-
1 Attachment(s)
My new 6040 improvement plan.
Hi,
I recently purchased a China CNC 6040z (2.2kW, 4 axis, usb version with extras) for £1800.
I bought with FULL EXPECTATION AND ACCEPTANCE that it would require some upgrades and tweaks right off the bat. No problem.
I'm starting this thread to post about the problems and solutions s as I do them, in case it might help others in future (the forum spirit :-)
Here is the machine I purchased (attached).
Attachment 23330
-
Re: My new 6040 improvement plan.
My immediate attention was the water pump- threw it in the bin and got a much better and silent pump for £20 off eBay. Old pump binned. Never seen such a crap pump in my life!
-
2 Attachment(s)
Re: My new 6040 improvement plan.
Second (and probably the biggest of the lot)- SHIELDING- or lack of it!
Absolutely nothing is shielded not even the VFD cable!
I started with external cables to Spindle and Stepper motors.
Supplied VFD cable looks nice flexible rubber 'pond flex' cable. It's plain unshielded 0.75mm2 3 core and earth. The earth wire IS connected to spindle (thank god), but no shielding.
I replaced the entire cable with shielded 1.5mm2 CY control cable. To be extra careful, I also added external copper braid shield. It's now double screened.
I didnt replace the stepper cable, I suply added a copper braid sleeving to the entire length. Obviously, the sleeve is connected to earth....
Actually, no. The aviation connector barrel on the chassis is making contact with paint, not metal. NO EARTH CONNECTION! I had to scrape off paint inside the case to sort that.
Next job is shielding the cables inside the control box, then probably moving VFD to its own enclosure.
Attachment 23332
-
Re: My new 6040 improvement plan.
(X) Location, (Y) Location, (Z) Location!
The rest is just window dressing if the first 3 are not worth the cardboard it was shipped in :D
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
magicniner
(X) Location, (Y) Location, (Z) Location!
The rest is just window dressing if the first 3 are not worth the cardboard it was shipped in :D
Eh?
-
Re: My new 6040 improvement plan.
Hi Paisley.. where are you in the country mate?
-
Re: My new 6040 improvement plan.
I suspect Nick was on the sauce last night ;-)
But his point was if the basic machine can't hold tight tolerances, then everything is else is superficial.
Shielding is not as big a problem as people often think it is. None of my Denford machines came with anything shielded other than two sensors on the Triac mill. Everything else, including the spindles (VFD on the Cyclone lathe, and DC spindle on the Triac) used unshielded wiring, but then they're not using TTL level logic for inputs.
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
pd110961
Hi Paisley.. where are you in the country mate?
I'm in Paisley. Scotland.
-
Re: My new 6040 improvement plan.
I get that, however, as it's often repeated on this forum- not all China cnc are the same. Much of the reputation was for poor electronics was from early controller boards and VFD etc. I was very careful to get one with a newer controller (HC4-IV), decent steppers and a good spindle. There's nothing inherently wrong with the table and gantry design.
I know my way around electronics, so I wasn't bothered about doing some extra work to improve it. Even without the improvements, it hasn't glitches on me yet. It's done everything I've asked of it perfectly well.
At £1800 it's not the cheapest out there- I certainly wasn't going to spend £10k+
Plenty of people making really cool stuff with 6040's.
-
Re: My new 6040 improvement plan.
There is plenty wrong with the basic machine design.
If you're only doing softer materials with light cuts, it's not a problem, but if you try pushing the spindle, you'll get resonance/poor cuts.
If you have a DTI, try setting it up against the spindle noseat a typical cutting height, then apply some pressure against the spindle and see how much deflection you get. Having three sets of unsupported rails between the bed and the spindle does not produce good rigidity.
Then try testing for backlash. The setup used for the ballscrew endfloat is a couple single row ball bearings (which are usually cheap rubbish), with preload controlled via a single nyloc nut. Then the stepper motor couplers will most likely be cheap aluminium bellow type, which will crack if driven hard.
