Mike's EyeZap Laser Cutter

[mikegrundvig]

Hi all; since parts have started to arrive for my laser cutter, I figure it's time to start writing the build log. I've got a fair bit of CNC experience and own a large CNC milling machine that I will use to make many of the parts. I converted a small mill to CNC a few years ago so I've got a fair understanding of what's involved. I've only used a laser cutter once before but it showed me a few things I feel are necessary in making a great machine and so that's where many of these requirements are coming from.

Requirements
My laser project has some specific requirements that must be met or I'll not consider it done. These are in addition to the typical things you'd expect in a laser cutter.

• At least 60 watts of laser goodness and ideally 80 watts. I want to be able to slice and dice big stuff.
• Rapid tool chain for use. This currently means a DSP and CorelDraw but the Lasersaur system is looking pretty hot too. This will likely be the last thing I figure out in the system. It will not be Mach3/EMC and g-code, that's for dang sure. I like Mach3 a great deal but I have no interest in generating g-code to use the laser, I want to draw a line and cut it directly.
• At least 2' x 4' fully usable cutting area. This means it will really be a few inches larger in each direction so I can fit a 2' x 4' piece of material into the machine easily.
• Front/rear load/unload capable. Due to the large working area, I'd like to be able to slide a full 4 x 8 sheet of plywood into the machine. Basically slide it in, cut, advance 2 feet, cut, etc. This will facilitate some cool project ideas I have planned. The first part of this is to provide for removable front and rear cutting-area panels - beyond that, we'll see what it takes.
• Hold-down system. Since I plan on using large sheets with the machine, I need a way to hold down warped pieces to keep the surface flat. This will also be useful for keeping it in place when I feed large pieces through the machine. In my one previous laser cutter experience, this was a real problem and caused me a lot of issues. It seems an easy fix though so I think I'll just build it in initially.
• Home corner locator and rulers. Basically an easy way to position material in relation to the home point of the machine consistently. I also want the rulers as a quick-and-easy way to ensure I have enough material on the stage for a given part.
• Fully self-contained. I want everything to be completely internal if possible. The coolant system must be internal and have a radiator to cool things - this includes the tank and pump as well.
• Absolutely reliable. The system will be built like a tank and will NOT require frequent maintence or adjustment. I expect this to work like a microwave - I tell it what to do and it does it reliably every time.
• Sturdy-enough to move. This goes along with the last point but to be specific, I want to be able to move the cutter without having to realign it constantly. As a second aspect of this point, I want the machine to be sturdy enough that it's panels are not structurally required. This means heavy joints and connections between all the 8020 and rigid mounts for optics, motors, etc. No slop anywhere at all. It also means the machine is going to weigh a ton and I'm OK with that.
• Easy to work on. While I don't want to have to work on the machine at all once it's complete, I recognize it will be a slog to get there in the first place and easy access is key to that. I'd like to get the panels to be easily removable - maybe held in via magnets or some such but I'll dig into that as I go.
• Cost conscious. This will be an expensive project but I want to keep the cost down when feasible. This is a bit of a balancing act though as I'm going out of my way to use commercial/industrial grade components in multiple places which raises the price. I plan on machining a ton of the parts as a way to reduce cost.

Design Decisions
So with all those requirements it's safe to say that the machine is going to be "inspired by" rather than "based on" the buildlog.net 2.x laser cutter. I've made a few critical design decisions that impact all other pieces of the project. I'll try and break those down here.

