so steppers can be tucked out of sight, 1: 1 gearing? is it worth added parts?

A little worried about the X/Z carriage getting complicated. If rails on front face and ballscrew on top, then couldn't it be a single plate again?

I am assuming this design cannot cut beyond the table, but by removing the gantry sweep back and maybe mounting the rails on the face of the gantry (and removing the control panel) I could create sufficient over run.

The smaller closed-loop motors (<=3nm) all tend to be 3 phase

The ones I was looking at for price were like these (https://www.ebay.co.uk/itm/HSS57-Hybrid-Servo-Driver-57HSE2N-Nema-23-Closed-loop-2N-m-Stepper-Motor-Kit/223661314475?_trkparms=aid%3D555018%26algo%3DPL.SI M%26ao%3D1%26asc%3D226064%26meid%3Db4325b829b234d6 ebd5b6b7cfd241db1%26pid%3D100005%26rk%3D1%26rkt%3D 12%26mehot%3Dpf%26sd%3D283049333185%26itm%3D223661 314475%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3 DSimplAMLv5PairwiseWeb&_trksid=p2047675.c100005.m1851) appear to be just steppers with encoder and therefore not 3phase though these (https://www.ebay.co.uk/itm/Nema23-2Nm-Closed-Loop-Stepper-Motor-Driver-3phase-Hybrid-Easy-DC-Servo-Kit-CNC-/201571286480) look similar but are described as 3phase and are £40 more so guess your advantages of 3phase closed loop will cost a little more. Know little about steppers besides frame size (NEMA) and torque (Nm) plus a vague idea that inductance needs to be worried about.

Don't use 15mm for the Z-axis as it makes more difficult to build regards clearances and they are fiddly. 20mm cost very little extra and make for a much stronger and easier to build Z-axis.

Again feedback from real experience appreciated. How much should I be worried about keeping Z axis weight down? I was assuming that on a small machine, I want to keep the weight being flung about to a minimum to ensure good acceleration and performance whilst allowing modest (lower cost) motors and drivers to be spec-ed.

Working on a Z axis, need to upgrade the rails to 20mm!

JAZZCNC

11-04-2020, 05:16 PM

From your previous posts I am assuming I am looking at
- 45x90 extrusions on Y axis with two for the L gantry.
- 12mm Plate for ends and gantry sides
- 20mm linear rails all axis
- 1610 ballscrew, 1605 on Z driven via belt and pulleys so steppers can be tucked out of sight, 1: 1 gearing? is it worth added parts?

Yes 45 x 90 with 10mm slot Bosch Rexroth or equivalent with this style of machine. This is type and size is required to allow easy fitting ball screws because the slots match up with Bk12 bearing blocks so no extra plates are required.

12mm could be used for the end plates but I wouldn't use it for the gantry sides and Z-axis. Normaly I would use 15mm for the end plates and making motor mounts etc and use 20mm for the gantry sides and the Z-axis.

A little worried about the X/Z carriage getting complicated. If rails on front face and ballscrew on top, then couldn't it be a single plate again?

Well yes and No.
Yes could be done but with this design, it compromises the machine in other ways. Rails on the front face only mean the distance between the rails is narrow so there's less support to the Z-axis rear plate.
Next the ball screw on the top means extra plates will be required so the bearings can be mounted, this means extra work and it also raises the screw high up the Z-axis rear plate causing an imbalance in how the forces are applied.

I am assuming this design cannot cut beyond the table, but by removing the gantry sweep back and maybe mounting the rails on the face of the gantry (and removing the control panel) I could create sufficient overrun.

No, it can't, well it does but not by much. This design doesn't suit cutting past the front. If you want to cut past the front then use a gantry design like what's used on the other machine along with a slightly different base frame for rail placement.

That machine uses ITEM style profile 120 x 80 with an 8mm slot. It makes a very stiff gantry and if you look closely you'll see one rail is on the front face and the other is on the top.

If you like I could quickly knock you up a model of how it would look.?

The ones I was looking at for price were like look similar but are described as 3phase and are £40 more so guess your advantages of 3phase closed loop will cost a little more. Know little about steppers besides frame size (NEMA) and torque (Nm) plus a vague idea that inductance needs to be worried about.

