Reduction Drive by belt - a collection of various designs and how to build your own.

[Gerald D]

MultiGear.JPG

The yellow are the horizontal links of the parallelogram - they can swing up and down:

paral1.gif

The alu plate is slotted at the red marks - very similar to the stabilising slots in the MM motor plates. Their system is just way more complicated, with no obvious benefit over what we are doing.

[D. van Randen]

Hey thanks for that!

I had been scratching my head trying to figure out the two adjusters. At first I thought the slots you drew were at some kind of slight angle that allowed the adjusters to draw the gear up to an exact position , but that didn't explain the spring. Now it makes more sense.

I can only think of two benefits.
1) ergonomics, it makes for a very flat side as the motor is tucked in the cross beam for the Y axis.

2)Possibly the motor cannot drive the gear off the rack , it is constrained by the slots and linkage from moving too low to grind the teeth and stalls instead. But the slots are still big enough to allow the spring to pull the assembly upwards and keep the backlash very low.

Bottom line is that belt drives are a valid method for driving your CNC machine

I love my Alpha Step SB machine but I am not convinced that it was the best way to go. I now think gear reduction through belts with no feedback on the similar size motors would give better cut results for less cost.

D

[Alan_c]

Busy making prototypes for a customer on a tight deadline who's normal supplier of this item has dropped them. Not the most technically challenging job but interesting none the less - apparently these are destined for Cape Town newest swishest Hotel in the Waterfront (refer to recent star studded opening of another hotel from the same group in Dubai)

Attachment 3656

cut from soild Oak, using straight 11.25mm router cutter, 3 passes rough (2mm oversize) 1 pass finish on size. Radiused edges done on the table router.

Attachment 3657

I am having a vision... I see gearboxes in my future...

[MariusL]

Sorry for the delay but the MM webserver or ISP blocked my IP from connecting to the forum.
Well here goes, we completed the machine last week and have done some cutting. I now find the biggest problem is to obtain the tools we need to do the cutting jobs that we have. I have a 8mm and a 12mm collet with the bosch router but found out that those are not the popular sizes for tools. I also need longer tools to cut the 3d plugs from foam. I guess this will be an ongoing battle.
The dust collection system works very well, almost to well. It leaves nothing behind.
I opted for a 4:1 reduction on all motors. See pics.
Thanks Gerald your effort made it possible for us to have a good working machine in under two months.
Also thanks to Greg from CncDirect for all his help.

[Gerald D]

Marius, that's a beauty!

Even your dust hose is a matching colour!

Those belt drives are very interesting, it looks like you got standard flanged bearing unit somewhere . . . . . . (some car engine water pumps are similar . . . old merc. . . )

[MariusL]

Allan,
I attached the drawings. Take note that the Z axis has a problem. I had to lift the motor plate by 40mm on order for the plate not to snag on the spider plate bolts. I took one of the large spacers and welded a 40x10 flat bar with a hole onto it and therby lifting the motor plate. I also had to extend the rack in order to achieve the correct travel that I wanted.

[javeria]

Good Job Marius - especially the belt drives.

where's the video?

[MariusL]

I meant to include these two pic to clarify the reduction assymbly. What is not shown on the drawings is that you must counter sink the bearing flange mounting holes and mount with m6 x 12 CSK cap screws from the front.
Take note of the hand of the motor plates. They only mount one way after you counter sink them. The Z axis plate only fits one way as well.

[Jayson]

I haven't posted in a while so I thought I had better give an update.
I have not made anything spectacular just cut out a few MDF letters for a friends kids. Something for them to paint and put on the wall no pictures but you get the idea.

Now on to something I do have pictures for

I have started working on the belt reductions. They are based on the ones that J.R. made, thanks for sharing... I ordered the pulleys and belts from a local supplier who got them in promptly for me. Unfortunately they did not get exactly what I wanted and instead of a 3:1 reduction I ended up with what would have been 2.9333333333333333333333333333333:1. This was not going to be acceptable as far as I was concerned, so they returned the 44 tooth pulleys and got me some 48 tooth. This results in a ratio of 3.2:1. There was not as much room with the original belt as I had hoped but at least it should still work.

