Triac Z axis counter-balance

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Roy
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Triac Z axis counter-balance

Post by Roy » Thu 27 Dec , 2007 15:30 pm

Below are a few pictures of the counter balance i have made for my Triac.

This is to ease / equal the load on the z axis stepper and ballscrew, thus reducing the chances of the stepper stalling when moving in the Z + direction.

The counter-balance weight is 20kg. This is an estimated weight of the head and motor.
Attachments
Pc270826.jpg
framework/pulleys
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wire attachement studs and plates
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Pc270828.jpg
20 kg counter-balance weight
Pc270828.jpg (71.26 KiB) Viewed 7744 times
Pc270829.jpg
framework
Pc270829.jpg (78.72 KiB) Viewed 7744 times

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Post by sneakym8 » Tue 04 Mar , 2008 20:25 pm

Hi roy

I am going to do a similar thing to my triac , I am retrofiting dc servo's so the balance is needed to,
A. stop the servo drive burning out just sitting holding the axis up.
B. stop the z axis shooting towards the table when the drive is switched off.

Thanks for the look at yours, i might do something similar.
I put a spring balance on my z axis with no motor connected and it took about 28 kg to get the balance .

regards colin

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Post by sneakym8 » Fri 07 Mar , 2008 20:00 pm

Hi Roy

what do you think of this, it works great and takes no space up. I got an adjustable gas spring off ebay and balanced the head perfect.
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Post by Denford Admin » Thu 13 Mar , 2008 14:47 pm

I got an adjustable gas spring off ebay and balanced the head perfect
I would never thought something so simple would have worked.
(Certainly my favourite method, just for ease of fitting)

How did you balance/setup up the gas spring ?
Did you monitor motor current going up and down ?
Is average motor load higher now its having to drive(ie not drop) down as well ?

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Post by sneakym8 » Thu 13 Mar , 2008 21:43 pm

Hi

The gas spring I bought was a stainless steel adjustable pressure spring, The pressure is at 640n when bought and you can let them down, being very careful not to go too far as you can only go down not up,

Go too far and your looking for another one.

When I first fitted the spring I disconnected the motor and the head went up
so I held the pulley at the top of the lead screw and released some gas, just a little at a time until the Z axis was in perfect balance.

The balance does not seem to alter very much at all, if the z axis is at the bottom or the top of its stroke it is still in balance.

I think that it is preferred to have the head slightly negative (pushing down)
But for the time being I left mine in perfect balance

So the motor has very low load when travelling up or down !! Good eh.

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Roy
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Post by Roy » Sun 16 Mar , 2008 17:53 pm

Hi Colin,

Great simple idea!

Seems as though this will do the job.

My only concern, would be that you keep an eye on the spring. In my experiances of Gas springs, they tend to fail at the most inconvinient time!

Good idea though, let us know how it performs!

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Post by sneakym8 » Mon 17 Mar , 2008 10:03 am

Hi Roy

I was thinking along the same lines and what i may do is fit one to each side,
When they fail I think they tend to fail gradually over a long period and I don't think they are that unreliable or there would be a lot of people with bad heads and compensation claims against car manufacturers.
:doh:

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Post by dazz » Thu 20 Mar , 2008 11:27 am

Gas springs can be charged to any pressure (within limits).
Regards

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Re: Triac Z axis counter-balance

Post by Rgvbaz » Sun 25 Feb , 2018 18:39 pm

Hi

Not sure if you are still on here Colin but I have your machine!

I bought it as a project as it had some issues which I am keen to sort out.

The guy I bought it from was up-front and said there were issues with the machine and may need a new Z axis ballscrew...

Did you ever measure the force to turn the Z axis.

I had a look and found in both directions (the gas strut must still be working) it was 2.2lb at 3 inch which is: .75 Nm or .55 Lb Ft


Cheers

Dave

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Re:

Post by Rgvbaz » Sun 25 Feb , 2018 18:42 pm

sneakym8 wrote:Hi


When I first fitted the spring I disconnected the motor and the head went up
so I held the pulley at the top of the lead screw and released some gas, just a little at a time until the Z axis was in perfect balance.
Guess I need to disconnect the gas spring...

Dave

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Re: Triac Z axis counter-balance

Post by sneakym8 » Mon 26 Feb , 2018 10:16 am

Hi Dave
Nice to know its still around it was a good project. I never did measure the force on the z axis although it was very light to move , with the gas strut in place and with it removed the axis ran away on its own . If theres anything i can help you with i will although its a while since i did it.