Those would work reasonably ok even thou 2 phase. The more important spec to look for is the voltage the drives can be run at. I
inductance is important but it goes hand in hand with voltage and I won't get too deep into why now, let us just say more volts allows higher rpm's and negates slightly if inductance is on the high side.

Now those drives allow Max 60vdc but that is the maximum and you never want to run at or near the maximum so we allow roughly a 10% tolerance on the voltage. So the ideal voltage for those drives is 54Vdc which will still allow the motors to give decent RPM.

However, if I was going with 2phase these are what I would use. The extra Nm means you can push the machine harder but more than this the extra Voltage range allows for higher speeds. Another advantage and money saver is that they will run on AC or DC so if you run on AC you only need a transformer. Whereas with DC you need to build the PSU with capacitors and bridge rectifiers which costs more money.

https://www.aliexpress.com/item/32799547111.html?spm=2114.12010612.8148356.3.69e73 421AESKcL

Again feedback from real experience appreciated. How much should I be worried about keeping the Z-axis weight down? I was assuming that on a small machine, I want to keep the weight being flung about to a minimum to ensure good acceleration and performance whilst allowing modest (lower cost) motors and drivers to be spec-ed.

With 3Nm with 50+ Vdc or the motors, I suggested then for normal woodworking conditions with a typical 2.2Kw spindle, etc you don't need to worry at all.
Only if you have special needs or are going to use the machine for work like 3D which has lots of high-speed positional moves and attach a heavy spindle-like ATC spindle will you need to consider weight or fitting higher rated motors that can handle it and give you the speeds you need?

Andrewg

11-04-2020, 06:12 PM

If you like I could quickly knock you up a model of how it would look.?

If you have the time it would be very helpful!

So the X/Z carriage with rails top and bottom and ballscrew behind, ends up being an inverted G rather than C - do you have a picture of the back?

Lichuan 5.5N.m closed-loop step motor (https://www.aliexpress.com/item/32799547111.html?spm=2114.12010612.8148356.3.69e73 421AESKcL)
Ok those are seriously stronger motors than I was thinking off, but I guess it is good you are revising my expectations for when I finally try and calculate what power I need/can afford! I wont worry about weight then, as I can see you are directing me toward a seriously solid solution.

Andrewg

12-04-2020, 09:23 AM

Ok, Just banged out a rough budget.
I'm sure there is much to add and adjust, but for now we are still near enough the £2k mark (£2,112 as I post this)

It is Google Spreadsheet here (https://docs.google.com/spreadsheets/d/1Bd4SjRMC_6B4LgfR-7Ur1NwGRP4fK09buj-zDJldTtQ/edit?usp=sharing)

Break it to me gentle what I have missed or under estimated

Also: Links were just what I used for budget numbers, and does not indicate intention to use supplier or endorsement of them

Doddy

12-04-2020, 09:44 AM

As of 9:30 - I guess your spreadsheet will be live and therefore subject to change as you respond to comments?

I note the comment re. suppliers, but buying from China - usually the best option - figure on getting stung for import duty especially for big/heavy/shiny items like these.

Those particular stepper drivers need DC so, depending on the transformer selection you might be cutting it fine (by £20 or so) for the rectifier & caps. Unless you've found a suitable toroidal transformer for £50. Hmmm, 36V?, and those stepper drivers?, you'll be compromising the potential performance - but that's a different question to the one you've asked here.

You've completely over-egged your CY cable costs - but that's no bad thing. You can cover the costs of all cabinet wiring and marking with the budget you have.

Oh, What about a cabinet to hold the control gear (+£75)? E-Stop ("oh shit!") button, miscellaneous switches, relays and bases, add £100 (or take that off your budget for the PC). Connectors etc, into the cabinet - add another £60, unless you're hard-wiring everything (I'd not recommend this option!).

You'll need a 24V and 5V supply also. Think if you're using DIN rail and terminals in the cabinet.

