Yes I forgot about adding Redsail to my list above, also like your theory about ebay.Quote:
Originally Posted by HankMcSpank
Edit: Just had a quick search and Redsail don't look too healthy now or maybe I didn't look in the right place ?
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Yes I forgot about adding Redsail to my list above, also like your theory about ebay.Quote:
Originally Posted by HankMcSpank
Edit: Just had a quick search and Redsail don't look too healthy now or maybe I didn't look in the right place ?
There is a lot of crap written about unsupported rails.
Yes I know supported is better than unsupported but lets look at what were are faced with.
On the 6040 machine as an example the 60 which means 600mm travel is supported, it;s the Y at 400mm and the Z that are on unsupported rails.
The one I saw has 16mm rails fitted with 16mm ball screws. So taking the max length of the Y to be about 500mm can golden bollocks work out the MAX deflection of two of these rails ?
I would imaging it's very small.
These machines do have some drawbacks after seeing a few examples. So far what I have seen is often the motor mountings / bearings are kludged up. Seems to be on a haphazard basis as to where it was assembled as opposed to who's selling them.
Biggest drawback is the controller box with is absolute rubbish and an accident waiting to happen, however if you factor in a new BoB and three 542 drivers you still have a machine worth more than the sum of it's parts given that most of the mid priced ones have a high speed spindle and VFD included.
OK a custom build would be better, not necessary cheaper but many people can't or don't have the skills to do this but want a machine so that they can get working straight away. For them the end product is the goal, not machine building.
As regards cutting at high speed, they can't because they are not big enough to get up to speed before it's run out of room. Will they cut alloy ? yes but slowly but if you want to cut alloy you have chosen the wrong machine.
There is far too much emphasis on this forum about cutting speeds and cutting alloy to the extent that it's probably driving beginners away.
I have a little Roland 2200 engraver here, year dot, works by dragging the carriage on bowden cable on a plastic capstan. I have removed the spindle motor and replaced it with a diamond drag.
It's powered by a 24v Yoohoo board which was spare.
The whole thing is crap, it's slow, max speed is 3.2 furlongs per fortnight but it works and if I engrave some small letters in stainless [ Yes will do stainless ] then run the same program it doesn't double cut at all so accuracy and repeatability is spot on.
Thing is it does the job which is engraving gauges. If i posted this as a build on this forum I'd get shot down in flames but this is an example of the work.
Attachment 10856
That circle is 50mm diameter and the small script name is less than 1/2mm high.
Can only work out the deflection if you know the force, which obviously depends on what you're cutting and how you're cutting it. It's more meaningful to calculate the stiffness. You can do either with the spreadsheets that have been posted on this forum years ago...
So 32mm/min .. that's about what my mill did when I first converted it using an old unipolar stepper driver!Quote:
Originally Posted by John S
I certainly wouldn't do any shooting there, as an engraving machine is the right application for unsupported rails. The obvious reason is the cutting forces are low, so the appropriate size unsupported rail isn't too large. As soon as you require a bit better material removal rate, the required unsupported rails size is so large that it's much more economical to use supported rails. The problem is all too often people post a design with unsupported rails and expect it to work well at much more demanding tasks.Quote:
Originally Posted by John S
When someone (who will remain nameless) posts a machine with unsupported rails and calls it 'something more rigid that also has good performance' or says it 'will cut through a range of materials with ease and no chatter or wobble to be found', then then they really are asking for it.
John has we all know I'm not a fan of Chinese unsupported round rail or that matter supported but not because of strength. ? It's the quality that let's them down badly.
Push the machine remotely hard for any length and they soon become sloppy.
Same goes for rest of machine has well, the build quality is piss poor and has you know the devil is in the detail and these machines are thrown together in the cheapest possibly way.
It's the small details like ball screw end fixing just using cheap nasty deep Grove bearings, totally defeats the point having ball screws if they are going to float like a turd.
It's these small details that soon raise there ugly head when machines pushed.
Now to me the whole point to CNC machine is accuracy and repeatability and why woud you want to buy machine where you throw half of it away, has in the electronics, only to be chasing the slop out of the other half and scared to push machine for fear of turning it back to slop. ?
IMO even the mid priced machines are not worth the trouble.!
So I need to get you to build me a 6040 for about £1500 then without all the faults ?
Hypothetical question really seeing as I have recently bough a high quality MDF router off Geoffrey :thumsup:
Next question is will it do alloy at 27528 metres / min ?
Put it in the bloodhound car and it should just about do it.Quote:
Originally Posted by John S
Ok john well lets work on the same principles has the Chinese machines and throw another £500 in the mix which you would end up having to spend just to make it work anything like it should then has a one off deal just to shut you up I will build a machine with profiled linear rails, ball screws etc that will knock the Chinese rubbish into outer space.?Quote:
Originally Posted by John S
Instead of proving something that should be obvious (and is more easily proven by posting a list of component cost), I'd put my efforts into making a machine that pushes the boundaries. Coincidentally, the material cost of my recent machine including all the electrics apart from the spindle was £2k. About half of that was spent on aluminium!Quote:
Originally Posted by JAZZCNC
It was a Serious offer Numb nuts I wasn't trying to prove anything. Also what's the point of "pushing the boundaries" just to cut wood and plastics.? I already have a proven machine design that does this Job standing on it's head and that's what I'd make for John.Quote:
Originally Posted by Jonathan
The machine you built While being a nice strong thing built with care and thought and a credit to you, I wouldn't exactly say it pushes boundaries either.? It just does the Job it was designed for and doesn't do anything special or better than any other machine correctly built and designed to do a job.!! Also you say 2K material costs which I don't disbelieve for minute but what your not saying is the hours of work that's needed to machine and Assemble it. Add this to the Mix and you'd probably need another 2K to make it worth your while.?
I know. I expect you've made a similar offer to the Bob who started this thread.Quote:
Originally Posted by JAZZCNC
So you weren't offering to make it to prove that it can be done for that price?Quote:
Originally Posted by JAZZCNC
I have neither claimed that it pushes any boundaries, or intend to make that claim.Quote:
Originally Posted by JAZZCNC
Obviously. The point I was making is that for someone who has got sufficient free time, they can make a machine worth owning within a £2k budget.Quote:
Originally Posted by JAZZCNC
I didn't charge anywhere near that, but those were special circumstances so your point is valid.Quote:
Originally Posted by JAZZCNC