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Odd noise during screw movment

Posted by Jeff 
Odd noise during screw movment
April 06, 2015 11:04AM
I have noticed during jog and cutting movements on my x-axis when the carriage reaches a certain spot (about 2" to the right of home) ts kind of grinds or rubs for about a 1/2"-1" or movement. On slow movement speeds (~1"/sec) this does not affect the positions, but when I try to run at the recommended jog speeds (~2"/sec) it throws the positioning off.

I have one of the original kickstarter bots. It has always done this, but became more noticeable after swapping the base plate and backlash nut .
Though that might also becaused by the fact I now have a separate dust room for the handibot and no longer need to wear ear protection while cutting since I can leave the room.

Does anyone have any idea what could be causing this? I looked through the troubleshooting documentation and did not see anything to that might be out of adjustment. I have no issues with my cuts, the just noise is worrisome.
Re: Odd noise during screw movment
April 06, 2015 01:48PM
I have a similar issue. The noise has always been there but the X repositioning failure is something recent and has gotten worst. I have been trying the work through the issue with support, while they have been supportive with ideas we have not found a solution.

In my case I found the X reposition, at the start of cuts, was failing about 1 in 5 times but I have has occasions where I have failed 5+ times in a row. It is now to the point where if I can do the work manually or with a handheld router I do so!

I did find that if you thoroughly clean the Handibot, I pulled the base plate and cleaned with a toothbrush, the then reset the XY zero position several times before each cut it seems to help, that is I was able to get 10 cuts before it failed for the first time after. I could also be just wishful thinking. Obvious this is not a solution and why in order to get some work done I have reverted back to manual drilling/cutting and handheld router.

For me, this is a major headache, that is in addition to part cutout, I used the Handibot to do CNC carving which requires several bit changes. Being a little slow on the stop button can result in destroying hours of work, not to mention the expense of turning hardwood in the scrap.

It is good and bad to hear I have a fellow sufferer, but only good in the fact that maybe with more than one victim we can find the root cause and a solution.


Re: Odd noise during screw movment
April 06, 2015 04:47PM
Hi there, folks. It sounds like it may be some mechanical binding. As always, feel free to call into our Tech Support team (888-680-4466) if need be.

In the meantime, try this:

Please turn the power off and move it by hand through those areas. If the issue still persists, please feel free to call ShopBot for help.
Re: Odd noise during screw movment
April 06, 2015 05:14PM
One other, slightly more tricky way to diagnose this is to take the bearings loose one by one (by removing the four screws holding them in place) and sliding them around. You may find that they all move easily and this should mean that there is an alignment problem, which should be fixable. Or you might find that the bearings bind when you try to move them around on their own, which could mean that the bearing itself is failing. We can help with this. Just remember to reinsert the screws in each bearing before checking the next one so that you preserve your current alignment.
Re: Odd noise during screw movment
April 22, 2015 01:32PM
I'll take a shot at this one ...

First, appreciate that stepper motors make a lot of weird noises and vibrations, particularly at low speeds. If you are not used to listening to them, their musical nature is initially a bit of a surprise.

But, the symptoms here also involve losing position. That makes it a very different issue. The thing to keep in mind is that stepper motors are also at the greatest power when they are going slow. That means, that if the issue tends to show up as speed increases as it does here, then the failure is likely happening because the motor is not able to overcome some sort of resistance -- and moving it with a little less power reveals it.

With a Handibot, this is likely to be due to one of 4 things:

1. The lead screw of an axis has gotten out of alignment and the nut is binding on it. This is usually most pronounced as the nut approaches the motor. So a good test is to jog towards the motor at a nice high speed, say 4-5ips, and see if the motor stalls before the car hits the end (don't worry, you won't hurt anything). If so, then you probably have an alignment issue and the first and easiest solution is to just release the bolts holding the nut when the car is positioned close to the motor. Let the parts relax into a better position. Re-tighten them. And, then test again.

2. The bearings are binding on the rail. This is a lot less likely but is possible. Easiest to test this as Brian describes above -- take the screws out of one bearing at a time and move them back and forth on the rail.

3. Maybe software-related; inconsistent streaming causes stepping to stutter and location to be disrupted. This is very unlikely at the low Handibot speeds ... and it most often happens in complex curves that involve transmitting the additional speed changes in the streaming ...

4. Something else that has not occurred to me ...

Let us know what you figure out or if you need more help.

Ted Hall, ShopBot Tools
Re: Odd noise during screw movment
April 22, 2015 02:18PM
I will try some more diagnostics possibly this weekend. I should mention the first time I saw the positioning issue was after switching to a new Dell tablet and upgrading to the latest sbedit program. I doubt this has anything to do with but thought I should mention it.

As I mentioned with the reliability issue I have had to discontinue using the Handibot for carving, but continue to try to use it for single tool routing/cutting. As you know carving usually requires tool changes and positioning issues between tool passes is more inhibiting. I desperately want to get this issue solved, carving and sign making are usages I justified the Handibot for.