JAZZCNC

12-04-2020, 12:11 PM

Ok well, your high in some areas and missing stuff in others but it will all balance out to be around that figure if you shop a little better.
Though be honest prices are changing all the time with the world being in meltdown so I'm going to revise my estimate and say £2500 might be a more realisitc figure with the spec your at now by the time it's finished.
However you'll have a machine that is worth double that amount and will blow the likes of I2R, Felder, Axiom out the water.

PC cost is way to high, £75 will get you a PC to run this no problem.

Aluminium can be sourced cheaper is you try local metal suppliers. I pay roughly 30% less than Ali warehouse ask, then you save carriage on top if you collect.
If you have any local engineering place it's worth calling in and asking about there Scrap bins, sometimes they what they call little pieces of scrap we call gantry sides.!

Just little things and savings like this all add up. 5 for less than your 3.

https://www.ebay.co.uk/itm/5x-Inductive-proximity-sensor-detection-switch-PNP-DC6-36V-free-postage/193388427005?_trkparms=aid%3D1110006%26algo%3DHOME SPLICE.SIM%26ao%3D1%26asc%3D225076%26meid%3Dbcf02e 21976341b4a8aa2a282d7e75b3%26pid%3D100010%26rk%3D5 %26rkt%3D12%26sd%3D193335997795%26itm%3D1933884270 05%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDef aultOrganicWithTitleNsfwFilter&_trksid=p2047675.c100010.m2109

Now you have gone with the Uc400 but this means you'll need a breakout board which you haven't accounted for. This is why I mentioned the AXBB rather than uc300 or 400. It saves you money and as everything you need.

The drives you stated like Doddy says are 50Vdc max so you can't use a 36V toroidal as you'll blow them up. Remember the 10% safety margin.
This is another reason why it's worth paying an extra $20 for the bigger drives/motors. You also don't need the Capacitors and bridge rectifier so your costs for PSU are just the toroidal transformer.

Regards customs and buying from China. Try to buy everything from same place, for instance, Fred at BST can supply everything but the drives/motors, as it will save you money on shipping.
I would build the Z-axis my self as it would be cheaper and better.

Customs will charge VAT on the (**)invoice amount declared(**), there will also be an admin fee of around £15-20 from the shipping agent.
Ask the supplier to keep the (**) low.

With a little careful buying, you'll get the costs down more but you have missed a few reasonably pricey things, like an electrical cabinet but like I say it will probably balance out with things you have overpriced.

Andrewg

12-04-2020, 03:20 PM

Thanks Doddy and JazzCNC

Updated sheet to reflect your suggestions plus factored in 25% (VAT plus import fees) increase on imported items.....And indeed we seem to be hovering around £2,500 now, though with no attempt to push back much at this stage and I agree it is a well spec-ed machine.. I posted the link to GSheet as I couldn't work out how to post a table, but now it is a live tally of information accumulated in this thread.

Advice on sourcing from China noted and Fred at BST Motion had come up often enough here to know he is the go-to guy. When the time is right I will bother him for a full quote.(and hopefully trim the budget)

I have least understanding of the Electrics/Electronics (as you can tell from my first attempt at parts), but assume if I have sufficient budget, spec good components and take my time and the advice of this forum I will get through OK. Having sense checked the budget (growing but not out of control...yet), I am now focused again on generating a mechanical design I am confident I can make.....and as Jazz indicated it is all about getting the details right! Fusion 360 is your friend when you can get it to do your bidding! I've used it a lot for furniture design but importing parts and positioning and joining is new so on a bit of a leaning curve there.

So Jazz..what does that orange beauty look like from behind?

JAZZCNC

12-04-2020, 05:30 PM

So Jazz..what does that orange beauty look like from behind?

Here you go watch this.

https://www.youtube.com/watch?v=ro1ARsctFIo&feature=youtu.be

JAZZCNC

12-04-2020, 05:36 PM

Here's the other design with it's clothes off.

https://www.youtube.com/watch?v=qBUMYFMebwU&feature=youtu.be

Andrewg

19-04-2020, 11:55 AM

So I am still mulling design options
Is there something wrong with me finding the sight of Dean's machine undresses slightly arousing?! I certainly now 'get' the neatness and economy of this single leadscrew Y axis design: Standard BK.LK12 bearings mounting 1610 leadscrew on underside of 45x90 central heavy extrusion, motor tucked away by addition of GT timing belt and 1:1 pulleys. With single traveling homing/limit sensor fitted to Y axis under-gantry and drag chain safely out of the way under table......very nice.