• Gantry-mounted tube - This is something I've seen a lot in the Kern lasers and a few other brands but never in the smaller Chinese and hobby lasers. I won't lie, this single feature makes me a bit nervous though it has a lot of great advantages I like. Specifically, mounting the tube on the gantry significantly reduces how far the beam path has to travel in the end - really simplifying alignment. For instance, in a 2'x4' machine the beam would have to travel in alignment a touch more than 6' at the minimum. The first mirror bounce is stationary but the second and third move in relation to each other. With a gantry mount, the max distance in my design is slightly more than 4' and only one mirror is moving in relation to anything else. The downside is that you need to move coolant to the gantry as well as support the tube on the gantry. The increased weight makes for a larger y-axis stepper as well.
• Linear Rails rather than MakerSlide - This is probably one of the more controversial changes and likely the most expensive. For better or for worse, I'm going with 15mm HiWin linear rails rather than MakerSlide. MakerSlide looks solid but is young and immature. I have some personal concerns about the long term durability and rigidity of the design that might be proven wrong in the future but until then I'm investing in the tried-and-true industrial solution for linear movement. The linear rails are attached to the 8020 extrusion via socket cap screws from above into long t-slot nuts I will machine on my mill.
• Custom mirror holders - For the mirror mounts, I plan on milling them right into the y-axis bracket on one side. Only one mirror mount needs to be adjustable either closer or farther from the gantry to account for different diameter laser tubes. This sliding mount will lock into place with bolts on the top and bottom once it's positioned properly for the tube. The other side will be at the correct fixed distance to point at the center of the laser head. Both mirrors will be locked in at a 45 degree angle to the gantry to ensure they are accurate. The mirrors are held in place between a retaining ring and the mount. Both sides of the mirror are compressed against 18mm ID o-rings. Fine adjustment will be made by compressing the mirrors against the o-rings. To ensure the finest possible adjustment, the adjustment screws are mounted as far as possible from the mirror. This means more turn of the screw is needed to move the mirror.
• Custom tube mounts - This is a simple one, since the tube is mounted on the gantry, it needs to be locked very tightly into position. This will be done with mounts that slide together to form a "diamond" shape around the tube. They will secure the tube without damaging it, firm rubber will be added to the mounts where they touch the tube.
• Custom focus lens mount - Originally I just wanted to use the higher-end system that Light Object sells but after some checking it would require a messy mount to get it to mate up with the linear rail I'm using. Because of that, the mirror and focusing lens will be integrated together into a single assembly that is solidly locked to the linear rail carriage. I'll end up machining this on the mill as well.

Parts List
This is far from a comprehensive list - first off, it only contains things I've already ordered. I'll keep updating it as I get new parts for the laser into my grubby hands. I'm not going to list small bits and bobs here at all, just some of the larger components or less obvious things. I wont be documenting nuts, bolts, raw aluminum, extrusion, etc. I'm just laying these out there to keep track of em and to give people an idea of what I'm using. Many of these choices could be interchanged with other parts. In most cases, I went with what I knew worked well or was recommended to me by someone also using it. In almost all cases, I've gone larger or higher quality than needed. Sorry for the eBay links when they break in the future...

-=-=-=-=-=-Electronics-=-=-=-=-=-

• X-Axis stepper motor - I went with this motor because I like Keling (he is great to work with and the quality is excellent for the price) and this was a good amount of power in a tiny package. This should be more than enough to move the laser head very quickly. $20 - NEMA 17 BIPOLAR STEPPER MOTOR 62 oz-in
• Y-Axis stepper motor - As before, another Keling choice. This motor is likely major overkill and I might go to a less "torquey" motor in the future if I need more speed. $49.95 - NEMA 23 Stepper Motor: KL23H2100-30-4BM (1/4” Dual shaft with a flat) 495 oz-in
• 36v Power supply - These switching power supplies are a dime a dozen on eBay and quite well made. I opted for 36v to really drive the heck out of my stepper motors. This does mean that I will need to use a pair of LM317-based voltage regulator circuits to output 12v for Arduino control (flow, fluid level, and temperature sensors) as well as 24v for the DSP. A bit of a hassle but not too bad considering all the other work going into the system. $37 36V DC 10A 350W Regulated Switching Power Supply
• 2 x Stepper drivers - These stepper drivers come highly recommended from an expert friend of mine using them for his pick and place machine. They are cheap, durable, and reliable while still providing for a ridiculous number of micro-stepping options - $43 each - CNC Stepper Motor Driver 2M542 4.2A Driver
  
