New to CNC

[johnd10]

I just joined cnczone and I am going to build the JGRO router with help from you all. I would like to know what would be the best stepper motors and bearings for the linear guides and lead screw supports? Also, does the 1/4-20 all thread rod work well for the lead screws? How about the flexible connectors from motor to lead screw? I appreciate all help and am going to start building the structure this week. Thanks - johnd10

[jalessi]

John,

As long as the stepper is perpendicular to the screw flex couplers are not that important. If you use mounting screws that are slightly smaller than the holes in the stepper motor, that will allow you to align the stepper motor shaft to the screw.

Acme screw verses threaded rod will be better.

The least expensive is Enco 1/2-10

http://www.use-enco.com/CGI/INLMKD?S...01=1&SICOUNT=1

Dumpster makes a inexpensive anti backlash nut.

http://dumpstercnc.com/

Welcome to the Zone,

Jeff...

[jalessi]

John,

The machine will be painfully slow with 1/4-20 threaded rod due to 20-1 reduction.

Stepper motors run out of torque at relatively low rpm.

See attached chart.

At 1500 rpm it will only have about 20% of the total rated torque.

Jeff...

[johnd10]

Jeff - Thanks for the info. Question - I was thinking about Xylotex 269 oz-in motors with the 1/4-20 screw. Do you think this is big enough motor for 1/2-10 acme or do I need bigger motors like 425 oz-in? Also, enco has acme rod in oil finish steel for about $9 for 6 ft. but there alloy steel rod is about $40 for same size. Is oil finish steel Ok . I appreciate your help. John

[jalessi]

John,

You may want to email DumpsterCNC and ask his opinion about which brand acme screw he prefers.

Do you all ready have a stepper driver?

Jeff...

[johnd10]

Jeff - No I don't have any of the electronics yet. I thought I needed to choose the correct size motors/drivers for the thread size I use. I think 296 oz-in would be good for 1/4-20 thread but I don't know if this is enough torque for the 1/2-10 acme thread. Thanks for your advice. John

[jalessi]

John,

If you already had a unipolar stepper driver only certain motors will work also the amp output of the stepper driver must match the motor, that is why I asked the question.

If you are looking for the least expensive solution the HobbyCNC
driver board and motors are a great deal.

There 23-305-DS8A motor has a 425oz-in bipolar rating and a
305oz-unipolar rating, using there unipolar drive would provide 305oz.

The reason why a unipolar solution has less available torque is because it only energizes one coil at a time.

http://www.hobbycnc.com/
http://www.hobbycnc.com/products/stepper-motors/

The thread pitch is only a part of the equation, see the links below for more detailed information.

http://www.shinano.com/xampp/docs/St...&%20Theory.pdf

http://www.micromo.com/n390432/n.html

Jeff...

[jgro]

Jeff - No I don't have any of the electronics yet. I thought I needed to choose the correct size motors/drivers for the thread size I use. I think 296 oz-in would be good for 1/4-20 thread but I don't know if this is enough torque for the 1/2-10 acme thread. Thanks for your advice. John

The 269 oz-in are more than enough to drive 1/2-10 acme screws. I drove 1/2-10 acme screws with 116 oz-in motors for a long time with no problems.

jgro

[johnd10]

Hi to all. I have all the stuff I need and have started to fabricate the router and my son is going to work on the electronics and programming for it. I am looking for ideas as to what I need to do to get the machine properly aligned after I finish building it. I guess I would like to know the accuracies required and the best way to do the alignments. Any help in this would be greatly appreciated. Thanks John D