As I am still looking around at other designs for ideas and still open to buying rather than making, wanted to draw peoples attention to another very nice UK router CNC kit that addresses the low-cost capable niche. UKCNC's D-500 kit (https://ukcnc.net/index.php?route=product/product&path=61&product_id=252)is £4.450+ VAT currently - 500x500 cutting area, all aluminium plate construction with linear rails and ballscrews all around.

Having just complemented Dean's single screw Y axis, the folks from UKCNC have come up with a very nice dual screw Y axis design. This is of interest to me who wants to machine board ends, as the middle 2/3 of the bed is open and unobstructed so no need for the spindle run beyond the end of the bed.

These guys seem to know what they are doing and so interesting to see their particular design choices:
1610 ballscrews all round, direct drive X and Z, 2:1 belt gearing on Z - this seems to be accepted wisdom then across many designs
15mm linear rails all round, 2 each side on Y - so perhaps interesting trade off between number of parts and size, as single 20mm rail per Y side more standard here for self build, but then a kit seller has sourcing savings when buying single spec rail in volume
Closed loop steppers - this seems to be a theme I'm picking up if you want reliability and performance on a budget
All CNC machined Ali plate construction - as they point out in the description this is not a cheap option for one off builds, but when engineered for low volume batch production this changes, and quality more controllable than when using extrusions.

It is certainly an attractive offering if self-build was off the table. The specs are slightly lower than what I started costing up from Dean's guidance, So say the self build budget materials were £2k min, additional £500 for tools etc then that is a £2-3k premium to have a proven design,support and fewer months of designing and making. For me it is a definitely an option should I have the money and 500x500 will meet my workshop needs.

Doddy

19-04-2020, 11:57 AM

So I am still mulling design options
Is there something wrong with me finding the sight of Dean's machine undresses slightly arousing?

Yes.

As I am still looking around at other designs for ideas and still open to buying rather than making, wanted to draw peoples attention to another very nice UK router CNC kit that addresses the low-cost capable niche. UKCNC's D-500 kit (https://ukcnc.net/index.php?route=product/product&path=61&product_id=252)is £4.450 currently - 500x500 cutting area, all aluminium plate construction with linear rails and ballscrews all around.

...and a grand in VAT, if that's of concern.

Andrewg

19-04-2020, 12:01 PM

....and a grand in VAT, if that's of concern.

Yes good catch - was about to correct, Probably £5,500 by the time delivery and VAT added

Doddy

19-04-2020, 12:05 PM

A couple of things grab me, though only glanced briefly at the site. Looks to be a single prox. sensor on the twin-screw axis - you'll be having to manual tram the machine if you crash it. Manual spindle speed control (I can't argue, my mill is currently like this), but obviously geared towards making sawdust. It's a machine-in-a-box, granted, and it's an easy entry if it suits your needs.

What we need is an enterprising soul that's prepared to pull together a similar kit of parts for a manly machine :)

Doddy

19-04-2020, 12:06 PM

...an do my eyes deceive me... is that an Arduino Mega in the kit?

Edit:

Aha!, they've cunningly slaved an Ardy on there for GRBL support. The electronics are built down to a cost - with some significant compromises.
Like I said - kit-in-a-box. I don't think it'd suit everyone.

Edit 2:

Not just closed-loop steppers, but integrated driver, too. I reserve judgement until I read up..... 2NM, 36V supply, 250kHz max input frequency, NEMA 23 size. Think the supply side of things will limit performance but... kit-in-a-box.

JAZZCNC

19-04-2020, 12:48 PM

JAZZCNC

19-04-2020, 12:52 PM

JAZZCNC

19-04-2020, 01:09 PM

Or a Twin screw single motor version.!!

27875

Andrewg

19-04-2020, 01:09 PM

Thanks Doddy, clearly those trying to design a 'kit in a box' have slightly different design and costs pressures to the self builder, so I am interested in the cognescenti here views on the design .

