PDA

View Full Version : Making a drive belt for a Hermes MV engraver



nc5a
02-26-2019, 11:12 PM
I'm not real familiar with engravers but I figured $20 wasn't too bad a deal even though it was missing the drive belt. No problem I said, I'll just make one from o-ring material and I did. It lasted for about 3 seconds then broke. So I made another one, being very careful to clean the Buna N o-ring material, cut the ends square, use new super glue and glue the ends square. It lasted about 3 seconds, breaking at about 2000 rpm as the motor was ramping up to 10,000 rpm.

So I looked at the New Hermes web pages and discovered the o-ring drive belts are made from silicone. So I ordered silicone o-ring material and made a new one. 14" of 1/8" diameter silicone o-ring stock, 100% silicone adhesive sealant, 1/8" clear heat shrink tubing. Cut the ends square, place a small dab of silicone on one end and slide the ends into the heat shrink which keep them in line. let set 24 hours or so before cutting the heat shrink off.

https://i.imgur.com/BMLuoLY.jpg
https://i.imgur.com/Q7eTh4p.jpg
https://i.imgur.com/GUpcBQ8.jpg
https://i.imgur.com/VICC46S.jpg

nc5a
02-26-2019, 11:17 PM
Here's the engraver the belts goes to. If any of you guys know about engravers I like to hear what you have to say.

Ron

https://i.imgur.com/fcMtam8.jpg
https://i.imgur.com/z2PJJLA.jpg
https://i.imgur.com/BZVeoJH.jpg
https://i.imgur.com/l2FcMDb.jpg

mattthemuppet
02-26-2019, 11:18 PM
neat, never heard of that. I like the heatshrink trick for keeping them aligned. Cutting each end at 45deg might give you a slightly stronger joint, though trickier to get the angles just right.

TGTool
02-26-2019, 11:19 PM
Well, I'm anxious to hear how this one does.

And let me be the first smartass to say I think it will vibrate a bit with that heat shrink splice.

skunkworks
02-26-2019, 11:43 PM
I don't think you meant smartass... ;)

He says he is removing the tubing...

J Tiers
02-27-2019, 12:10 AM
I'll be watching this one..... I have had about zero success using silicone sealant as a tension adhesive.

Maybe it will work for you.

nc5a
02-27-2019, 12:23 AM
neat, never heard of that. I like the heatshrink trick for keeping them aligned. Cutting each end at 45deg might give you a slightly stronger joint, though trickier to get the angles just right.

I actually considered doing just that. But with two failures under my belt I didn't want to get too involved, especially since silicone o-ring material is OEM.

DR
02-27-2019, 01:35 AM
Hmmm......I believe that engraver is the same one I had. Sold it recently because the little engraving I need can now be done on the CNC.

As to the belt the only belts of this type I'm familiar with were made of urethane with a heat weld. A local belt maker had a hot wire cutter and quickly pushed the cut ends together while the belting was still liquidy soft. The weld cools quickly, any lumps can be ground off and the belt used immediately..

BTW, it appears the "tires" for my Delta bandsaw were made this way since the weld appears obvious. The tire welds hold very well with all the stretching you need to do to get it on the bandsaw wheel.

lakeside53
02-27-2019, 01:42 AM
I also didn't think you could glue cured silicone with silicone adhesive.

We have 1000's of miniature round belts on our conveyor. They are typically urethane and for repair replacements we joint then with a hot disc on a soldering iron - they last years, and the conveyor runs 15 hours a day.

Noitoen
02-27-2019, 01:44 AM
You could also make from leather cord with a staple just like the old sewing machines.

I don't think 24 hours is enough for the silicone to cure under the sleeve in that sealed condition

darryl
02-27-2019, 01:58 AM
I have to ask- is that o-ring material meant to be joined? If so it must be a special formulation that can bond with uncured silicone. I've never heard of such a thing, but that doesn't mean it doesn't exist.

J Tiers
02-27-2019, 02:29 AM
....
As to the belt the only belts of this type I'm familiar with were made of urethane with a heat weld. A local belt maker had a hot wire cutter and quickly pushed the cut ends together while the belting was still liquidy soft. The weld cools quickly, any lumps can be ground off and the belt used immediately..
....