  -=-=-=-=-=-Mechanical-=-=-=-=-=-
• 15mm linear rail block - As I stated above, I'm using linear rails from HiWin so I snagged one to see how it will work. In the end, I'll need three of these. $43.16 - EGH15CAZ0H
• 15mm rail - This is what the block slides on. I snagged 800mm - more than enough for one side of the machine. $84.99 EGR15RxxxxH
• 2 x 1/4" to 3/8" shaft couplers - I opted to use 3/8" shaft for two reasons: a bigger shaft diameter is a bit less likely to "whip" at high speeds and it let's me use larger bearings. These are "clamp" style couplers that I like better than set-screws because with the set-screws you have a chance for slipping causing backlash (something I've run into on a CNC machine in the past). Another thing, they are not lovejoy or spider-style to reduce the amount of backlash and to keep the price down a bit more. High-end lovejoys cost a lot. $11 each - 6.35mm x 9.5mm Flex Coupler 1/4" to 3/8" Shaft Coupling
• 10 x 3/8" bearings - To support the larger diameter shaft and pulleys, I'm using these 3/8" bearings from VXB. There are good quality and I've had great luck with VXB over the years. - $14 for 10 - 10 Sealed Bearing R6-2RS 3/8"x7/8"x9/32" inch Miniature Ball Bearings
• 3 x 3/8" shaft, 3/8" width XL timing-belt pulley - I opted for the widest XL (.200 pitch) pulley I could get to give me the least amount of belt stretch and most torque while still being easy to source. This ended up being 3/8" wide. I sure wish they were shaft-loc and not set screw secured but these will have to do. I've ordered 3 for now but I bet I'll need 8 in the end and 1 1/4" shaft version for the X axis. - $6.98 each A 6Z 3-16DF03712
• ? x 3/8" wide XL timing belt by the foot - I'm including this only because I know a lot of people have trouble sourcing the belt. I've going out of my way to ensure my design doesn't require full loops of belt so I can get it by the foot which is much more convenient. I love McMaster for many things and was pleased to see they carry this too. I ordered 10 feet to play with but I bet the machine as whole will need more like 20-30 in the end. $2.43/foot - XL, L, H, and AT10 Urethane Belting, XL Trade Size, .200" Pitch, 3/8" Width - Part #1840K1
  
  -=-=-=-=-=-Optical-=-=-=-=-=-
• 3 x 20mm Si Mirror - These are a bit pricey but after talking with some laser experts, they came highly recomended so I went with it. These are a bit higher quality than the gold mirrors and so handle higher wattage lasers like I plan on using. $45 each - 20mm Si Reflection Mirror for DIY CO2 Laser machine
• 20mm ZeNe lens with 100mm focal length - This was a bit of a gamble. I figure I'm going to do vector cutting of thick materials far more than anything else and so after much debating, I went with a long focal length lens, almost 4 inches. $48 - 20mm ZnSe Focus Lens CO2 Laser Cut 100mm focal

Whew, I think I should earn a prize for writing the largest post known to man. In a day or two, I'll update this post with my current design pictures for the custom components. I've already machined a few test pieces out of MDF to see if they work and work out the kinks. I figure I'll be machining the first real components from aluminum in a week or two. I'd love any feedback or input. Thanks!

-Mike

[twehr]

Requirements
My laser project has some specific requirements that must be met or I'll not consider it done. These are in addition to the typical things you'd expect in a laser cutter.

• Hold-down system. Since I plan on using large sheets with the machine, I need a way to hold down warped pieces to keep the surface flat. This will also be useful for keeping it in place when I feed large pieces through the machine. In my one previous laser cutter experience, this was a real problem and caused me a lot of issues. It seems an easy fix though so I think I'll just build it in initially.

Mike,

If you can get all of this done on a budget that is anything less than what you might spend for a commercial product, you will certainly have a fantastic machine.

Of all your requirements and comments, one struck me as very interesting - handling the warped materials. The interesting part is that "It seems an easy fix...".

I am curious what that easy fix is. For light (1/8" or 1/4" plywood), I have found that holding all four edges flat does a good job. But sometimes that is not enough - central area can still have a bit of a wave to them, at times. For engraving work, the idea of a suction table comes to mind, but that is not possible with doing cutting jobs.

So, I am curious: What is your planned easy fix for holding material flat (from from paper-thin to roughly 1/4" inch thicknesses)?

[TLHarrell]

I am definitely interested in this project. Waiting to see more.

For the X-axis (gantry), I would still consider using something like Makerslide instead of the far more expensive linear rails. I would use it as if it were linear rail, bolting it to your gantry. The laser head is very light weight and doesn't need more support than that.

[r691175002]

Your decisions all seem solid. I'm a huge fan of gantry mounted tube + linear rails. The makerslide system is great but it was never intended for large high precision machines.

You might want to reconsider doing custom mirror mounts. An o-ring really is not the best way of doing things, there is a lot of complicated geometry that goes into a proper mirror mount to make sure all the adjustments are completely independent. http://en.wikipedia.org/wiki/Mirror_mount

I tried something similar (using felt instead of an o-ring) in the past and had some problems. It kind of worked but the problem is that there is nothing that prevents the mirrors from shifting laterally and that will throw off alignment. As well, it is basically impossible to adjust a single axis without slightly changing the other one. Since you are doing such a good job with the rest of the system I'd highly recommend not skimping here.