Broadly one off self builds benefit from overspecifying their parts, as the costs are not significantly greater and there is less experience to show where corners can be cut. However kit makers need to reduce parts costs inorder to have a margin. Some of those decisions will be good and worth learning from if properly understood, others potentially to compromise too far.

So for example JazzCNC has recommended strong 4Nm AC closed loop steppers, this kit has entry level closed loop steppers. Clearly both are sold on the advantages of closed loop, which is a good signal as the kit builder would question the extra cost.. That they might (oh, just have��) disagree on spec would not surprise me because the kit builder will have the minimum you can get away with.

Andrewg

19-04-2020, 01:14 PM

There is twin screw version as well.!

27871

Which is why when you recommend single screw as sufficient for a 600 wide machine, we listen, as you have done them all, not just stating what you did in your single build!......but anything you do like about their approach?

JAZZCNC

19-04-2020, 01:38 PM

Thanks Doddy, clearly those trying to design a 'kit in a box' have slightly different design and costs pressures to the self builder, so I am interested in the cognescenti here views on the design .

The design is ok and can't fault it really because to be honest Shaun as took most of my design principles and used them, just with different materials and put is own twist on it with twin rails. But essentially he's used my design principles, whether he'd admit that or not I doubt it.!!

Now I see issues with it which I'm not going to enlighten him or you with.!! . . . But what I would ask is why would anyone buy a machine they have to build themselves, which effectively means all they are doing is saving them selfs drilling and tapping holes in aluminum plate.?

Also, why buy a machine who's got an electrical spec which is far less than ideal and run on a Micky mouse control system running on a £9.50 development board fastened to another board that you can only buy from them when it goes Boom.!

Ok it's got closed loop but they are cheap nasty things with unknown integrated drives and running on 36v.! . . . Those that know, know that 36V is pathetic for router and these guys know this.!!. . . So a good question to ask would be why are they using 36V.?

Oh and then for £5.5K you still have a bloody Dremal for a spindle.!!

Doddy

19-04-2020, 04:45 PM

Thanks Doddy, clearly those trying to design a 'kit in a box' have slightly different design and costs pressures to the self builder.

Including recover of NRE, operating costs and profit. I'm not bashing them - they are a commercial concern, but I would expect for what I can expect their sales for a machine like this their skim off the top will be in the order of £1000-1500.

As an amateur, or enthusiast, or amateurish enthusiast then I make a decision as to the worth of that, and my tinker time. For me, I'd build from scratch, or bung Jazz 3k. If you want an off-the-shelf kit then it could be a viable approach.

Kitwn

20-04-2020, 02:59 AM

Andrewg

20-04-2020, 10:53 AM

How desperate are you to get the machine up and working for you? That's the real buy v build question since the cost of building an equivalent quality machine, including paying for a decent hobby-grade pillar drill and other tools, will be well below the prices quoted above. You'll need some of those tools for additional work on the parts you make with the router anyway.

Yes you are right - at £4.5k for a proven design, I though UKCNC's kit might stand against a self build with £2.5k parts cost, but at nearer £5.5k and lower spec components in some key areas it does not IF you have the ability to successfully pull off a self-build yourself and have the time. I hope their kit is successful and finds a market but I am still here banging on about self-build.

I guess my theme is that for a home workshop machine, 'MAKE' seems still to be a viable cost effective solution IF you have a suitable, 'worked out in detail, proven' design to follow and the understanding of the processes required. I think this forum champions this and has contributors that help others succeed. HOWEVER inferring from the many build logs that peter out and other discussions here, it appears many new builders grossly underestimate the time and expense that their dreams will require, are over ambitious and the majority FAIL to get from aspiration to using their CNC as a tool in their business or hobby.

As Doddy mentioned - perhaps a MYCNCUK reference design would be a good aspiration. It sort of is hiding in the shadows of many a build log and post here (and has JazzCNC's finger prints all over it). As talk is cheap, I want to resolve a design and approach that works for me before committing any money to my own build, and hope others will benefit from the process. meanwhile I hope someone offers a kit or product that compares favorably to my developed spec, so I don't have to waste my time reinventing the cnc router and get on with process and product development using it in my furniture workshop.