.....
We have 1000's of miniature round belts on our conveyor. They are typically urethane and for repair replacements we joint then with a hot disc on a soldering iron - they last years, and the conveyor runs 15 hours a day.

I have had several heat-welded urethane belts working for years, on a jeweler's lathe and a little drill press.

Silicone is such a slippery surface, and the sealant is not a good glue..... Plus silicone does not heat-weld that I know of. I'd be betting the OEM silicone belts are molded in one piece, or maybe joined mechanically,

But the proof is in the results.

I agree on the time taken. The sealant is almost surely some form of RTV material, which needs moisture in the air to cure, unless it has been mixed, after being squeezed out of the tube, with a catalyst (I think some metallic compounds are catalysts for it). Obviously it cannot have any catalyst in it when it is in the tube, or it would cure in there.

With the tube around it, there may not be much access to moist air, and it may cure very slowly. The gasket type silicone may cure more rapidly, as it is designed to cure in a similar sort of situation with limited air access, but I do not know if it is any good as an adhesive.

Jim Williams
02-27-2019, 11:37 AM
I hope the silicone stays together. I had to replace the drive belt on a New Hermes cutter grinder and found that the old one was urethane. I got some round urethane stock and joined it withheat as described in one of the other posts. My two New Hermes pantographs use flat belts. They are both larger machines than yours. I have a number of extra 1/8 inch diameter cutters that probably fit your machine and can sharpen them to requirements as to angle and point width.

A.K. Boomer
02-27-2019, 11:44 AM
Not trying to be a downer but I cannot see this working - iv joined O-rings with super glue that were made of neoprene or butyl rubber with some success but never silicone,

Now their might be some kinda special glue that's formulated to join silicone together but im pretty sure it's not silicone tub and tile caulk...

nc5a
02-27-2019, 11:57 AM
Just to be clear, I've never done this before so it might fail just like my first two attempts with buna-n. After all I've come to realize there are some pretty sharp individuals on this site. So gentlemen I'll give it my best shot and if need be I'll try something else.

old mart
02-27-2019, 02:00 PM
Super glue works with some rubber types, back in the 70's when SG first came on the market, I used to make drive belts for the firms watch makers lathe out of 1/4 od thick walled rubber tube used in pitot static test sets which we overhauled.

ftownroe
02-27-2019, 04:32 PM
My dad was a watchmaker and for many years we repaired the belts on his lathes by using the technique previously mentioned; heating a thin blade from a palet knife in the flame of an alcohol lamp and then bringing together the two ends of the belt against the hot blade until they both got hot and pulling out the blade to fuse the two ends together. This was a two man operation. The joint was then cleaned up with a razor blade. Worked very well.

nc5a
02-27-2019, 06:02 PM
Making a drive belt for a Hermes MV engraver, Update.

It has been 17 hours since I built the silicone o-ring drive belt. At the 12 hour mark I slit the shrink tube the full length with a razor blade to help with the curing process. Now at 17 hours I removed the heat shrink tubing, which slid off like it had been greased and to my surprise there is zero cleanup required. Gently flexing the splice joint shows no sign of coming apart and tugging lightly on it feels like it is quite secure. I'm going to give it 24 hours cure time before putting it to work. I'll let you guys know how it goes.

Ron

nc5a
02-27-2019, 07:45 PM
Well after much flexing and tugging on the drive belt and finding it very secure I decided to test it in the engraver even though it's been only 18 hours since I made it. I think most of those that replied believed it wouldn't work but I'm here to tell you that it absolutely works. The way the two ends were attached with the 100% silicone I used works beautifully as you will see in the photos. However, I did make one mistake. I made the belt too big. I used my best judgement based on the mechanics of the engraver to size the belt. I only have still photos of it but you can clearly see the belt whipping in the wind with the motor at 10,000 rpm.

I couldn't find much in the way of details for this MV engraver on the web so I have no idea how to size the belt, any ideas guys? The one on it now is 14" long, roughly 4.5" diameter. The motor is spring loaded to keep tension on the belt when off. But when it starts ramping up the torque is enough to stretch the belt probably 1 1/2 times it's relaxed length by the time it hits 10K rpm.