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Re: Triac Z axis counter-balance

Post by Rgvbaz » Mon 26 Feb , 2018 12:50 pm

Hi Colin - great to see you are still here and I'm sure I'll have plenty of questions for you if you are happy to answer?

I think the z -ball screw will need replacing - the pulley needs grasping with my hand to turn it and it does feel a little notchy. The guy I bought it from said he reckons it needs replacing too. I found the nut that secures the z screw to the top bearings loose and the screw itself was moving up and down as you turned the pulley causing a lot of resistance.

All axis's moved when I went to look at it but it would trip when moving the X and Z. The guy who sold it to me said he thinks this was because the screws have had it. I got a new X screw and ball nut with the buy so I'll fit that and see if it stops the X tripping.

It's had new spindle bearings too so hopefully once the screws are fitted/replaced it will be up and running nicely.

Really like the fact it is on servo drives :)

I don't suppose you know how the Z axis screw is removed? It looks tight. I'm guessing the bottom single bearing retainer plate it removed and the screw and the bottom bearing move down far enough to remove the top of the screw shaft from the two top bearings?

Cheers

Dave

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Re: Triac Z axis counter-balance

Post by sneakym8 » Mon 26 Feb , 2018 14:10 pm

Not sure how the zaxis ballscrew comes out i never had to remove any of the screws, it sounds like its been in a damp place if there's trouble with all the screws as they were mint. If the shafts are ok you can re-bal l

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Re: Triac Z axis counter-balance

Post by sneakym8 » Mon 26 Feb , 2018 14:12 pm

Re -ball them . You can buy selectiv size balls so you can eliminate backlash.

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Re: Triac Z axis counter-balance

Post by Rgvbaz » Mon 26 Feb , 2018 23:20 pm

Thanks Colin - I will look into re-balling the Z ball nuts if I can.

Interestingly I disconnected the gas strut. The force required to lower the Z halved and doubled to raise it - i'd say the strut is still working perfectly.

I did have a feel of the Z servo motor - it is very notchy. I checked the X servo and that is lovely and smooth. I'm guessing the Z axis not running free has possibly damaged the servo? I'll have to look for another :(

I took the table off tonight to get to the X ball screw - as I loosened the nuts it freed off and the screw turned a lot easier. As the guy who I bought it from said the nuts just need shimming so they run free when tightened.

I think I am derailing this thread now so I will start a new one tomorrow and stick a few pics up. I'll try to update so there is a record of what I do.

Cheers

Dave

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Re: Triac Z axis counter-balance

Post by Rgvbaz » Mon 26 Feb , 2018 23:32 pm

sneakym8 wrote:Re -ball them . You can buy selectiv size balls so you can eliminate backlash.
Just found this thread with contact info of a company that does re-balling :)

viewtopic.php?f=47&t=4714

Dave

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Re: Triac Z axis counter-balance

Post by sneakym8 » Tue 27 Feb , 2018 13:54 pm

Dave
I don't know who you got the machine from but when i sold it there was a spare motor with it , as i was going to put a 4th axis on it . I saw some similar motors on ebay last week .
I have just bought a denford microrouter and was thinking about converting it to servos.

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Re: Triac Z axis counter-balance

Post by sneakym8 » Tue 27 Feb , 2018 13:58 pm

Rgvbaz wrote:
sneakym8 wrote:Re -ball them . You can buy selectiv size balls so you can eliminate backlash.
Just found this thread with contact info of a company that does re-balling :)

viewtopic.php?f=47&t=4714

Dave
Dave the reballing is really easy to do and costs pennies . I will have a contact for the balls if you struggle to findsome.

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Re: Triac Z axis counter-balance

Post by sneakym8 » Tue 27 Feb , 2018 14:03 pm

The motor probably just needs new
bearings

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Re: Triac Z axis counter-balance

Post by Rgvbaz » Wed 28 Feb , 2018 19:14 pm

sneakym8 wrote:Dave
I don't know who you got the machine from but when i sold it there was a spare motor with it , as i was going to put a 4th axis on it . I saw some similar motors on ebay last week .
I have just bought a denford microrouter and was thinking about converting it to servos.
Colin - sorry I missed this post.

There was no spare motor with it :( but I have seen the servo motors too.

Is there any way of servicing these. Not had a look inside yet but I will.

Dave

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