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Mike.Mara

Any interest in a guitar specific CNC design?

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5 hours ago, Mike.Mara said:

Well, I had a little play and came up with something like this: Not complete obviously.

RnmSUTr.jpg

The brown parts being MDF.

The cost for framing, aluminium, rails, leadscrews + nuts and couplers is right around £580. I'm going to take a wild guess and say the rest is about £200 for the T-nuts, bolts, bearings, shaft collars ect. (Not ballscrew bearings).

So should be just shy of £800 for all the mechanical parts. Electronics + spindle + USB driver (incase people want to use laptops) ~£430.

So in total about £1,250.

Work area is ~X 500 x Y 1100 x Z 150. (Z could be raised or lowered by adjusting the length of the Y plates.) Machine footprint 1400x720x430 minus electronics.

Like I said, just rough... Just testing an idea to see if you guys see anything I don't or if you have a better idea.

(20mm rails on X and Y, 16mm on Z. Extrusion is 40X80mm, MDF can be either 18mm or 3/4" without any modification.)

I think if that is the amount of mdf you are planning on using, then going with AL extrusion for a few more dollars would be better.

 

 

gantry1a.jpg

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I was actually going to suggest the opposite. If the intention is to make an a machine capable of acceptable precision at rock bottom prices, then the Al extrusion framing is probably overkill. Cutting the extrusions squarely for the home builder will be difficult unless they have access to a decent quality drop saw with a metal cutting blade.

What about limiting the metalwork to only the rails and bearings?

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1 hour ago, curtisa said:

I was actually going to suggest the opposite. If the intention is to make an a machine capable of acceptable precision at rock bottom prices, then the Al extrusion framing is probably overkill. Cutting the extrusions squarely for the home builder will be difficult unless they have access to a decent quality drop saw with a metal cutting blade.

What about limiting the metalwork to only the rails and bearings?

My point was The drawing referred to a lot more AL than MDF or Cab grade ply. If the goal is the AL frame then eliminate the MDF/wood otherwise, yes make it more like a Gatton, or Joes type build.

MK

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Yep. Perhaps need more boundaries laid out for the build limitations. If it's mostly Al with a bit of MDF then the difference in going to 100% Al will be negligible (assuming the builder can machine it properly). If cost is a concern then minimise the use of the expensive stuff and stick with MDF for the majority of the components.

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1 hour ago, curtisa said:

Yep. Perhaps need more boundaries laid out for the build limitations. If it's mostly Al with a bit of MDF then the difference in going to 100% Al will be negligible (assuming the builder can machine it properly). If cost is a concern then minimise the use of the expensive stuff and stick with MDF for the majority of the components.

If only using AL plates and need drilling that is easy. Templates can be made for that. I use label paper single sheet and print out DXF files to scale for intricate  drilling jobs if I need to, It is important you know how to use a center punch though. LOL!!!

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All valid points indeed. If AL plates though, how would the average person go about milling a bearing pocket?

@MiKro I was actually thinking the exact same thing about the extrusion uprights just before going to sleep lol. I was thinking about the forces of the whole machine and during difficult or too aggressive X axis cuts, the MDF would be sure to flex.

Well... With the extrusion being square, Misumi Europe do an incredible job, mm perfect and square as you'd want. However you need a business to shop there.

@curtisa But wouldn't we have the same problem if it was mostly MDF too, can the average person with a modest workshop ensure square cuts with modest tools? I personally would consider my workshop modest, and I have no table saw. I can get pretty damn close with a jigsaw, square and router with a straight guide. But that's obviously not ideal as a mm out over ~1400mm would mess with the alignment and accuracy of the machine as a whole. Unless of course you have any woodworking trickery you'd like to let the rest of us in on ;).

Right, so as Curtisa suggested... What are the boundaries? What can the average person work with a good degree of accuracy?

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1 hour ago, Mike.Mara said:

All valid points indeed. If AL plates though, how would the average person go about milling a bearing pocket?

@MiKro
@curtisa

 

As far as milling a pocket, use bearings that come with bearing blocks and mount those to plate with brackets. As far as larger holes for round rails and possible ball nut mounts. use an arbored hole saw for the specific diameter.

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2 minutes ago, MiKro said:

As far as milling a pocket, use bearings that come with bearing blocks and mount those to plate with brackets. As far as larger holes for round rails and possible ball nut mounts. use an arbored hole saw for the specific diameter.

The problem with that would be that housed bearings that match leadscrew diameters are expensive. Or the couplers from motor to leadscrew are difficult to find.

The only leadscrew diameters that match standard housed bearing sizes are 12mm and 20mm. That's not to say the others can't be found, I have a bunch of 16mm ones, but they cost about twice the price. By the time you've bought 6 for the X and Y you're looking at £60 for 12 or 20mm and £120 for 16mm. Or about £20-30 if using standard bearings or angular contact.

