Newbie has lurked, now questions...

[sploo]

I’ve been after a CNC router for ages, but lack of time to build (or budget to buy) has so far stopped me.

I’ve been lurking for a while, and hopefully learning, so now I have a few questions…

I’d like a machine with a maximum working area of around 25x40x5” (a little less in all axes would be fine). However, machines of this size here in the UK usually retail at around 14,000GBP (approx 25,000USD)!

I was thinking about K2 CNC’s KG-3925, but there seem to be some quality control issues that I really wouldn’t fancy sorting out (what with being on a different continent) - and that’s before I consider shipping costs, plus all the taxes that’ll be slapped on it when it enters ‘rip-off island’ (UK).

So, I was considering building a machine to the design that jgro generously posted.

The main use of this machine will be cutting lots of shapes out of 3/4" MDF. I was wondering if a machine made of MDF, with acme screws, steppers and nuts made from Delrin is really going to be suitable.

How accurate is the jgro machine, and how long would you expect it to last before a rebuild was required?

Of course, I suppose I could build a frame and try to source linear bearings and ball screws, but is this pretty pointless when coupled with an MDF frame?

Any info greatly appreciated!

[joecnc2006]

you can check out my machine, i cut 3/4" MDF all the time and also HDPE, it has a cutting area of 26"x45"x4.5" close to what you want.

http://www.cnczone.com/forums/showthread.php?t=10067

Joe

[ger21]

If you haven't read it yet, here's a good thread on alternatives to MDF, expressing the same concerns you have. http://www.cnczone.com/forums/showthread.php?t=11612
The acme screws and Delrin nuts shouldn't be a problem. Baltic Birch is a stronger material than MDF. Joinery and fabrication will probably be the determining factor for the longevity of the machine, I think.

[sploo]

Gents,

Thanks for the replies.

I've actually already read both those threads (much time spent lurking )

Joe, I'm seriously impressed with the stuff you're doing. I think reading your thread was what sparked some thoughts of alumin[i]um - as in making the jgro machine, then using it to make another one out of metal (probably very slowly).

Are you happy that an MDF machine with acme screws and steppers is suitable for medium term use - i.e. you can get quite a bit of use between having to replace bits? I'm not looking for commercial reliability, but I don't want to be spending more time fixing the machine than making stuff with it!

I'm trying to balance up the extra reliability and accuracy I might get by using linear bearings and ballscrews vs. the rather large cost (and time) to obtain such parts.

I had previously thought about using real nuts rather than tapped Delrin for making AB nuts, so it's nice to see someone's already done it. I take it they're working fine?

ger21 - many thanks for the info also. I suppose making the whole machine out of HDPE, like Joe seems to be messing with, looks like an idea. But I suppose I should just get a machine going with MDF (as I'm happy working with it), and then try some 'fancy' stuff.

Cheers!

[ger21]

Originally Posted by sploo I suppose making the whole machine out of HDPE, like Joe seems to be messing with, looks like an idea.Cheers!

I'd wait 'til Joe gets done and see how it works out. Seems to me like the plastic will flex and sag a bit much.

[joecnc2006]

Originally Posted by sploo Gents, Thanks for the replies. I've actually already read both those threads (much time spent lurking ) Joe, I'm seriously impressed with the stuff you're doing. I think reading your thread was what sparked some thoughts of alumin[i]um - as in making the jgro machine, then using it to make another one out of metal (probably very slowly). Are you happy that an MDF machine with acme screws and steppers is suitable for medium term use - i.e. you can get quite a bit of use between having to replace bits? I'm not looking for commercial reliability, but I don't want to be spending more time fixing the machine than making stuff with it! I'm trying to balance up the extra reliability and accuracy I might get by using linear bearings and ballscrews vs. the rather large cost (and time) to obtain such parts. I had previously thought about using real nuts rather than tapped Delrin for making AB nuts, so it's nice to see someone's already done it. I take it they're working fine? ger21 - many thanks for the info also. I suppose making the whole machine out of HDPE, like Joe seems to be messing with, looks like an idea. But I suppose I should just get a machine going with MDF (as I'm happy working with it), and then try some 'fancy' stuff. Cheers!

I Use the Machine from 3-5 hrs a day and have no problems with it cutting an average of 30ipm, the nuts for the anti-backlash works good, I just use silicone based lubricant and keep all three axis sprayed.

