My CNC Router Build Adventure

[JayneV]

If the GT3 series timing belts have little to no backlash over a short length, then I’m thinking I could relocate the Y motors inside the frame so they are not sticking out the back. Carlos has grown a little larger than the target 1500x1200 maximum footprint which I’d like to try and stick to. With the motors inside the frame, that will cut the overall length by about 150mm without reducing the working envelope.

Jayne

[davida1234]

Hi Jayne,

In the inboard case, make sure they are either attached to a thick plate and/or you have a fan inside the profile for heat management as they get quite hot. You also should think about how you want to attach them and adjust the belt tension. On my steppers, I tapped the stepper mounting holes for the next size screw.

[JayneV]

Hi David,
I wasn't planning to close the walls in on the outside face so the motor would be open to the ambient air and also be bolted to a chunky piece of aluminium. For tensioning, I was thinking about elongated mounting holes for the motors. I could also attach the motor to a sliding mounting plate and the plate can be adjusted with a grub screw or "tensioning" bolt.

I don't understand what you mean about tapping the stepper mounting holes for the next size. Do you mean drilling the hole oversize so the bolt has some space to be moved around?
Jayne

[peteeng]

Hi Jayne - I 've used this company for belts & pulleys been very good. Reflexing the motor is good for your reasons. Since you are machining your parts you can machine the bearing supports into the end plates on Y axis and gantry... Peter

https://www.ptparts.com.au/products/...J-timing-belts

[JayneV]

Hi Jayne - I 've used this company for belts & pulleys been very good. Reflexing the motor is good for your reasons. Since you are machining your parts you can machine the bearing supports into the end plates on Y axis and gantry... Peter

https://www.ptparts.com.au/products/...J-timing-belts

Hi Peter, thank you for the link, I've saved it in my list of suppliers. When you say machine the bearing supports into the end plates, do you mean making the holes to accommodate this style of end support (see attached image), or do you mean to source the actual bearings and insert them directly into machined holes in the end plate?

If you mean to use screw end supports like the ones in the attached image, I considered doing that on the gantry but it would make the motor stick out further. I wasn't planning to reflex the X axis motor, but it is probably worth considering to save a little more space. I'll look into it.

Jayne

[peteeng]

Hi Jayne - I mean buy the bearing and machine the hole for it into the end plate. Don't buy the bearing and the block unless you want to allow the block to wiggle for alignment but you should be able to machine the parts accurate enough so they align correctly. Regards Peter

I think David means to tap the holes in the stepper then provide a slot on the mount so the motor can slide allowing the bolts to be snugged up without a nut. I put a belt tensioner on my belt machines see attached photo I use the same bracket for the motor and the screw pushes the motor.

[JayneV]

Hi Peter, the floating bearing end seems straight forward enough to do, I'm not real sure how to accomplish the task with the fixed end. I haven't seen a ballscrew setup in person, only photos and drawings on the internet. I'd have to buy at least one fixed end bearing block to understand how the screw is held in place axially to do the same on the end plates. Fewer components is good so worth thinking about.

Pushing the motor with an adjustable bracket is a nice solution. Does the stepper motor housing have enough materials allow for tapping the holes?

Jayne

[peteeng]

Hi Jayne - I have done this in the past with motors and it works well (threading that is). If you have an adjusting mechanism you don't need to thread them. Or if you have 3 hands that makes it easy to pull the motor, hold the spanner and hold the nut. If we had four arms we could hold the cup of coffee as well. But even with 2 hands its possible to snug the nuts tap the motor with a block snug and tap to get tension. By the way don't drop stepper motors or hit the body hard that usually kills them... dislocates the internals somehow and their cactus... Peter

[JayneV]

Hi Peter,
Lol....In my day job fixing planes, I'm used to working in awkward positions where three hands, 4 elbows and double jointed fingers would be beneficial, but anything that helps make life easier with the usual number of limbs and joints has got to be a good thing. I wouldn't be hitting the motors with anything, but thanks for the heads up.
Jayne

[davida1234]

Hi Jayne, as Peter explained with threading the stepper holes.

[jckstrthmghty]

Does the stepper motor housing have enough materials allow for tapping the holes?

Mine came threaded.

[JayneV]

Hi Jayne, as Peter explained with threading the stepper holes.

Hi David, I understand now, thank you. So you do something like this.

[JayneV]

Mine came threaded.

Good to know. Thank you.

[JayneV]

Hi everyone,

I’ve made a few more adjustments to Carlos. All the ballscrews are now 16mm instead of 20mm, 1610 for the X and Y axes and 1605 for the Z. I also replaced the BK/BF end supports with FK/FF type. Peter suggested mounting bearings directly into the end plates which would be clean and tidy but I wanted to allow for some wiggle room to adjust the ballscrews. Since this is a bolted together structure and my first attempt at building a machine with any kind of precision I thought it might be better to have some means of adjusting the critical components in the likely case that the frame isn’t perfectly aligned.

The other big change from the previous version is the X and Y motors are now mounted within the envelope of the frame and driving their respective screws through a belt. It’s an idea that I started experimenting with this past week and briefly discussed it a few posts back. I’ve decided to stick with that idea and made the necessary changes to the model (see attached images). One part I’m unsure about is the front vertical plate the Y motor is mounted on. Above the motor is the FK end support and that part of the plate is cantilevered and kind of just sticking out there. Since all the Y axial loads are transferred to the frame through that end support, I feel that vertical plate might need some additional structural bracing. One option is to make a larger top bracket (see image with red markup). Another option would be a diagonal brace from the top of the plate to the lower part of the frame. Any suggestions what I should do?