I'm not sure what prices are in the rest of the world, but here it starts to add up.

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And just for the sake of pleasing many budgets and workshops:

5RDxE02.jpg

What do you guys think?

Both the same dimensions and can be upgraded from MDF/Ply to aluminium without modifying the rest of the machine.

The difference is clear at ~£136 for the extrusion with MDF bed (not including brackets, t-nuts so more like £180.) Or ~£17 for MDF (Not including screws.)

I'm sure you could get the MDF cut at most home stores too if they have one of those big vertical panel saws.

@MiKro I'm guessing for most people the saving on the MDF there would negate the price of the housed bearings so good point, they can come into play to save having to mill pockets. So ignore my last post, I jumped the gun on that one lol.

Edit: Or replace the MDF supports with 20x80 aluminium extrusion for a mid-range budget. Making that about an £86 option (Minus T-nuts again.)

Edited by Mike.Mara

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3 minutes ago, MiKro said:

Hell for that matter something like this kit is reasonable.

Indeed, I have looked at those kind of kits before. The only issue I have with them is that dimensions are pretty... Well, they don't exist lol. (And I've heard a few people have been sent bent rails.)

Don't you think 12mm rails and screws are a bit skinny? I may be over-engineering in my head again. :lol: (I have a habit of doing that).

It is an attractive price for rails and ballscrews though... That's for sure.

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1 hour ago, Mike.Mara said:

Indeed, I have looked at those kind of kits before. The only issue I have with them is that dimensions are pretty... Well, they don't exist lol. (And I've heard a few people have been sent bent rails.)

Don't you think 12mm rails and screws are a bit skinny? I may be over-engineering in my head again. :lol: (I have a habit of doing that).

It is an attractive price for rails and ballscrews though... That's for sure.

It was an example. yes 12mm are too small min 15 prefer 20 or larger. :)

mk

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1 minute ago, MiKro said:

It was an example. yes 12mm are too small min 15 prefer 20 or larger. :)

mk

Sure thing, didn't know if I was going overboard with sizes again. ;)

Do you think 1050 x 550 x (some useful number) would work? Means no through neck basses (Or at least none I have designed).

Because if it would, there is this kit from the same seller.

Obviously if we could do it all from bolt on to through neck, short scale to long scale it would be better, but for some people I imagine sourcing parts is a bit too much effort.

I'll try to work out something as drill-by-numbers as possible. Preferably one design with parts interchangeable so if you want ballscrews, then use them, trapezoidal, use them, MDF/Extrusion, all the same plan. It just so happens that a 20mm ballscrew mount will take a 16mm trapezoidal nut perfectly, so it's all up to the builders budget.

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So here is how I setup drill templates if I am not able to use a mill to center drill. These are cut from full sheet label paper. They are printed to scale from DXF files at 0.75point. I need to center punch these and then they can be drilled on the Drill press / pillar drill. These blocks will attach my Z axis mounting plate to the Y axis rail trucks. One thing I learned doing this is to center punch and remove as soon as possible. Otherwise it is a B!%ch to remove. :)

MK

 

temps1.jpg

temp2.jpg

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6 hours ago, Mike.Mara said:

@curtisa But wouldn't we have the same problem if it was mostly MDF too, can the average person with a modest workshop ensure square cuts with modest tools? I personally would consider my workshop modest, and I have no table saw. I can get pretty damn close with a jigsaw, square and router with a straight guide. But that's obviously not ideal as a mm out over ~1400mm would mess with the alignment and accuracy of the machine as a whole. Unless of course you have any woodworking trickery you'd like to let the rest of us in on

Router with pattern bits and a straight edge to follow will give you pretty good straight cuts with a perpendicular edge, which will get you out of trouble for most of the major components. Most of the parts in a CNC are in pairs, so once you've made one of a widget, you can use that widget as a template for the next one.

Mike's printed labels as templates is a good idea, whether you work with Al or MDF, provided you can verify your printer is generating accurate images first.

 

6 hours ago, Mike.Mara said:

Right, so as Curtisa suggested... What are the boundaries? What can the average person work with a good degree of accuracy?

MDF to begin with. Your picture of the two bed designs is a good starting point. The MDF version can be stiffened up a lot by adding cross members as you've done with the Al version.

When I was researching my build, the comments I saw floating around about running those types of rails and bearings in the orientation you have done made me a bit leery of using them. The impression I got was that the open-sided bearings that fit those rails will give better results when the forces pressing down on them are mostly in the opposite direction to the open side. The suggestion I saw was that if you swing the rails around 90 degrees so that the bearing runs on top of the bed it may be better in the long run, preventing the bearing openings from stretching under the forces and static weight of the gantry.