Plus the general tolerances will be questionable.
And in case you're wondering why I know all this, is I bought a 3040z as the base for a digitizing machine, knowing full well it's shortcomings. It does it's job as digitiser, but I certainly wouldn't want to use it as a router and expect it to produce good quality cuts and not need continual fettling.
-
Re: My new 6040 improvement plan.
I understand what you're saying and I agree to a point. Of course it's not going to be as good as a £10k+ machine, but I don't think it's as bad as you say. The newer models are build far better than the older (coupla years only) models. Either way, my only option is to try to improve in its weaknesses as much as I can and learn whilst doing it. It's fun anyway.
Take a look at this video (especially around 8minutes in). He's on my school of thought that the wiring is the main problem now, not the mechanics.
https://youtu.be/fdfJ_WZTxJY
-
Re: My new 6040 improvement plan.
Is it supported or unsupported rails?
If its for a hobby and occasionally using it, there is nothing wrong. / Did i just say that??? :hysterical:/ . But if you are trying to make something and sell it... And not to speak of if you are accepting online orders. One needs a totally reliable machine for this. Or it will be pulling hair 24h
-
Re: My new 6040 improvement plan.
The y axis rails are supported, the x axis is 2x20mm unsupported shafts (and ballscrew).
Z axis 2x13mm unsupported shafts with ballscrew.
-
Re: My new 6040 improvement plan.
Hi, you seem to be fixing problems you may not have
-
Re: My new 6040 improvement plan.
Prevention is better than cure.
-
Re: My new 6040 improvement plan.
Yep I’ll go with that. Is this your first adventure into home cnc ?
-
Re: My new 6040 improvement plan.
Yes. Never had a cnc before.
I work with electronics. Computers, circuit boards and garage equipment (brake testers etc). I'm forever having to knock together an enclosure, adapter, circuit board or prototypes for my own test jigs etc. The CNC is gonna make my life better!
Just today I was going to order some m16 washers with earth lugs. £36 for 50. I only need four. I'm gonna cut them myself from some 0.5mm copper sheet. That kinda thing.
I'm totally looking forward to using it for fun though- 3d reliefs, engravings etc.
-
Re: My new 6040 improvement plan.
Morning, you sound like you have an interesting job. I also have a 6040 and had to iron out quite a few problems along the way. I've started a new blog to help newbies to home CNC to share the problems and solutions.
The CNC Blog
-
Re: My new 6040 improvement plan.
Cool. I like that dust attachment. I was planning to do something like that. I have some 1" hose I want to attach to spindle. Could you post a pic of how you attached yours?
-
1 Attachment(s)
Re: My new 6040 improvement plan.
Hi there, the hose is a push fit (tightish) both onto the spindle and for the plastic hoover hose. I made it 0.1mm smaller than the dimensions on the drawing below. you can do this by reducing your cutter dia. Eg. cutter is dia 8.0 so tell the machine the cutter dia is 8.1
The material used is 12mm MDF
-
1 Attachment(s)
Re: My new 6040 improvement plan.
Here is the inside of my controller box. Plenty of issues to deal with.
NOTHING is earthed or shielded.
The VFD should bt even be in this box and the VFD output wires are draped right over the unshielded inputs of the controller.
Many if the power cables are undersized. Labelled as 1.5mm, but looking at them, I don't even think they are 0.75mm2.
Plan... rewire the whole thing. Shield and ground everything. Move VFD to seperate shielded enclosure...Attachment 23398
-
4 Attachment(s)
Re: My new 6040 improvement plan.
That last post was from 2 days ago.
I've rewired and shielded everything.
Moved VFD to its own box.
Fixed a few electrical safety issues.
Pump switch removed. If the controllers on, cooling pump is on. Simple.
It's all technically sound, but I think I need to go back in later and make it a bit neater.