Re: Odd noise during screw movment
April 22, 2015 09:07PM
Can you give me a little more idea of the kind of carving you are doing? Thanks, =Ted
Re: Odd noise during screw movment
April 22, 2015 11:16PM
I add 3D carvings to plaque and signs. Some stock items, some produced in Cut3D or similar products. The photo attached is a sample carve, needs some sanding but you should get the idea.

I have learned much about CNC and the capabilities of the Handibot. While it may not be the best CNC router for carving, jigging things to allow tool changes makes it workable. It also fills a number of the other uses I have. I may have been better off with a larger table top unit, or something like the Stepcraft 2 840 that just funded on Kickstarter but they all have a size limit so the Handibot can do a lot they would not be able to, one tile at a time. I am really looking forward to the crawler! But a tool changer would be a dream come true at this point. winking smiley


open | download - IMG_0026.jpg (204.4 KB)
Re: Odd noise during screw movment
April 24, 2015 07:02PM
Hi M,

In the carving files of the type you illustrated, I'm guessing that you do the tool-change because you are doing a roughing pass to cut away material before you do a finish pass with a different bit? I'm wondering if you've considered just doing the final, finish tool-path (I'm assuming this is a raster)?

I ask because we find that with the bit that many ShopBotter use for these carvings -- that is a tapered 1/8" ball nose -- because the entry for the "dished" design is very gradual and the step-over very slight, it usually works well to only do that one, finish path. You can usually skip the the roughing and still get a really nice finish.

This may not work well in really hard material, but the tapered cutter actually seems to like having the nice consistent wall of material to cut against in most cases.

When you are not using the dished design but are still rastering a similar type of carving, you can get the bit down to an initial deep cutting depth by editing the file to create a gradual plunge to depth ... this is usually a workable to way to put the finish cutter on the raster path without it having to cut too aggressively during the first pass. Let me know if you want this illustrated in more detail ...

On the question of a tool changer ... while it's unlikely that a Handibot will ever have a real industrial tool changer (just far too expensive). We are thinking that it may be useful to set the Handibot up to easily swap out routers that have their bits set to an exact height. That would happen by making it easy to plug and unplug the router, have a quick release on the router bracket, and put an adjustable ring on the router to give it a define location in the bracket. I'm thinking there are already a few Handibotters out there who have configured their tools this or a similar manner. (Might be interesting to hear about their experience ???)

Ted Hall, ShopBot Tools
Re: Odd noise during screw movment
April 26, 2015 11:14AM
I am not sure I completely understand your suggestion(s). You are correct in that I use a 1/4" up spiral bit to do rough out, then switch to 1/16 tapered bit (or 1/32 for finer stuff and dependant on wood type). That is for the carving portion, I then switch to a larger straight or V-grove bit for the lettering portion of the sign. I have several Amana bits including the AMS-136 CNC Carving Set (http://www.amanatool.com/products/cnc-insert-router-bits/cnc-carving-router-bits/carving-cnc-2d-and-3d-router-bit-sets/ams-136-8-pc-solid-carbide-2d-3d-carving-ball-nose-zrn-coated-cnc-router-bit-collection-1-4-inch-shank.html) and the AMS-132 CNC Signmaking Set (http://www.amanatool.com/ams-132-18-pc-signmaking-advanced-cnc-router-bit-collection-1-4-inch-shank.html). I am looking at the new front plate, thinking that would help with the bit changes, currently I unmount the Handibot and flip the unit over to change bits. I have a set of angle iron rails that I mount the Handibot into so I can return the the correct position after bit change, I need to refine this. The large material indexing jig is great, use it for the lettering portion, but it is just not accurate enough for multi-pass carving, or at least I have not been successful with it in my attempts. Of course that issue relates to the tool changing or carves larger than 6x8.

Any suggestions are welcome!! I have been doing this by hand and with a plunge router for a few years, but the CNC approach is new to me and I am still trying to figure things out.

Back to the point of the original conversation, I continue to struggle with the X-axises positioning at the start of a cut and to Jeff's point there is a grinding type noise when the X movement seems to slip. I have tried several of the suggestions set to me by Customer Support. Presuming I am disconnecting the right things on the bearing test, they sent me the attached image so I pretty sure I got the right thing. The bearing moves very stiffly in the positive direction, like two hands to move it, and far easier in the negative direction, I personally think that is were the problem is.

At your suggestion I tried sending the car (did not know that name) in the positive direction from 0 to 5", at 1-ips the noise is less pronounced and the positioning seems to work, (without a more accurate measurement system to verify final position). But at 5-ips, the noise is very pronounced and the final position is visibly off by more than an inch. In the negative direction it always seems hits 0 no matter what speed I use. I am not sure what bolts you are suggesting I loosen to fix the alignment, a image would help as I am a visual guy.