[gene]

I'll be watching this as well to see how a larger sized laser turns out. Very interested in the gantry mounted design and I know Bart was planning to eventually make one as well so you may want to talk to him to compare notes

[mikegrundvig]

If you can get all of this done on a budget that is anything less than what you might spend for a commercial product, you will certainly have a fantastic machine.

Thanks, I'm pretty hopeful it won't be too crazy expensive. I've ball parked the price of the other major components below to see what it's looking like...

So, I am curious: What is your planned easy fix for holding material flat (from from paper-thin to roughly 1/4" inch thicknesses)?

Sadly, my idea is not a perfect fix but it does work quite well for many things. Let me try and describe my current plan for the table and see if this helps out. Please pardon the rambling as this is giving me a chance to put all the ideas in one place. Also, the heavy formatting is to help me when I go back through this thread to design things in CAD, makes it easy to find. This is going to be difficult to explain as I don't yet have a diagram of my table design put together yet.

Table Design
Basic Layout
Picture a 2' x 4' rectangle bounded with extrusion so the inside dimensions of the rectangle are 2' x 4'. This rectangle will be extremely rigid with core screws as well as corner plates on the bottom. Now place an aluminum cutting grid in the center. The grid is held up via tabs attached to the extrusion. The grid itself floats so it can be easily removed but it can't slide in the rectangle as it's a tight fit with the tabs. The tabs keep the grid high enough so that the top of the grid is flush with the top edge of the extrusion, creating a flat surface. Small extrusion braces will span the bottom of the grid, between the sides of the rectangle, to prevent it from sagging in the center. The machine origin (x 0, y 0 / home position) will be at the inside corner of the extrusion on the upper-left side of the rectangle. Everything else is based off of this basic table design.

Rulers Requirement - The requirement to add rulers to the table is a piece of cake to meet, I'll just use the adhesive steel rulers sold by McMaster-Carr. Specifically part #1909A41 looks perfect for these applications.

Rolling Material Onto Table from Front/Rear - This is a little trickier but still pretty straight forward. To move large pieces of material into and out of the machine, I think it will be easiest if it rolls onto the table. Think of those rolling conveyors used in warehouses to move boxes. Attached to the 4' length of the rectangle on the side opposite the aluminum grid will be brackets that hold a 1/4" ID rod in a few places. On the rod, spaced every 6-12 inches will be skate rollers. The top of the rollers will be the same height as the top of the table surface. Go here to see what skate rollers look like to get the idea. To support the material on either side of the machine, you'd use something like this.

Orienting material very accurately to the machine origin - This is a common machining technique that someone at CNCZone (GREAT site) taught me and it's been very useful over the years. To orient a rectangular object consistently and accurately to the exact same position, you can use three points. This image shows the basic idea of using three dowel pins as locators for a part. I'll create three small rectangles with a round 1/4" diameter bump on the right side. The rectangles will be channeled so they "lock" into the t-slot of the extrusion automatically which will align them to the extrusion accurately every time. The 1/4" bump will be cut so it lines up with the edge of the cutting grid and extrusion. These blocks can then be added and removed or re-positioned as needed when aligning parts. This should get me a bit better than a hundredth of an inch of accuracy (and possibly much better) without being hard or slow to work with. More than good enough repeat-ability for anything I have planned on the laser.

Holding down parts to flatten out sheets - I've used this trick when milling shallow pockets (.045" deep ) on 0.09" aluminum sheets with my mill and it worked well. I believe it will scale up to bigger wood sheets pretty well - particularly since the Z-axis of a laser cutter requires pretty minimal accuracy when compared to other machining. The basic idea is that a small piece of extrusion will go the full 4' over the length of the table in the long axis. Blocks that can slide up or down the outside edge of the short dimension of the table will each have a 1/4-20 threaded vertical hole in them. The 4' bar on top will have a small block secured to it via t-slot nuts with a 1/4" hole through the block and through the bar on each side. A pair of 1/4-20 socket-cap bolts run through the bar on top and into the blocks that slides on the 2' edges of the table. Tightening the bolts on each side causes the bar to press down. Now it is possible to tighten unevenly but generally you can feel when it's pulling to one side or the other. The idea is that there will be two (or more) of these bars going horizontally on the table. The length of the bolt dictates how much work it is to secure something down as well as the max thickness. In practice, the right length bolt can be used with only a couple of turns and still secure something very tightly. Those same sliding blocks can be used for the vertical hold down too. If you need both vertical and horizontal hold downs then a slightly different block design can be used on the horizontal bars - you just need to use twice as tall vertical bars because they will be higher. Whew, I hope that made sense. I can see it in my head quite clearly but it's hard to describe. I'll try and CAD it up this weekend to show it.