The belt when the shrink tube was removed.
https://i.imgur.com/V6QQ39a.jpg

Relaxed belt
https://i.imgur.com/Y7gKya4.jpg

Motor at 10,000 rpm and belt whipping.
https://i.imgur.com/MYSCD5f.jpg
https://i.imgur.com/AYfs82b.jpg

J Tiers
02-27-2019, 08:00 PM
Well, I am surprised.

I have never had that work.

Good for you.

If it is stretching, it may just be too soft a grade of silicone. See if you can get a higher durometer material.

Jim Williams
02-28-2019, 02:47 AM
You have a lot left in the motor tension spring. Make one a lot shorter.

nc5a
03-01-2019, 03:12 AM
neat, never heard of that. I like the heatshrink trick for keeping them aligned. Cutting each end at 45deg might give you a slightly stronger joint, though trickier to get the angles just right.

Since I needed to make a smaller o-ring belt I decided to try it your way for kicks. It wasn'r all that difficult to get the two ends lined up and once again there was no cleanup because of the snug fit of the shrink tube. This time I let the 11" belt cure for 7 hours before putting it under load. And to my surprise the belt whipped all over the place, worse than it did before. So it's back to the drawing board.

https://i.imgur.com/u4IvtTW.jpg
https://i.imgur.com/hNOkp5E.jpg
https://i.imgur.com/3OPfl95.jpg
https://i.imgur.com/V4t1k9F.jpg

Noitoen
03-01-2019, 03:47 AM
silicone might be too soft and stretchy. Amazon has polyurethane cord not so expensive.
https://www.amazon.com/High-Performance-Urethane-Belting-Transmission-Polyurethane/dp/B07L3Y8ZMY/ref=sr_1_4_sspa?crid=2RTRUS8GXYW4K&keywords=polyurethane+round+belt&qid=1551429869&s=gateway&sprefix=poliurethane+round+belt%2Caps%2C281&sr=8-4-spons&psc=1

Mcgyver
03-01-2019, 08:06 AM
The pulley on your motor is OEM and is for flat belt. I don't know of it matters, is it moving around on the motor end?

The last joint looks excellent, You need a joint that good on high speed stuff to avoid vibration. What's with the loose belt in the last photo? Surely that was not how it was run - did it stretch? The motor should be auto-tensioning on spring so the belt is never loose....stretch ...or is it just off the spindle pulley? For it to "whip all over the place", its either not the right material, its not tensioned properly, the mismatched pulleys are causing it or possibly some irregularity in the belt

Experimentation is good, but if it was me, I'd make a matching pulley for the spindle and make up a 1/2" flat urethane belt and be done You can also have the factory make the belts, which I've done before as you do want a perfect joint for smooth running

RichR
03-01-2019, 09:21 AM
... Surely that was not how it was run - did it stretch? The motor should be auto-tensioning on spring so the belt is never loose....stretch ...or is it just off the spindle pulley? ...

I think that picture was taken with the motor running using the flash to show the belt in action.

Greg_B
03-01-2019, 09:47 AM
We have one at work that has flat spindle pulleys also. We have been running the same flat belt for years. Have you checked to see if the flat belts are still available?

Mcgyver
03-01-2019, 12:30 PM
I think that picture was taken with the motor running using the flash to show the belt in action.

lol, think you're right - that makes a lot more sense! I'd say not enough tension or too elastic a belt

nc5a
03-01-2019, 12:37 PM
Well guys I've invested about 5 hours in cleaning the engraver and building belts and have 4 failures for 4 attempts. I'm not sure why the last belt didn't work but it appears to be too soft a material as some of you already mentioned. However, the limited information I found researching belt material clearly indicated 1/8" silicone o-ring material with 70 duro hardness which is what I ordered. So as I'm writing this it occurred to me that I could use a larger cross section belt, 3/16" or even 1/4" and that would probably stop the belt whip at 10,000 rpm. But as some have mentioned in their replies the engravers they have used or seen used have flat belts. So now I'm hoping a trip to the sewing machine repair shop in town will score me a flat belt that works.

And yes, the belt whipping in the photos is a still action of the 0-ring belt with the motor at 10,000 rpm. If I was to let it run the whip would get worse until it threw the belt off.

This little project, though not machining related has taught me a few things.

Ron