Here is the belt tension I use.

I was taught a long time ago by an engineering prof. that, this is a good method for tensioning tooth belts.

The optimum tension is the thickness of the tooth belt (when pressed) not including the tooth.

This is how I tension my belt. I have not had any problems with missed steps or belt slippage.



You should always avoid over tension, as it puts a lot of stress on bearings and shafts causing excessive wear and binding.
If you have any backlash problem, make use of the X-Axis backlash settings in the USB-CNC software to help correct the problem.
Make sure the rollers roll smoothly. If you feel any binding, check for foam dust that may have become compressed and stuck to the tooth belt or pulley. I have had this problem.
It's an easy fix. Just clean the machine.

Hope this helps.
Cheers.
George

 

I had ordered the above pulley from spd-si. I normally don't buy from places that don't take paypal. I made the mistake and bought from them, giving them my credit card. They charged me $8.68 for the pulley but they also charged me $13.44 for shipping and handling for a total of $22.12. Unfortunately buy the time I got the email the part was already shipped and I couldn't cancel my order. I'm so upset! I would have never bought that pulley for $22.12. What a bunch of ripoff artist.

 

I hear ya....$8.68 for the pulley, $9.38 for shipping and $3.00 for handling! It really is
bullsh!t and a sure fire way to lose customers. Voice your feelings to the company and tell them you will seek other suppliers in the future.

A few years back, Ebay did a study and found that people quit buying off EBay because of the high shipping and handling charges sellers had. They went on a campain to get sellers to stop that nonsense. If you notice now shipping charges are more reasonable.
Then again, if you haven't shipped anything lately, you may be surprised at how expensive it has gotten.

 

I did call them this morning, dhc8guru, and the guy said to me something like 'I can't do nothing for you but you can send an email'.

BTW, I also bought that day some AAA batteries from a place in Texas. 36 batteries and the shipping is $5. Each battery is way bigger than the pulley so I know how much shipping is now.

 

Yep, shipping is still reasonable with USPS standard shipping. That pulley probably would have been a $1.50 to ship. I usually get Priority mail and it has become outragous and no doubt would have been $12.
The guy on the phone with you probably hears it all the time and can't do anything about it. They probably don't have much competition, so they charge what they can get away with.

We did an online airport parking reservation with Budget. It was like $6 a day for 6 days, ($36). After I entered the card and confirmed the reservation, the real bill showed up, tacking on a $25 airport fee and another $35 for "online" reservation handling. I was like WTF! $97!. None of this was devuldged before hand and was a blatent scam. Coming from a big company like Budget rent a car, I was very surprised. After the trip, going to actually pay for the parking (they don't charge until you check out)
The guy made a mistake calculating how long we stayed, the real bill came out to $50. I thought about being honest and pointing out the mistake, but I figured if Budget was dishonest with me, I will do the same to them. Not something I like doing.And I hate being in that position.

 

I am having X axis skipped steps. My first cuts were OK and then the problem started when I was drawing on foam board with a sharpie attachment. It was very easy to see the missed steps on the drawing.
I discovered that the belt had become a bit loose so I tightened it up. I also saw that the idler rollers were not turning easily so I loosened them.
I then started the machine up and drew a perfect picture using the sharpie tool. Next I put in another sheet of foam board and half way through I noticed that I was loosing steps in the X direction. When I checked the bully tension is was less and then I discovered a weak spot on the timing belt where the belt was stretching between two teeth.
I took the belt off and see that it is a little frayed on the tooth side where I observed the stretch.
I hope that I over tightened the belt causing the stretch, and that it was a bad belt...
I need a new X axis drive belt quick. Where can I get one?

also, on the MkIII how the heck can you tighten up those little nuts on the stepper motor? No wrench fits in those tight corners.

thanks,
wilson

 

hey gang found a new belt too try.its a trun motion by gates at spi.