I’m happy with the way the X axis motor is mounted except for the exposed timing belt and pulleys, so I designed a cover which will be 3D printed (shown in dark blue in the attached image). I’m running out of things to change which must mean Carlos is very close to being called ready for construction. I thought I’d play around with adding some colour to see how it looks. The blue parts in the images represent anodised parts. Maybe blue or gold anodising? My brother also has a nice looking pinkish/purple colour which might also work.

Jayne

[mactec54]

Hi everyone,

I’ve made a few more adjustments to Carlos. All the ballscrews are now 16mm instead of 20mm, 1610 for the X and Y axes and 1605 for the Z. I also replaced the BK/BF end supports with FK/FF type. Peter suggested mounting bearings directly into the end plates which would be clean and tidy but I wanted to allow for some wiggle room to adjust the ballscrews. Since this is a bolted together structure and my first attempt at building a machine with any kind of precision I thought it might be better to have some means of adjusting the critical components in the likely case that the frame isn’t perfectly aligned.

The other big change from the previous version is the X and Y motors are now mounted within the envelope of the frame and driving their respective screws through a belt. It’s an idea that I started experimenting with this past week and briefly discussed it a few posts back. I’ve decided to stick with that idea and made the necessary changes to the model (see attached images). One part I’m unsure about is the front vertical plate the Y motor is mounted on. Above the motor is the FK end support and that part of the plate is cantilevered and kind of just sticking out there. Since all the Y axial loads are transferred to the frame through that end support, I feel that vertical plate might need some additional structural bracing. One option is to make a larger top bracket (see image with red markup). Another option would be a diagonal brace from the top of the plate to the lower part of the frame. Any suggestions what I should do?

I’m happy with the way the X axis motor is mounted except for the exposed timing belt and pulleys, so I designed a cover which will be 3D printed (shown in dark blue in the attached image). I’m running out of things to change which must mean Carlos is very close to being called ready for construction. I thought I’d play around with adding some colour to see how it looks. The blue parts in the images represent anodised parts. Maybe blue or gold anodising? My brother also has a nice looking pinkish/purple colour which might also work.

Jayne

You can put the fixed end bearing mount on the other side, if you have no travel problems, that way your Timing pulleys will be closer to the frame, use bigger Timing Pulleys the more tooth count the better the belt engagement.

[mactec54]

Hi Peter, the floating bearing end seems straight forward enough to do, I'm not real sure how to accomplish the task with the fixed end. I haven't seen a ballscrew setup in person, only photos and drawings on the internet. I'd have to buy at least one fixed end bearing block to understand how the screw is held in place axially to do the same on the end plates. Fewer components is good so worth thinking about.

Pushing the motor with an adjustable bracket is a nice solution. Does the stepper motor housing have enough materials allow for tapping the holes?

Jayne

If you want to get creative seeing you have a Mill you could do your motor mounts like this.

[peteeng]

Hi Jayne - You seem to have an axle extension on the motor in one image. Mount the pulley as close to the motor as possible. The shaft is not rated very high in bending and they can fatigue and break . A belt needs to be tight to work right, The allowable moment on the shaft is specified if you want to look it up. So pick a motor with a big shaft 10mm is good. Look at Nema24s maybe. Being a short belt the width could be smaller to help with this issue, what width have you drawn it at? Peter

[JayneV]

You can put the fixed end bearing mount on the other side, if you have no travel problems, that way your Timing pulleys will be closer to the frame, use bigger Timing Pulleys the more tooth count the better the belt engagement.

Hi Mactec, I haven't seen any of these end supports up close, can the nut be moved to the other side of the mount if it's mounted the other way around? Travel won't be impacted by mounting the bearing the other way around, there is enough room. The timing pulleys in the images are not modelled on any particular part, they are just there as a visual aid. When I find a suitable part to use, I'll update the drawing. Would a pulley around 50mm diameter be a good size?

If you want to get creative seeing you have a Mill you could do your motor mounts like this.

Except for the oval shaped nuts, the motor mounts are almost exactly like the ones in your attached images. I spoke with my brother and he said making the nuts will be easy so that is a good option.

Hi Jayne - You seem to have an axle extension on the motor in one image. Mount the pulley as close to the motor as possible. The shaft is not rated very high in bending and they can fatigue and break . A belt needs to be tight to work right, The allowable moment on the shaft is specified if you want to look it up. So pick a motor with a big shaft 10mm is good. Look at Nema24s maybe. Being a short belt the width could be smaller to help with this issue, what width have you drawn it at? Peter

Hi Peter, the pulleys are just visual aids at the moment until I find an actual part to make a model from. The Nema 23 motor I was looking at has a 10mm shaft (see attached data sheet). It doesn't mention anything about allowable moment on the shaft, is that a value based on the shaft material and diameter which you then apply to the motors or do different motor manufacturers specify this value in the specs? The belt I drew in the model has a width of 15mm, but again, that is not based on anything other than being a visual aid.

Jayne

[peteeng]

Hi Jayne -10mm is good, big shaft and big bearing. If you send a note to stepperonlione requesting mechanical specs for motor they will supply. max Axial load, and moment or a force at a particular distance from the motor face. Sometimes this will be the bearing limits, sometimes the shaft at a cycles limit... a full spec will be both. 15-16mm wide belt is a good width. Peter

[JayneV]

Hi Peter,
Thanks, I'll send an email to stepperonline asking for the full specs.
Jayne