Thanks for your quick response. I couldn't agree more about using recommended devices. I guess that's part of what I was looking for - recommendations. And, as I said, I am not interested in buying cheap knock offs, so I am open to suggestions as to where to buy them.

The WorkBee kit is offered by Maker Store - USA [might be related to Open Builds??] They offer a high torque motor '
High Torque 2.45N.m' The torque is expressed differently than other specifications I've seen - I don't know if it's stronger - weaker - the same as . I'm guessing the N.m designation is Newton Meters. Other motors use an ounce measurement - may inch / ounce. If all that's correct, the one they offer is over two times as 'strong'. Am I on the right track?

 

Welcome to the forum @Mr McPenny - you have come to the right place for advice!

If you want genuine Openbuilds parts (and the support you get with them) then look here;

OpenBuilds Workbee 1010 (40" x 40")

and here;

BlackBox Motion Control System

You can choose the options you want in the first link, and the second link is to the blackbox controller - designed from the ground up with beginners in mind.

Alex.

 

OK! Now we're getting somewhere! That information is very helpful. I'll get the high torque motors and the Black Box - I see in the documentation for the Black Box, there is a power supply recommendation. I'll get those things and put together minus the mechanics to make sure it all works with my computer and your software. Once I can get the motors wiggling on command, I'll be ready to lay the cash for the mechanics. You've all been most helpful. I appreciate your input.

 

My personal take on motors is that the stock 185 oz in is more than sufficient for normal use. Larger motors are used for larger machines that have more inertia. Also, the larger motor has more limited specs, particularly speed and acceleration. The 225 oz in is also a good choice. IMHO, the 425 oz in is overkill for a machine this size. CNC Router Parts uses 425 oz in motors on their 4'x8' machines. Higher drive voltage and/or higher current will have a large effect on speed. Larger motors tend to be higher inductance, which limits maximum speeds. Get the lowest inductance motors you can find for best performance.

Yes, NEMA 23 refers to the flange size of the motor, all NEMA 23 motors are interchangeable. Only the body length varies.

Meanwell makes good power supplies, I have never had one fail out of more than 100 machines. Just make sure you get them in the US, and that they have UL approval. A single power supply is sufficient for NEMA 23 motors. Needs to have a current rating equal or greater than the sum of all motors. If your drivers can handle it, go with a 36V power supply. That will usually get you a good performance increase. If not, 24V is sufficient.

Stepperonline makes good stuff, even though they are a China based company. Make sure you buy brand name drivers, a lot of the Chinese clone designs are junk. Gecko also makes great quality components, but at a price. Stepperonline also has a good selection of motors available on Amazon.

MG

 

Metal, thank you very much! Lot's of good detail - very helpful.

I was looking at Stepperonline, but then a little concerned too - I don't want to seen as a traitor to Open Builds. You guys are my only mentors! I won't be taken to the wood shed if I don't get Black Box?

 

Hi guys, I was making some eccentric clamps yesterday, and I noticed some chatter (jerking in the X axis) while doing and adaptive clearing operation and contouring operations. A lot of tool marks and not a perfect circle. Broke an end mill in the process. Here are some of my feeds and speeds from Fusion360. The material is 17mm birch plywood. Any feedback will be appreciated.

 

Have you checked that nothing has worked loose on your machine. You don't give us any details of the machine (size, leadscrew or belt drive, controller etc) What happens if you machine (light cut - say 0.5 mm) a simple circle as a 2D contour.
Alex.

 

Thanks Alex. Sorry, my bad. It is a workable 1010 lead screw. I have jogged the machine in all directions a few times. Haven't noticed any issues. I am wondering if the feeds and speeds and depth of cut are too much for a 1/8 bit on birch plywood.

 

They didn't look too far off to me. This chart might help - it gives speeds and feeds for a 1/4" bit (but doesn't say what type of bit - No of flutes etc)

Speeds and feeds

 

Thanks, I’ll check out the link. Here are some images of the part milled.
The round holes are not round, there are a few tool marks here and there. The lower round section has some flat spots.
The workpiece was placed with wood grain parallel the X axis.

