Is my twisted makerslide causing the gantry to rack?

Simon P
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Joined: Wed Mar 12, 2014 9:17 pm
Location: Wiltshire, UK

Is my twisted makerslide causing the gantry to rack?

Post by Simon P » Sun Apr 20, 2014 2:38 pm

Today I took my shapeoko apart so that I could grind a flat on the X and Y stepper motor shafts and threadlock the GT2 pulley grub screws in place. I needed to do this because, as per my previous posting, I discovered my X-axis pulley had come loose on the stepper shaft. I now have pulleys that are firmly attached to my steppers and will not yield at all to my attempts at torquing them, however, I believe the improvement has highlighted a major flaw in my shapeoko kit.

In my excitement at putting the kit together first time around I found one of my pieces of 500mm makerslide was badly twisted but used it on my Y-axis anyway since I just wanted to see the shapeoko moving and doing it's thing. This, of course, was a compromise and led to one extreme of Y-axis travel being a bit slack and the other being tighter. My shapeoko was able to move despite this but always made a juddering vibrating sound when it travelled along the Y-axis. At the time I thought this was the GT2 belt vibrating but I now think it was the gantry vibrating in a racking motion as it moved from tight to loose or vice versa as it travelled along the Y-axis. With my original half baked job of attaching the pulleys this did not seem to bother the motors.

This time when I put the machine back together again the vibrating noise with Y-axis travel was still present and I still had a looser extreme and a tighter extreme on the Y-axis but now whenever the gantry vibrates in it's racking motion (assuming it is doing so) the dual Y-axis motors seem to argue with one another. I think that when the gantry racks it must, at some point, be pulling against the movement of one of the dual-Y steppers and this causes that stepper to resist and, because they are connected in parallel electronically (albeit in reversed motion from one another), this causes some sort of feedback loop which results in the both motors juddering around and eventually stalling completely.

When I disconnect everything, remove the GT2 belts completely and just push the gantry along the Y-axis with my hands I can feel the slack portion of travel, the tighter portion and I can also feel the vibrations as the gantry crosses from one portion of travel to the other. Other than this the gantry slides smoothly enough and easily enough that I cannot believe it would stall the motors through friction so I can discount that as a problem. I have not changed my wiring at all and my wiring seems completely fine, nothing is loose. I have not shielded my wiring but, since I've not changed anything about them, and they did not previously show signs of interfering with one another, and the motors don't act up when I remove the belts from both Y-axes, I doubt the wiring is at fault.

This is my personal best guess as to what is happening, hopefully those with a bit more experience will be able to tell me if I'm barking up the wrong tree. I would submit video but it's Easter and the family are already annoyed that I'm spending time with the shapeoko. :lol: Assuming it is the racking which is causing the motors to lock up and which in turn is caused by the twisted makerslide I will be ordering replacement makerslide as soon as the amberspyglass store opens up again. The twist in my makerslide is sufficient that if 3 corners are held on a flat surface the 4th corner will stand 5mm off the surface and if I knock it I can watch it roll from side to side for quite some time. I assume this twist would also have some knock on effects for accuracy at the spindle so it is probably worth replacing regardless of whether it is causing the racking and subsequent motor lock ups.

Thanks for your opinions,

Simon

Edited to add the photograph
Attachments
Twist Quantified.JPG
Three corners touching but this one is out 4.68mm
Twist Quantified.JPG (92.82 KiB) Viewed 1787 times
Last edited by Simon P on Mon Apr 21, 2014 6:55 pm, edited 1 time in total.
Shapeoko 2 #3697 - Dewalt D26200 Spindle, Precisebits Collets, 250mm Z-Axis Makerslide

cvoinescu
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Re: Is my twisted makerslide causing the gantry to rack?

Post by cvoinescu » Sun Apr 20, 2014 5:05 pm

That's a pretty serious twist in what I assume is a 500 mm piece. It's definitely out of spec, and Inventables would have replaced it, but given where you are and where they are, it's probably easier to order it from me when I reopen the shop.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

crazeegeek
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Re: Is my twisted makerslide causing the gantry to rack?

Post by crazeegeek » Sun Apr 20, 2014 7:33 pm

Until, then contact Inventables. They are really good about making things right.

WillAdams
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Re: Is my twisted makerslide causing the gantry to rack?

