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Messages - Justin-B

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1
General Mach Discussion / Re: Advice Needed- retrofitting lathe to CNC
« on: January 19, 2017, 06:09:08 AM »
Hi Rich,

Awesome, I will put some things together and post soon. Many thanks

Justin

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General Mach Discussion / Re: Advice Needed- retrofitting lathe to CNC
« on: January 17, 2017, 10:39:38 AM »
Thanks Rich,

Great suggestions. In terms of cost, I think I have quite a cushion, as I could not find much in the benchtop size for cnc, gangtool, with automated collet closer. The retrofit Hardinge machines seemed to be in the 15 K range and up. Perhaps i am missing something? The machine I have cost me $500.

Target spindle speeds: I seems to be usually working at around 5000 rpms and above manually, any thoughts or suggestions for ideal speeds for these materials?

Thanks for the spindle bearing suggestion!

I will try to post some of the options and parts I am considering soon and would be most appreciative for any further thoughts or suggestions,
thanks again,
Justin

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General Mach Discussion / Re: Advice Needed- retrofitting lathe to CNC
« on: January 16, 2017, 12:09:11 PM »
Hi Craig,

Interesting, still trying to figure out the advantage over a pair of 20mm rails though. Perhaps it is a solution to minimize the chance of problems with the installation?

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General Mach Discussion / Re: Advice Needed- retrofitting lathe to CNC
« on: January 15, 2017, 11:06:30 AM »
Hi Craig,

Great, thanks for clearing up the issue of the guides, interesting idea mounting them on the sides. Is it significant that the ways were designed to, and presumably were capable of supporting cutting with this slide setup? Or is it not relevant because the z axis would always have been fixed st the time of cutting, while if we used linear guides mounted to the ways, the slide would not be as rigid with a moving z axis? Regarding a servo spindle motor, what sort of specs would I be looking for if I decided to go for one?

Some photos below,

Thanks!

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General Mach Discussion / Re: Advice Needed- retrofitting lathe to CNC
« on: January 15, 2017, 03:11:20 AM »
Hi Craig,

Many thanks for your reply. The lathe does not have any leadscrews. It has a lever operated slide that has 2 lever operated slides mounted on it, one is compound and both travel in the z axis by means of gear racks. So I am pretty sure I will be having the linear guides installed. Would it be an option to have some shallow tracks milled in the ways to register the rails? I am considering the HIWIN MGR15 series. I have read that these are for 3d printers etc, but am wondering if the largest one, the 15mm, will be sufficient for machining soft, small diameter materials? The reason is that I think I might need to conserve on height as i start stacking rails and blocks for the 2 axes or else I might reach center and have no room left for tool holders.

Any thoughts on the spacing of the z axis rails? It seems like they would benefit from a wider spacing, but then...there is never any load on them except for directly at the spindle. I am thinking of desktop or even bench top cnc lathes that have a narrow bed but seem to do fine.

I am pretty sure rolled ballscrews will suffice, as the accuracy I require is not that high.  What pitch would you recommend for speed?

Yes, I will post more photos and measurements soon,

Thanks again for your thoughts, much appreciated,

Justin

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General Mach Discussion / Advice Needed- retrofitting lathe to CNC
« on: January 13, 2017, 07:01:38 AM »
Hi everyone,

I am considering converting this lathe to CNC. I want to convert this lathe into a gang tool production lathe for making small parts in plastics and wood. Part size will be 16mm dia. max and 70mm long. The initial questions I have for you all are as follows:

Collet Closer: Having the ability to advance the stock through the spindle is essential, which is why I chose this lathe. Is there a mechanical way of operating the lever, without relying on compressed air? Like a large stepper motor or servo? If air is the best option, what recommendations do you have for setting this up and integrating it into the control.

Spindle Motor: Would it be advisable to use a servo motor as the spindle drive to simplify controlling speed, on/off etc?

Linear Guides: What size would be best for this setup? The bed is only about 60cm long and I will not need to have guides nearly that long, would HIWIN MGR15 be appropriate? Also, could I mount the guides directly to the bed or would they be too close together? Would it be better to mount them to a plate that then gets attached to the bed? I am concerned about mounting them precisely, as the only machinists I have access to are not known for precision work. Is it really true that the guides themselves are not straight enough to mount directly?

Ball Screws: recommendations for the exact specs and where to locate them? For the Z axis should it be in the center of the bed or in the front?

Stepper Motors: size?

Planning to use Mach 3.

Thanks in advance for your ideas and suggestions,

Justin

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Hi everyone, my name is Justin. I had a bit of experience with CNC and Mach 3 on a desktop lathe about 8 years ago. I ended reverting the lathe back to manual and have been working by hand since. One of the reasons was lack of collet closer and ability to get the thing to make parts in a production mode. Now I am interested in trying again, and am hoping to retrofit a small toolroom type lathe to CNC. I will be posting a photo of the machine on the General area along with several questions. Thanks in advance for sharing your expertise and experience!

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