 

If circles are not round the most likely cause is backlash. Looking at your pictures I would suggest you start looking for play in the X axis. Start at the bit and gradually work back looking for anything that moves - if your steppers are powered they shouldn't move when jiggling things by hand.
Alex.

 

Thanks again Alex, I will take a look at my X axis. I need to take it apart anyways for a mod I’ve been wanting to do, so I’ll inspect it carefully.

 

Great tips. Prior to this project, I used only pine which was no problem with adaptive passes sans a final tool pass. I am guessing this plywood is pretty hard in comparison to pine.
I started with 170mm x 170mm x 17mm piece of birch plywood. The machine is calibrated with the proper steps, but I will double check.
I appreciate all your help and will post back my findings.

 

I think I may have found the problem - Alex . I checked the X-axis play, and indeed there was some play. I recall soon after I had crashed the X axis a couple of weeks ago and didn't bother checking the aftermath. The anti backlash blocks were knocked out of place. I did a quick adjustment and it appears everything is back to normal. I run out of stock plywood but will run some circle milling tests later today on the remnants I have left. Will post back.

 

Thanks Peter. It makes sense. I will dial it back a little. I did scale back the travel speed thru the Open Builds Control software during the cutting operations, but that was after on bit broke.

 

Pleased to hear that - the clue was that your circles had flat spots.
Alex.

 

When your circles have discontinuities on the top and bottom (Y plane), that means your Y axis has backlash.

When your circles have discontinuities on the left and right, (X plane), that means your X axis has backlash.

The discontinuities will appear every time the axis reverses direction.

Crashing into the end stops can cause things to loosen up. Usual suspects are lock rings on the lead screw, not very often the Lead Nuts get knocked out. This is a clue that the screws were not tight enough.

Here is a small g-code program that does a couple circles and squares so you can check for problems. If the diameter of the circle or width of the square is out, it means your calibration needs to be checked. Note that this is a text file, change the extension to whatever your G-Code Sender program recognizes. It does 2 passes of 1.5mm each on the Z axis. Note that this g-code is metric, not Imperial.

MG

 

Cool stuff. I tried adjusting the lock collars first, but the play although better was still there. To adjust the anti backlash blocks, I first loosen them up, loosen one lock collar and the stepper motor collar as well. I then turn the lead screw by hand one direction to remove the play of one block, tighten it, turn the lead screw in the opposite direction, tighten the other block. I then proceed to tighten the lock collar and the stepper collar. If there is a better way, please share. I never had an issue with the Y axis, but the Z axis backlash has been challenging to adjust at times.

 

If the play is only the nut blocks, loosen one nut block, squeeze gently together, tighten nut block.
Alex.

 

Found a big enough scrap of plywood to run another job. Retuned milling operations to leave some stock and do a final clean contour. It came out really good. One thing that I am trying to figure out is that the part came out consistently ~0.50mm-0.60mm bigger pretty much everywhere. I’ll have to measure the end mill tomorrow, but I am glad I got rid of that backlash issue.

 

Hello everybody
It's almost one year that I'm building my custom workbee screw driven.
I mean custom because I made it with pieces found around the web and around my city, with plates made by 10mm alu milled by a friend of mine. 10mm alu was already in his workshop.
I'm almost at the end of the building process and I must say it wasn't easy.
C-Beam profiles must be exactly cutted and with perfect squared tips, plates must be perfectly flat, long acme screws aren't easy to find or at least they weren't for me.

Anyway
Here are some pics of my machine.
I'mg going to control it with an original protoneer arduino CNC shield V3.51

I'm in doubt if Y motors are best placed in front or on the back of the machine.
On the back I must drive longer wires to come to front, where I think I will set my control unit
On the front I need less wire but they can be hit with things.
What do you suggest?
Thanks
Pietro

 

You're doing fine Pieri, but for the sake of a bit of wire, personally, I would have the motors at the back.