I will be building another machine from all HDPE and using the Hobby cnc kit with 200oz motors which i have already recieved, and also try the acme lead screws for more speed.

Joe

[sploo]

Originally Posted by joe2000che I Use the Machine from 3-5 hrs a day and have no problems with it cutting an average of 30ipm, the nuts for the anti-backlash works good

Sounds good. I doubt I'd be using the machine that hard (lots at the weekend, then a few hours in the week).

When you say 30ipm, is that cutting, and at what depth? In other words, if I wanted to cut a shape out of 3/4" MDF, would it be working at 30ipm, and (roughly) how many passes would be required?

Originally Posted by joe2000che ...and also try the acme lead screws for more speed

Oh dear... shows how much I have to learn. I knew about 'normal' threaded rods, and the expensive square profile stuff. I wasn't aware that acme referred to, well, what it refers to. It does look like a good idea though, and talking to the guy I'm thinking of building a machine with (he'll do the electronics) he thinks he can get acme screws at a decent price.

Originally Posted by ger21 I'd wait 'til Joe gets done and see how it works out.

Yep, you're absolutely right. I've settled on starting with MDF (as I know I can work it), and maybe an alum version will follow later.

A more general question - I've been reading lots about Geckos, break-out boards, g-code etc. etc.

Assuming you're using steppers, am I on the right lines assuming you'd need a PC (obviously), a break-out board, 3 stepper drivers (Geckos?) and a power supply?

You use some form of CAD program, but I take it there's software to control the steppers and translate g-code to stepper movements (Mach 2)?

Loads more questions to come of course!

Many thanks!

[ger21]

Originally Posted by sploo he thinks he can get acme screws at a decent price.

Check http://www.mscdirect.com for good prices on Acme leadscrews.

Originally Posted by sploo Assuming you're using steppers, am I on the right lines assuming you'd need a PC (obviously), a break-out board, 3 stepper drivers (Geckos?) and a power supply? You use some form of CAD program, but I take it there's software to control the steppers and translate g-code to stepper movements (Mach 2)? Loads more questions to come of course! Many thanks!

A breakout board makes connecting drives a bit easier. Especially Geckos. Some drives, like the HobbyCNC and Xylotex, will plug directly into the parallel port.

You draw (2D) or model (3D) your parts in a CAD program, and use a CAM program to create g-code from the drawing or model. Then load the g-code into the machine control software, such as Mach3 or TurboCNC.

[sploo]

Originally Posted by ger21 Check http://www.mscdirect.com for good prices on Acme leadscrews.

That's the first site I've seen that not only has a (reasonably) clear search system for this kind of gear, but also prices (and pretty good ones too).

I see they've got all sorts on there - including linear bearings. Very interesting thanks.

I dread to think what it'll cost to get bits to the UK (post + tax + import duty) but it's still probably going to be cheaper than UK suppliers.

Originally Posted by ger21 A breakout board makes connecting drives a bit easier. Especially Geckos. Some drives, like the HobbyCNC and Xylotex, will plug directly into the parallel port. You draw (2D) or model (3D) your parts in a CAD program, and use a CAM program to create g-code from the drawing or model. Then load the g-code into the machine control software, such as Mach3 or TurboCNC.

Understood, and not too far from what I thought. Many thanks again!

[wizard]

Originally Posted by sploo I’ve been after a CNC router for ages, but lack of time to build (or budget to buy) has so far stopped me.

A problem not unknown on this side of the pond. Never hurts to buy tooling though This side of the pond we refine the art of scrounge up parrts for our machines. Getting close as we speak.

I’ve been lurking for a while, and hopefully learning, so now I have a few questions… I’d like a machine with a maximum working area of around 25x40x5” (a little less in all axes would be fine). However, machines of this size here in the UK usually retail at around 14,000GBP (approx 25,000USD)!

Sounds like a lot, not having priced out a commercial machine I don't know. I do know however that there seems to be a 2X factor applied to costs of hardware in Ireland and it seems as though Great Britain is worst. Not sure what that is all about, it might be cheaper to pick up the family and move here!

I was thinking about K2 CNC’s KG-3925, but there seem to be some quality control issues that I really wouldn’t fancy sorting out (what with being on a different continent) - and that’s before I consider shipping costs, plus all the taxes that’ll be slapped on it when it enters ‘rip-off island’ (UK).