I also plan to replace the 24v fan with a 240v version.
I haven't decided whether to move VFD control panel to new VFD box or leave it there. I'll think some more about it.
Attachment 23399
Attachment 23400
Attachment 23401
Attachment 23402
-
Re: My new 6040 improvement plan.
Over the top springs to mind, especially since everything was working with no problems.
I'm sure you'll carry on with what you think is right, however I'm just posting for the benefit of anybody inexperienced who might read this and think that all this is necessary. It might reduce the chance of problems, but there are thousands of machines that run with unshielded wiring and VFDs inside control boxes, with no issues what so ever.
And if you really were doing everything correctly, your new choke/filter for the VFD should be mounted on a sub-plate, not directly to the case ;-)
-
Re: My new 6040 improvement plan.
My machine has no shielding.
As far as the wire gauge goes the steppers on this type of machine only pull 3A max
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
Kev2960
My machine has no shielding.
As far as the wire gauge goes the steppers on this type of machine only pull 3A max
The underrated wires were the 240v power lines, feeding the 2kW VFD and the 24V power supply. The low voltage wires to the steppers were actually a lot meatier.
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
m_c
And if you really were doing everything correctly, your new choke/filter for the VFD should be mounted on a sub-plate, not directly to the case ;-)
It's just the photo, it's not mounted to the case, it's actually suspended in mid air. With the stiffness of the wiring looms, it's not going anywhere.
-
Re: My new 6040 improvement plan.
I see, I thought you meant the drivers and stepper wires my mistake
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
PaisleyPCdoctor
It's just the photo, it's not mounted to the case, it's actually suspended in mid air. With the stiffness of the wiring looms, it's not going anywhere.
I never realised the ferrite ring was still mounted in that bit of the photo. I was on about the silver box mounted to the side of the enclosure at the bottom of the photo. Technically any power components shouldn't be directly mounted to the case, they should be mounted on a sub-plate.
As there's a ferrite ring, I wouldn't bother shielding any of the power cabling in the case. Ferrites are very effective at stopping the noise that can potentially cause problems. I would however use good quality shielded and twisted pair wiring for the VFD speed control wiring, as noise on that can cause spindle speed instability. The control wiring less so. It will all be 12 or 24V, and it would take a lot of interference to cause any problems there.
-
Re: My new 6040 improvement plan.
Good advice. Thanks. The control wires are all double shielded. The silver box you mentioned is an EMI filter for the mains inlet, but you are right, it should be on a sub board. Its earthed and so is the casing. I'm gonna leave it for now. Next time I rejig the innards, I'll move it.
-
Re: My new 6040 improvement plan.
From personal (and expensive) experience with unsupported rails from one of England's finest CNC manufacturers of fluffy-dice, look at the amount of deflection you get over the x-axis travel, particularly if you ever fancy trying isolation routing of PCB (sounds like you're in that sort of ballpark), and also spindle rigidity.
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
PaisleyPCdoctor
Actually, no. The aviation connector barrel
I've heard these referred to as aviation connectors before now - as I understand it they are used for the headphones on radios. So, yes, they fly, but let's not oversell them. My main concern with them is these (and they are in common use for these machines) is that they aren't really rated for the currents that you might expect. For example
http://www.cliffuk.co.uk/products/cliffcon/zc.htm
You can see these are rated unto 1A. Probably not much of an issue for a small machine - your switching currents are going to be around 1.5-3A, but clearly out of spec for the connectors. My last iteration of <strike>upgrading</strike> updating my controller I replaced all with XLRs.
-
Re: My new 6040 improvement plan.
Like Doddy, I use XLR connectors for my steppers. Ideally these should be hard-wired but I found that I was taking the control box in and out of the router frame quite a bit while building and testing and the XLRs work fine in practice. I also use those "aviation" connectors for signal wires (limit switches, VFD control connections, etc) and they are fine for that. I bought a bag of 5 or 10 from eBay or Aliexpress or somewhere like that fairly cheaply. I think they were described as "GX16", and come with various numbers of pins. Watch for the ones with a lot of pins - they aren't the easiest thing in the world to solder if you aren't a dab hand with a soldering iron!
