What are the acceptable tolerances of the Z-Axis leadscrews?

gtsh_user_1
Posts: 2
Joined: Fri May 07, 2021 3:27 pm

What are the acceptable tolerances of the Z-Axis leadscrews?

Postby gtsh_user_1 » Fri May 07, 2021 4:14 pm

I have received my E2 last week - packing was in pristine shape, transport clamps in place where they were supposed to be. Printer started up fine.

When firing up the printer and doing the first steps of calibration I immediately noticed that both Z-Axis leadscrews are bowed. Visible in the circular motion of the screw-end (I haven't measured the runout, but I would estimate more than 1 mm in each direction for a full revolution). Audible in some squeaking. The squeaking got better after applying some PTFE grease to the screws.

The printer is sitting on a dedicated, flat, and level shelf.

What can be considered "normal" or "within specifications" here? For me (engineer), really any bow or runout in a drive / shaft component is a reject but could you please share what level of non-straightness you would consider normal? On my other printers, the screws are dead straight as I would expect them to be. When those screws run, the free end is not showing any lateral movement in spite of not being guided.
The E2 has a comparatively rigid guide of the X-Axis, so (for now) no lateral motion of the screws is transferred to the gantry. Instead, the screw is permanently being bent by the mechanically constrained nut on the X-Gantry.

Other than that I am happy with the printer - after spending quite some time here and on the internet pre-purchase it works as expected. I needed an IDEX printer with enclosed build volume, removable print surface, and reasonable outer dimensions and so far the E2 is meeting expections. I will start tuning in ASA filament next and get into printing the parts I bought it for.

But seeing the leadscrews wobble as they do makes me cringe.

Thanks for your perspective.

GTSH

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Steven@Raise3D
Posts: 477
Joined: Thu Dec 17, 2020 11:24 pm

Re: What are the acceptable tolerances of the Z-Axis leadscrews?

Postby Steven@Raise3D » Fri May 28, 2021 1:08 am

Sorry for the delay our engineers got back to let us know that they do not have a spec for the tolerance of the lead screws. Instead, the primary check is the functionality of the machine. All machines are tested in the factory and if there is an issue with the fit of the leadscrew in the machine or some noticeable issue with the printing performance the machine would not get shipped.


gtsh_user_1 wrote:I have received my E2 last week - packing was in pristine shape, transport clamps in place where they were supposed to be. Printer started up fine.

When firing up the printer and doing the first steps of calibration I immediately noticed that both Z-Axis leadscrews are bowed. Visible in the circular motion of the screw-end (I haven't measured the runout, but I would estimate more than 1 mm in each direction for a full revolution). Audible in some squeaking. The squeaking got better after applying some PTFE grease to the screws.

The printer is sitting on a dedicated, flat, and level shelf.

What can be considered "normal" or "within specifications" here? For me (engineer), really any bow or runout in a drive / shaft component is a reject but could you please share what level of non-straightness you would consider normal? On my other printers, the screws are dead straight as I would expect them to be. When those screws run, the free end is not showing any lateral movement in spite of not being guided.
The E2 has a comparatively rigid guide of the X-Axis, so (for now) no lateral motion of the screws is transferred to the gantry. Instead, the screw is permanently being bent by the mechanically constrained nut on the X-Gantry.

Other than that I am happy with the printer - after spending quite some time here and on the internet pre-purchase it works as expected. I needed an IDEX printer with enclosed build volume, removable print surface, and reasonable outer dimensions and so far the E2 is meeting expections. I will start tuning in ASA filament next and get into printing the parts I bought it for.

But seeing the leadscrews wobble as they do makes me cringe.

Thanks for your perspective.

GTSH

Bikeracer
Posts: 135
Joined: Sun Jun 28, 2020 11:54 am

Re: What are the acceptable tolerances of the Z-Axis leadscrews?

Postby Bikeracer » Fri May 28, 2021 5:48 am

Steven@Raise3D wrote:Sorry for the delay our engineers got back to let us know that they do not have a spec for the tolerance of the lead screws. Instead, the primary check is the functionality of the machine. All machines are tested in the factory and if there is an issue with the fit of the leadscrew in the machine or some noticeable issue with the printing performance the machine would not get shipped.


So what you are saying is that Raise3D produce printers and don't bother about manufacturing tolerances ?
http://www.cncroutersource.com/acme-screws.html#

Quote from link..........
Lead Screw Straightness

Lead screw straightness refers to the tolerance of straightness of the screw. Straightness is also given as deviation per length, such as, 0.001 inch/foot or 1 mm/meter. The straightness of a lead screw is important for maximum rpm capabilities.

It is important when handling lead screws to always keep them supported evenly as possible to maintain the straightness. In general, quality rolled and milled lead screws of the centralizing type will maintain a 0.010 inch/foot tolerance. However, this is again up to the manufacturer. Ground lead screws usually hold a higher tolerance than rolled or milled, as low as 0.001 inch/foot tolerance.

If you are end machining the acme screw, you must support the lead screw throughout its length in order to maintain the straightness while milling. If you have the end machining done elsewhere, request that they straighten the lead screw after the machining is performed.

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ccclarke
Posts: 169
Joined: Wed Apr 08, 2020 6:09 pm

Re: What are the acceptable tolerances of the Z-Axis leadscrews?

Postby ccclarke » Fri May 28, 2021 1:02 pm

It is unlikely the vendor supplying lead screws to Raise3D doesn't have a drawing with machining tolerances which the Raise3D engineers factor into their design. Every (good) manufacturing design starts with a list of requirements which drive the design. The leadscrew runout should be included on the manufacturer's drawing. My company has drawings for every component with specs for anything we buy from outside vendors. We aren't unique in that respect. We also have an Incoming QC department that measures samples of vendor-supplied parts to ensure conformance to the drawings.

So the right (pointed) question is to ask for the vendor drawing. Final product check is the the just that - the last QA gate to be checked before a product is packaged and shipped. That isn't the best time to find out a leadscrew is out of tolerance.

Raise3D isn't prone to releasing product technical details, but at the least, an exploded view with part/numbers would be very useful.
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