Thanks in advance,

open | download - image001.jpg (32.6 KB)
Re: Odd noise during screw movment
April 26, 2015 01:27PM
If it is taking two hands to move the x axis with the drive screw disconnected you definitely have something dragging that should not be. Depending on how adventurous you are you can disconnect each bearing individually and check their drag. Also I find 5ips to be optimistic for quicks even when everything is right. I'd go into settings and change it to 3ips. In a day of cutting you will never notice.

Ted :
I'd absolutely love to see a quick disconnect on 2.0, not just for a spare router but for things like lasers.
Re: Odd noise during screw movment
April 27, 2015 07:02PM
Hi M,

That info helps...


Let me respond first on the binding issue as it's important. On the "grinding noise" -- let me explain what I believe this noise is (I could be wrong, but can't really be sure without being there). When a stepper motor misses steps (this is also described as losing sync with it's step signal), the rotor just spins, but it spins across a series of little magnetic fields or notches that give it a fast stuttering or grinding sound and vibration. You will hear it if you drive the axis into the end-stop with the Keypad -- and then keep going. This "grinding" does not hurt the motor (assuming you don't keep drilling it into the wall for hours). But importantly, it is not the cause of the motor missing steps and the axis losing location; it is a telltale result. In fact, if you hear it, you've likely lost your location to at least some degree.

The grinding happens when the axis binds (resists motion) or is held. Usually on a Handibot, this happens if the motor, screw, and nut get out of alignment. BUT, the bearing blocks on which the car rides might also bind. They may have gotten crud in them; there might be a flaw in the bearings or bearing cage.

So with respect to the diagnostics that the Support team suggested -- After moving the X axis to the far right and removing the two bolts marked in the figure. The X-Z car is now disconnected from drive nut. You should be able to push the car freely up and down the X axis because the screw and motor are not engaged and the car is just sliding on its bearings. The bearings will be firm, but it should only require pressure from a finger or two to move the car up and down the axis in either direction. If the car has been correctly disconnected from the motor and screw, then needing "two hands" of force is not right -- and certainly the issue.

As Mark suggests, you can further refine the diagnostic by removing the 4 bolts in each bearings, one bearing at a time, and push the bearing out from under the car to test it individually. This might allow you to figure out which bearing(s) is hanging up ... and if you were really brave, you could remove the motor so that you could take the bad bearing(s) off to inspect and clean. But I think that at this point we should swap out your tool for a new one so that we can have a look and see what the bearing issue is. It is not something we've had much experience with ...

Per Mark's comment on Jog Speed. I did not mean to suggest running files while Jogging at 5ips, only using 5ips as a diagnostic test for alignment/binding because it will quickly reveal where there is serious binding on a tool. I also like 3ips as a good default Jog speed for the Handibots.

Tool Path

Per the discussion earlier on tool-pathing your carving files, I was suggesting skipping the 1/4" roughing pass in the case where you have a rastering finish path in a "dished" carving, or, where you program the first line of cutting so that it works it's way down to depth. In both cases the raster nature of the machining means that the cutter is only removing a small amount of material on each pass. In most cases it is not necessary to first clear the area out with a roughing pass. And this way, at least for the carving component, you don't have to worry about registration after swapping out a roughing bit.

Ted Hall, ShopBot Tools
Re: Odd noise during screw movment
May 20, 2015 11:17AM
To provide some closure on the topic, at least for my circumstance. Ted and team were great and very helpful, I cannot thank them enough for their efforts. My Handibot is once again my go to tool for sign making and many other tasks. I can't say the plunge router has been put back in the cupboard but it has been remounting in the router table and awaits my edge shaping needs.

Over the last week I managed to get caught up on a number of projects that were stacking up. I still have a long way to go in my understanding on how to do more, or do it better with the Handibot but at least I am back on the right path. Besides some sign carving, I sketched up the sides for some Murphy Doors, basically to do the fixed shelve pockets and drill for movable shelve pegs, would have been a lot of setup to do manually, but with the Handibot I had the sides done literally in minutes!

Ted et al thank-you for all your help, I have lots more questions but each project makes me a little wiser!


Re: Odd noise during screw movment
May 26, 2015 07:22PM
I finally had time to sit down and run through all of the suggestions here. It wound up being an issue with the x-axis screw alignment. If you watched it closely during moment you could see it shift alignment with the position of the carriage. It is not the the screw is warped( then it would flex as it rotate and would have hit at multiple points in a jog). To fix it I tried tightening the top two screws holding the x-axis motor in place as recommended in the axis alignment document, No matter how tight I made these the axis screw still hit the edge of its clearance hole, thorough it did get better. To fix it completely I would up removing the top screws one at a time and adding washers so I had more thread to tighten on and the force was spread over more area so the wall did not get damaged by the over tightening.

If you look closely during the jog it is still not centered, so I am worried it wll sage again over time and I will have the same issue again.
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