[sintratech]

I am looking at a new machine build. (cnc router) possibly second build of a mill. I have used steppers in past. Can anyone give me advice on which way to go? Cost and affordability is an issue. Can someone also tell me what price range servos and boards cost. Also power supply recommendations?

[mactec54]

sintratech

If you are wanting to use servos, the Dmm system is the way to go, They are easier than a stepper to set up, & you have encoder feed back, so the loop is closed at the Drive, no lost position or steps that can happen with steppers

DMM Technology Corp.

[wildwestpat]

Hi sintratech

IMHO you start by deciding the accuracy (in terms of both repeatability & absolute positioning) then machining envelope (X,Y&Z) machine then throughput speed and finally the all important budget and or availability of parts.

All machine design is a compromise of the above factors and only you can decide ton the inevitable compromises as you have declared a cost sensitivity. It is my experience that stepper motor designs operated as open loop configuration will be a fraction of the cost of a close loop servo with their associated feed back element - the accuracy requirement will determine if the feedback element is a linear scale or a rotary encoder as well as the linear drive type.

Since you say budget is a concern think carefully about what you are expecting in the way of accuracy as this has the largest impact on cost.

The Zapp Automation web site will give you the all important price comparisons. Yes the prices are in sterling and there are sources nearer to you. This is one of the few sites that put prices on the web for all to see. http://www.zappautomation.co.uk/

regards - Pat

[mactec54]

wildwestpat

The Dmm AC servo system is much less cost than what Zappautomation has to offer, & does not cost a lot more than a good stepper system

Cost will also depend on what he needs in motor size, are you going to use ballscrews, How heavy will the Zaxes be

[sintratech]

Z axis won't be that heavy I am going to be using plans offered by automated wood works.com I believe his use belt pulley system for zero backlash. I don't know that I will be needing a lot of power at first but in case in the future I want the extra power with out losing accuracy I would rather use servos.

[mactec54]

sintratech

I just looked at the build,& watched the videos,With the servos you won't hear any noise like you can in the videos

There 400W servo motors would do you for that build

[wildwestpat]

Hi sintratech

OK so you are building something similar to the 4x4 or 4x8 wood router as shown on the Automatedwoodworks.com web pages. In this case you have the advantage that they have sorted out the size of motor (stepper type) and given the performance they can achieve. (Caution bigger does not necessarily mean better when sizing stepper motors. For a closed loop servo motor there has to be enough torque available to start from rest. Use the calculator link below to explore the nature of each type of drive. )

You can compare servo v stepper choice using a calculator such as the Motioneenring software calculator available as a free down load from MOTIONEERING® | Kollmorgen
This calculator will let you explore servo and stepper motor sizes along with all the other major contributors to performance.

matctec54 has given you a link to a supplier of vfm (value for money) servos and having used the Motioneering calculator or similar you can ask them for a quote. I don't want to open up a debate on stepper v servo drives as each has their place and their characteristics are very different - it is for the designer to choose - that is fun of a fresh design.

Good luck with the design - regards Pat

[sintratech]

in regard to your post mactec54 what website should I go to find the 400W servo motors?

[mactec54]

sintratech

Just hit the link below, & you will find what you need, If you need more help send me a PM

DMM Technology Corp.

[wildwestpat]

Hi sintratech

You might be interested in this link http://www.cnczone.ru/forums/index.p...e=post&id=7543

Regards - Pat

[sintratech]

I only plan on having a 3 axis machine xyz. So as far as going to the DMM site. I only need 3 servo motors and 3 servo drives? I have built stepper motor designs before. This is my first attempt at dealing with servos and what componants I need to make this system work. Thanks

[mactec54]

sintratech

If you buy the 3axes package, it will be complete,Estop, Limit switches, Breakout Board, cables,set up software Etc, anything else you need I can help you with that

[wildwestpat]

Hi sintratech

The invoice link I gave you http://www.cnczone.ru/forums/index.p...e=post&id=7543 Assuming the posted invoice from DMM is genuine and prices have not changed it indicates the price per axis is $155 for the DMM 400 watt motor and $125 for the associated amplifier to which you need to add the power supply at around $50 per axis. These prices are similar to several other sources of servo drives with motor shaft encoder feedback. IMOH you need to size the motor to match the loads imposed by your machine taking all the loads into account.

Good luck with your purchase as the stepper versus servo is getting blurred with the performance achieved from hybrid stepper motors driven with digitally processed waveforms that relate the back emf from the motor to the drive current waveforms compared to the simple PWM drives. http://www.leadshine.com/UploadFile/...o%20System.pdf

Regards - Pat

[sintratech]

how much will it run me with the 400w motor package before shipping?

[wildwestpat]

You need to talk to DMM if you want to get current prices. You also need to make sure Mactec54 has taken the details of the machine you are building into account in suggesting the DMM 400 watt motor. Wattage is just one of the factors to take into account in getting the right motor. There is not enough information on the DMM web pages to be sure so ask them then you have some recourse in the event of problems.

Regards - Pat

[wildwestpat]

Hi Sintratech

Just noticed you are using a wood router design that uses two stepper motors to drive the gantry legs. That is 1,360 oz inch and with steppers they behave when ganged as by definition they move in steps or stall! Hence you need advice or to calculate the motor size to suit your traverse rates and dynamic loads when cutting I have reservations about those 400 watt motors.

If you don't want to do the calculations you should wait until someone jumps in to verify motor size with experience of a build using similar construction to the CNCRouterParts design. There is a forum for wood routers and this might more response.

Regards - Pat

[mactec54]

wildwestpat

With a 1,000w of peak power they are more than enough, for the machine he is planing to build, there are many users that have the same motors on there machines with years of running, & no problems with performance