Attachment 3962

Due to the belt and pulleys not being exactly the same as J.R. used I had to change the design slightly.

Attachment 3963 Attachment 3964

The plates machined well and I managed to press the bearings in without much hastle. (made on my CNC mill)

Attachment 3965 Attachment 3966

My motors have 14mm shafts, but the only bearings I could get quickly and cheaply have 1/2 inch bores. This meant that I needed to make shafts with a small step in them, not a big deal to do just a little more time.

Attachment 3969

I also make a few spacers for the bolts between the plates

Attachment 3970

I was a little concerned as to how I was going to bore the small pulleys but I came up with a plan. I bored a piece of aluminium the same size as part of the pulley and then used loctite to "glue" the pulley into this while it was still in the lathe. I then drilled and bored the pulley. This kept it as close to centered as I could get it. I was very happy with the way this worked, and none on them slipped.

Attachment 3967 Attachment 3968

That’s about it for now. Hopefully I will get the pulleys drilled and tapped over the next few days so I can test them out.
There will be no working on the machine on Saturday though as I am off to an Air show with a friend but I am sure to be eager to get it finished once I get back.

http://www.airshow.net.au/avalon2009/index.html

[Jayson]

Sorry all for not posting on the weekend, I was just too excited about getting the gearboxes finished. They went together perfectly and have made a difference of course. My maximum speed has been reduced from 27 meters per minute down to 15 meters per minute. I am still happy with 15m/min rapids, the table is not all that big so it gets from one end to the other quickly. The added safety of the slower speeds is also a bonus
Some pictures...

Attachment 4019 Attachment 4020
One X axis gearbox and the y installed

I got a delivery of some 6mm acrylic sheet during the week that I had hoped to make an edge lit sign with. The sign is 230mm high by 530 long and is to go over a friends BBQ area. I was not sure how it would go so I was conservative with my machining feeds and speeds. The finished depth was 4.5mm and this was done in 4 passes at 1900mm/min using a 12mm 45 degree V cutter. It took around 45 minutes to machine. If I was to do it again it would probably be in 2 passes at the same speed.

Attachment 4021

The picture does not do the finished product any justice, it does look fairly good even if it’s me that says so

Attachment 4022

Here is a close-up of one of the letters just so you can see how badly the machine does curves...

I still need to mount some LEDs and a way to hang the sign but so far so good.

That’s it for now, off to dream up another small project before I start the next big one.

[jeffa]

Jayson,

I assume you're being sarcastic about "how badly the machine does curves". This looks really good. Congratulations!

Jeff

[Jayson]

Hi Jeff,

Yep I was being sarcastic. I feel very happy with the cut quality.

Regards,

Jayson.

P.S.
Attachment 4051
Sign Finished.

[Rad Racer]

Here's a couple of pictures of the complete reduction units...all axis's now have a 3:1 reduction drive installed.

There is a noticable difference in the smoothiness of operation and cut. Definently a worthwhile upgrade.

[mikefoged]

I decide to try and gear my Mechmate, the arc cutting quality began to be a little irritating. So I went out and bought some parts and the last ones came today.

Looking forward to get it all mounted, hopeful this will work out better for me.

The gearing is 3.2 : 1

[domino11]

Mike,
Did you machine the plates for your reduction on the MM? Give us some details on your reduction build!

[mikefoged]

I had the plates machine in a machine shop just 2 min drive from my home, the also made the shaft and machine the drive wheels. I made the drawings after J.R.'s model with a small modification. Thanks J.R. for sharing with us.
I just finish mounting the gears and I must say that it is running much better with the reduction on, tomorrow I will test cut to see if my ARC is smoother.

My feed rate is now 12000 mm/min and I'm very happy with that.

[DeadGuy]

A few more gearbox pictures.

Dennis

[MattyZee]

I am planning on having a belt reduction drive. (3.2:1). The geared motors are too expensive for me an i think i remember reading the performance of the belt drive should be superior than the gearbox motors (esp. w.r.t backlash).

Here are some CAD pics

Attachment 4789
Attachment 4790
Attachment 4791

[domino11]

Matt,
Those pics look good. Are you planning on cutting them on the MM once it is done with the direct drive llke JR did?

