V-Carve Desktop and Mach4/UC100 Issues!!!

[whitetiger28th]

Thank you. I am about to just tear it down to bear bones and build it back up.

Need to add limit switches, stop button, get it to move full throws without binding at each end, etc.

I think the last person that owned it picked it up by the guide rods and moved th out of position, although that didn’t have anything to do with the issues I am having.

All my movements were within the non binding section.

Once I get back to calibration I will post my progress and any issues I have. Thanks again for the support.

V/r

Jeremy

[GEdward]

Good idea and good luck. I did some research and if the specs didn't change one item that really sticks out is the lead screw pitch. They use a 10 pitch 5 start thread which gives you .500 inch of movement per revolution. That is great if you have a light load like a 3D printer or a high output drive motor. I checked the specs on the motors you are using and I feel that you are seriously under powered at 270 in/lb.

The default micro stepping for your drivers is 16 which, if that is indeed where the dip switch settings are ,then your positioning resolution is plenty high at 0.00015625. From that standpoint you might get a little more stable performance by taking that setting back to 8 as you would still have 0.000312 positioning accuracy and cut your pulse output in half. That would mean going from 3200 to 1600 pulses per revolution. All this is based on the assumption that the your motors/lead screws are not geared down.

If you are geared down, say 2 to one, then having a 16 micro stepping drive is going to push the limits of the UC100. The UC100 has a 100 Kbps through put with a small buffer. Also USB communication has its limits as well and is susceptible to interference. I ended up getting a shielded USB cable with a ferrite choke at one end to overcome some stray signals that gave my setup some fits from time to time.

Also, if the specs are accurate, your stepper drivers are capable of 4 amps of output. You could easily upgrade your motors into the 500-600 in/lb range, as long as you have it apart, and be more in tune with the demand that having high displacement lead screws presents.

Again, good luck.

[whitetiger28th]

GEdward,

I measured the lead screws. They are 10 threads per inch. .100 per inch I believe 1/10. The gap between the threads measure .040 pitch if I measured correctly.

Should be good with the motors I have, yes? Not sure.

V/r

Jeremy

[wmgeorge]

So if this was built from a kit and all the kits are the same, correct or not? I would go back to that website and the guy who runs it and ask these questions. Otherwise rebuilding it will accomplish nothing except use up your spare time. Your issues are with the machine not with VCarve.

I am sure you saw this video:

[GEdward]

Look at the end of the lead screws to determine the number of "starts" there are. The part number that the web site gives for the lead screw material is a 5 start thread. If that is the case then the travel per revolution is 5 times the pitch (0.10) or .5. With that said, it may be that your lead screws are something else. If they are indeed a single start, like a regular bolt, then your motors will have plenty of torque and no upgrade need be considered. Even with 5 start screws it is possible to "get by" with what you have; it is just that you will be quite limited in performance and you will have an increased chance of missing steps under heavy loads and rapid movement commands.

If they are indeed single start threads then you need to consider this: 3200 pulses per revolution X 10 revolutions per inch X 60 inches per minute (1 inch/second) = 32000 pulses/second per motor. Since Y and A are slaved, I assume you have two Y lead screws, then for say a homing command and all three axis are traveling at 60 ipm ( which is pretty slow actually) then you are sending 4 X 32,000 or 128,000 pulses/second to your UC100 which can only through put 100,000 pps. That spells trouble in short order!

[whitetiger28th]

No part number on any end of the screws. I count 5 starts. Looks like one long screw was cut into 4 separate screws for two Y, one X and one Z axis.

There are ten threads per inch so, it is as you said .10. Should be enough to “get by”.

I am tearing it completely down, cleaning all the threads with a wire wheel to get the rust, wood dust and greese out.

The backlash plastic guides are gummed up also. There is a little rust on the guide rods that probably cause some hesitation at the ends, so hopefully after cleaning it all up the mechanical part will work smooth.

Trying to determine if I can put bearings at the ends of the lead screws to give it a smoother guide. Right now the screws are resting in a plastic 1/2 inch piece of plastic and the lead tips are spinning against the metal frame.

I think when it comes down to it, I just need to get the proper tunning with the motors. At least hoping that will fix it. Any suggestions on upgrades? Not that I want to sink anymore money into this particular system, but it is what it is and I need to get it working properly.

[whitetiger28th]

Maybe just replacing all the lead screws and screw guides? With what though, utilizing the same motors?

