Wiggly cuts

[acourtjester]

This is who I have been using for #35 chain and sprockets seem to have better prices and size selections. also for the #50 I used on the plate roller.
https://www.surpluscenter.com/Power-Transmission/

[Black Forest]

Whereas you have hubs on your sprockets it is a simple matter to chuck them up in a lathe and bore the holes over size and press in a sleeve with the correct bore. Simple and fast. Not expensive. Just don't let someone do it on a hobby lathe. It would be a good fix and you don't have to wait for parts.

[Bigrhamr]

As mentioned above I tend to think the chains are just going to be problematic when compared to belts in the same application.
Can you just do a direct replacement of belts and pulleys in place of chain and sprockets? I get mine from these guys, they have steel core or kevlar core belts and all kinds of pulleys. http://www.polytechdesign.com/index.php
I haven't checked to see if they ship internationally or not.

[sphurley]

Ben, if you want anything from McMaster, let me know. We are there multiple times a day and if they let me move in, I would.

[BensPlasmaAu]

Ben, if you want anything from McMaster, let me know. We are there multiple times a day and if they let me move in, I would.

Thanks Steve i appreciate that, ill keep it in mind for next time.

Pretty much i think i made a terrible mistake with using the roller chain. I am heading back to the T5 pulleys but making sure i reuse the keyed shaft i have now. Ill be down for another week or so till thats sorted, which is disappointing. As well as the pulleys being redone, i will be organising to make the reduction drive assemblies with a spring tensioner to take any preload problems out of the pinion to rack meshing problems i think im also having.

I reckon this tightness of chain has been my problem with most of the cuts over the past few weeks. Pretty much not being able to move the pinion by hand proves to me what the issue has been.

This site is bloody awesome. You are all a credit to the spirit of what we are trying to do as an online community. I couldnt be happier (unless the machine was working properly for the first time) and plan on helping out as many people with troubles as i can.

[beefy]

Ben,

you can get off the shelf timing pulleys with un-bored hubs. Bearing supply shops are one type of place you can get them. You've got a lathe in your shop so all you have to do is bore the hubs out to suit your existing shafts, then drill and tap some grub screw holes in the hubs.

Of course you have to be quite certain the pulleys are centred in the lathe before boring. Use a dial test indicator, etc. Fit as many grub screws in the hubs as you can and use grub screws with a sharp round ridge that bites into the shaft.

Keith.

[exapprentice]

Ben

I am sure by now that you are going along the route of fixing rather than buying

hardest bit with making the change between chain and belts will be deciding the correct length of belt to suit your chosen pulley sizes
but if you google you can find calculators to help you get the correct length

or just do the maths, all you need to know is your pulley centers and diameters (effective diameters) of your pullys

good luck and crack on

[BensPlasmaAu]

Ben,

you can get off the shelf timing pulleys with un-bored hubs. Bearing supply shops are one type of place you can get them. You've got a lathe in your shop so all you have to do is bore the hubs out to suit your existing shafts, then drill and tap some grub screw holes in the hubs.

Of course you have to be quite certain the pulleys are centred in the lathe before boring. Use a dial test indicator, etc. Fit as many grub screws in the hubs as you can and use grub screws with a sharp round ridge that bites into the shaft.

Keith.

Yep, I'm off to Eastern Bearing Supplies tomorrow to find them. As with everything, its never as easy as just boring it out on the lathe. I had to steal the lathes 3 phase plug to get the compressor running. So also off to L&H electrical as well. I also want to broach a keyway in it seeing as I took the time and effort to get the keyway machined on the shaft when I did the roller chain shennanigans. And I don't have a broaching tool or machine. Hmm might have to work something out there, possibly file.......... its inly ally. Ahhh engineering butchery.

[beefy]

I didn't use any keyways in mine and it seems to be holding up OK. I just made sure I had aggressive biting grub screws and stuck as many of them as I could in the hub.

If you use a keyway then you need almost an interference fit because of the backwards and forwards motion. Doesn't matter with something like a motor which only powers in one direction but a tight fit is important for a keyway on plasma table shafts.

[exapprentice]

Hi Ben

If I were you I would ditch the keyway and go for the grub screw / s.

