[Fenza CNC]

Hi there, I need pointing in the right direction. I have very little electronics experience so I'm kind of out of my comfort zone here. The simplistic, probably quite vague question is, can you make a 4 axis PC based control system (with motion controller and ancillaries) to perform to a similar performance as the industrial controllers? And for under the price of say $3000? (not including motors and drivers)

Maybe that was a bit vague I'll write a bit more info. I want to use AC Servos in a closed loop feedback configuration on a homebrew CNC Mill. The Idea is to create a Mini VMC much like, but smaller than a Haas Minimill 2 (probably weighing around 1000kg or 2200lb), it will be tailored around higher speed machining of aluminium than anything else but should still be a very capable machine. The main question is, can you get the High Speed Machining functionality, high feed rates and rapids common to industrial controllers for under say $3000? (again without motors and drivers)

I'm not too sure what's possible in the hobby world of CNC, most retrofits or even homebrews, tend to use steppers which my research has led me to believe require far far simpler electronics, so I'm not sure if what im asking has ever been done, or can be done for that matter.

Also if you're thinking just get a Tormach, I live in the UK and from what I've heard a Tormach would cost an arm and a leg to ship here, plus I'd like a fair bit more performance than the Tormachs. The reason I'm considering this approach over just buying an older machine is, it's to be used in my garage which would be difficult to get something like a Haas Minimill down my drive and into the garage, also expensive. The only machines in my budget range are pretty old like pre 2001 and I've heard these older machines aren't capable of stuff like High Speed Machining and 3D Contouring (could be wrong) but still old electronics scare me even more than new electronics. So that's why i thought of making my own, plus it'll be tuns of fun and ive learned a boat load already just from research.

That post is pretty messy but hopefully I've got my question in there somewhere. Hope you experts can help, I may just be trying to get too much from too little here. Anyway thanks in advance :cheers:

Fenza

[Danny1978]

Take a look at dmm tech they have ac servo style systems I think they range from 200watt upto 2 kw prices look like they would fit into your budget.you would be suprized at the performance of some hobby cnc equipment. I have a 6040 router I rebuilt the controller with a gecko g540 running only a 24volt power supply the first thing I tried after the build was a 3d relief carving I was stoked at the performance,i also own a 2001 ycm machining centre doing 3d on the 6040 was a lot quicker.there is also closed loop stepper systems you may want to look at .cheers. Danny

[Fenza CNC]

Thanks for the reply Danny, I've seen DMM before, they look perfect for my application. I think the 1.5 kw motor will easily run my mill. Pretty cheap too!

Do you think I'll be able to achieve ~400IPM feed rates with hobby grade electronics? Not 3D contouring speeds that high but still fast. I want the machines overall performance to be limited by the motors not the controller.

Stepper motors just can't achieve the speeds that I'm after but if you can point me towards a servo controller that can, I'll be very grateful.

Thanks, Fenza.

[Fenza CNC]

Thanks for the reply Danny, I've seen DMM before, they look perfect for my application. I think the 1.5 kw motor will easily run my mill. Pretty cheap too!

Do you think I'll be able to achieve ~400IPM feed rates with hobby grade electronics? Not 3D contouring speeds that high but still fast. I want the machines overall performance to be limited by the motors not the controller.

Stepper motors just can't achieve the speeds that I'm after but if you can point me towards a servo controller that can, I'll be very grateful.

Thanks, Fenza.

[Danny1978]

I think those speeds are achievable but there is a lot to consider for instance motor speed ballscrew diameter and pitch , a servo spinning at 4000rpm on a 5mm pitch ballscrew will give nearly 800 ipm in theory anyway, ballscrews have a limit to the speed they should be ran at before they start to whip so maybe look at the length of your travels and checkout some specs on ballscrews, I'm pretty shore mach3 will allow those speeds but your encoder resolution will be the limiting factor, I think that's right? What will the machine setup be like? If your going to have a machine doing high speed and quick direction change you want it to be pretty stable ,will you be using linear rails? What type of material are you building it out of? Also is there enough travel to reach the rapids you want, if your travels are pretty short it will be acceleration you will want

[Fenza CNC]

Cheers for the response Danny, I like the Mach3 software purely for the reason there is so much support around for it, but I've heard you cannot perform PID closed loop feedback control with Mach3, is this right? You say the encoder resolution will be the limiting factor, what exacly does that mean?

