Router Build Mk 1

[Neale]

I could I suppose easily convert to direct drive later if backlash becomes an issue.

There are plenty of us using belt drive without backlash issues. Properly set up amd with the proper belt/pulley combination, backlash isn't a problem with belts. I use two drive motors for the master and slave X axis ballscrews on my router with short belts but there are quite a few builders who have gone for one motor with a long belt which works fine. I think that you should make the direct/belt drive choice based on other factors. I went belt drive as it meant that my motors are tucked in inside the overall build envelope, I can change drive ratios if I need to, and I get a bit of isolation of motor stepping from the ballscrew. It's also easier to build and adjust mechanically. Direct drive means very careful alignment (even if you are using Oldham/Lovejoy/flexible couplings). Both are viable methods but be aware of all the trade-offs before deciding.

[Desertboy]

There are plenty of us using belt drive without backlash issues. Properly set up amd with the proper belt/pulley combination, backlash isn't a problem with belts. I use two drive motors for the master and slave X axis ballscrews on my router with short belts but there are quite a few builders who have gone for one motor with a long belt which works fine. I think that you should make the direct/belt drive choice based on other factors. I went belt drive as it meant that my motors are tucked in inside the overall build envelope, I can change drive ratios if I need to, and I get a bit of isolation of motor stepping from the ballscrew. It's also easier to build and adjust mechanically. Direct drive means very careful alignment (even if you are using Oldham/Lovejoy/flexible couplings). Both are viable methods but be aware of all the trade-offs before deciding.

I've scrapped quite a few commercial printers over the last 5 years and I keep seeing the same thing, the main drives are direct drive by either ballscrews or often leadscrews. The ink is always delivered by nema 23 using belt drive with tensioners gearing to ~4 to 1. With a properly setup up belt tensioner I can see backlash is so slight as to be negligible. Thing is though making any system backlash free is a major hassle and even ballscrews exhibit backlash over time as the bearings wear unless using a 2 nut style system. The reality is though most people won't even notice minor backlash and if you can notice it then you have more than minor backlash lol.

What put me off was the belt tensioner, it's easier for me to direct drive then belt drive.

[hoppo]

There are plenty of us using belt drive without backlash issues. Properly set up amd with the proper belt/pulley combination, backlash isn't a problem with belts. I use two drive motors for the master and slave X axis ballscrews on my router with short belts but there are quite a few builders who have gone for one motor with a long belt which works fine. I think that you should make the direct/belt drive choice based on other factors. I went belt drive as it meant that my motors are tucked in inside the overall build envelope, I can change drive ratios if I need to, and I get a bit of isolation of motor stepping from the ballscrew. It's also easier to build and adjust mechanically. Direct drive means very careful alignment (even if you are using Oldham/Lovejoy/flexible couplings). Both are viable methods but be aware of all the trade-offs before deciding.

Thanks Neale, that's reassuring. My main reason for going belt drive was to increase speed with the 1605 ballscrews. I've ordered HTD5 pulleys with 9mm width and belts. I figure I'll just cut slots in the vertical mounts to be able to adjust by sliding the motor to increase belt tension rather than using a separate belt tensioner.

Cheers

[hoppo]

It's been a while since my last post, but things have moved on considerably. Here is the next installment of my build I hope you enjoy.


Fashioning a bracket to hold the stepper motor at 90 degrees to the ballscrew. This is where I drilled the holes. The aluminium was precut from the supplier.


After a bit of countersinking and filing I managed to get it to look like this.


For some reason, after assembling it became apparent that it wasn't necessary, but after a lot more countersinking and some dodgy radial loads being applied with my pilllar drill, brute strength and plenty of ignorance I achieved my aim of countersinking the slots to sink the stepper motor holding bolts into. It's not the best looking piece of metal work, but I guess that's why I'm building the thing anyway! It should do the job.


After marking through the holes on the stepper bracket mount with a transfer punch, I drilled them with a tap drill (4.2mm) for an M5 tap. This was the first of many taps. My advice to anyone attempting their own build is to buy a decent tap wrench and set of taps. I started off with the one seen here which came as a set with a set of taps and dies. It was bloody hard work, the handle kept falling off and eventually later on a cheap tap snapped off and remains in a hole on my build. I paid out for a snap on M5 and M6 tap and tap wrench. Probably cost the best part of £30 but one of the best purchases in hindsight and made the build a hell of a lot easier. As you'll see later there are plenty more holes to be tapped yet.


Attaching the spindle brackets to the front plate of the z axis. Again in hindsight this isn't the best design as the bolts holding them on are inaccessible from behind once the rails are attached. Eventually I'll get round to turning the bolts around and using captive nuts on the back side. I would have liked to have drilled the holes and tapped them but cannot get the accuracy right without the use of a CNC machine. Chicken and Egg comes to mind.


The front of the spindle brackets attached. Just because I can.


Linear bearings attached to the rear plate of the z axis.


The linear rails attached to the front plate of the z axis.


And the ballscrew also attached to the front plate of the z axis.


Rear plate and front plate of z axis married together and working well.


As above but from a different angle.


Attaching the stepper motor holding bracket to the top of the front plate.


Final assembly of all components of the z axis. All in all fairly straightforward. As mentioned above the hardest parts were 'milling' (repetitive drilling and filing) out the slots for the stepper motor and tapping the threads with the worlds cheapest tap wrench and taps.

Plenty more to come. I hope you find it useful and or interesting.

[Clive S]

How much Z travel have you aloud for? Its unusual to fit the motor on the spindle plate

[Desertboy]

How much Z travel have you aloud for? Its unusual to fit the motor on the spindle plate

I had to take a 2nd look at his cad model at the beginning of the thread to see what was going on, the nema is a dual shaft nema sticking through the end of the plate and then belt driven.

I'm sure you saw this straight away but it confused me lol.



Looks like the travel is quite small.

[hoppo]

How much Z travel have you aloud for? Its unusual to fit the motor on the spindle plate

Hi Clive, total travel on the z axis is just over 3 inches. Or 8 cm. this was the most I could realistically squeeze out of it due to the length of the z axis rails, also I wanted to keep the bearing blocks as far apart as possible to maintain rigidity of the z axis in both the x and y planes. I mentioned in an earlier post that one of the regrets I had was buying the rails and ballscrews and designing my build around those, rather than designing my build and ordering bespoke lengths to suit. Hindsight hey? Still 8cm is more than adequate for my needs at the moment.
I have loads of spare travel on the z axis ballscrew so I figure I could expand the z axis travel if needs be by adding longer rails which would hopefully not be too much of an expensive upgrade.
I can't remember the exact reason I chose to fit the stepper motor on the moving face of the z axis. I have been working on this design and build for best part of 5 years I reckon now. I'm sure there was a valid reason but can't for the life of me remember why. I put it down to age. I'm off to rack my brain and figure out what I was thinking at the time and what my reasoning was!