Now if you need to cut the full board even with hold downs, you do it in multiple stages. Use a bar to lock down the middle and flatten out the board. Cut the top of the board and the bottom, passing over the bar. Add two more bars, one that splits the top of the board and one that splits the bottom. Now remove the middle bar (the original one you placed). Your orientation is unchanged and you can cut the middle and the lines will be perfectly joined as though it was done in a single pass assuming you didn't jar anything out of alignment. This is very common in milling and I'm willing to bet money it works great for laser cutters too. If I end up doing this a lot, I'll probably make a CorelDraw macro to do it for me. The idea would be to load up the image and then split it into two images: top and bottom with a blank middle and then the middle with a blank top and bottom. Run one job, re-position hold downs, run second job. This is the same technique I plan on using to cut a single 4' x 8' sheet at one time if I can get it to work well - cut 18", advance 18", repeat until done - clamping the top and bottom each advance.

For the X-axis (gantry), I would still consider using something like Makerslide instead of the far more expensive linear rails. I would use it as if it were linear rail, bolting it to your gantry. The laser head is very light weight and doesn't need more support than that.

The linear rail and sled for the X-axis will cost a touch less than $190 all told. While I know it's overkill I also know it's totally reliable, durable, accurate, rigid, proven, and effective. MakerSlide might well be all of those things as well but we won't know until it's been used on many projects for a long time. I consider the $190 an investment in headache/hassle insurance. If you are curious to really know more about the rails, check out the tech specs from HiWin. Ultimately though, I feel that precision ground and polished steel rail mated with stainless steel recirculating ball bearings is worth the price increase over single-side-supported Delrin pulleys running on anodized aluminum with skate bearings. Ironically, with all that said I'm likely using MakerSlide in a small 3d printer I plan on building after this project.

Your decisions all seem solid. I'm a huge fan of gantry mounted tube + linear rails. The makerslide system is great but it was never intended for large high precision machines.

Thanks, it's a lot of risk but worst case scenario I can go back to a design without the tube on the gantry and I'm only out my time and effort on the milling/design side.

You might want to reconsider doing custom mirror mounts. An o-ring really is not the best way of doing things

I see I didn't explain myself well enough and without a picture of what I intend, it's really hard to follow. I actually referenced that Wikipedia article when I first started playing with this. Effectively, I'm counting on the accuracy of my mill to ensure close alignment of everything. The mirrors will be aligned to each other down to a few thousandths of an inch before I need to do any adjustment. The gantry head and y-axis mount will lock them together very tightly. Now for the mirror mounts themselves... Basically I have a block of aluminum that will have a pocket in it that is 20.25 mm in diameter - .25mm larger diameter than the mirror. This will be a close tolerance fit but not a press-fit - the mirrors will not be able to move laterally.The depth of this pocket will be the thickness of the mirror (don't know it yet) divided by two plus .75mm (which is 75% the thickness of the o-ring). The retaining ring for the mirror is a match of this except it has an 18mm hole all the way through it inside of the pocket. The whole assembly goes block, o-ring in pocket, mirror in pocket on o-ring, o-ring in pocket on retaining ring, retaining ring. The o-rings will start to compress with .5mm gap between them - almost .02". The adjustment holes are spaced quite far from the center of the mirror so they require more turning to make small adjustments. I'm going to try and use 4-40 but I'll go all the way to 0-80 if that's what it takes. The retaining ring will have tapped holes while the mirror mount will be through holes. I'll then be able to snug up high-quality lock nuts on the ring. Since the retaining ring holes are threaded this will act like a jam nut and be very secure.

I'll be watching this as well to see how a larger sized laser turns out. Very interested in the gantry mounted design and I know Bart was planning to eventually make one as well so you may want to talk to him to compare notes

Thanks, Bart is a far, far better engineer than I am so I hope he hurry's up and gets it done before I start making things so I can learn the right way to do it!

