Drum Sander Conversion

[valensign]

I am in the process of making a 32" Drum sander attachement for my SB. My question is How much weight can the Z axis hold without any undo wear on the bearings and motor. Im wanting to machine a Drum that fits in the router bracket so i can raise and lower the sanding drum but im concerned once I do that and the weight of the motor to drive the drum and the drum itself I might be pushing the limit of the stepper and bearings. Im prob at 25 pounds now without the mounting bracket. If I get to this to work I'll post some pics and the plans here. If I cant do it this way Ill make a screw drive to raise and lower the main drum and just mount the assembly to the Y Axis instead and Just plug in a new conector to my A or Z.

[grant@shopbottools.com]

There are a couple ways to look at that question, William, but the short answer is that I would stick to about 36lbs of load for a standard z axis and z axis motor. Our automatic tool changer ShopBot has a 5 horse Colombo spindle, a pneumatic chuck changer, an aluminum spacer plate, and a handful of hardware. This comes out to about 50lbs. This is possible because of the use of a 7.2 reduction gearbox to roughly double the torque of the standard motor, which is a 3.6 reduction. There is a speed sacrifice for the boost in power. We can special order for you a 30:1 reduction gearbox motor, which will allow loads of up to maybe 80 lbs, but will have a maximum positioning speed of .7 inches per second and higher backlash than the 3.6 or 7.2 gearboxes. Additionally, you may want to enhance the rigidity of the structure in order to get good performance from such a massive load. So there are three answers for you. 36lbs if you don't change your tool in any way, 50lbs with a different motor that is slightly slower, or 80lbs with a higher backlash and much slower motor. More weight will carry additional concerns with it - you may have to use slower than normal move and ramp speeds and may exceed factory tolerances for part accuracy. These factors will really depend on the specifics of your application and installation, but nevertheless this is a fair guideline.

[rgbrown@itexas.net]

William,

A couple of questions I have is are you trying to thickness sand or just finish sand. If you are thickness sanding, it may require a very solid frame and some kind of power. If one is trying to do finish sanding an inflatable drum sander or random orbit sander and 'passes' might be another option.

I am curious to your intent and results.

Ron Brown - rgbrown@itexas.net

If Stupidity got us into this mess,
then why can't it get us out? - Will Rogers

[danhamm@abccom.bc.ca]

William,
I follow what you are trying..."but" have you considered mounting it to the xaxis and using the
zaxis as a pivot axis ..the consideration then
becomes much less for your zaxis..methinks you
mite be on to something..using the yaxis motion for sanding a large area..

[valensign]

What my original plan was to use the Z Axis for my Height for thickness sanding but I have changed my design and I will manually raise and lower my z with a ball screw as you dont have to raise and lower that much when doing that type of sanding. I am Making a drop in unit that will go in the Y carage and move back and forth along the X axis. The drum will be turning around 5000 RPM.(So I better have it balenced good(DUCK!!!) It will be a little heavy. Email me and I will send some pictures of what I have so far as my web site isn't up yet.