When I built my table (using belts) I rely on one grub screw (M5) to lock the pulley onto the shaft
The only thing I did was to drill into the shaft where the grub screw sat onto the shaft to the same as the outside diameter of the screw deep enough to locate the screw and did them up tight, very tight

[Rodw]

Ben, I'm assuming the au in your forum title means you are in Australia. If you happen to be in Brisbane, i have a set of metric broaches so might be able to help.

[RAD]

I'd be careful with un-bored timing pulley hubs, I had a bad experience with getting them bored concentric. Especially if its a narrow pulley with flanges! Get them to match your shaft size if you can or even with a slightly smaller bore and drilled out to match your shaft. You can file a flat spot on your shaft to increase surface contact and use the Correct type of locktite on your grub screws.

[beefy]

I'd be careful with un-bored timing pulley hubs, I had a bad experience with getting them bored concentric. Especially if its a narrow pulley with flanges! Get them to match your shaft size if you can or even with a slightly smaller bore and drilled out to match your shaft. You can file a flat spot on your shaft to increase surface contact and use the Correct type of locktite on your grub screws.

Rad,

Ben has his own lathe so he's not relying on a 3rd party. It's actually very simple to set something up concentric in a lathe, just stick a dial test indicator on the surface where the belt sits (i.e. don't use the flanges) and rotate. Adjust the pulley position in the chuck until the dial test indicator doesn't move, then the pulley is running concentric with the lathe spindle.

The part you have to be most careful of is "sneaking up" on the final cuts and making sure you don't overshoot. A quality set of digital calipers or whatever is a big help.

Keith.

[RAD]

^ thanks Keith. The guy that bored mine held the pulley in the chuck via the flanges because the hub was not deep enough to hold in the chuck, this made a mess of the pulley ie. bent flanges and eccentric hole and leaving me with a useless pulley. I ended up using planetary gear boxes tho!

[beefy]

Planetary gearboxes, now you are just making me jealous.

And let me guess, the guy that messed up your pulleys charged you for the privilege. He should have been paying you so you could buy replacement pulleys.

If he did charge you he'll be very safe in a knife attack, what with skin that thick.

Keith.

[BensPlasmaAu]

^ thanks Keith. The guy that bored mine held the pulley in the chuck via the flanges because the hub was not deep enough to hold in the chuck, this made a mess of the pulley ie. bent flanges and eccentric hole and leaving me with a useless pulley. I ended up using planetary gear boxes tho!

Tell me more also. Where did you get these planetary drives from? Got anypictures of your machine?

[RAD]

I bought them used from ebay, I paids around $60 USD for one, they are 10:1 gear ratio. I also bought, servo motors and drives but havent got them spining yet, I am using steppers motors for now, I am able to get about 325 ipm with the steppers tho, so in no hurry for the servos yet.
My machine is Not up and running yet, its a work in progress (going in a few years now!) due to lack of time and money, two of which I don't have much these days! and it dosen't make it easier living in Trinidad & Tobago, everything cost more to ship here! But I'll post some old pics I have off my phone and some details, maybe it could help someone or vice versa

The machine main structure is 2" x 2" hollow section, the longitudinal frame is welded and the transverse members are bolted. The cutting capacity would be 4' x 4'.

Linear motion are via Hiwin 20mm Linear guide rails on all 3 axis with 20mm wide helical rack and pinion (thrust bearings used wth all g/boxes) The guide rails and rack & pinion are mounted on 4" I-beams on both sides of the machine which can be adjusted independently to ensure both rails are in the same plane (leveled using a machinist level)

The gantry is 4" x 2" aluminum I-beam connected to 1/4" thick alu. end plates, the end connection was designed to allow the gantry to flex slightly in a kind of "wringing" motion if the two side rails dont lie perfectly in the same plane. (alot simpler than you might think, I'll post some pics of this later)

Like i said i'm using 10:1 planetary g/boxes with stepper motors for now. The coupling between the g/box and pinion gear is a rigid coupling but this would be changed to a flexible diaphragm coupling, the entire project was actually hinging on this component, I didn't want to risk damaging the g/boxes with the rigid coupling, I tried helical couplings but backlash was too nasty! Funny enough the diaphragm couplings would arrive tommorow after a looong wait from china

I'll post more current pics later

[RAD]

More pics

[BensPlasmaAu]

Nice one, that rack looks great. it may lead me to the upgrade of mine. I have only got standard Mod 2.0 gear rack.