Post by WillAdams » Mon Apr 21, 2014 4:00 pm

Please, contact Inventables --- the ``Customer Success'' team will send you a replacement piece of rail if it arrived that way.
Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

Simon P
Posts: 28
Joined: Wed Mar 12, 2014 9:17 pm
Location: Wiltshire, UK

Re: Is my twisted makerslide causing the gantry to rack?

Post by Simon P » Mon Apr 21, 2014 5:59 pm

I bought this kit through a place called robosavvy here in the UK but it is an Inventables kit. Can I still contact Inventables about this?

The piece was definitely twisted on arrival and the box it shipped in showed no signs of damage. I have attempted to roughly untwist the piece by attaching 1 meter long bar clamps to each end and applying opposite twist with as much strength as I could muster. My efforts had no effect. It is surprisingly stiff stuff. These facts convince me that the twist was most likely introduced during manufacture, or at least prior to kitting. My other Y-axis rail is also able to rock ever so slightly on a flat surface but much less so than the piece I'm talking about, can we quantify what the tolerance on this is please?

My shapeoko has been taken apart now while awaiting a replacement but I'm still no wiser as to why the dual y-axis motors were locking up, could racking cause this? Running them in the air with the gantry removed from the Y-axis rails they show no signs of trouble.

Thanks,

Simon

PS. I am absolutely amazed and very impressed at just how well this product is backed up and, more importantly, how much the people behind it actually care about it and their customers.
Shapeoko 2 #3697 - Dewalt D26200 Spindle, Precisebits Collets, 250mm Z-Axis Makerslide

ZachKaplan
Posts: 89
Joined: Fri Apr 13, 2012 1:38 pm

Re: Is my twisted makerslide causing the gantry to rack?

Post by ZachKaplan » Mon Apr 21, 2014 6:13 pm

Hi Simon,

I am sorry about the problem. We (Inventables) are in regular communication with Robot Savvy. Working together we will get this fixed for you. If you could contact them so they are aware of the problem and can track it in their system and match it to your order they will reach out to our Customer Success team who will get it resolved.

Once again I'm sorry about the issue.

Regards,
Zach

Simon P
Posts: 28
Joined: Wed Mar 12, 2014 9:17 pm
Location: Wiltshire, UK

Re: Is my twisted makerslide causing the gantry to rack?

Post by Simon P » Mon Apr 21, 2014 7:01 pm

Zach, thanks for the advice, I'll shoot an email over to Cat at RoboSavvy tonight and see what unfolds.
Shapeoko 2 #3697 - Dewalt D26200 Spindle, Precisebits Collets, 250mm Z-Axis Makerslide

blox
Posts: 3
Joined: Wed Apr 23, 2014 2:30 am

Re: Is my twisted makerslide causing the gantry to rack?

Post by blox » Wed Apr 23, 2014 2:54 am

+1 to the Inventables team! They shipped me a replacement rail within an hour of emailing them about a dent in one of my slides. Definitely worth talking to them/your supplier and I am sure they can work out a replacement for you.

Nigel K Tolley
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Re: Is my twisted makerslide causing the gantry to rack?

Post by Nigel K Tolley » Fri Apr 25, 2014 9:07 am

Technically, it should be straight as a die, from which it was formed.

Yes a twist like that will wreck things as it will be a different distance as it runs along, and your wheels will likely bind eventually. Whatever, it won't help.

When does the store re-open? I want to buy a full kit still. I know FizzPOP makerspace want one, and London Hackspace have been talking about it too.

Sent from my SM-N9005 using Tapatalk

cvoinescu
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Re: Is my twisted makerslide causing the gantry to rack?

Post by cvoinescu » Fri Apr 25, 2014 9:50 am

Store's open; working on updating the price for the kits. Got a nifty Tr 8 x 2 leadscrew option and a "deluxe" frame option. Should be done by tonight (late).

About the twisted MakerSlide: the die is fairly short, so there's a lot of opportunity for it to bend and twist as it exits the die. If the profile is not symmetric and/or the die isn't perfectly balanced, it'll tend to come out curved or twisted, the same as macaroni coming out of a pasta maker. Even when extruded straight, some types of temper require it to be kept hot for a few hours, and it can sag during this time, depending on how it's supported (as far as I know, that's not the case with MakerSlide, though). So it does require some engineering to keep it straight -- it's not that simple. :)
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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