-=-=-
Whew, last bit - let's see how well I can WAG the price at this early stage to see what we are looking at...

Everyone above: ~$600 w/shipping
6 more pulleys: $42
16 more feet of belt: $40
Rod, nuts, bolts: $60 (I'm a freak about using the fewest possible sizes for everything - makes things easy)
Raw aluminum stock: $120 (this might be on the high-side, I have a lot of raw bar stock here, tough to say)
80w laser - 10k hour model: $700
Laser power supply: $297
Light Object DSP: $465
Extrusion: $500 (total WAG here, I bet I can bring it down with some planning - I have a few big pieces already)
Rails and blocks: $320

Thus far - ~$3150 if I go with the huge laser and DSP up front. I figure another few hundred to finish it off with panels, water cooling, etc. Call it $3500 all told and that's probably pretty reasonable though I've gone high on some of the estimates to be safe. If I go with Lasersaur's control system and 60watt than I drop down to about $3k. With a 40 watt laser and the Lasersaur control it goes down to ~$2600.

Thanks everyone for all the feedback. I'll try and get some pictures uploaded to this thread tonight so you can see what some of the parts are going to look like.

-Mike

[mikegrundvig]

Whew, lots of images in the post showing individual parts. Since I had that huge post with all that table discussion, I figured I would finish the full table design this weekend. I believe I've incorporated all the requirements I listed above into the design. Everything looks pretty solid at this point.

Here is the entire table in a shot.

Here is a picture of the table with two hold downs attached. Normally the hold down base pieces would always be attached so it will take just moments to place the a hold down.

Here is a detailed view of the roller assembly and the locators. The locators will normally always be on the table but they would be removed to run large sheets through.

Edge Locator - here is the bottom-isometric view of the edge locator. As I mentioned above, there are three of these used to locate parts to the origin of the machine. One of the detail diagrams below shows three of these placed. These (and the wheels) are the only part of the table that extends about the surface. Everything else is completely even.

Horizontal Clamps - the next three images show how the horizontal clamping system will work. This is a pretty simple system but more than enough to clamp down large sheets and flatten out warped material. I might add vertical supports if needed as well but just going with horizontal for now.

This first image shows the bottom-iso view of the clamp that holds the 8020 strap. It will attach to the 8020 via the two smaller holes. The larger hole on the left is a through hole for 1/4-20 socket cap screw.

This shows the bottom piece of the clamp. This piece attaches to the table frame itself and provides the threaded portion of the 1/4-20 hold down screw.

And here is a detail image of the hold down setup in place.

Support Strap - nothing too exciting here except to support the long center of the cutting grid, I needed to support it with a bar. But since the grid is 1/2" thick, I need move the strap down. To do this, I'm using a basic bracket then a second riser. The riser lets me use much cheaper material to make two parts rather than a larger hunk of raw material - I might re-think this just to reduce my milling if I get lazy enough.

Skate Roller Rod Holder - Since I wanted to support a way to roll material on and off of the table, I needed to get some skate rollers in there. They contain their own ball bearings and just need a rod to support them. The wheels are 2" in diameter so I raised the rod slightly to give a few hundredths of an inch roller above the table. This should make it possible to roll on and off more easily without interfering with accurate placement.

Whew, and there is still one more part to add in the next post.

-Mike

[mikegrundvig]

Ok, last custom table part.

Cutting Grid Clip - This last part is a small clip to support the edges of the cutting grid and keep from from sagging. There are a good number of these all told.

I'm open to any and all input on how to improve anything you see so bring on the comments. Thanks!

-Mike

[TLHarrell]

Just to be sure, is the thickness of your clamp less than the distance from the table to your laser lens/focus assembly? I'd hate to see you do a traverse across the table and snap your lens holder off.

[mikegrundvig]

is the thickness of your clamp less than the distance from the table to your laser lens/focus assembly?

Good question - in the model currently it's 1.5" tall as I'm using 1515 extrusion. I can drop to 1" tall with minimal changes. As the table isn't yet set into the machine design itself I'm not certain if I'll need to do that or not. Even with care though, it will almost always be possible to crash the clamp so it's just something to be aware of. It's a similar problem in milling - crashing the clamps and vises just happens if you are not careful.

-Mike