Small cnc lathe, 3D printed pulley to check belt adjustment
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- Опубликовано: 8 сен 2024
- The problem I have is that the maximum speed at which I can tap is 600rpm, my Z axis cannot move fast enough to let me use a higher rpm. I am worried that at this speed in high range the lathe will not have enough torque to do the job. A 24T pulley would give 2000rpm which might help the torque at 600rpm.
A little history of these lathes
Manufactured by Hercus in South Australia, these lathes were sold to many educational facilities and to countries all over the world. They were sold in the USA under the name of Rockford Pro 2000. An industrial version of the PC200 is the Novim, which comes with an industrial enclosure for coolant capture.
The lathes began as a “Computurn” model which used electronics by a company called ANCA. These lathes were stand alone cnc lathes, a small version of what might be found in industry.
These were replaced by lathes which had a Hercus control system and used an interface card in a desktop PC to connect with, and control the lathe.
These lathes used the same castings but their appearance was much changed as they no longer contained all the controls for the lathe. These were now all in the PC, apart from a small Pendant which offered some controls when in Manual mode.
Early PC200 models used a CAD/CAM software that ran in DOS on a PC that had an ISA slot (long discontinued on new PCs) and had analogue electronics. The 8 tool turret option on these lathe was operated by a small motor and gearbox and used shot pins to lock the tool in position.
As PC operating systems were upgraded, Hercus released Windows CAD/CAM software. These machines still ran analogue electronics. The last version of the machine used digital electronics and used 32 bit Windows based CAD/CAM. Both these machines used a turret with a motor and worm and worm wheel drive. Options for all these lathes included a Leader air chuck with no through hole, an air operated collet chuck, a 8 position tool turret, a tailstock, a QC tool post and a coolant pump. 
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If these are standard HTD belts, you could try a smaller belt with a smaller pulley to increase the torque. PT parts in Northcote have reasonably priced belts, you'd have to order online for pick up though. They charge a fair bit more if you go buy it there, no clue why.
As you saw at the end, I have a 20T that I run with a 270 belt to get 1666, I was just hoping to get a little more. I have 400 parts to make and the faster it goes the less time I am waiting for the job to finish. I really hope that at 600rpm I will get the part tapped while in high range at 3000rpm. This exercise was more a look at the possibility. Thanks for your comment and the tip about PT parts
Can't you make a bracket that goes from the left side of the aluminum housing that ends with a wide ball bearing that can be used as an idler wheel, so you can tighten the ball bearing more or less against the belt?
I could do that but if a 25 works and gives 2080 rpm, I would go with that and save my self the work of making a bracket and buying a bearing. Thanks for your comment. Nigel
I actually use a pulley I printed in petg as the drive pulley on my taig turn
Provided the keyway does not rip out that should last well. Have you been using it for a while?
@@smallcnclathes around 2 years. The standard pulley mounts with just a set screw so I added a steel collar and bolted the pulley to the collar.
@smallcnclathes I don't run production on it though. It's luck to get used twice a week
@hi1172 that sounds nicely done, thank you for your comment
You need to find a guy to cast you a pulley! Know anyone?
Mark
Mark, Sadly the bloke he knows who could cast a pulley is now pretty much beyond being able to do so 😪...... Martin
Hi Mark, at 35aud to buy ready for a conelock insert that I already have, I would not bother Martin anyway. Thanks for your comment
Could you run a idler pulley to give you the range you need?
Probably possible, not sure at this stage if I can be bothered. The lathe may do what I want in high range, just have get round to setting that job up. Thanks for the suggestion.