I found this Flashcut USB Signal Generator USB Signal Generator Flashcut seem to be a reputable company, this seems ideal. From the look of the diagram on their website, the signal generator bridges the gap between the PC and the drivers but I'm not too sure about the closed loop feedback. It seems great and for only $1,300 comes well under the $3,000 budget, but its features like '100,000 steps per second per axis' that i don't understand. Is 100,000 alot, or very little? I'm probably wrong but if it is steps related to the encoder, the DMM Tech encoders are 16,000 ppr and at 50 revolustions per second, that's 800,000 steps per second... I just don't want to buy an inadequate controller and suffer as a consequence.

I'm sure what im saying doesn't make a lot of sense but then again if i knew exactly what I'm talking about i wouldn't need to be here asking the experts :cheers:
So is that Flashcut USB Signal Generator the kind of thing i need to be looking more into or will i need something that packs a little more punch to get my desired HSM and fastish 3D Contouring speeds?

Oh also I'd like to keep this thread primarily based on the Controllers and drives etc. not the actual mechanics of the machine. It won't be a conventional retrofit or DIY project, lets just assume it will mechanically perform to the task at hand to keep it simple for now

Hope this helps to answer my questions

Thanks, Fenza.

[greggv]

You might want to look at Delta Tau for your electronics. These guys are top of the line, not hobby stuff at all, more like laboratory grade! They do make cnc controllers, etc.
Hard to figure out, but worth your trouble!

[ger21]

The simplistic, probably quite vague question is, can you make a 4 axis PC based control system (with motion controller and ancillaries) to perform to a similar performance as the industrial controllers? And for under the price of say $3000?

Depends on the control you're comparing it to, but if you plan on using Mach3, I'd say that the trajectory planner is not nearly as good as an industrial controller. At least not as good as the proprietary controls on the industrial routers I use at work.

As far as the 100,000 Khz. I believe that the DMM drives can be configured for electronic gearing to reduce the frequency requirements.

[wayneb]

Depends on the control you're comparing it to, but if you plan on using Mach3, I'd say that the trajectory planner is not nearly as good as an industrial controller.

Could please elaborate on trajectory planners.?

Cheers
Wayne

[underthetire]

You might want to look at Delta Tau for your electronics. These guys are top of the line, not hobby stuff at all, more like laboratory grade! They do make cnc controllers, etc.
Hard to figure out, but worth your trouble!

First off, delta tau is waaaay over his cost, and second it's too complicated for novices. Everything I've worked on from delta tau is not very rugged either. They are good for slower super high precision contouring, but not real impressed on high speed. Lab grade is about right.

Might want to look at the Ajax stuff as well, cheap and easy.

[Fenza CNC]

Hey thanks for all the imput guys and sorry for my late response.

I've had a look at Ajax as Underthetire suggested and they really seem to do exactly what i need, the MPU11/GPIOD4 boards are actually what Centroid use in their M400 control. From looking on the forum the MPU11 supports 6MHz encoders so the DMM servos should be able to be driven without electronic gearing which is exactly what I need, high speed and high precision. http://www.ajaxcnc.com/ajax-cnc-centroid-mill-kits/ The ones I'm interested in are the bottom 3.

The Ajax Motion Controller can be used with either Centroid or Mach3 software, with Centroid being the $400 more expensive option. So this lays down the question Mach3 vs Centroid for my semi proffensional work invironment? The Motion Contoller interfaces with the PC via Ethernet so Mach3 won't be limited by the parallel port, does this mean Mach3 will be a viable option for me or will it be limiting?

[underthetire]

The Mach plug in works, but it gets more convoluted, and it has a couple quirks. The centroid software has been around for years, and personally think it does a better job at closed loop systems. I don't see any reason you couldn't try both, except the 400.00. Ajax also seems to have better support with the centroid.