[whitetiger28th]

Looking at the following on dumpsterCNC for upgrades. The collars I have are size “C”

ACME 1/2-6 TPI 1start
ACME 1/2-8. 1Start
Or
ACME 1/2-10. 1start


There are also 2,4,5 start screws

Not sure which if any that would be an upgrade to the motors that I already have.

V/r

Jeremy

[GEdward]

Your lead screws were indeed cut from a single 6 foot piece. It came from McMaster Carr and the part number is 98940A020. They price is $69.52. The part you call backlash guides are lead screw nuts and are either part number 1349K103 @ $31.28 ea, or part number 95075/a247 @ $22.55 ea.

If you choose to clean up and use your current hardware make sure that you do not have pitting on the screw threads or otherwise damage the threads while you are cleaning them. You will have to decide if the price for new, and cutting it into the appropriate lengths, is justified. Once you are up and running be advised that the PET plastic nuts don't really need lubrication and if you do choose to use lube then either use a dry type lube or adhere to a routine wipe down regime using a very lite coat of thin oil like three in one.

If there is too much damage or you decide to bite the bullet and replace the screws and nuts then I would suggest 1/2-8 two start or 1/2-10 two start along with the appropriate nuts.

By bearings on the ends of the lead screws you mean the end opposite of the driven end then I'd say no. The reason is that the lead screw need to float with the guide rod location. Installing a bearing introduces a tolerance that has to be adhered to in order to avoid stressing the relationship of the guide rods and lead screws. Some high dollar industrial machine tools put bearings on both ends but there is always a provision to allow them to float into position with the axis fully extended before the mounting flange is bolted, and sometimes pinned. I once observed an inexperienced maintenance tech not follow that procedure and snap a brand new $5,400 50 mm X 1800 mm ball screw on its first move. The alignment was only out by 0.012 appx.

With regard to the screws hitting on the metal frame, I see that as a definite problem. The screws' axial movement should be captured by the bearings on the driven end. Not sure how this is set up but something seems not quite right. Maybe explain that setup a bit or post a pic or two.

[ger21]

If you already have 5 start screws, I would not change them. Are the screws supported by bearings at the motor end, or just the coupler?

I'd lower the velocity settings to 50, and see if that helps.

You're dealing with a very low quality machine. There's really no point in trying to upgrade it. I'd getting it working the best you can, and start saving for something better.

[whitetiger28th]

Thank you GEdward and Ger21

I have torn the machine apart and spent all day cleaning grease, grime, sawdust, rust, etc off of everything.

Getting it put back together slowly.

No pitting in the lead screws. Everything seems to be straight and true. No bends.

Think I figured out the binding issues. Combination of the framework not being level, guide rods, lead screw nuts and lead screws packed with grease dirt grime sawdust etc.

Need to reassemble, but everything so far slides and rotated smoothly within the guides and plastic lead nuts.

The lead screws have 5 starts, 1/2(.5) dia.

Once back together I will change all motors to 50 vice 120 and see if that helps.

Wondering if some of the notches made across the arcs were due to binding/ sticking along the guide rods and screws. Didn’t think that the case since the machine was moving smooth within the project range.

Lead screws are not in bearings, only setting in plastic coupler/ holes. I tried attaching pics but they will not attach via my phone.

This is the third time I have sent this message over the past 14 hrs. When I try attaching pics the whole Med disappears.

Will let you know what happens once I get everything back together.

Jeremy

[wmgeorge]

Now I think your on the right track. You got some good straight forward advice from Ger21 he has been doing this CNC thing forever. Consider this project a learning experience. There is only so much you can do with a plywood framed unit. However all is not lost. You still have all your parts and the Mach4 and VCarve Desktop license you could make a more robust frame out of aluminum extrusions, upgrade your controller to use external heavier duty stepper motor drivers and perhaps larger stepper motors if needed.

[whitetiger28th]

This is not a plywood frame. It is solid steel. Very heavy unit. That’s why I thought upgrading would be good. If you look at the garage works website where Dave Gatton is assembling an orange unit, the blue one in the back that says Sidewinder CNC is the unit I have.

V/r

Jeremy

[ger21]

If this is the machine, don't bother upgrading. This is not a very good machine.

Get it running, and learn as much as you can. You'll soon find that you want something better.

[whitetiger28th]

Similar. Not that unit, but the one in the background looks like it. Larger unit and gantry sides look the same as the one in the background to the right.

Guides and couplers are the same. Red aluminum and plastic couplers.


Originally wanted to buy the Shark extended bed. Too expensive for me at this point.


V/r

Jeremy