[MattyZee]

I am in the process of seeing what they will cost to be made. I would try and cut them with direct drive but my motor brackets have a bore slightly smaller than my motors so they don't fit directly to the plates. So the Aluminium plates has been sized to fit my undersize motor plates and accept my motors. I will post pics when/if/how they are made.

[stan stuart]

Hi Matt
Under motor selection it does say the belt drive is better as far as backlash is concerned. If the price is ok woud you be interested in getting 2 sets made at the same time.

[Robert M]

Hi Matt,
3.2 :1, interesting combo !!
I too am planning to make my trany,

Attachment 4792

Attachment 4793

not only to save a few $$$....but mostly and the obviously, doing it for this sefl fuzzy fun feeling of making your own...

I managed in the past to find source & material (drive, driven gear & belt) to get 3.0:1 reduction, but could not find source & material to configure 3.2:1 ?
Could I ask you to tell us more about your source & part# for your gears & belt set up so we all could look it up ?
Thanks in advance, Robert

[MattyZee]

Hey Robert,

Nice CAD model. What pitch belt are you using there?

Funny we a re talking about this today because my pulleys and belts arrived today.
Attachment 4794

I have gone with the T5 (5mm pitch) size. To get the 3.2:1 i have chosen a 15T &48T combo. Used with a 56T (280mm) belt gives a centre distance of ~55mm. This only gives 5 teeth engaged at any one time which is 1 less than the recommended 6 so i went with the wider 16mm to compensate. It allows for quite a compact design.

I sourced them from a local supplier. www.piesau.com.au i'm sur they can be sourced easily anywhere.

[Robert M]

Matt,
My drawings and part for this drawings are strictly for a temporary conception purpose. I used for this set up a “XT pitch” with a 3/8” wide belt.
I understand it may be “frail” for our MM set up !!
Haven’t gone spending the required in verifying & calculating this YET
This tempo set up has an easy 6teeth engaged, so I stop at that and figured when time comes I’ll take the required time to select the proper set-up...TBC !

Out of curiosity, would you know who makes (what brand) are those pulleys ?

[Castone]

This post was originally put in a thread of it's own, but it became clear that it was another belt drive....

I made this drawing after looking at JR's drawings. It is made using two flange bearings, the oringinal motor mount design other than changing the holes size for the bearings and one laser cut mount. The flange bearings are recessed into each of the plates. This would be a low cost build for gear reduction.Once I get one put together and it will work properly, everyone is welcome to a copy of the drawings , as long as Gerald does not have a problem with me doing that.

[Gerald D]

Leo, the only big area of concern is the backlash between the gears. Maybe some springloading can be arranged?

Keeping them clean doesn't seem to be a big issue - the belt guys don't seem to loose sleep over dirt that might get into their drive. We don't have hassles with our z-axis rack/pinion either.

You are welcome to post drawings.

(As you have drawn it at this stage, your flanged bearing will foul the gantry)

[bradm]

Gerald, if I'm not mistaken, that looks like a belt drive, drawn with "belt removed for clarity".

Leo, I think placing the flanged bearing on the other side of plate that attaches to the gantry will solve the fouling, if you have enough room in there.

[Gerald D]

Leo picked the title "gear reduction" in a new thread separate to the belt reduction thread, so I assumed the novelty was in having gears instead of belts. But I wasn't quite sure so I changed the title to "gearbox" and kickstarted a gear discussion - it is worthwhile discussion, even if Leo meant something else (that has already been exhaustively covered)

Don't know if those flanged bearings exist in true life - they look a lot slimmer than the stuff I can get around here.

[javeria]

if gears are the point of discussion - my friend with the chinese machine has them all over the 3 point of motion.

its a simple spur gear arrangement - with a metal gear on the stepper and a nylon gear on the shaft providing the drive to the pinion.

I told him that if this does not last long enough we always have the beltdrives to replace em!

RGDS
IRfan

[Castone]

It is a belt drive design. I know it has been talked about in great detail. All I am trying to do is make it a little cheaper and easier . The bearing is from Mcmaster Carr Part # 5913K71. $11.33 each. Turning the bearing over did fix the clearance problem. I will post some pics when I get one together.Thanks , Guys