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27 minutes ago, curtisa said:

>snip<

Mike's printed labels as templates is a good idea, whether you work with Al or MDF, provided you can verify your printer is generating accurate images first. >snip<

When I was researching my build, the comments I saw floating around about running those types of rails and bearings in the orientation you have done made me a bit leery of using them. The impression I got was that the open-sided bearings that fit those rails will give better results when the forces pressing down on them are mostly in the opposite direction to the open side. The suggestion I saw was that if you swing the rails around 90 degrees so that the bearing runs on top of the bed it may be better in the long run, preventing the bearing openings from stretching under the forces and static weight of the gantry.

Agreed, also they must understand the importance of tramming the drill press, especially when lowering or raising the table.

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This is all good! Centre punch is an invaluable tool, I used one to mark out the Y axis plates on my CNC. Having drilled without one too, it's a must have!

@MiKro Label printing paper is an awesome way of doing that! I've been using spray adhesive (which I hate both the smell and overspray) and it's a pain to remove even if done quickly. That trick will serve me well.

@curtisa I'd heard that too about the bearings, especially when used on a Z axis. On further investigation, it actually takes pretty extreme forces to cause any issues. That being said though, as it's a valid concern for the longevity of the machine and one of the more expensive parts, I agree it would be wise to adjust the plan to take that into account. Do you have any thoughts on ways to attatch them to the gantry sides in that orientation?

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OKay so here they are drilled, ready for tapping on the edge holes. also test fit on rails before tapping

 

edge100.jpg

zaxisblks.jpg

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3 hours ago, Mike.Mara said:

>snip<

Obviously if we could do it all from bolt on to through neck, short scale to long scale it would be better, but for some people I imagine sourcing parts is a bit too much effort.

>snip<

If they get that far then tiling a project should not be an issue. :)

MK

 

one thing to notice is I have my rails on top and bottom, Not on the side. This added distance decreases flex and racking, as well as keeps my spindle closer to the CG of the upright support. Just an FYI.

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2 hours ago, Mike.Mara said:

@curtisa I'd heard that too about the bearings, especially when used on a Z axis. On further investigation, it actually takes pretty extreme forces to cause any issues. That being said though, as it's a valid concern for the longevity of the machine and one of the more expensive parts, I agree it would be wise to adjust the plan to take that into account.

For all I know the recommendations may have originated from people poo-pooing the idea of using those rails for a machine being designed to mill steel. Your scope is a bit more relaxed than that, so it may not be a problem in the long run. Anyone trying to mill steel on a MDF machine is likely to destroy the frame and gantry before the bearings give way.

 

Quote

Do you have any thoughts on ways to attatch them to the gantry sides in that orientation?

As Mike has suggested - one rail top, one rail under.

 

2 hours ago, MiKro said:

one thing to notice is I have my rails on top and bottom, Not on the side. This added distance decreases flex and racking, as well as keeps my spindle closer to the CG of the upright support. Just an FYI.

You're also using profiled rails and carriages, which are designed to withstand more force in directions other than perpendicular to the bearing mounting face. Although, the same principle applies to the supported rails that @Mike.Mara is looking at. - they're probably not as resilient as the Hiwin types, but mounting over and under will maximise their strength and stability given the circumstances.

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3 hours ago, curtisa said:

@Mike.Mara>snip<- they're probably not as resilient as the Hiwin types, but mounting over and under will maximise their strength and stability given the circumstances. >snip<

These are the hiwin type?

 

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I meant, you appear to have used Hiwin equivalent rails/bearings on your build. Mike.Mara is looking at using supported rail (coded 'SBR' by Chinese auction sites) which may have limitations on which way around they are oriented for maximum strength.

My comments referred to installing the SBR rails in the same configuration as your method to give maximum strength to a product that may already have inherent weaknesses.

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14 hours ago, curtisa said:

As Mike has suggested - one rail top, one rail under.

I meant on the Y axis, as we then need to create a 90 degree joint to the Y axis plates.

I feel like we're running the risk of taking this beyond the realm of your average person. What with needing to get multiple parts perfectly square in order to have the machine cutting perfectly. The original idea was to have as few parts to make as possible, reducing the likelihood of something being out-of-square. You've both made extremely valid points, so without either upping the original guide budget to go for hardware that's less awkward about which orientation it's mounted in it's not looking too good. HIWIN rails would be ideal, but are more expensive than the supported round type. Round type being ~£282 and HIWIN being £604.90.

A decent pillar drill without a ton of runout isn't something I would think most people have so making lots of precision parts by hand may be out of most people's reach without first investing in more tools.

Thoughts?

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Here in is the most likely reason you do not see a machine this size at an affordable cost that has the needed requirements to get the job done.

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22 minutes ago, MiKro said:

Here in is the most likely reason you do not see a machine this size at an affordable cost that has the needed requirements to get the job done.

Indeed, not that it can't be done of course... Just the right tools or right suppliers are needed.

I think there wouldn't be any issues mounting the rails on their side for this application, but if one person has concerns I feel others will too. That alone would probably make it a non-starter.

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