I don't know about that in any event there are numerous manufactures of such hardware. Still think you ought to move here Europe in general is expensive. Of course you could easily deal with this by getting your town to commit to having Wall Mart move in one of their stores. That generally has a very positive impact on pricing for the consumer

So, I was considering building a machine to the design that jgro generously posted.

One thing that impresses me about router type hardware is the tremendous opportunities you have with respect to the desig of the machine. For the first machine it is really a matter of picking one that fits your interests.

Part of the trick here is keeping the parts cost low for the first machine. It is a learning adventure as much as anything.

The main use of this machine will be cutting lots of shapes out of 3/4" MDF. I was wondering if a machine made of MDF, with acme screws, steppers and nuts made from Delrin is really going to be suitable.

While I'm not a big fan of MDF there is no reason why such a machine would not work out nicely. The only thing about delrin that I'd like to mention is that you can get a plastic type material with graphite embedded in it. Might help some.

How accurate is the jgro machine, and how long would you expect it to last before a rebuild was required?

I can't answer that as I'm in scrounging mode right now. You have two things to worry about. One is the inherent strength in the design. The other is your ability, with tools at hand, to put the unit together smartly. That being said I woud not consider the machine suitable for a heavy production environment.

Of course, I suppose I could build a frame and try to source linear bearings and ball screws, but is this pretty pointless when coupled with an MDF frame?

Well agian I don't like MDF but pointless is maybe a bit strong. There are many options for purchased linear motion. This includes THK slide assemblies at one end and V ways and rollers at the other.

Any info greatly appreciated!

Seriously consider scroungeing up parts. I'm not famliar with industry in Britain but it shouldn't be to difficult to find free or next to nothing hardware sources. Often this means the purchase of scrap machinery. Sometime you get lucky and find things that have had very little use but are so specialized that are only good for scrap when dispoised of. Look for linear components, motors and extruded aluminum.

Thanks
Dave

[wizard]

Originally Posted by sploo Yep, you're absolutely right. I've settled on starting with MDF (as I know I can work it), and maybe an alum version will follow later. A more general question - I've been reading lots about Geckos, break-out boards, g-code etc. etc.

Yep a lot to learn. I'm not sure how they function in Britain but you might want to check out your local model engineering shows. I know over here there is growing interests in CNC at the shows. They are a good place for seminars, and a reasonable chance to talk to vendors,

Assuming you're using steppers, am I on the right lines assuming you'd need a PC (obviously), a break-out board, 3 stepper drivers (Geckos?) and a power supply?

Yep you need all of that and a cabinet to place everything into. That is in terms used over here a panel box for the electrical components. I suppose that if you really wanted to you could get by without a breakout board and do you own interfacing, but in any event you do need something.

You use some form of CAD program, but I take it there's software to control the steppers and translate g-code to stepper movements (Mach 2)?

Yes a number of applications including EMC on LINUX.

Loads more questions to come of course! Many thanks!

Keep the questions coming, I always learn something myself here. One source of inspiration is the Gingery series of books that detail making machines out of aluminum scrap. I say inspiration because obviously you don't need to cast you first machine out of aluminum but the ideas an spirit of the writings can certainly put you in the fight frame of mind.

Dave

[cbass]

Hi sploo (I assume that isn't your real name)

I just wanted to get my two cents in as I almost entertained thoughts of building my machine. I didn't. I broke down and bought a K2 setup. It hasn't arrived yet but when it does, I hope to find their QC problems a thing of the past.

-IF- i were to build my machine, I would not use MDF. I would use aluminum extrusions or steel tubing. From my experience in using MDF, it will warp sooner or latter. It is like a sponge and swells from moisture in the atmosphere (the UK is a pretty moist country from what I've seen). All the precision components you will be using amount to nothing if the machine structure starts to warp. I still don't know how people get away with it in their designs. Even adding a protective coat of urethane or lacquer will not stop the ingress of mopisture over time. If I was going to put all this energy into making a machine, I would spend a little extra time and energy to ensure its longevity.

I realize aluminum is not cheap. But there must be scrap yards where you live.

Regardless of which way you go, I wish you luck!

Regards,

Carlo

p.s. This post is not meant to discredit all the MDF routers out there!