Kitwn

20-04-2020, 01:28 PM

There is almost too much information available for a beginner to know where to start and I simpathise greatly. If you look at other forums and blogs from CNC users you find people cutting wood using machines that would be laughed out of town by MYCNC forum members. Angle iron (or even aluminium) and skate bearings for rails, plywood frames for base and gantry, Makita routers as spindles and so on. If you want to make carved signs, bass relief maps of New Zealand to hang on the wall or other decorative pieces they will work well enough, but my own experience tells me that if you want to cut out pieces of wood that will fit closely together, which I believe is your aim, then you need the kind of machine described on this forum.

Whether that commercial machine is capable of such accuracy I have no idea but some demonstration from the manufacturer before you purchase it would be advisable. You should also confirm that the spindle can cope with the kind of cuts you want to make. I'd want to see an example machine cut out some pieces to my design before parting with that much cash. One of the things you'd expect to be paying for by buying a commercial product is a guaranteed level of performance.

I like the idea of a MYCNC reference design, and there are several close approaches to be found here, but there would need to be at least half a dozen variants to suit different budgets and requirements. The steel v aluminium choice will be different for different people and a wood-only machine can be a little less robust than a machine for cutting aluminium, though the dimensional accuracy still needs to be very good. Probably one of the trickiest parts of the design is deciding how you are going to do the final alignment of the machine and how to design it to make that as easy as possible. You need to keep this in mind from the start and a good reference design would include how to align it for best possible performance from the materials chosen.

Sorry, that turned into a bit of a brain-dump but what else are we going to do stuck indoors every evening? Maybe that should be a topic of it's own!

Andrewg

20-04-2020, 04:17 PM

Sorry, that turned into a bit of a brain-dump but what else are we going to do stuck indoors every evening? Maybe that should be a topic of it's own!

No thanks for thoughts - having more time to think about these things and hoping a few of you would too, is why I started my thread now.

You are right I am after a reliable wood workshop tool. It therefore does not need the duty cycle of a production CNC but must be robust and quick enough that when you turn to it, you can set it up and run a cut in a few minutes. Like other workshop machinery it will probably run a for a few minutes 5-15 times a day with a few longer jobs from time to time. I want to cut joinery so 0.1mm accuracy and repeatable must be delivered. I know that issues like safety enclosure, dust collection, fixturing and programming are just as important to get an effective tool, but first I need the right design.

Any reference design ere would have to 'show it's working' so each builder could decide whether to follow, enhance or cut corners but a few things are coming clear (I think) for the first time builder like me:

Aim, to minimise part count, processes (like no milling or welding), tools, time and complexity and so risk of getting to a working machine.

1. Size - You will always want to make it just a little bit bigger, but the challenges get tougher with size. So with ballscrews keep it below 1.5m and ideally below 1m in any axis. The shorter the axis the better for a first machine! So I am shooting for 600x600x125, but the design should scale to 100500x1000x175

2. Frame - Welded steel with triangulation for rigidity is best budget performance for self build, if you have access to welding. Epoxy leveling can give you the precision alignment of surfaces without post machining. However Aluminum Extrusion and 20mm Aluminium end plates is capable for a smaller non-metal cutting machine if heavy duty versions are used. I keen to avoid steel work and welding so am going the Aluminum extrusion route. Ideally plate designs will rely on precision marking and drilling of holes only to provide

3. Linear motion - Hiwin style profile rails should be used on all axis, all be it cheaper Chinese copies are good enough. They not only deliver the essential rigidity in all but the direction of motion, but the rails are a major precision structural element of the frame, don't need adjustment or maintenance. 20mm rails all around are ideal for this size of machine, whilst 15mm rails could be used.

4. Ball screws - Again cheap C7 Chinese ballscrews give high precision, low maintenance, low backlash, high efficiency so should be used throughout. 1610 on X and &m, 1605 on Z or 1610 with 2:1 gearing

5. Y Axis - Single central ballscrew fine for up to 750 width, but beyond that twin ball screws better, and allow for smaller motors (Same as other axis)

6. X Axis - L shaped gantry design. Rails on top/bottom of front of gantry. Ball screw on back. L from two 45x90 Bosch style extrusions allow BHK/BF12 bearings for ballscrew to mount directly to it, as does 20mm rails.