-
Re: My new 6040 improvement plan.
There are most definitely better connectors out there, but they are fine for the steppers. I still have one, actually 2 (male and female) at the VFD end of my spindle cable. Why 2?
The supplied VFD output connector was male. HUGELY DANGEROUS to have live connectors exposed like that! Live side of connectors must be female.
As I couldn't find a female panel mount socket, I opted to bring out the cable on a short lead with a female inline connector which mates with the male connector coming from spindle cable. I didn't want to wire it in directly cos I want to disconnect occasionally.
Anyway, after about an hour of constant (light) milling, the connector (inside) was no more than room temperature. I'm not worried.
-
Re: My new 6040 improvement plan.
I think for now, I've went as far as I want to improve the wiring- mainly shielding, replacing cables and repositioning components.
My next area that I'm going to look at is the flexing of the unsupported x-axis 20mm linear bearing shafts. They can be flexed, tilting the spindle back and forth on the y axis direction. With decent pressure on top and bottom of spindle, I can deflect it by as much as 1.5mm (estimate) either way.
I knew about this design weakness BEFORE I purchased the mill, knowing that I may need to address it. No big deal- I'm having fun!
I have some ideas to mitigate the effect and later to help cure it.
-
2 Attachment(s)
Re: My new 6040 improvement plan.
The first and easiest (and free) change is to the Z-axis assembly.
On this model, a 35mm spacer block has been added on top of the top bearing, increasing the Z axis length/travel by 35mm.
The way it's been built, I can very easily remove it and instead, mount it under the bottom bearing. The entire Z axis will be moved 35mm closer to the bed, but I can recover exactly that much by raising my spindle in the mount. I couldn't do that before as my tools wouldn't reach.
This will shorten the length of the "see-saw" motion, so in effect, the spindle tool will not move as far.
I'll measure deflection properly both before and after the modification.
Here a picture of the spindle and the 35mm spacer block.
Attachment 23408
Attachment 23409
-
Re: My new 6040 improvement plan.
If you're going to do what I think you are, it won't have any effect on the X-axis deflection. The pivot point (the rails), and the spindle/tool, will still be in the exact same positions relative to each other.
It will make a difference to the Z deflection, however I'm not convinced it will be that great. The Z-axis, although using unsupported rails, is quite a compact and stiff assembly. Although changing things around will reduce the pivot distance between tool and Z-rails, I wouldn't expect it to flex that much anyway. Certainly not much in relation to the flex of the X-axis.
-
Re: My new 6040 improvement plan.
Thanks for the reply.
You are of course right, the pivot point and tool tip will be exactly the same distance so deflection will remain unchanged. However...
The mod will allow me to move the spindle (and tool tip) 35mm CLOSER to the pivot point (by raising the spindle motor 35mm in its mounts.
I'll work out the deflection angle and I'll be able to exactly predict (using distance to pivot point and angle) the deflection distance before and after.
I couldn't raise spindle any further without the mod because of tool reach.
-
Re: My new 6040 improvement plan.
Although... on thinking about it, I'm really just lowering the spindle one way just to return it to the same position another way.
My head hurts. Lol.
I'll need to do some more thinking. Good catch! Appreciated!
-
Re: My new 6040 improvement plan.
Quote:
Originally Posted by
PaisleyPCdoctor
My next area that I'm going to look at is the flexing of the unsupported x-axis 20mm linear bearing shafts.
Give us a pic.
-
2 Attachment(s)
Re: My new 6040 improvement plan.
Here are pictures of the y axis assembly. Excessive flex in x axis direction.
Attachment 23421
Attachment 23422