7. Z axis/X plate - Z axis is simple challenge of sandwiching rilsa and ballscrews between two plates, with 20mm raisl 15mm narrower than ballscrew assembly. X plate more complicated

8. Spindle - 2.2kw water cooler spindle seems standard, mostly as the ER20 collet takes up to 1/2in router bits and is quiet for long runs. I'm still wondering if this is overkill for wood cutting where max of 8mm cutters might be enough for most jobs.

9 Steppers - You need power not so much for speed as acceleration. Closed loop are now more affordably and give more power, smoother/quieter running and accuracy/safety as they will error if steps lost rather than spoiling project and/ ripping machine appart in accident! High voltage and low inductance motors allow the power to be delivered, so motors and drivers can be selected appropriate - 3Nm Nema 23 or bigger probably;y required

10 Wiring and control box - Each step is simple but there is a lot of it. Drag chains,earthing, connectors, safe separation of mains and low voltage. Electrical
interference, especially if there is a VFD for the spindle. etc Know little at this time about this area so much more work needed to define.

So before I order my rails+ballscrews set and my steppers plus driver from Aliexpress, my extrusions from Motedis and my controller from UNCNC. I need to be confident I have a design and and a route to the required machined Aluminium plates to pull it all together along with abuild approach (as you pint out, and I have only recently picked up - alignment of rails etc is critical)

SO another too long brain dump - you can see why I need to get this out, ti feels 2/3 complete but mising bits...back to CAD

Andrewg

26-04-2020, 09:45 PM

OK getting to grips with Fusion360. So just to show I have been listening (hopefully), here are some drawings showing the critical clearance and overall dimensions of my Z axis. A little more adjusting probably needed, as I am trying to get the standard components into as tight a practical design as I can manage. Have I over done it? A lot of faff to reinvent the wheel I suspect but a warm up for the more challenging X axis!

2798827989.

Still feeling like I am panning for gold on this site! Found some great photos of a XZ assembly in Joe's 1000x600x200 Build Log (http://www.mycncuk.com/threads/13178-Joe-s-1000x600x200-steel-and-aluminium-router-started/page5). Thanks devmonkey.

Also appreciate NordicCNCs build log - Whilst he is going for something much bigger and metal cutting, the mantra of keeping part count down and design simple chimes with what I want to do.

A few design choices still bug me:

Gantry: I absolutely get the L design and advantage of 45x90 extrusion for bolting the BK12 directly to. However I am not wild about the complexity this brings to the X /Z assembly. A 'C' shaped gantry where the screw can run between the rails would allow a simpler plate like. A 'C' from 45x90 (ie 180x90) seems overkill....but then if the BK/F 12 bearings (or FK/FL) are mounted to the gantry end plates then there is more flexibility in positioning ball screw and maybe using 3 slightly lighter extrusions 30x60 (ie 60x120 C gantry). Sure others inc Jazz have been here before, am I wrong to fear this?

Stepper Mounting: Direct drive fits with my minimal parts concept, but if I go for the more powerful Lichuan closed loop steppers they get quite long at 125mm! I liked how the UKCNC kit accommodated the direct drive steppers within the frame, but they are much smaller motors. So if 1:1 pulleys and HTD5 belt are only going to add £10-15 per axis and allow tighter envelope, then maybe. Are there other performance benefits, like acting as mechanical fuse?

Spindles: For wood, I'm not sure I need 2.2KW and ER20. I think 1.5KW and ER16 would be plenty as that would allow up to 10mm (covering common 1/4" and 8mm tooling). I can only imagine wanting to use 1/2" tooling to get 2" depth of cut or run a big surfacing bit. Then again I can see the 2.2KW water cooled spindles cost not that much more. Given the Shapeoko and Openbuilds crowd seem enthusiastic about adding 2.2KW beast to their less robust machines , what am I missing, or is it all for Aluminium cutting?